Performance of mortars with incorporation of fine glass ag ... · Performance of mortars with incorporation of fine ... Dr.ª Eng.ª Maria do Rosário da ... Prof.ª Dr.ª Ana Paula

Performance of mortars with incorporation of fine glass ag-

gregates

Filler effect and pozzolanic effect

Renata Borges Oliveira

Master Thesis in Civil Engineering

Extended abstract

Jury

President: Prof. Dr. Luís Manuel Alves Dias

Supervisor: Prof. Dr. Jorge Manuel Caliço Lopes de Brito

Co-supervisor: Dr.ª Eng.ª Maria do Rosário da Silva Veiga

Members: Prof.ª Dr.ª Maria Paulina Santos Forte de Faria Rodrigues

Prof.ª Dr.ª Ana Paula Patrício Teixeira Ferreira Pinto França de Santana

September 2012

Performance of mortars with incorporation of fine glass aggregates - Filler and pozzolanic effects

1

1. Introduction

Besides being a major consumer of natural resources, the construction sector is also re-

sponsible for a significant part of the waste produced in Portugal, a fact consistent with the

situation reported in the other countries of the EU. The global production of construction and

demolition waste (CDW) is estimated at 100 million tons (APA, 2011). According to the

same source, there are problems with the quantity and the characteristics of such waste. Its

management is complex due to the heterogeneous nature of the debris, a very wide dimension

span and the varying levels of hazardousness.

CDW is made of several materials, the most relevant of which are mortars (from concrete

or masonry), soils, road pavement residues, wood, metals, glass, paper, plastics, insulation ma-

terials, textiles, plaster, dangerous wastes and asbestos (Brito, 2004). With the rising use of

glass in construction, this material is increasing its weight in the total percentage of CDW.

According to the European Flat Glass Industry, cited in Brito (2004), 2% to 5% of the

total weight of a building corresponds to glass panels. This material is highly recyclable, if

removed with no contamination (metal, paper and plastics). With aggregate characteristics,

glass is offered at a higher cost but at a considerable energy saving when recycled, comparing

to the original material.

Besides being present in CDW glass also represents a considerable percentage of the

urban solid waste (USW), estimated at 5% in 2006 by Russo (2009). Other notable sources of

glass residues in the national economic landscape are the automobile industry, due to end-of-life

products being taken for decommissioning, and the glass industry itself.

It is clear that glass waste has the most diverse origin, distributed along several sectors of

society and that such waste can be a major asset if recycled and reused.

This work is presented within a sustainable development context, by the study of a

new application for glass waste, as an alternative to landfilling.

The main objective of this work is to provide an analysis of the viability of the in-

corporation of fine glass aggregates in coating mortars by studying two vectors: the filler

effect and the pozzolanic effect. Another aspect that is traditionally discussed when con-

sidering the use of glass in mortars or concretes is the alkali-silica reaction, not studied in

this work, since parallel studies were carried out by Paulo Penacho in this regard.

At a first phase a wide bibliographical review was carried out, in order to gain signifi-

cant insight and study the current state-of-the-art on the topic. At a second phase the experi-

mental campaign was detailed and programmed, based on the data collected in the first phase.

After the conclusion of the experimental campaign, a third phase, the analysis and

discussion of the results, was carried out, favouring comparisons with results from differ-

ent studies whenever possible.

2. Experimental campaign

This work’s objectives are studying the performance of mortars with the incorporation

of fine glass aggregates, regarding the filler effect (vector I) and pozzolanic effect (vector II)

and assess the use of such mortars as wall coatings. The filler effect is achieved by the elimi-

nation of voids existent in the traditional mortar by the lack of fine material, and the poz-

zolanic effect is studied by the reduction in the cement ratio. Even if considered separately,

these two vectors are related since in vector II the binding properties of the fine material in-

Extended abstract

2

troduced in vector I are studied.

