7

CHAPTER II

LITERATURE REVIEW

2.1 Introduction

Concrete roof tiles have long used as roofing for a wide variety of buildings and exhibit

advantages in some respects over others materials such as wood, slate or asphalt.

Source from the Britmet Tileform Ltd (2009), United Kingdom reported concrete

roof tiles are advantageous over wood shingles because of their fire resistance. However,

concrete roof tiles are considerably heavier than wood. Roofs are expensive to maintain

and even more expensive to replace. According to Jeffery, J. O. (2008), roof coatings

applied to a roof system can extent the systems service life for many years in delaying

replacement. Coating protects the underlying membrane from exposure to ultraviolet

(UV) light and heat also slowing the roof’s aging process. Highly reflective white

coatings also significantly reduce the membrane’s temperature which leads to improved

long-term performance of the system. This lower temperature also reduces the building’s

heat load resulting in lower cooling costs for the building (Karen, H., 2006).

8

2.2 History of Concrete Roof Tile

Roof Consultants Institute, Florida (2000) reported that concrete roofing tiles were

invented by Adolf Kroher in Bavaria in the middle of the 19th

century. Manufacturing by

hand spread through Germany during the next 50 years and commenced in England on a

German press in about 1895.

Mass production was first developed in the United Kingdom by hand continued

on a small scale until the 1920s. By 1930s concrete roofing tiles were manufactured on

continuous production lines and steadily increasing share of the market from the

traditional roofing materials such as natural slates and clay tiles. The first high pressure

extruded, “dry mix”, interlocking, concrete roof tile machine in the United States began

operations during 1961 in Fremont, California. Every tile was extruded onto an

aluminum mold which not bends under extreme pressure, precise tolerances could be

maintained assuring better fit and weather tightness. Bright, long lasting colors were

applied to the top surface only, instead of throughout the body, using cement-oxide

slurry.

According to Dunton et al (1995), a frequent problem is that the roofing material

to be replaced may be of a lighter weight, such as for examples wood shingles and

shakes, asphalt shingles, asbestos cement roofing and slates. Thereby the building

structure concerned may not be able to support the additional load structure resulted

from re-roofing with conventional concrete roof tiles. Clews, P. (2000) stated that with

timber framed buildings, it is often necessary to reinforce the existing roof timbers to

ensure that they will bear the additional load. This costly and time consuming which in

practice often leads to abandoning the use of concrete roof tiles for re-roofing work.

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2.3 Elements of a Roof Tile

In most countries a roof protects primary against rain. Depending upon the nature of the

building, the roof may also protect against heat, sunlight, cold and wind.

The characteristics of a roof are dependent upon the purpose of the building that

it covers, the available roofing materials and the local traditional of construction and

wider concepts of architectural design and practice and may also be governed by local or

national legislation. The elements in the design of a roof are (Steven, W. P., and Monica,

K.B., 1996):

(i) The material

(ii) The construction

(iii) The durability

The material of a roof may range from banana leaves, wheaten straw or sea grass

to laminate glass, aluminum sheeting and precast concrete. In many parts of the world

ceramic tiles have been the predominant roofing material for centuries. The construction

of a roof is determined by its method of support and how the underneath space is

bridged and whether or not the roof is pitched. The pitch is the angle at which the roof

rises from its lowest to highest point. The pitch is partly dependent upon stylistic factors,

but has more to do with practicalities. Some types of roofing, for example thatch roof

from coconut palm fronds require a steep pitch in order to be waterproof and durable.

Other types of roofing for example, Francis, C. (2009) proved that pantiles are

unstable on a steeply pitched roof but provide excellent weather protection at a relative

low angle. In regions where there is little rain, an almost flat roof with a slight run-off

provides adequate protection against an occasional downpour. The durability of a roof is

a matter of concern because the roof is often the least accessible part of a building for

purposes of repair and renewal, while its damage or destruction can have serious effects.

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2.4 Types and Manufacturing of Roof Tile

2.4.1 Asphalt shingles

Asphalt is a dark brown to black cementitious material, solid or semisolid in which the

predominant constituents are naturally occurring or petroleum-derived bitumen. It is

used as a weatherproofing agent.

The term asphalt shingle is generically used for both fiberglass and organic

shingles. Asphalt shingles come in various colors. Fiberglass shingles commonly known

as asphalt shingles consist of fiber mats that are coated with asphalt and the covered with

granulates. Granules are opaque naturally or synthetically colored aggregates commonly

used to surface cap sheets and shingles. Over the years, one of the most popular roofing

materials has been the asphalt shingle-e piece of felt or fiberglass that is covered in tar

and then tiny small stones are literally glued onto the surface. However, over time the

roof loses its protection due to worn off stones and causes ongoing deterioration of the

shingles, leading to leaks and eventual structural damage (Hashem et al, 2005).

Granules cover over 97% of the surface of a typically asphalt-soaked fiberglass

shingle. Granules are applied to asphalt shingles for several reasons, including UV

protection, coloration, ballasting, impact resistance, and fire resistance. Granule

manufacturing plants are typically sited near quarry of suitable base rocks, including

andesite, coal slag, diabase, metabalast, nephaline syenite, quartzite, rhyodacite,

rhyodacite, and river gravel. The essential characteristics of the base rock include

(Hashem et al, 2005):

(i) Opacity to ultraviolet light, to protect the asphalt from ultraviolet damage.

(ii) Chemical and physical inertness, to provide resistance to acid rain, leaching,

freeze/thaw, wet/dry cycling, oxidation and rusting.

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(iii) Low porosity, to improve physical strength, binding between coating and rock,

and efficiency with which the pigment coating covers the surface.

(iv) Tolerance of high firing temperature.

(v) Other necessary characteristics include moderate hardness, to remain intact

during the granule coloring process; moderate density, to weight the shingle

against wind lift; uniformity, and crush equidimensionally, to prevent directional

embedment in the shingle manufacturing process, which changes shingle

appearance.

2.4.2 Clay

Clay tiles are a traditional roofing material come in a variety of types and styles. Clay

tiles are a combination of various clays and water. The density of the clay is determined

by the length of time and temperature at which it is heated.

Clay tiles may be glazed and also may have surface texture treatments applied.

Color is added to the surface of the tile with a slurry coating process before the tile kiln-

fired (Hashem et al, 2003). In many parts of the country, clay or concrete roofing tiles

are used because of its composition. Michael, J. (2002) has investigated clay tiles are

perceived as a high-end, quality construction material are long lasting and virtually

maintenance free, fireproof and impervious to insects and rot will withstand hurricane

winds better than other roofing products and many resist the effects of freeze-thaw

cycles. The Unified Facilities Criteria (2006) reported that the disadvantages of clay roof

tiles are more difficult to install than other roofing products. Clay roofing tile has a

relatively high first cost because of the limited number of clay roofing tile

manufacturers, the material may be have to be shipped long distances, increasing costs

dramatically.

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Clay tile production begins by mixing and crushing various raw clay materials.

Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory (2003)

reported the raw clays are thoroughly mixed with water and aged for 4-5 days. The

aging process allows the dry material to fully absorb the moisture, improving plasticity.

Several extrusion machines and dies are employed to produce clay tiles of various

shapes, prior to extrusion, the clay flows through a vacuum chamber to remove air for

proper verification which makes the tile weather resistant i.e., resistant to

freezing/thawing intrusion; see Standard Specification for Clay Roof Tiles: ASTM C-

1167 for more detail. The wet extruded tile then dried in a sequence of temperature-

controlled chambers for about 24 hours typically starts with circulating ambient air at a

temperature of about 20-30ºC, gradually increasing the temperature to about 90ºC using

waste heat from kiln-cooling process.

Drying reduces the tile’s mass moisture content from 15% to less than 1%. The

glazing is a mixture of water, pigments and clay additives then passed through a kiln

fired for 14-20 hours. The kiln has three stages: preheat, heating and cooling. In the

preheating zone, the tiles are gradually heated to about 700ºC by warm drawn air from

the heating zone. On the heating zone, the tiles are directly fired for about 4 hours by gas

flame, reaching a maximum temperature of about 1050ºC. Then the tiles are gradually

cooled to about 300-400ºC by drawing outside air though the kiln. The clay tile colors

permanent and do not fade with exposure to the sun. Photos of several steps in the

process are shown in Figure 2.1.

(i) (ii)

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(iii) (iv)

(v) (vi)

(vii) (viii)

Figure 2.1: Clay manufacturing processes: (i) production begins by mixing and crushing

raw clay components; (ii) extrusion machines and molds produce variously shaped tiles;

(iii) the wet extruded tile is dried in a sequence of temperature and humidity controlled

drying chambers for about 24 hours; (iv) the dry raw tiles are inspected for defects and

sprayed with glossy or mat glazes; (v) the coated tiles are stacked with spacers (typically

1.25 cm) to allow an even heat distribution in the kiln; (vi) the coated tiles are kiln-fired

for 14-20 hours; (vii) the finished tiles are shipped to customers; (viii) shows various tile

samples.

