Unit-1 Lecture-2 - Light Weight Construction Materials by Brig. S.K. Sharma

UNIT-1 LECTURE - 2

Brig. S.K. Sharma (Retd.) Pro Vice Chancellor and Professor Department of Civil Engineering, The Northcap University, Gurgaon

UNIT-1LECTURE 2LIGHT WEIGHT CONSTRUCTION MATERIALSTHE NORTHCAP UNIVERSITY1

INDEXTYPES OF FOAMED CONCRETEADVANTAGES & DISADVANTAGES OF FOAMED CONCRETEGROUP OF LIGHT WEIGHT CONCRETE (BY AGGREGATES)

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TYPES OF FOAMED CONCRETE & THEIR USES(BY DENSITIES)Foamed concrete with density of 300-600 kg/m3: This concrete also called foamed cement or foam concrete, is made of cement and foam only. This material is used for thermal insulation of roof and floors, soundproofing and is applied on rigid floors. It is used for tennis courts and void filling between brickwork leaves in underground walls, insulation filling in hollow blocks and any other filling situation where high insulating properties are required.Foamed concrete with density of 600-900 kg/m3: The constituents of this concrete are cement sand and foam. It is used for the manufacture of precast blocks and panels for curtain and partition walls, slabs for false ceilings, thermal insulation and soundproofing screeds in multistorey residential and commercial buildings. The concrete of this density range is also suitable for bulkfill applications. THE NORTHCAP UNIVERSITY3

TYPES OF FOAMED CONCRETE (Continued)Foamed concrete with density of 900-1200 kg/m3: This concrete made of cement, sand and foam, is used in casting the concrete blocks and panels for outer leaves of buildings, architectural omamentation as well as partition walls, concrete slabs for roofing and floor screeds.Foamed concrete with density of 1200-1600 kg/m3: This lightweight foamed concrete containing cement, sand and foam is used in precast panels of any dimension for commercial and industrial use, in-situ casting of walls, garden omaments and other uses where structural concrete of light weight is recommended.


Foamed lightweight concrete: The lightweight matrix formed by the mixture of cement, water, lightweight aggregate and foam, can be used without the tendency to float when the mix is vibrated. Typical aggregates used are expanded shale or clay, pumice, vermiculite or fly ash. The inclusion of such material shale or clay, pumice, vermiculite or fly ash. The inclusion of such material is only recommended if it is locally available as its procurement from outside source may result in a higher cost of the final product.TYPES OF FOAMED CONCRETE (Continued)THE NORTHCAP UNIVERSITY5

Foamed dense-weight concrete: The addition of up to 10 per cent foam into a normal dense-weight concrete mix reduces its density and the cost. The increase in the slump allows the water-to-cement ratio to be reduced. Introduction of foam eliminates bleed water, allows early troweling of the surface, makes the concrete pumpable even in hot weather and improves the resistance to freeze-thaw attrition. Although the reduction in water-to-cement ratio produces an increase in strength, it is usually necessary to slightly increase the cement content of the mix to maintain the specified compressive strength.

TYPES OF FOAMED CONCRETE (Continued)THE NORTHCAP UNIVERSITY6

ADVANTAGES AND DISADVANTAGES OF FOAMED CONCRETE/MORTARS

ADVANTAGES:Economy: Due to accurate geometrical dimensions the foam concrete blocks and panels may be laid on glue, to avoid frost bridges in a wall and to make the inner and outer plaster thinner. The weight of foam concrete is about 10 to 80 per cent less than the conventional vibrated concrete. This reduction in weight leads to sufficient economy particularly on foundations and basements. Foams concrete is easy to work with using common tools. The saving in cost is generally of the order of 10 per cent.Durability: Foam concrete is a durable material and deterioration with time is very small. It is as durable as rock.THE NORTHCAP UNIVERSITY7

Advantages (Continued)Thermal insulation and microclimate: As already covered, foamed concrete has far superior thermal insulation properties than the conventional normal-weight concrete. Due to high temperature lag, buildings constructed with foam concrete products may result in huge saving in the energy consumption of the order of 20-35 per cent. Thus, the foamed concrete which is almost a humidity-proof material prevents loss of heat in winter by build up of very high temperatures in summer, and controls air humidity in a room by absorbing and releasing moisture as per environmental conditions. Thus, it helps in creating a favorable microclimate. Acoustic insulation: As brought out under properties, foamed concrete has superior acoustic properties as compared to other dense-weight products due to its excellent sound absorption capacity; it does not reflect sound. In buildings constructed with foamed concrete, the general requirements for acoustic insulation are satisfied.