Three distinct experimental phases were developed. The first consisted in testing the

mortars components. At the second phase a set of tests for all developed mortars were carried

out (with different percentages of fine glass aggregates, for vector I), with the purpose of de-

termining the one with the best performance. For the mortar with the best performance in vec-

tor I, several ratios of cement to aggregates are studied (vector II). The second phase repre-

sents a filtering step, selecting the mortars susceptible to be considered for further testing in

phase three. This consists of more detailed tests, as well as comparisons with reference mor-

tars. A detailed characterization of the mortars as wall coatings is now possible.

2.1. Mortars components

Traditionally a mortar is composed of water, sand and cement. In this work fine glass

aggregates were added as a fourth component, to assess the performance of the mortar.

The water used for all mortars was from the public supply and the sand is from the Ta-

gus River, the most commonly used in the Lisbon region. The cement used is Portland type

CEM II/B-L 32.5N, since it is the most widely used in Portugal for the production of mortars.

The fine glass aggregates used come from the fragmentation of re-processed plane glass, but

only sizes below 0.149 mm were used in the production of the mortars.

2.2. Addition of fine glass aggregates

For vector I, in phase two, a series of tests were performed on a reference mortar (with

no glass aggregates) with cement to aggregate volumetric ratio of 1:4. Three mortars with the

same volumetric ratio but with glass aggregates were also tested. The three modified mortars

presented a percentage of fine glass aggregates (size below 0.149 mm) in relation to the total

aggregate content of 10%, 15% and 20%.

In the third and last testing phase, regarding vector I, only the reference and the selected

mortars are considered.

2.3. Cement ratio reduction

At the second test phase, relative to vector II, the cement to aggregate volumetric ratio

was changed, with tested ratios of 1:4, 1:5 and 1:6, for both the reference and modified mor-

tars (considering the identified optimal fine glass aggregates percentage for vector I).

In phase three, regarding vector II, other characteristics of mortars with ratio 1:4 (both tradi-

tional and modified) were tested and compared with the mortar with the best performance in

phase two, where the cement ratio was reduced (also with both traditional and modified mortars).

2.4. Tests performed

The tests performed were divided by the three phases and are listed in Table 1.

3. Results and discussion

In this section the results from the tests referring to the components and the mortars,

both traditional and modified, are presented and discussed.


3

Table 1 - Test distribution in the three phases and corresponding norms

Phase Test Material type Norm

1st

Particle size analysis Sand; glass EN 1015-1 (1998)

Apparent bulk density Cement; sand; glass Cahier 2669-4 (1993)

2nd

Consistency by flow table Mortar paste EN 1015-3 (1999)

Bulk density of fresh mortar Mortar paste EN 1015-6 (1998)

Air content Mortar paste EN 1015-7 (1998)

Dry bulk density Hardened mortar EN 1015-10 (1999)

Dynamic elasticity modulus Hardened mortar NF B 10-511 (1975)

Flexural and compressive strength Hardened mortar EN 1015-11 (1999)

Water absorption due to capillary action Hardened mortar EN 1015-18 (2002)

Drying Hardened mortar Non-standardized

Susceptibility to cracking Hardened mortar Non-standardized

3rd

Water retention Mortar paste prEN 1015-8 (1999)

Dimensional variability - shrinkage Hardened mortar Cahier 2669-4 (1993)

Ultrasound mechanical characterization Hardened mortar FE Pa 43 (2010)

Water permeability Hardened mortar EN 1015-21 (2002)

Pull-off Hardened mortar EN 1015-12 (2000)

Accelerated aging Hardened mortar EN 1015-21 (2002)

3.1. First phase

3.1.1. Particle size analysis

The size grading curves of the sand and glass materials are presented in Figure 1. Only

aggregates with size below 2.38 mm (sand) and 0.149 mm (glass) were used.

Figure 1 - Grading curves of sand and glass materials

3.1.2. Apparent bulk density

Apparent bulk density was determined for all solid components of the mortars: cement,

sand (size below 2.38 mm) and fine glass aggregates (size below 0.149 mm). The results are

presented in Table 2.