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2.4.3 Concrete

Concrete roof tiles are made of Portland cement, sand and water in varying proportions.

The water fraction depends on the manufacturing process. The material is mixed and

extruded on molds under high pressure.

Concrete tiles are either air-cured or autoclaved. The concrete roof tiles are cured

to reach the required strength. The exposed surface of a tile may be finished with

cementitious material colored with synthetic oxide additives. Color is added to the

surface of the tile with a slurry coating process or added to the mixture during the

manufacturing process. Concrete roof have its own unique set of problems, which

include water intrusion due to their extremely porous make-up. The roofing tiles become

cracked by moisture seeping through the pores of the tile and going through the

freeze/thaw cycle (CMRS, 2008).

Sand, cemetitious materials, limestone fillers and water are main ingredients (by

mass) of concrete roof tiles as referred to Figure 2.2. Concrete tile production begins by

mixing aggregate (sand) and fillers. Recycled aggregates and quarry waste are also used

in the mixture. Milled calcium carbonate, an inexpensive material that improves the

quality of concrete, is used as filler. The aggregate and filler are mixed with

cementitious materials before water is added to the mixture. At this stage, pigments may

be added to color the concrete mix. The mold and wet concrete tile run on a conveyor

where the tiles are partially dried. The tiles and the mold are packed in a curing chamber

for about four hours, where the concrete tile is cured and dried. The molds and tiles run

though a separator that removes the molds. The dry raw tiles are inspected for defects

before they are sprayed with colored coatings. The tiles are then covered with post-

coating polymers. The coating is a mixture of water, pigments, and polymetric additives.

The coated tiles are then dried, stacked, and packed for shipment (MonierLifetile, 2009).

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Figure 2.2: Typical composition of a concrete roof tile, by mass and by cost

(MonierLifetile, 2009).

2.4.4 Metal

Most metal roofing products consists of steel or aluminum, although some consists of

copper and other metals. US Department of Energy and Lawrence Berkeley Laboratory

(2003) reported steel is invariably galvanized by the application of zinc or aluminum

coating, which greatly reduces the rate of corrosion.

Metal roofing is available as traditional seam and batten, tiles, shingles, and

shakes. Products also come in variety of styles and colors. Metal roofs with solid

sheathing control noise from rain, hail and bad weather just as well as any other roofing

material. Metal roofing costs more than asphalt, but it typically lasts 2 to 3 times longer

than asphalt shingles. Metal production for the roofing industry may be divided into two

phases; Coil coating plants and Metal forming plants (Hashem et al, 2005).

Coil coating plants by using raw metal coils are cleaned, metallic coated, primed,

and paint coated. Coil coaters produce rolled metals in the thickness, width, metal

coating type and color. An advanced metal coil plant typically has four major production

lines: a pickle line, where the hot-band coil is uncoiled, is cleaned of oxides, had its

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edges trimmed and is oiled in preparation of further processing; a cold mill line, where

the picked bands are reduced in thickness 65-80% to meet ordered thickness, are rolled

to a suitable shape, and have texture applied to the surface; a metallic coating line,

where the coils are cleaned again, a layer of metallic coating is applied, and the surface

is treated in a bare metal application; and a paint line where primer and finish coatings

are applied. Metal forming plants cut and press painted or unpainted metal coils to form

either flat panels or simulations of non-metal roofing products (e.g., shake, tile, and

slate). A very few fabricators apply granulated material to the painted panels in order to

simulate asphalt shingles. However, most fabricators of shingle or tile type profiles use

embossing or stamping to achieve the desired look.

2.5 Lightweight Concrete Roof Tile

According to Lazim, M. Z. (1978) lightweight concrete can be defined as a type of

concrete which includes an expanding agent that increase the volume of the mixture and

giving additional qualities such as nailbility and lessened the dead weight.

From the reported by National Ready Mixed Concrete Association Structural

(2008), lightweight concrete has an in-place density on the order of 1440 kg/m3 to 1840

kg/m3 compared to normal weight concrete with a density in the range of 2240kg/m

3 to

2400 kg/m3. The primary use of structural lightweight concrete is to reduce the dead

load of a concrete structure, which then allows the structural designer to reduce the size

of columns, footings and other load bearing elements. Structural lightweight concrete

mixtures can be designed to achieve similar strengths as normal weight concrete. The

same is true for other mechanical and durability performance requirements.

Structural lightweight concrete provides a more efficient strength to weight ratio

in structural elements. The marginally higher cost of the lightweight concrete offset by

size reduction of structural elements, less reinforcing steel and reduced volume of the

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concrete, resulting in lower overall cost (Roji, M., 1997). National Ready Mixed

Concrete Association Structural (2008) states in buildings, structural lightweight

concrete provides a higher fire-rated concrete structure. Structural lightweight concrete

also benefits from the energy conservation consideration for improved insulation

properties. The porosity of lightweight aggregate provides a source of water for internal

curing of the concrete that provides continued enhancement of concrete strength and

durability.

2.5.1 Advantages of lightweight concrete roof tiles

A side from the reduction in costs and materials, there are other advantages of choosing

lightweight roof tiles. The reduction in dead load means savings can be made in

foundation design. There are several advantages of lightweight roof tiles (Decra, 1997):

(i) Dramatic reductions in construction times.

(ii) Improvements in the predictability of building projects.

(iii) Potential cost savings.

(iv) Higher quantity and fewer defects.

(v) Improvements in health and safety.

(vi) Large reductions in onsite installation time, consequently reducing disruption to

surrounding tenants and homeowners.

(vii) Air circulation is often enhanced with the use of roof tiles.

(viii) Concrete is a very durable building material.

(ix) Concrete roof tile are available in large range of colors and designs.

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2.5.2 Components of lightweight concrete roof tile

(a) Portland cement

Portland cement is the chief ingredient in cement paste, the binding agent in

Portland cement concrete (PCC). Portland cement is a mixture of compounds

made by burning limestone and clay together at very high temperatures ranging

from 1400ºC to 1600ºC which the two materials interact chemically to form

calcium silicates (Mindess, S., and Young, J. F., 1981). This heated substance,

called “clinker” is usually in the form of small gray-black pellets about 12.5 mm

in diameter. Clinker is then cooled and pulverized into fine powder that almost

completely passes through a 0.075 mm sieve and fortified with a small amount of

gypsum. It is combined with water, hardens into a solid mass. Interspersed in an

aggregate matrix it forms PCC.

(b) Sand

Sand is composed of finely divided rock and mineral particles, finely grained

minerals that are product of chemical and mechanical decomposition of rocks

over long periods of time. These minerals include quartz with traces of mica,

feldspar, and magnetite. Concrete containing fine sand requires more water for

the same consistency while coarse sand have undesirable effect on finishing

quality. Sand particles have an interlocking effect and less freedom of movement

in the freshly mixed concrete (Fisher, A., 2001).

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(c) Water

Water is the key ingredient, which when mixed with cement, forms a paste that

binds the aggregate together. The water causes the hardening of concrete through

a process called hydration. Hydration is a chemical reaction in which the major

compounds in cement form chemical bonds with water molecules and become

hydrates or hydration products. The water needs to be pure in order to prevent

side reactions from occurring which may weaken the concrete or otherwise

interfere with the hydration process. The role of water is important because this

water to cement ratio is the most critical factor in the production of perfect

concrete. Too much water reduces concrete strength, while too little will make

the concrete unworkable (Nataatmadja, A., 2002). Concrete needs to be workable

so that it may be consolidated and shaped into different forms i.e. walls, domes,

roof tile, floor and others because concrete must be both strong and workable, a

careful balance of the cement to water ratio is required when making concrete.

(d) Superplasticizer

Superplasticizer or dispersants are additives that increase the plasticity or fluidity

of the material to which they are added, these include cement, concrete,

aggregate and sand. Superplasticizer are a class of plasticizers that have fewer

deleterious effects, and can be used to increase the ability of fresh concrete mix

and reduce the water content of a concrete. Superplasticizers for concrete

increase the workability of the wet mix, or reduce the water required to achieve

the desired workability and ate usually not intended to affect the properties of the

final product after hardens (John, N., and Ban, S., 2009).

(e) Aggregate

Aggregates are chemically inert, solid bodies held together by the cement.

Aggregates come in various shapes, sizes, and materials ranging from fine

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particles of sand to large, coarse rocks because cement is the most expensive

ingredient in making concrete, it is desirable to minimize the amount of cement

used. 70% to 80% of the volume of concrete is aggregate, keeping the cost of the

concrete low. The selection of an aggregate is determined, in part, by the desired

characteristics of the concrete. For example, the density of concrete is

determined by the density of the aggregate. Soft, porous aggregates can result in

weak concrete with low wear resistance, while using hard aggregates can make

strong concrete with a high resistance to abrasion (Jennifer, L., 1995). Smith, S.