Advantages (Continued.)Fire safety: Foamed concrete is fire resistant, i.e., unlike normal-weight concrete it neither spalls or splits or blows nor gives off toxic gases under direct exposure to fire (typically for foamed concrete with density less than 14 Kn/m3).Aesthetics: Due to the high workability and light weight, foamed concrete is extensively used in architectural ornamentation. Speed of construction: Due to he light weight of foamed concrete, largesized blocks and panels as compared to bricks, can be cast resulting in high speed of laying these large-sized elements. Foam concrete is convenient to process and can be cut to desired size; and to drill holes for electrical wiring, sockets, and pipes. The speed of construction is further enhanced through lower tolerance (+/-1 mm) in linear dimensions. Quality: It is amenable to efficient production with consistent quality. Foamed concrete has minimum bleed water and improved pumping characteristics. THE NORTHCAP UNIVERSITY9

Advantages (Continued.)Ecological compatibility: Foamed concrete is environment friendly, both in the production process and product application, its ecological compatibility is second only to wood. Transportation: The available combination of weight, volume and packaging makes foamed concrete a favorable construction material which is convenient to transport by highway or railway system. It has lower transportation costs as one cubic meter of foam is produced only from one liter of concentrate and is mixed at the site.Wide Range of applications: Foamed concrete is ideal for thermal and acoustic insulation of roofs, walls and floors; subscreeds and filling under-floor voids; production of blocks and panels for removable partitions in buildings. It is most suitable for filling redundant voids such as disused tanks, sewer systems, pipelines, and culverts-particularly where access is difficult.

Video: YouTube, Foamcrete: Building with simple panels, 05:24


DISADVANTAGESCompressive strength of foamed concrete reduce as its density reduces.The cellular structure of foamed concrete requires specialized fasteners for the attachment of both structural framing members and non-structural fittings. Metal-sleeved expanding anchors are not used as they become loose. The retention values of attached fixtures depend on the density of the product. Particular attention needs to be given to those areas where continuous impact occur, e.g., door jambs.All drilled holes in foamed concrete require the use of high speed twist drills suitable for steel or wood, (masonry drill bits and hammers cannot be used).To provide holding power to fastners, expansion and friction grips need be provided within the concrete.The production of foamed concrete requires a specially designed equipments for mixing as the foam tends to float at the surface of the mix and thus its effectiveness is considerably reduced. Injecting the foam into the mix rather than onto the mix is preferred in the case of an open mixer. The problem of mixing is readily addressed to in the case where foam is introduced into a flowing product line. THE NORTHCAP UNIVERSITY11

GROUPS OF LIGHT-WEIGHT CONCRETE(BY AGGREGATES)No-finesConcreteLight-weight aggregate concreteAerated ConcreteChemical aeratingFoaming mixtureGravelClinker Aluminium powder method Preformed foamCrushed stoneFoamed slag Hydrogen peroxide and bleaching powder methodAir-entrained foamCoarse clinkerExpanded clay Sintered pulverized fuel ash Expanded shaleExpanded clay or shale Pulverized fuel ashExpanded slateVermiculite Foamed SlagPumice


CONCLUSION/FUTURE THOUGHTSStructural light-weight aggregate concrete is a concrete having 28 day compressive strength more than 17 Mpa and 28 day air dried unit weight not exceeding 1850kg/m3. Structural light weight concrete is going to be one of the important materials of construction. A concrete which is light in weight and sufficiently strong to be used in conjunction with steel reinforcement will be a material which is more economical than the conventional concrete. Therefore, a concrete which combines strength and lightness will have the unquestionalbe economic advantage.Video: YouTube, Autoclaved Aeated Concrete, 06:37THE NORTHCAP UNIVERSITY13


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