Table 2 - Apparent bulk density of the cement and aggregates

Material Apparent bulk density [kg/m3]

Cement 1009.7

Sand 1467.5

Glass 832.1

3.2. Second phase

3.2.1. Consistency by flow table

This test finds the optimal amount of water in order to obtain a pre-set spreading. Accord-

ing to the European norm EN 1015-2 (1998), for coating mortars the target spreading value is

175 ± 10 mm. However, due to the wide range of this interval, a more strict value of 170 ± 3 mm

0.1

49

0.2

97

0.5

90

1.1

90

2.3

80

4.7

60

0

20

40

60

80

100

120

Accu

mu

late

d m

ate

ria

l

[% o

f m

ass

]

size [mm]

Grading curves

Areia

Vidro Used glass fraction

Sand

Glass

Extended abstract

4

was adopted. In this test samples with approximately 2 kg of non-dry mortar were used, produc-

ing the results in Table 3.

Table 3 - Consistency by spreading for vectors I and II

Mortar Water required per dm

3

of mortar [ml] Spreading average [mm] Water/cement ratio

I and II (1:4_0%) 285 171.5 1.41

I (1:4_10%) 250 170.5 1.24

I (1:4_15%) 245 173.0 1.21

I and II (1:4_20%) 240 169.0 1.19

II (1:5_0%) 280 142.5 1.66

II (1:5_20%) 245 144.0 1.46

II (1:6_0%) 275 129.0 1.91

II (1:6_20%) 240 129.0 1.66

In vector I it was observed that as the percentage of glass material increased the required

amount of water in order to obtain the same spreading decreased. This is a direct consequence

of the filler effect, since the voids between the sand grains, previously filled with water, are now

filled with the fine glass material. As seen in Table 3, the target spreading value (170 ± 3 mm)

was not achieved in all mortars produced. In any of the mortars with a reduction of cement ratio

(1:5 and 1:6, both traditional and modified mortars), in order to obtain the target spreading, a

strong exudation took place, making the mortar inadequate for handling. Even if the same

spreading in all mortars being analysed in vector II was not achieved, they were all considered

similar since they presented the same adequate handling characteristics.

3.2.2. Bulk density of fresh mortar

In Figures 2 and 3 the values for the bulk density of fresh mortars are presented in the

context of vectors I and II.

Figure 2 - Bulk density (mortar paste) for vector I

Figure 3 - Bulk density (mortar paste) for vector II

Figure 2 (vector I) shows two contradicting effects that need to be taken into considera-

tion. The filler effect should make the bulk density of the mortars increase with the addition

of fine glass aggregates, but it also implies that a large amount of air is entrapped in the mix,

leading to a reduction of the bulk density of the fresh mortar. Therefore, for percentages of

fine glass aggregates up to 15% the air introduction offsets the filler effect. For 20% of glass,

even if the bulk density is still lower than that of the reference mortar, the filler effect over-

weighs the air entrapment effect. The glass material also presents an apparent bulk density

largely lower than the sand aggregate, which might also help explain such results.

Regarding vector II (Figure 3), as will be detailed further, the air introduction between

traditional and modified mixes was bigger for 1:4 mortars than for the remaining ratios. Within

1929

1892 1884

1901

1860

1880

1900

1920

1940

Bu

lk d

ensi

ty (

mo

rta

r p

ast

e)

[kg

/m3]

Bulk density (mortar paste)

1929

1901 1891

1906

1884 1892

1860

1880

1900

1920

1940

Bu

lk d

ensi

ty (

mo

rta

r p

ast

e)

[kg

/m3]

Bulk density (mortar paste)


5

the 1:4 ratio, comparing the traditional and the modified mortar, the air introduction was the

predominant effect, leading inevitably to a reduction of the bulk density of the non-dry state.

For other ratios (1:5 and 1:6), the difference in air entrapped was smaller, and the results portray

the consequences of the filler effect.

3.2.3. Air content

The results of the test for entrapped air content in the mortars produced in the context of

vectors I and II are presented in Figures 4 and 5, respectively.