E., (2009) reported that using aggregate makes concrete much stronger, with the

aggregate as a type of reinforcement. The aggregate increases the lifetime of the

concrete and makes it more durable. Charles, K., (1999) stated synthetic

aggregates may be either byproducts of an industrial process such as blast-

furnace slag, expanded clay, shale or slate and crumb rubbers that are used for

lightweight aggregates.

Table 2.1: Classes of aggregates (Jennifer, L., 1995).

Class Examples of aggregates

used

Uses

Ultra-

lightweight

Vermiculite, ceramic

spheres, perlite

Lightweight concrete which

can be sawed or nailed, also

for its insulating properties

Lightweight

Expanded clay shale, slate

crushed brick, crumb rubber

Used primarily for making

lightweight concrete for

structures, also used for its

insulating properties.

Normalweight

Crushed limestone, sand,

river gravel, crushed

recycled concrete.

Used for normal concrete

projects

Heavyweight

Steel or iron shot steel or

iron pellets

Used for making high density

concrete for shielding against

nuclear radiation

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(f) Concrete

Concrete is a material used in building construction, consisting of a hard,

chemically inert particulate substance known as an aggregate usually made from

different types of sand and gravel that is bonded together by cement and water.

Concrete is used to make pavements, floor, bridges, brick, wall, roof tile and

others. There are many types of concrete available, created by varying the

proportions of the main ingredients such as Portland cement, water, sand,

aggregate and superplasticizer. By varying the proportions of materials, or by

substitution for the cemetitious and aggregate phases, the finished product can be

tailored to its application with varying strength, density or chemical and thermal

resistance properties. The mix design depends on the type of structure being built

to form this structure (Jennifer, L., 1995).

2.5.3 Classification of waste lightweight aggregate

The concrete industry is using more and more natural aggregates, and this resource is not

only becoming depleted, but also having a considerable adverse environmental impact.

There is thus increasing interest in using some of these waste materials as

concrete aggregates. As shown in Table 2.2, in the United Kingdom alone, about 150

million tons of waste materials that might make suitable aggregates at least for some

applications are produced annually.

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Table 2.2: Potential quantities of material available for use as aggregate in concrete in

the United Kingdom (Dhir, R. K., 2004).

Material Arising (per annum) Uses in concrete

Recycled aggregates 109 million tons As coarse aggregate

Strength classes 10-50 MPa

Glass >2 million tons As fine aggregate

Strength classes 10-50 MPa

Improved freeze/thaw and abrasion

resistance

Incinerator ash 1 million tons As aggregate. Finer fraction has

potential pozzolanic properties

Strength classes 4-35 MPa

Rubber aggregate >40 million used tires Specialist concretes for improved

freeze/thaw resistance, thermal

insulation, or impact resistance

Strength classes 4-35 MPa

(a) Recycled aggregate

Recycled aggregate is defined in BS 8500-1 as the generic term for aggregate

resulting from the reprocessing of inorganic material previously used in

construction. In addition to significant quantities of natural aggregates, recycled

aggregates are likely to contain impurities such as wood, metal, asphalt and

plastic; these need to be controlled to acceptable levels dependent on the

proposed use of the recycled aggregate. The recycling of construction materials

has long been recognized to have the potential to conserve natural resources and

to reduce the energy used in production. Recycled aggregate can also be used in

some concrete grades meant for internal reinforced concrete members. However,

in such instances, a designer has to appreciate deficiencies of recycled aggregate

regarding workability and the problems presented in the form of harshness of the

mix, together with porosity and inadequate durability of the hardened concrete.

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(b) Glass

Glass is a unique inert material that could be recycled many times without

changing its chemical properties. In other words, bottles can be crushed into

cullet, then melted and made into new bottles without significant changes to the

glass properties. Most of the glass produced is in the form of containers, and the

bulk of what is collected post-consumer is again used for making containers.

Glass aggregate in concrete can be problematic due to the alkali silica between

the cement paste and the glass aggregate, which over time can lead to weakened

concrete and decreased long-term durability. Blewitt, J., and Woodward, P. K.

(2000) concluded that crushed waste glass has some potential for use as a fill or

drainage material but there are no reports of it having been used for these

purposes. There are also reports of it having some potential for use as a concrete

aggregate, but its use for this purpose should be treated with great caution

because of the possibility of the glass aggregate reacting with the alkalies in the

cement.

(c) Incinerator ash

The use of incinerator ash as an aggregate in bituminous bases and Portland

cement concrete has been researched in the past but rarely practiced. The

economics of use depend on local conditions and involved significant initial

costs to set up a plant removing unwanted constituents from the ashes. However,

its use in some areas has been shown to be economically justified. It may be

environmentally unacceptable. Two types of ash are produced as a result of the

incineration of municipal wastes, fly ash, which is taken from the filters in the

flues, and bottom ash which is left after the combustion of the materials. The fly

ash has high concentrations of toxic materials which make it entirely unsuitable

for use (Bond, N., 2000) and only the bottom ash, which is considered here, has

any potential uses in road construction.

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(d) Rubber aggregate

Rubber aggregate is a material produced by shredding and commutating used

tires. There is no doubt that the increasing piles of used tires create

environmental concerns. Kamil, E., and George, P. E. (2008) investigate the

long-term goal of the research to find means to dispose of the rubber aggregate

by placement of the rubber in Portland cement concrete and still provide a final

product with good engineering properties. The Arizona Department of

Transportation and Arizona State University have initiated several crumb rubber

concrete (CRC) test sections throughout Arizona over the past few years.

Laboratory tests were conducted to support the knowledge learned in the field

and enhance the understanding of the material properties of CRC. Rubber

aggregate is defined as rubber that has been reduced to a particle size of 3/8-inch

or less. Mesh or sieve size is commonly used to describe or measure the size of

rubber aggregate. Rubber aggregate is sized by the mesh screen or sieve through

which it passes in the production process. A 30 mesh means there are 30 holes or

openings per linear inch of screen. Depending on the size of the rubber aggregate

produced and under what conditions, 99% or more of the steel and fabric can be

removed. Ten to twelve pounds of rubber aggregate can be derived from one

scrap passenger tire (Bignozzi, M/ C., and Sandrolini, F., 2005). Texas Natural

Resource Conservation Commission (1999) reported that the typical process to

make rubber aggregate involves three stages. First, the scrap tire is reduced to 2

½-inch to 4-inch size shreds by a slow speed “shear” shredder or shredders.

Second, the shreds go through two or three successively narrower blade

shredders to further reduce the shreds to 3/8-inch or less. Finally, the rubber

particles are processed to even smaller mesh sizes by using cracking or grinding

rolling mills. Screens and gravity separators are used to remove metal, and

aspiration equipment is used to remove fibers.

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2.6 General Coating

Coatings are routinely used as protective barriers against abrasion, chemical attack,

hydro-thermal variations and to improve aesthetics. Currently, most of these coatings are

in the micrometer range. New materials and techniques are being developed for nano-

meter thick coatings that are durable and generate less heat due to reduced friction.

Coatings could be self-cleaning and self-healing. In most cases the performance

of these coatings are evaluated using experimental techniques. The major parameters

evaluated are: durability of coatings under various exposure conditions, abrasion

resistance, friction resistance, high temperature and electrical resistance. Performance of

the coating film and the interface between the film and the parent material play

important role in the overall durability of the system (Balaguru, P., and Chang, P.,

2003). Coatings have many uses in industrial situation. They are used for corrosion

control, chemical resistance, heat resistance, temperature control, identification

decoration, camouflage, fire retardation, noise control, anti-fouling protection and many

other reasons as shown in Figure 2.3 (Lloyd, M. S., 1996).

Terminology used in the industry can be confusing. The terms paint, coating and

lining sometimes are used interchangeably, but there are differences in their meanings.

The paint and coatings dictionary (Paints Coating Dictionary, 1978) defines paint and

coating as follows:

(a) Paint

Any pigmented liquid, liquefiable or mastic composition designed for application

to a substrate in a thin layer that is converted to an opaque soled film after

application. Used for protection, decoration, or identification, or to serve some

functional purpose such as the filling or concealing of surface irregularities, the

modification of light and heat radiation characteristic, etc.

26

27

(b) Coating

A liquid, liquefiable or mastic composition which is converted to a solid

protective, decorative, or functional adherent film after application as a thin

layer.

Based on these definitions, the major difference between paint and coating is that

paint is pigmented, while no such requirement is mentioned for coating. They both are

liquid, liquefiable or mastic components that are converted to a film after application as

a thin layer. Therefore, varnishes and clear coats are coatings but not paints. Processes,

such as galvanizing and metalizing also meet the definition of coating.

Coating generally refers to materials used for protection of functional purposes,

while paint refers to materials used for aesthetic or decorative purposes. Thus, a

structure is coated while a room is painted. This differentiation is further emphasized by

some who refer to the materials used in industrial situations as protective coatings. The

definition of lining, from the Industrial maintenance Coatings Glossary, is a material

used to protect a container against corrosion and to protect the contents of a container

from contamination by the container shell material. Liners commonly are thought of as

thick, built-up systems containing matting or similar reinforcing material. However, the

definition does not exclude coating from use as linings.

2.6.1 Coating components

Traditionally, coating has been considered a liquid made up of several components that

when applied and cured imparts a thin plastic film. Coatings have traditionally contained

petroleum based solvents to aid in application. Solid coating, such as powder coatings

and paints containing no solvents that are electrodeposited, are now available.

28

These materials have given rise to the term coatings instead of paints. A coating

can contain as few as three or four ingredients or as many as 20 or 30 ingredients,

depending on the formulation. The three main components of a coating are the resin,

pigment and solvent as shown in Figure 2.4 (Jeans, S. W., 1996). Resin and solvent

comprise the liquid portion of a coating and referred to as the film solids, since they are

the materials left after the coating has dried (Martens, C. R., 1968).

Figure 2.4: Coating composition by volume (Jeans, S. W., 1996).

(a) Resins

The resin or binder is responsible for most of the coating’s physical and chemical

properties, including hardness, abrasion resistance, chemical resistance, weather

resistance, adhesion and cohesion. The type of resin system also determines a

coating’s curing mechanism. Resins can be classified as thermoplastic and

thermoset. Thermoplastic resins can be repeatedly softened by heating and

hardened by cooling. They also can be dissolved by the original solvent used in

the coating. Coatings based on thermoplastic resins usually are packaged in the

one container. Thermosetting resins, however, undergo a chemical reaction by

the action of heat, catalysts, ultraviolet light, etc., that makes them relatively

infusible. The type of resin:

29

(i) Acrylics contain suspended polymer particles. When the solvent and

water evaporate, the polymer particles remain and form a film. Acrylics

produce a shiny, hard finish with good chemical and weather resistance.

(ii) Alkyds are made from chemically modified vegetable oils, and are

relatively low in cost, easily modified to change the paint properties.

Alkyds reacts with oxygen in air (in ambient conditions) to form a

crosslinked film, thus are very functional for a wide variety of

applications.

(iii) Epoxies provide excellent water resistance and superior chemical

resistance. Epoxies can be formulated in a variety of ways, from one-

component formulations that require elevated temperature curing to two-

component systems that cure at or below ambient conditions. Epoxies

lose their gloss from ultraviolet light exposure, but the damage is rarely

structural.

(iv) Urethanes combine high gloss and flexibility with chemical and strain

resistance. They require little or no heat to cure and demonstrate excellent

water and weather resistance. Urethanes result from a reaction between

an isocyanate and alcohol.

(v) Others such as Polyesters are similar to alkyds in chemical structure, but

must be heat cured. Isocyanate and TGIC (triglycidyl isocyanurate)

crosslinked polyesters are two popular powder coatings. Silicones have

high heat-resistance and superior resistance to weather and water. Vinyls

can have a wide range of flexibility. Vinyls used extensively in marine

applications, as interior metal for liners (polyvinylchloride), and for

structural wood finish (polyvinylacetate).

30

According to Anika, Z. R. (2010), polymer from renewable materials such as

waste cooking oil has a potential for the production of polymeric products. Palm

oil is used as cooking oil, to make margarine and is a component of many

processed foods. Boiling it for a few minutes destroys the carotenoids and the oil

becomes colourless. Palm oil is one of the few vegetable oils relatively high in

saturated fats like coconut oil and thus semi-solid at room temperature. Palm oil

and palm kernel oil are composed of fatty acids, esterified with glycerol just like

any ordinary fat. Both are high in saturated fatty acids, about 50 % and 80 %

respectively (Atanu et al, 2008). The oil palm gives its name to the 16 carbon

saturated fatty acid palmitic acid found in palm oil; monounsaturated oleic acid

is also a constituent of palm oil while palm kernel oil contains mainly lauric acid.

Palm oil is the largest natural source of tocotrienol, part of the vitamin E. Palm

oil is also high in vitamin K and dietary magnesium.

Figure 2.5: The approximate concentration of fatty acids (FAs) in palm oil (Ang

et al, 1999).

31

(b) Solvent

Solvents are added to paint to aid in its application. The main function of the

solvent is to provide ease of coating application. A solvent is typically selected

based on its ability to dissolve binder components which is resins and its

evaporation rate. Solvents dissolve or disperse the resin, provide flow-out and

leveling during application, and control adhesion and durability of the dry film

(Lambourne, R., 1987). One of the examples of solvents is toluene. Toluene is

colorless, mobile liquid with a distinctive aromatic odor somewhat milder than

that of benzene. The name toluene derives from a natural resin and was

discovered among the degradation products obtained by heating this resin

(Dickson, E., 2006). Toluene is widely used as raw material in the production of

organic compounds and as a solvent. Use of toluene as solvent in surface

coatings has been declining, primarily because of various environmental and

health regulations. It is being replaced by other solvents such as esters and

ketones, and changing the product formulation to use either fully solid systems or

water-based emulsion systems. It is readily absorbed from the gastrointestinal

and respiratory tracts and to a lesser degree, through the skin. Toluene is

distributed throughout the body, with accumulation in tissues with high lipid

content. It is metabolized in the liver, primary to hippuric acid and benzoyl

glucuronide, compounds that are rapidly excreted in the urine (Sean, E., and

Masahiro, I., 2010). The physical properties of toluene are present in Table 2.3

below (Smith, B. D., and Srivastava, R., 1986):

Table 2.3: Physical properties of toluene (Smith, B. D., and Srivastava, R.,

1986):

Property Value

molecular weight 92.14

melting point, K 178.15

normal boiling point, K 383.75

critical temperature, K 591.80

critical pressure, MPaa 4.108

critical volume, L/(g.mol) 0.316

critical compressibility factor 0.264

32

acentric factor 0.262

flash point, K 278

Autoignition temperature, K 809

Gas properties,

298.15 K

Hƒ, kJ/mol b 50.17

Gƒ, kJ/mol b 122.2

Cp kJ/(mol.K) b 104.7

Hvap, kJ/mol b 38.26

Hcomb, kJ/mol b -3734

viscosity, mPa.s( = cP) 0.00698

flammability limits, in air c , vol%

lower limit at 1 atm 1.2

upper limit at 1 atm 7.1

Liquid properties

298.15K

density, L/mol 9.38

Cp J/(mol.K) b 156.5

viscosity, mPa.s( = cP) 0.548

thermal conductivity, W/(m.K) 0.133

surface tension, m N.m ( = dyn/cm) 27.9

Liquid properties,

178.15 K

density, L/mol 10.49

Cp J/(mol.K) b 135.1

viscosity, mPa.s( = cP) 1.47

thermal conductivity, W/(m.K) 0.162

surface tension, m N.m ( = dyn/cm) 42.8

Solid properties

Density at 93.15 K, L/mol 11.18

Cp at 178.15 K, J/(mol.K) b 90.0

Heat of fusion at 178.15 K, kJ/mol b 6.62

a To convert MPa to psi, multiply by 1.45

b To covert J to cal, divide by 4.184

c At 101.3 kPa (1 atm)

Toluene is an alkylbenzene has the chemistry typically of each example of this

type of compound. However, the typical aromatic ring or alkene reactions are

affected by the presence of the other group as a substituent. Except for

hydrogenation and oxidation, the most important reactions involve either

electrophilic substitution in the aromatic ring or free-radical substitution on the

methyl group. Addition reactions to the double bonds of the ring and

disproportionation of two toluene molecules to yield one molecules of benzene

33

and one molecule of xylene also occur. The aromatic ring has high electron

density. As a result of this electron density, toluene behaves as a base, not only in

a aromatic ring substitution reactions but also in the formation of charge-transfer

(π) complexes and in the formation of complexes with super acids. In this

regards, toluene is intermediate in reactivity between benzene and the xylenes, as

illustrated in Table 2.4.

Table 2.4: Relative basicity and reactivity to toluene = 1.00 (Brown, H. C., and

Brady, J. D., 1952).

Xylene

Electrophile Benzene Toluene Ortho Meta Para

Ag+a

0.90 1.00 1.08 1.13 0.98

HCl b 0.66 1.00 1.23 1.37 1.09

TCE c 0.54 1.00 1.89 1.62 2.05

HF-BF3d 1.00 200.00 2000.00 100.00

NO2+e

0.045 1.00

Cl2 f 0.003 1.00 13.1 1250.00 6.3

a Solubility in aqueous Ag

+

bK for Ar+HCl Ar HCl in π-heptane at -78ºC

c K for association with tetracyanoethylene (TCE) in CH2Cl2

d Basicity by competitive promotion

e CH3COONO2 in (CH3C)OO at 24ºC

f Cl2 in CH3COOH at 24ºC

(c) Pigments and additives

Pigments are tiny particles which are insoluble in coating. Pigments are

incorporated to enhance physical appearance or improve physical properties.