Figure 4 - Air content for vector I

Figure 5 - Air content for vector II

As stated before, Figure 4 shows that the addition of fine glass aggregates led to consid-

erable air introduction in fresh mortars, possibly due to the predominantly laminar shape of

the glass particles that potentiates air entrapment. In Figure 5 it is noted that the reduction of

cement percentage, in traditional mortars, also led to larger values of air content. This is likely

due to the fact that such mixes with less cement content are more heterogeneous than at a 1:4

ratio. It is observed that as the cement content decreased, the difference in air content between

traditional and modified mortars with 20% glass aggregates also decreased.

3.2.4. Dry bulk density

The dry bulk density was determined at the 28th

and 90th

days (Figures 6 and 7).

Figure 6 - Dry bulk density for vector I

Figure 7 - Dry bulk density for vector II

The behaviour of this variable, for vector I, did not match the trend of the bulk density

of fresh mortar. Figure 6 shows that in both ages there is a dry bulk density increase with the

addition of fine glass aggregates (with the exception of the mortar with 15% glass aggregates,

at the 28th

day that, as shown by the measurement at the 90th

day, was likely poorly com-

pacted). This increase in the dry bulk density is due to a filler effect. In fact, the air entrap-

5.7

10.2 11.1 11.5

0 2 4 6 8

10 12 14

Air

co

nte

nt

[%]

Air content

5.7

11.5

8.4

12.0 11.3 12.0

0 2 4 6 8

10 12 14

Air

co

nte

nt

[%]

Air content

1600

1650

1700

1750

1800

1850

Dry

bu

lk d

ensi

ty [

kg

/m3]

Dry bulk density

28 dias

90 dias

1600

1650

1700

1750

1800

1850

Dry

bu

lk d

ensi

ty [

kg

/m3]

Dry bulk density

28 dias

90 dias

days

days

days

days

Extended abstract

6

ment, that is a determining factor in bulk density of fresh mortar, loses importance for the dry

state since part of this air is released during compaction and subsequent stabilization. For vec-

tor II (Figure 7), it is observed that the dry bulk density, for the same cement aggregates ratio,

increased with the introduction of 20% fine glass material, which is justified by the filler ef-

fect, that made the mortar more compact.

3.2.5. Dynamic elasticity modulus

The dynamic elasticity modulus was determined at 28th

and 90th

days (Figures 8 e 9).

Figure 8 - Dynamic elasticity modulus for vector I

Figure 9 - Dynamic elasticity modulus for vector II

In Figure 8 it is shown that, as the glass content of the mix increased, the elasticity

modulus increased, in both ages. Such an increase is justified by the incorporation of fine ag-

gregates and a decrease of the water consumption, leading to a more compact and rigid mortar

(Braga, 2010). From Figure 9, it is clear that, for any ratio and age, the addition of fine material

led to an increase of the dynamic elasticity modulus. As expected, a direct relation was also

detected between cement content and dynamic elasticity modulus, for both types of mortar, with

the decrease of cement dictating a decrease in stiffness.

A reduction in the dynamic elasticity modulus from the 28th

to the 90th

day is noticeable,

contrary to expectations. Such effect may be the consequence of internal micro-cracking occur-

ring between such dates.

3.2.6. Flexural and compressive strength

Similar to the dynamic elasticity modulus tests, the flexural and compressive strengths

were also determined at the 28th

and 90th

days (Figures 10 to 13).

Figure 10 - Flexural strength for vector I

Figure 11 - Compressive strength for vector I

0

2

4

6

8

10

12

Dy

na

mic

ela

stic

ity

mo

du

lus[

GP

a]

Dynamic elasticity modulus

28 dias

90 dias

0

2

4

6

8

10

12

Dy

na

mic

ela

stic

ity

mo

du

lus[

GP

a]

Dynamic elasticity modulus

28 dias

90 dias

0

1

2

3

4

Fle

xu

ral

stre

ng

th [

MP

a]

Flexural strength

28 dias

90 dias

0

2

4

6

8

10

Co

mp

ress

ive

stre

ng

th

[MP

a]

Compressive strength

28 dias

90 dias

days

days

days

days

days

days days

days


7

Figure 12 - Flexural strength for vector II

Figure 13 - Compressive strength for vector II

In Figures 10 and 11, the overall mechanical strength (both flexural and compressive)

clearly increased with the addition of fine glass aggregates, for both ages studied. According

to Angelim et al. (2003), such results may be justified by the smaller water to cement ratio

that mortars with glass material require, the high compactness of the dry-state mortar and the

pozzolanic effect that the glass powder may present.