Many pigments still contain lead, chromium, cadmium, titanium dioxide or other

heavy metals. These paints cannot be thrown away because heavy metals leach

out of landfills and contaminate groundwater. Their production is being phased

out because of their toxicity. Inorganic pigments have high thermal stability and

ultraviolet light stability. Organic pigments are brighter and clearer inorganic

pigments. Most pigments are inorganic compounds, although some bright color

pigments are insoluble organic compounds. For examples Titanium Dioxide, also

34

known as Titanium (IV) Oxide or Titania, is the naturally occurring oxide of

titanium, chemical formula TiO2. When used as a pigments or fillers, it is called

titanium white, Pigment White 6, or CI 77891. It is noteworthy for its range of

applications, from paint to sunscreen to food colouring, for which it was given E

number E171 (Goresy, E. L., and Ahmed, N., 2001).

Figure 2.6: Titanium Dioxide powder (Goresy, E. L., and Ahmed, N., 2001).

Figure 2.7: Molecular TiO2 (Greenwood, N. N., and Earnshaw, A., 1997).

35

Table 2.5: Characteristics of Titanium Dioxide (Greenwood, N. N., and Earnshaw, A.,

1997).

IUPAC name Titanium Dioxide

Titanium(IV) Oxide

Others names Titania

Rutile

Anatase

Brookite

Identifiers

CAS number 13463-67-7

PubChem 26042

RTECS number XR2775000

Properties

Molecular formula TiO2

Molar mass 79.866 g/mol

Appearance White solid

Density 4.23 g/ cm3

Melting point 1843˚C

Boiling point 2972˚C

Refractive index (nD) 2.488 (anatase)

2.583 (brooklite)

2.609 (rutile)

Hazards

MSDS ICSC 0338

NFPA 704

Flash point Non-flammable

36

Additives are chemicals used in coating formulation to impart specific physical

or chemical properties to the coating. Paint performance may be improved by

adding curing agents, defoamers, flow control agents, gloss modifiers, softeners,

stabilizers, thixotropes, antifreeze, or other agents (Jeans, S. W., 1996). In

addition to resins, pigments and solvents, many coating formulations contain

additives- specialty materials that vary widely depending on the resin type. Oil-

based coatings for example, contain dryers to promote curing. Hard, brittle

resins, such as vinyls contain plasticizers to produce a more flexible film.

Emulsion systems employ a number of additives, including wetting agents,

dispersants, freeze-thaw stabilizers, anti-microbial agents and film forming aids.

Methylene Diphenyl Diisocyanate (MDI) is one types of additive of curing agent

is a medium viscosity epoxy curing agent. MDI is used in a majority situation, at

low temperatures and to produce a rapid cure that develops the physical

properties quickly at room temperature. The ratio between bio-polymer and

cross-linking agent is 2:1. Methylene Diphenyl Diisocynate, most often

abbreviated as MDI, is an aromatic diisocyanate. It exists in three isomers, 2,2’-

MDI, 2,4’-MDI, and 4,4’-MDI. The 4,4’isomer is most practically useful, and is

also known as Pure MDI. MDI is reacted with a polyol in the manufacture of

polyurethane (Wollensak et al, 2003).

(a)

37

(b)

Figure 2.8: (a) Chemical structure of MDI and (b) Molecular MDI (Wollensak et

al, 2003).

Table 2.6: Properties of MDI (Wollensak et al, 2003).

Properties

Other names Pure MDI

4,4’-methylene diphenyl diisocyanate

4,4’-diphenylmethane diisocyanate

Molecular formula C15 H10N2O2

Molar mass 250.25 g/mol

Appearance White or pale yellow solid

Density 1.230 g/cm3,solid

Melting point 40˚C (313 K)

Boiling point 314˚C (587 K)

Solubility in water Reacts

Related compounds Polyurethane

38

2.7 Classification of Surface Coatings for LRT

The most common method of classification for coatings is generic type, which refers to

the chemical attribute – most often the resin type that is unique to a group of coatings.

Generic type is the most useful classification principle because coatings of the same

generic type have similar handling and performance properties (Farhat, A., 2009). The

name for most generic types of coatings is based on the resin (binder) in the formulation

as shown in Figure 2.9.

A roof coating is an additional layer of protection enhancing the roof’s ability to

remain undamaged from rain, hail, wind and sunlight, the coating is usually in the form

of a thin membrane that seals the materials used to create the roof, effectively

establishing a barrier between the elements and the actual roof. Malcolm, T. (2009)

reported that the coating slows down damaged to the roof by absorbing most of the

damaging effects of the sun’s UV rays. Since applying a new coating is significantly less

expensive and time consuming than installing a new roof is due to efflorescence and

fungal growth on roofs. Efflorescence often referred to as “lime bloom” is natural

phenomenon found in cementitious products such as concrete roof tiles. The cause lies

in the chemical composition of the cement. When water added to cement a series of

chemical reactions take place resulting in the setting and hardening. One product of

these reactions “lime” in the form of calcium hydroxide which is slightly soluble in

water and under certain conditions can migrate via capillaries in the concrete tile to the

surface. There is reacts with the carbon dioxide from the atmosphere forming a white

powder deposit of calcium carbonate crystal which is referred to as efflorescence.

At present there is no viable method during the production process of preventing

efflorescence. Small deposits of fungal lichen or moss on a fairly new roof can be

removed by using water and a hard bristle brush. Lichen has been prevalent for a

number of years. It should be treated with approximately 2% copper sulphate solution to

kill the growth. Concrete Manufacturers Association reported, the roof should then be

washed with a high-pressure water spray and a hard bristle brush and requires

39

40

repainting. This can be carried out by using an approved pure acrylic paint which can be

applied either by brush, roller or with spraying equipment. Epoxy or polyepoxide is a

thermosetting polymer formed from reaction of an epoxide “resin” with polyamine

“hardener”. Epoxy has a wide range application, including fiber-reinforced plastic

materials and general purpose adhesives. Epoxy is a copolymer, it is formed from

different chemicals. These are referred to as the “resin” and the “hardener”. The resin

consists of monomers or short chain polymers with an epoxide group at either end

(Liang, J., 2009).

2.8 Influence of Titanium Dioxide for Coating Materials

2.8.1 Titanium Dioxide as photocatalyst

Titanium Dioxide has several limitations, which inhibit more extensive utilization of

photocatalysis in commercial application. A major limitation is the lack of Titanium

Dioxide to visible light since it requires UV light below 388 nm for photoactivation

(Brussels, 2005).

In Figure 2.10, the main areas of activity in Titanium Dioxide photocatalyst are

shown. As already mentioned, in the last 10 years photocatalyst has become more and

more attractive for the industry regarding the development of technologies for

purification of water and air. Compared with traditional advanced oxidation processes

the technology of photocatalysis is known to have some advantages, such as ease of

setup and operation at ambient temperatures, no need for postprocesses, low

consumption of energy and consequently low costs (Bahnemann, D., 1994).

41

Figure 2.10: Major areas of activity in Titanium Dioxide photocatalyst (Bahnemann, D.,

1994).

2.8.2 Titanium Dioxide as superhydrophobicity

In practice, surface cleaning of building materials like roof tiles, facades and glass panes

causes considerable trouble, high consumption of energy and chemical detergents and,

consequently, high costs.

Sandia National Laboratories reported to categories self-cleaning material

surfaces by two principal ways: the development of super-hydrophobic or super-

hydrophilic surfaces. The wetting of a solid with water, where air is the surrounding

medium, is dependent on the relation between the interfacial tensions (water/air,

water/solid and solid/air).

By transferring the microstructure of selected plant surfaces to practical

materials, super-hydrophobic surfaces could be developed. The water-repellent surfaces

also indicate self-cleaning properties has been completely overlooked. Recently,

Barthlott, W., and Neihuis, C. (1997) investigated and proved the correlation between

the microstructure, wettability and contaminants in detail using lotus leaves. This was

42

called the Lotus Effect because it can be demonstrated beautifully with the great leaves

of the lotus plant. The microrough surfaces show contact angles higher than 130˚. That

means, the adhesion of water, as well as particles is extremely reduced. Water which

contacts such surfaces will be immediately contracted to droplets. The particles of

contaminants adhere to the droplet surfaces and are removed from the rough surface

when the droplets roll of as referred to Figure 2.11 (Barthlott, W., and Neihuis, C.,

1997).

Figure 2.11: Lotus Effect (Barthlott, W., and Neihuis, C., 1997).

Most of the real surfaces are rough. There are two options for the water droplet test:

(a) The Wenzel’s model describes the homogeneous wetting regime, as seen in

Figure 2.12 can be used (Whyman et al, 2008):

cos θ* = r cosθ ……………………………………… (2.1)

Where θ* is the apparent contact angle and r is the ratio of real rough surface

area to the projected perfectly smooth surface, in other words r is proportional to

the extension of surface area due to the roughness. Note that for a perfectly

smooth surface r = 1 and therefore cos θ* = cosθ. In practice this model is used

for the contact angle range 0º>θ>90º.

43

Figure 2.12: Wenzel Model (Whyman et al, 2008).

b) Alternatively, the Cassie-Baxter model describes the apparent contact angle for

composite material, which is given by equation (2) (Whyman et al, 2008):

cos θ* = -1+ fs (cos θ + 1) …………………………. (2.2)

Where:

fs : fraction of the liquid that contacts the solid

A surface is called super-hydrophobic when water contact angle exceeds 120º. In

this case usually a water droplet can bounce on the surface and also can roll-off

on it with a tilt of less than 5º. In other words the surface is water repellant. This

kind of surfaces is also called self-cleaning. On a hydrophilic or on a

hydrophobic surface the pollutants adhered to the water droplet, but the water

droplet sticks on the substrate. So the water remains and evaporates on the

surface and the pollutants remain on it. Consequently, the pollutants do not

remove from the substrate. On a super-hydrophobic substrate the water rolls-off

and leaves the surface taking the dirt with it. So, the water cleans the surface.

44

Figure 2.13: Cassie-Baxter Model (Whyman et al, 2008).

Furthermore, UV illumination of Titanium Dioxide leads to the formation of

powerful agents with the ability to oxidize and decompose many types of bacteria,

organic and inorganic materials (Fujishima et al, 1999). Titanium Dioxide coated

concrete tiles are considered to be very effective against organic and inorganic materials,

as well as against bacteria. In Figure 2.14, Hydrotect® tiles are shown which kill bacteria

at an extremely high rate of speed. With other words, the bacteria are killed faster than

they can grow to reduce the spread of infections on these concrete tiles and show super-

hydrophilic behavior. Water forms a uniform sheet over the surface at a contact angle of

7 (exterior) and 25 (interior) degrees compose grease, dirt and other staining materials

can easily be swept away with a stream of water. Superhydrophilicity, combined with

the strong photocatalytic oxidizing properties makes this tile self-cleaning in exterior

applications (Fujishima, A., and Honda, K., 1972).

Figure 2.14: Super-hydrophilicity (Fujishima, A., and Honda, K., 1972).

45

2.8.3 Titanium Dioxide as ultraviolet protection

The increasing use of ultraviolet (UV) light in buildings environments and even in

consumer products necessitates that greater attention be paid to the potential hazards of

this type of electromagnetic radiation. Hongying et al (2003) states to avoid any adverse

effects of exposure to this type of radiation, suitable protection fillers were produced to

block UV bands as an ultraviolet protection such as Titanium Dioxide.

UV light is electromagnetic radiation with a wavelength shorter than that of

visible light, but longer than X-rays, in the range 10 nm to 400 nm and energies from 3

eV to 124 eV. It is so named because the spectrum consists of electromagnetic waves

with frequencies higher than those that humans identify as the color violet. The

electromagnetic spectrum of ultraviolet can be subdivided in a number of ways. The

draft ISO standard on determining solar irradiances (ISO-DIS-21348) describes the

following ranges (Hockberger, P. E., 2002) as shown in Table 2.7:

Table 2.7: ISO-DIS-21348 standard on determining solar irradiances (Hockberger, P. E.,

2002).

Name Abbreviation Wavelength range in

nanometers

Energy per photon

Ultraviolet A, long

wave, or black light

UVA 400 nm – 315 nm 3.10 – 3.94 eV

Near NUV 400 nm – 300 nm 3.10 – 4.13 eV

Ultraviolet B or

medium wave

UVB 315 nm – 280 nm 3.94 – 4.43 eV

Middle MUV 300 nm – 200 nm 4.13 – 6.20 eV

Ultraviolet C, short

wave, or germicidal

UVC 280 nm – 100 nm 4.43 – 12.4 eV

Far FUV 200 nm – 122 nm 6.20 – 10.2 eV

Vacuum VUV 200 nm – 100 nm 6.20 – 12.4 eV

46

Name Abbreviation Wavelength range in

nanometers

Energy per photon

Low LUV 100 nm – 88 nm 12.4 – 14.1 eV

Super SUV 150 nm – 10 nm 8.28 eV – 124 eV

Extreme EUV 121 nm – 10 nm 10.2 – 124 eV

A wide variety of synthetic and naturally occurring biopolymers coating absorb

solar ultraviolet radiation and undergo photolytic, photo-oxidative, and thermo-oxidative

reactions that results in the degradation of the material. The degradation suffered by

these materials can range from mere surface discoloration affecting the aesthetic appeal

of a product to extensive loss of mechanical properties, which severely limits their

performance (Scott, G., 2001). In this study is focus on the deleterious effects of solar

UV-B radiation in different types of surface coating by using biopolymer doped with

various ratio of Titanium Dioxide.

The phenomenon is of special interest to the building industry, in this case on

LRT surface which relies on biopolymer coating on LRT surface that are routinely

exposed to sunlight during use. Most of common polymers coating used in such

applications contain photostabilizers to control photodamage and to ensure acceptable

lifetimes under outdoor exposure conditions. It is mainly the ultraviolet radiation in

sunlight that presently determines the useful lifetime of even adequately photostabilized

coating products in outdoor applications (Andrady, A. L., and Pegram, J. E., 1990).

Any increase in the UV-B content in terrestrial solar radiation due to a partial

depletion of the stratospheric ozone layer is therefore expected to have an impact on the

outdoor lifetimes of this category of materials. The damage to biopolymer coating under

exposure to UV-B radiation is generally intensity dependent. While the incremental

increase in UV-B in solar radiation due to ozone depletion is expected to be small, the

efficiency of biopolymer degradation processes at these wavelengths is generally high.

Marginal increases in solar UV levels can therefore translate into a noticeable decrease

in the service life of polymer coating products (Torikau et al, 2007).

The ultraviolet radiation (UVR) is composed of three types: UV-A (315 nm to

400 nm), UV-B (290 nm to 315 nm) and UV-C (100 nm to 290 nm). The UV-C

47

radiation is absorbed by the ozone layer, however, the UV-A and UV-B reach the earth

surface and cause serious problems such as skin cancer, sunburn, and photo-aging

(Reinert, J., 1997). Therefore, special attention has been focused recently on refractive

index ultraviolet by the study of biopolymer from waste cooking oil doped with

Titanium Dioxide (TOP) significantly to increase in the ultraviolet protection and bring

impart high ultraviolet radiation (UVR) scattering property on LRT surface. To qualify

the protection from the UVR, the term of the UPF (Ultraviolet Protection Factor) is

preferred. This factor is based on a refractive index.

Figure 2.15: Solar power distribution (Reinert, J., 1997).

48

2.9 Previous Research on Mechanical Properties

2.9.1 Compressive strength

Portland cement concrete has clearly emerged as the material of choice for the

construction in the world today. This is mainly due to low cost of materials and

construction for concrete structure such as wall, roof tile, floor and bridge as well as low

cost maintenance.

Therefore, much advancement of concrete technology have occurred depending

on the speed construction, the strength of concrete, the durability of concrete and the

environmental friendliness of industrial material like, fly ash, blast furnace slag, silica

fume, tire rubber, metakaolin and others (Mehta, P. K., 1999). Thomas, H. (2000) have

studied on the lightweight aggregate concrete which described a normally considerate

density between 1440 kg/m3 to 1840 kg/m

3 and the compressive strength is 17.2 MPa.

They have found that lightweight grade low density concretes generally contain

aggregates made from pyroprocessed shales, clays, slates, expanded slags, rubber

aggregate, and those mined from natural porous volcanic sources.

Mohammadi et al (2008) was investigated the strengthening building of

structural lightweight concrete with different particle size in the range of lightweight

aggregate which is 10 mesh, 20 mesh, 1 to 3 mm and 2 to 4 mm. According to the

obtained results, the air-dried specific gravity of 28 days standard sample in structural

concrete containing lightweight aggregates was about 1440 – 1900 kg/m3 and

compressive strength was more than 17.2 MPa. By reducing the particle size of

lightweight aggregate in concrete has effect on increasing the strength of the

correspondent concrete.

According to John, P. R. (2006), industrial applications for lightweight concretes

often require compressive strengths and densities in the intermediate between structural

and insulating concrete. These concretes may be produced with high air contents and

49

include structural lightweight aggregate, or sanded insulating lightweight aggregate

mixture, or they may incorporate both structural and insulating lightweight aggregates.