For vector II, in Figures 12 and 13, both mechanical strength parameters suffered a re-

duction as the percentage of cement was lowered, as expected. However, for each ratio con-

sidered, for an addition of 20% glass aggregates the strengths increased. This is consistent

with the registered behaviour of the dynamic elasticity modulus.

3.2.7. Water absorption due to capillary action

Water absorption due to capillary action was assessed at the 28th

day (Figures 14 and 15).

Figure 14 - Water absorption due to capillary action

for vector I

Figure 15 - Water absorption due to capillary action

for vector II

The smaller the water absorption coefficient due to capillary action of a mortar, the

higher the level of protection from degradation mechanisms. From Figure 14 it is observed

that the compactness of a mortar and the water absorption coefficient due to capillary action

are inversely proportional. With the addition if fine aggregates, these fill the voids in the mor-

tar by filler effect, and fluid percolation becomes more difficult. Figure 15 shows that, both in

traditional and modified mortars, the lesser the cement content the higher the capillary coeffi-

cient, due to the increase in the capillary porosities with the reduction of cement percentage.

The addition of 20% glass material, for any cement to aggregates ratio, significantly reduced

the capillarity coefficient.

0

1

2

3

4

Fle

xu

ral

stre

ng

th [

MP

a]

Flexural strength

28 dias

90 dias

0

2

4

6

8

10

Co

mp

ress

ive

stre

ng

th

[MP

a]

Compressive strength

28 dias

90 dias

1.57

0.97 0.91 0.76

0

1

2

Wa

ter a

bso

rpti

on

co

effi

cien

t

du

e to

ca

pil

ary

act

ion

[kg

/(m

2.m

in0

,5)]

Water absorption coefficient due

to capilary action

1.57

0.76

1.73

1.17

1.91

1.39

0

1

2

Wa

ter a

bso

rpti

on

co

effi

cien

t

du

e to

ca

pil

ary

act

ion

[kg

/(m

2.m

in0

,5)]

Water absorption coefficient due

to capilary action

days

days

days

days

Extended abstract

8

3.2.8. Drying

For the drying test, not standardized, the mortar blocks used for the capillary tests were em-

ployed. It was found that the behaviour of this property across the studied mortars spectrum was

very consistent with the reference mortar.

3.2.9. Susceptibility to cracking

The susceptibility to cracking test, not standardized, consists on a long-term observation of

the possible development of cracks in test blocks (bricks applied with mortar).

At the end of a 5 month period, none of the blocks, with any of the mortars, presented any

kind of cracking. In face of such results it is concluded that mortars with fine glass aggregate addi-

tion (vector I) and with addition of glass aggregates and simultaneous reduction of cement

content (vector II) are not very susceptible to cracking. Such conclusion contrasts with the

usual consideration that the addition of fine material can increase the susceptibility of the

mortar to cracking due to retraction (Veiga, 1998) (Angelim et al., 2003).

3.3. Third phase

3.3.1. Water retention

The water retention test was performed in two samples, in fresh mortar, of each mortar

to evaluate (Figures 16 and 17).

Figure 16 - Water retention for vector I

Figure 17 - Water retention for vector II

Figure 16 clearly shows that the mortar with fine glass material incorporation presented a

larger water retention capacity than the reference mortar. Such result was expected and is ex-

plained by the fact that the fine material blocks the pores that would otherwise be available for

fluid percolation, hence limiting water release. Such behaviour allows a bigger availability of

water for the cement hydration process, increasing the probability of a complete hydration. For

the same reason, in Figure 17 it is shown that for each ratio considered, the incorporation of

20% fine glass material raised the retention capacity compared to the corresponding traditional

mortar. Contrary to expectations, the traditional mortar with 1:5 ratio demonstrated a larger ca-

pacity compared to the traditional mix at 1:4 volumetric ratio.