Compressive strength from 3.4 MPa to 17 MPa are common with thermal resistance

ranging between insulating and structural concrete.

Achal et al (2009) studied the addition effect of lightweight fly ash on the

compressive strength of cement mortar cube. A significant increase in the compressive

strength of cement mortar cube at different ages (3, 7, 14 and 28 days) was achieved

with the addition of lightweight fly ash. The improvement in compressive strength is due

to deposition on the lightweight material and the pores of cement-sand matrix.

Karakoc, M. B. and Demirboga, R. (2009) considered the compressive strength

concrete containing expanded perlite aggregate. According to the obtained data, it was

observed that compressive strength increase with the increasing curing period at 3, 7, 27

and 90 days at 9.28 MPa, 10.11 MPa, 10.83 MPa and 12.05 MPa respectively. Akman,

M. S., and Tasdemir, M. A. (1997) concluded that compressive strength decreased

because the density decreased with increasing lightweight aggregate ratio instead of the

traditional aggregate. Faust, T. (2000) reported that the replacement of natural sand by

lightweight fine aggregate reduces the compressive strength.

Ramezanianpour, A., and Malhotra, V.M. (1995) stated there are potential

influences curing conditions of concrete with regards to strength and durability. It is

most essential be cured adequately. They reported that lightweight aggregate mortar

containing 60%, 70% and 80% lightweight aggregate was influenced by curing

conditions. Ungsongkhun et al (2009) investigated the effects on the compressive

strength of autoclaved aerated lightweight mortars. The proportions of lime, cement and

different percentages which are 50%, 60% and 70% of autoclaved aerated lightweight

has a lower compressive strength results at early age and the strength gradually

increased at later age.

50

2.9.2 Flexural strength

Kuder et al (2009) studied the influence of flexural performance of concrete mix

lightweight fly ash was examined for both unreinforced and reinforced beams. Due to

the brittle nature of unreinforced concrete, the plain beams fail suddenly once peak load

is reached, losing all load carrying capacity.

Reinforced beams, however, remained intact up to 1.0 mm of deflection even

without the presence of reinforcement. Based on investigated the flexural strength

results of concrete mixtures containing 35%, 45% and 55% fly ash achieved flexural

strength of 1.0 MPa, 0.92 MPa and 0.85 MPa, respectively at the age of 7 days. Concrete

mixtures at the age of 28 days were increased flexural strength at 1.2 MPa, 1.0 MPa and

0.9 MPa. It is evident that by increasing in flexural strength at later ages is also due to

the curing reaction of fly ash and then there was very slight reduction of flexural

strength in the increasing percentage of fly ash. These results indicated that fly ash could

be as effective in enhancing the flexural strength of high-volume fly ash concrete as in

concrete made without fly ash.

Ngo et al (2007) studied the effect of flexural strength and stiffness of

lightweight concrete. A parametric study has been carried out to investigate the effect of

high strain-rate on the ductility of reinforced concrete with lightweight aggregate, and

their flexural and shear capacities. The proposed strain-rate dependent model for

concrete is adopted in this study. The flexural capacity and the ductility of a reinforced

concrete were significantly increased due to the increase in yield strength of lightweight

and flexural strength of concrete at high strain rate.

Dinis, O., and Filhos, J. A. (2008) reported regarding standard National

Laboratory of Civil Engineering (LNEC) E227, the lightweight aggregate concrete

which is granulated cork has a compression rupture of 17.0 MPa and 0.5 MPa of the

tensile strength and flexural strength of 1.5 MPa. However, increasing by 0.5 the amount

of cement, lightweight concrete is very resistant to rupture by compression.

51

2.9.3 Vibration test

Vibration is the oscillating motion of an object relative to fixed point of reference. A

vibration-prone object will vibrate freely (free vibration) if it is displaced from its

equilibrium position and released. An object may also vibrate in response to an

externally applied source vibration as forced vibration (Harris, C. M., 1988).

Two basic quantities for describing vibration are frequency in cycles per second

or Hertz (Hz) and amplitude which can expressed as a displacement, velocity or

acceleration. Vibration be able the result of strong impact which can describe as shock

vibration. Shock vibration can induce large deformation and strain in objects or parts.

Shock intensity is measured in g units of acceleration where g represents the acceleration

due to the Earth’s gravity. Shock can cause substantial damage to most objects

(Brandenburg, R. K., 1991). Mechanical shock vibration is an energy response of an

object. It is characterized by substantial displacements and strain. Four outcomes are

possible (Harris, C. M., 1988).

(i) Low levels of shock may be absorbed and dissipated in the object without

damage. A bell provides an example striking it with the right object and the

amount of force makes it ring without any damage to the bell’s surface.

(ii) Impact may cause an object or parts to move, resulting in collision between

objects, object parts and their surroundings.

(iii) High shock levels may cause movement and induce strains in excess of critical

thresholds resulting in fatigue damage.

(iv) If the shock magnitude is high enough, damage occurs in a single event (stress

fracture).

Damage to buildings by construction vibration appears in a form that described

as cracking. It is types of damage is ongoing process for most buildings, even those

located in areas free of vibration, temperature and humidity fluctuations are important

causes of this effects in ground motion due to earthquakes. Table 2.8 shows the

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description of vibration effects and approximate relationship between intensity and

magnitudes for construction vibration and its effects on buildings (Rutherford and

Chekene Consulting Engineers, 1992).

Table 2.8: Vibration effects and approximate relationship between intensity and

magnitudes for construction vibration (Rutherford and Chekene Consulting Engineers,

1992).

Intensity

Scale

Effect on human Effect on buildings Maximum

acceleration

(Grms)

Richter

Magnitude

I Imperceptible No effect on buildings 0.01 and

below

M2 -

M2.5

II-III Imperceptible No effect on buildings 0.01 to 0.03 M2.5 -

M3.1

IV-VII Barely perceptible Felt indoors, hanging

objects

0.03 to 0.08 M3.1 -

M 3.7

VI-VII Level at which

continuous

vibrations begin to

annoy in buildings

Minimal potential for

damage to weak or sensitive

structures.

0.08 to 0.25

M3.7 -

M4.3

VII-IX Vibration

considerate

unacceptable for

people exposed to

continuous vibration

Threshold at which there is

a risk of architectural

damage to buildings with

plastered ceilings and walls.

(Masonry C& D crack)

0.25 to 0.60

M4.3 -

M5.5

VII or

higher

Vibration

considered

unpleased by most

people

Potential for architectural

damage and possible minor

structural damage.

(Masonry A & B crack)

0.60 and

above

M5.5 -

M7.3

53

A construction vibration consists of a composite or “spectrum” of many

frequencies and is generally classified as random vibrations. The normal frequency

range of most ground-borne vibration that can be felt generally starts from a low

frequency of less than 1 Hz to a high of about 200 Hz. While people have varying

sensitivities to vibrations at different frequencies, in general they are most sensitive to

low-frequency vibration.

Vibration in buildings caused by construction activities may be perceived as

motion of building surfaces or rattling of windows, items on shelves, pictures hanging

on walls, and rain drop on roof. Vibration of building components can also take the form

of an audible low-frequency rumbling noise, which referred to as ground-borne noise.

Ground-borne noise is usually only a problem when the originating vibration spectrum is

dominated by frequencies in the upper end of the range (60 to 200 Hz), or when the

structure and the construction activity are connected by foundations or utilities, such as

sewer and water pipes (Gordon, C., 2006).

Gargouri et al (2008) studied of mechanical and vibration properties of rubber-

aggregate concretes. Concretes contain rubber aggregate was investigated to improve the

vibration properties of concrete. From the result, the face coated with layer 0.5 cm

thickness with a tolerance of ± 0.1 cm, 7 plates was prepared for the vibration absorption

test with rubber proportion 0%, 10%, 20%, 30%, 40%, 50%, 70% and 100%. Figure

2.16 shows the effect of vibration peaks by different proportion of rubber. It is noticed

that when percentage of rubber increases, higher vibration amplitude was determined

between the frequency [200 ; 300], [400 ; 630] and [1600 ; 2500] which needed

improvement in the vibration absorption.

54

Figure 2.16: Effect of vibration peaks by the different proportion of rubber. (Gargouri et

al, 2008)

2.10 Previous Research on Physical Properties

2.10.1 Weight measurement

Sarawak Concrete Roof Tile (2009) investigated concrete roof tiles are under constant

monitoring and stringent quality control observance to the strict requirements imposed

by Standards and Industrial Research Institute of Malaysia (SIRIM) with average weight

per piece is approximately 4.30 kg.