3.3.2. Dimensional variability - shrinkage

The dimensional variability test was performed in three samples of each of the consid-

ered mortars (Figures 18 and 19).

63.2

78.9

0

20

40

60

80

100

Wa

ter r

ete

nti

on

[%

]

Water retention

63.2 78.9 74.1 79.6

0

20

40

60

80

100

Wa

ter r

ete

nti

on

[%

]

Water retention


9

Figure 18 - Shrinkage for vector I

Figure 19 - Shrinkage for vector II

Figure 18 shows that the mortar with fine glass aggregates exhibited, from the begin-

ning of the test, higher shrinkage than the reference mortar. Such a result was expected since,

according to Veiga (1998), the use of aggregates with a high fine content leads to higher

shrinkage, effectively increasing the probability of cracking by constrained shrinkage.

From the analysis of Figure 19, and according to that reported for vector I, for each of

the studied cement to aggregate ratios, the mortar with 20% fine glass material showed larger

shrinkage values than the equivalent traditional mortar. Furthermore, in agreement with ex-

pectations, both for traditional and modified mortars, the ones with lesser cement content dis-

played smaller shrinkage values. It is noted that the 1:5 ratio mortar with 20% fine glass ag-

gregates exhibited shrinkage values close to those of the reference mortar.

3.3.3. Durability assessment considering the artificial accelerated aging test

The artificial accelerated aging test was performed on two samples of each mortar,

every sample representing a small wall section, made by a brick and two halves, between

which the mortar was applied. The following characteristics were analysed:

a) Visual aspect

After the accelerated aging cycles, no cracking or flaking were detected in any of the

samples, from every mortar considered.

b) Ultrasound mechanical characterization

The ultrasound mechanical characterization was performed before and after the acceler-

ated aging test (Figures 20 e 21).

Figure 20 - Ultrasonic pulse velocity for vector I

Figure 21 - Ultrasonic pulse velocity for vector II

-0,07

-0,06

-0,05

-0,04

-0,03

-0,02

-0,01

0,00

0 20 40 60 80 100

Dim

an

sio

na

l v

ari

ab

ilit

y[%

]

Age [days]

Shrinkage

I (1:4_0%)

I (1:4_20%)

-0,07

-0,06

-0,05

-0,04

-0,03

-0,02

-0,01

0,00

0 20 40 60 80 100

Dim

an

sio

na

l v

ari

ab

ilit

y[%

]

Age [days]

Shrinkage

II (1:4_0%)

II (1:4_20%)

II (1:5_0%)

II (1:5_20%)

0

500

1000

1500

2000

Av

era

ge

ult

raso

nic

pu

lse

vel

oci

ty [

m/s

]

Average ultrasonic pulse velocity

Antes do

envelhecimento

Após o

envelhecimento

0

500

1000

1500

2000

Av

era

ge

ult

raso

nic

pu

lse

vel

oci

ty [

m/s

]

Average ultrasonic pulse velocity

Antes do

envelhecimento

Após o

envelhecimento

0.00

-0.01

-0.02

-0.03

-0.04

-0.05

-0.06

-0.07

0.00

-0.01

-0.02

-0.03

-0.04

-0.05

-0.06

-0.07

Before aging

After aging

Before aging

After aging

Extended abstract

10

Figure 20 shows, both before and after aging, that the recorded ultrasonic pulse velocity

is higher in the mortars with 20% fine glass aggregates, by comparison to the traditional mor-

tar. With higher compactness, the modified mortar was expected to exhibit such behaviour

regarding ultrasound propagation. Figure 21shows that, like for vector I, in mortars with 1:4

volumetric ratio, before and after aging, the addition of 20% glass aggregates leads to a slight

increase of ultrasonic pulse velocity. In the 1:5 ratio mortars, an opposite trend was observed,

with decreases of the average ultrasonic pulse velocity or mortars with added glass compared

to the corresponding reference mortar. This reduction is however also not very significant.

For the 1:4 ratio mortars, with also little variations, a laboratorial problem may very

well be the origin of the behaviour of the 1:5 ratio mixes. In both vectors it is noted that the

ultrasonic pulse velocity is smaller after aging. During the various climatic cycles, two phe-

nomena with diverging results may occur. In humidity-icing cycles, the added water may con-

tribute to the hydration of cement that was not hydrated originally, leading to and rise in ultra-

sonic pulse velocity\. However due to the differential thermal behaviour of the various com-

ponents of the mortar and the formation of ice, the formation of superficial cracks is expected,

inevitably reducing the ultrasonic pulse velocity in the medium. Since a reduction did occur, it

is concluded that the cracking effect was more relevant than the cement hydration effect.

c) Water permeability

Similarly to the previous test, the permeability under pressured water test was per-

formed prior and after accelerated aging (Figures 22 and 23).

Figure 22 - Water permeability for vector I

Figure 23 - Water permeability for vector II

It is noted that, as expected due to increased compactness, both before and after aging, the

mortar at 1:4 ratio and 20% fine glass addition exhibited a lower permeability to pressured wa-

ter than the traditional mortar, even if such difference is limited prior to the aging process. Such

trend is not respected for the 1:5 ratio mortars at the same stage, where the introduction of fine

material increased the permeability relative to the traditional mortar. Such increase is not par-

ticularly significant and is consistent with the results from the ultrasound tests, where the possi-

bility of a laboratorial problem was introduced.

Among the different ratio mortars, it was apparent that, as expected, the mixes with lar-

ger cement content (1:4 ratio) showed a smaller permeability, since according to Silva (2006), it

is commonly considered that a greater cement percentage reduces permeability.

For all considered mortars a reduction of the permeability was observed after the accel-

erated aging cycles. As stated for the previous test, residual hydration occurs in such cycles,

0 10 20 30 40 50 60 70

Wa

ter p

erm

eab

ilit

y

[mm

]

Water permeability

Antes do

envelhecimento

Após o

envelhecimento 0

10 20 30 40 50 60 70

Wa

ter p

erm

eab

ilit

y

[mm

]

Water permeability

Antes do

envelhecimento

Após o

envelhecimento

Before aging Before aging

After aging After aging


11

as well as cracking. However such cracking is mostly superficial, not affecting significantly

the permeability under pressured conditions. In this test the effect of the residual cement hy-

dration is dominant, reducing the permeability after aging of the samples.

c) Pull-off strength

Mortar adherence to support was also tested before and after the aging process (Figures

24 and 25).

Figure 24 - Pull-off strength for vector I

Figure 25 - Pull-off strength for vector II

A major observation is that, both prior and after aging and for all considered ratios, the

mortar with added glass aggregates always presented a higher adherence to the support, re-

garding the corresponding reference traditional mortar. Such behaviour is explained by the

increased water and fine material suction from the mortar by the support in the case of added

fine glass aggregates, effectively raising the adherence values. It is also possible to observe in

Figure 25 a decreased adherence in traditional mortars with the reduction of cement content.

This is consistent with Carasek and Djanikian (1997), which indicate a direct relation between

cement content and adherence characteristics in a mortar.

In Figures 24 and 25 it is clear that all mortars increased their adherence capacity after

the aging cycles. As discussed before, cracking that occurs as a consequence of such cycles is

mostly superficial, and the cement hydration phenomena are more relevant for this test.

Both traditional mortars, prior and after aging, presented a predominantly cohesive type

of rupture, the most favourable type. In contrast, the modified 1:4 ratio mortar presented, be-

fore aging, some adhesive ruptures in the interface between the coating and the support. After

aging, besides the two types of ruptures observed before aging, the samples also presented

cohesive ruptures in the support. Comparing with the previously discussed mix, the 1:5 ratio

mortar with 20% added fine glass material showed an improved performance, with only cohe-

sive ruptures in the mortar or adhesive in the interface between coating and support.