John, S., and Richard, C. (1987) declared that the United Stated of America,

concrete roof tile dimensions is about 422 mm length, 333 mm width, and 11.5 mm to

12.55 mm thickness and generally has a weight in range of 4.2 kg to 5.0 kg per tile

which are provided on the undersides of concrete interlocking roof tiles. Based on the

compositions, it has been possible to produce lightweight roof tile at densities is about

1400 kg/m3 to 1800 kg/m

3 and weight as low as 2.6 kg per tile.

55

Liu, X. M., and Zhang, M. H. (2009) indicated that cumulative lightweight

aggregate (LWA) content in the concrete, whether lightweight sand was used, and test

method may have influence on the results. In many applications, lightweight sand needs

to be used in order to reduce the unit weight of concrete. The incorporation with increase

in the cumulative LWA content in the concrete, the unit weight of the concrete reduced

somewhat. John, P. R. (2006) studied cementitious mixture for lightweight roof tile with

the percentages of 57% expanded clay aggregate (1 – 4 mm), 26 % of Porland cement,

10 % of styrene acrylic emulsion (superplasticizer) and 12.35 % of water. The result

shows the effect of lightweight roof tile was about 40 % lighter than commercial and the

flexural strength more than 1.0 MPa.

2.10.2 Porosity test

Liu, X. M., and Zhang, M. H. (2009) stated that lightweight aggregates (LWA) are

generally more porous compared with normal weight aggregates concrete (NWAC). The

interface translation zone (ITZ) between the aggregate and cement paste is generally

considered a potential weak link in NWAC due to its high porosity compared with the

bulk cement paste. However, the ITZ around the LWA is generally denser and more

homogenous due to the absorption of LWA.

Pantawee, S., and Sinsiri, T. (2008) studied the density of lightweight concrete

contained 55 %, 60 % and 65 % of perlite aggregate. It was found that the density

decreases with increasing the amount of perlite and the minimum density were 1.4 g/cm3

to 1.6 g/cm3 while the porosity increases with the increasing the amount of perlite

allowing a maximum absorption 15 % to 25 % of its porosity lightweight concrete.

Yun et al (2007) investigated the density of lightweight concrete manufactured

with furnace bottom ash. The results indicated that it is possible to manufacture

lightweight with density in the range of 1.2 g/cm3 to 1.8 g/cm

3 and porosity in the range

56

of 20 % to 30 %. However, with part of replaced with furnace bottom ash, the strength

decreased but the porosity of the resulting concrete improved.

2.10.3 Scanning Electron Microscopy (SEM)

Bremner, T. W., and David, R. (1993) studied the microstructure of four manufactured

lightweight aggregate using scanning electron microscopy and the results were used to

provide insight into the dimensional stability of concretes made from expanded shale,

sintered fly ash, pelletized cold bonded fly ash and expanded glass.

Scanning electron microscopy in Figure 2.17 revealed the nature of the aggregate

pore structure and the extent to which the vesicular structure, typical of most lightweight

aggregates is interconnected.

(a) (b)

57

(c) (d)

Figure 2.17: Microstructure of interconnected of lightweight aggregates; (a) Sintered fly

ash, (b) Expanded shale, (c) Expanded glass and (d) Cold bonded fly ash (Bremner, T.

W., and David, R., 1993).

Jacinto et al (2010) studied the microstructure of lightweight aggregates concrete

produced from different ratio of washing aggregate sludge and fly ash. The surface

morphology of the lightweight aggregate shown in Figure 2.18 (a) does not have distinct

external layer and there are no clear signs of expansion. However, Figure 2.18 (b)

presents a dense external layer which is well-differentiated. Unlike the external layer,

the internal material is vitrified and shows signs of bloating.

(a) (b)

Figure 2.18: Microstructure of lightweight aggregate concrete; (a) washing aggregate

sludge: fly ash (75:25), (b) washing aggregate sludge: fly ash (50:50) (Jacinto et al,

2010).

58

Ling, T. C., and Hasanan, M. D. (2000) studied on the investigation of recycled

waste tyre by using 1 – 3 mm crumb rubber as a replacement fine sand for face layer and

1 – 5 mm crumb rubber as a replacement coarse sand for body layer. Based on the

results, the composition up to 50 % of crumb rubber that curing for 28 days, modulus of

rupture concrete paving block (CPB) not less than 2.75 MPa can be produced without

facing layer, while 2.54 MPa for the CPB with facing layer. The rubber-cement matrix

interface was observed by SEM as shown in Figure 2.19.

(a) (b)

Figure 2.19: SEM images for rubber-cement matrix interface; (a) 1 – 3 mm crumb

rubber, (b) 1 – 5 mm crumb rubber; (A) rubber particle (B) cement paste (Ling, T. C.,

and Hasanan, M. D., 2000).

Turkulin, H. (2004) studied scanning electron microscopic analysis of coated

concrete before and after an exposure for 4 weeks shows in Figure 2.20. It is evidence

after exposure the cohesive weakness of particular surface layer, the adhesion properties

and water ingress into the interface and about the UV-induced damage under the coating

which the continuous changes of temperature, humidity or tension loads can be

concluded. Weathering can affect the link between the concrete and the coating and lead

to the cohesive failure and delamination of the UV-damaged coated concrete.

59

(a) (b)

Figure 2.20: SEM analysis of coated before and after exposure; (a) before exposed, (b)

after exposed (Turkulin, H., 2004).

Michael, A. P. (2007) studied SEM micrographs of uncoated and coated concrete

with sealer X-1 with the layer of 0.3 ± 0.05 mm thickness for concrete shows a surface

roughness in Figure 2.21. Figure 2.21 (a) evidence the uncoated appeared rough and

pitted but in the Figure 2.21 (b) the coated sample is smooth. It was revealed by treated

with sealer X-1, coated surface would less susceptible to detrimental.

(a) (b)

Figure 2.21: SEM micrographs uncoated and coated concrete with sealer X-1; (a)

uncoated concrete, (b) coated concrete (Michael, A. P., 2007).

60

2.10.4 Water droplet test

Gallyamov, M., and Nikitin, L. (2007) studied the formation of superhydrophobic

surface by the deposition of coatings from supercritical carbon dioxide on a number of

rough substrates allowed superhydrophobic properties to be imparted to the surfaces and

increase the value of the contact angle for water droplet to 150º and greater. The

geometry dynamics of a drying droplet on a substrate is studied.

Pavel et al (2009) studied porous polymer coating with versatile approach on

superhydrophobic surfaces. This study demonstrates the smooth surface of a polymer

film using photoinitiated copolymerization of butyl methacrylate and ethylene

dimenthacrylate shows static water contact angles (WCA) of 77º. However, when the

same monomers are polymerized after mixing them with cyclohexanol and 1-decanol,

the surface of the material that is obtained becomes superhydrophobic as 172º. The

reason for the observed superhydrophobicity is that the presence of inert solvents

(cyclohexanol and 1-decanol) in the polymerization mixture leads to phase separation

during polymerization once the growing crosslinked polymer chains achieve a critical

size and a highly porous structure consisting of interconnected globules is formed as

shown in Figure 2.22.

Figure 2.22: Shape of water droplets formed on porous and nonporous polymer layers.

(a) Poly(butyl methacrylate-co-ethylene dimethacrylate). (b) Poly(styrene-co-

divinylbenzene) (Pavel et al, 2009).

61

2.10.5 UV visible test

Kun, X., and Yiqing, H. (2010) studied fabrication of transparent PU/ZrO2

nanocomposite coatings with high refractive index were prepared by dispersing ZrO2

nanoparticles in a polyurethane matrix via ligand molecule engineering. After 56 days of

irradiation, UV-vis spectra indicated that the coatings still maintained transparency in

the visible light. The refractive index of the UV-cured films depends linearly on the

ZrO2 content and varies from 1.475 to 1.625 at 633 nm.

Bi-Yao, W., and Dao-Hong, Z. (2004) investigated the preparation of Titanium

Dioxide organic contents in V, P4, Q4 and R4 samples are 1.5%, 2.0%, 2.5% and 3.0%,

respectively and their corresponding refractive indexes are 1.5398, 1.6053, 1.5846 and

1.5346, respectively. The results showed that when methacryloxypropyltrimethoxysilane

were added to the sol system, their refractive index would be increased as shown in

Figure 2.23. This means that phenyl group favors increasing the refractive index of these

Titanium Dioxide organic solutions.

Figure 2.23: Refractive index of V, P4, Q4 and R4 (Bi-Yao, W., and Dao-Hong, Z.,

2004).

62

Tony et al (2003) studied high refractive index polymer coatings can improved

by applying a transparent high refractive index coating (> 1.65) onto the light-emitting

or light sensing portion of the device. The coatings combine polymer coating with the

high refractive index and metal oxide have developed a new coating having refractive

indices ranging from 1.60 to as high as1.90 at visible wavelength depending on the

metal oxide content as shown in Figure 2.24.

Figure 2.24: Refractive index of different percentages metal oxide content. (Tony et al,

2003)

63