4. Conclusions

Regarding research vector I (filler affect), in most properties analysed, the performance

of the mortars shows a direct relation with the content of fine glass aggregates in the mix. In

properties such as flexural and compressive strength and adherence strength, the modified

mortars outperform the reference mortars. From the considered modified mortars, the mix

with 20% of glass aggregates showed the best performance in this mechanical characteriza-

tion. Tests for the water absorption due to capillary action, water retention and water perme-

0,0

0,2

0,4

0,6

0,8

1,0

Ad

her

ence

[M

Pa

]

Pull-off strength

Antes do

envelhecimento

Após o

envelhecimento

0,0

0,2

0,4

0,6

0,8

1,0

Ad

her

ence

[MP

a]

Pull-off strength

Antes do

envelhecimento

Após o

envelhecimento

1.0

0.8

0.6

0.4

0.2

0.0

1.0

0.8

0.6

0.4

0.2

0.0

Before aging Before aging

After aging After aging

Extended abstract

12

ability also showed increased performance with the addition of fine glass material. For prop-

erties such as drying capacity and susceptibility to cracking no discriminating differences

were observed between the modified and traditional mortars. In terms of dynamic elasticity

modulus and dimensional variability the modified mortars behaved below the traditional mor-

tar.

Considering vector II, the addition of the glass aggregates lead to more surprising re-

sults than those reported for vector I. For the mechanical characterization, properties as the

dynamic elasticity modulus, flexural and compressive strength and adherence to support im-

proved after the aging process in mortars with reduced cement content and added glass aggre-

gates, compared to the reference 1:4 ratio mortar. Properties such as water absorption due to

capillary action and water retention also improved in such mortars. Similarly to that reported

for vector I, drying capacity and susceptibility to cracking were not significantly affected and

dimensional variability now joins this list, considering the reference performance. In proper-

ties such as water permeability and adherence capacity prior to aging, the 1:5 ratio mortar

with 20% glass aggregates exhibited a weaker performance than the 1:4 reference mortar.

It is observed that the addition of fine glass aggregates leads to better performing mor-

tars, particularly at the mechanical level, compared to the reference mortars, mostly due to the

filler effect. In addition, the reduction of cement content and simultaneous inclusion of fine

glass material also rendered very satisfactory results, especially considering mortars with 1:5

volumetric cement to aggregates ratio and 20% glass aggregates. Such mix outperformed the

reference mortar in most tests. Such positive results seem to indicate that fine glass aggregates

possess some pozzolanic properties.

5. References

Angelim, Renato R.; Angelim, Susane C. M.; Carasek, Helena; "Influence of the addi-

tion of fine limestone, siliceous and clay on the properties of mortars and coatings" (in Portu-

guese), V Symposium of Technology Mortars (SBTA), São Paulo, Brazil, June 2003, pp. 401-416. APA; Construction and Demolition Waste (in Portuguese), Portuguese Environment

Agency, 2011. Available in: http://www.apambiente.pt/politicasambienteResíduos/fluxresiduos/

respgestresiduo/RCD/Paginas/default.aspx [Consulted in October 2011].

Braga, Mariana; "Performance of mortars with incorporation of fine aggregates from

crushed of concrete - the filer and pozzolanic effects" (in Portuguese), Master Thesis in Civil

Engineering, Instituto Superior Técnico, Lisbon, 2010, 122 p.

Brito, Jorge de; "Recycling and reuse of construction and demolition waste" (in Portu-

guese), Conference on waste management and resources in Portugal, Lisbon, May 2004, 16 p.

Carasek, Helena; Djanikian, João; "Adhesion of mortars based on the portland cement

on masonry units" (in Portuguese), Newsletter PCC 179, São Paulo, Brazil, 1997, pp. 1-20.

Russo, Mário A. Tavares; "The national legislation and specific waste streams" (in Por-

tuguese), New Opportunities in Waste Management, Session 1: Legal Framework of Waste

Management, Lisbon, April 2009, 48 slides.

Silva, João; "Incorporation of red-brick waste in cementitious mortars" (in Portuguese),

Master Thesis in Civil Engineering, Instituto Superior Técnico, Lisbon, 2006, 224 p.

Veiga, Rosário; "Behaviour of rendering mortars - contribution to the study of its resis-

tance to cracking" (in Portuguese), Doctoral Thesis in Civil Engineering, LNEC, Faculty of

Engineering, University of Porto, Porto, 1998, 522 p.

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