Effect of polymer cement modifiers on mechanical and physical properties of polymer-modified mortar using recycled artificial marble waste fine aggregate

Various polymer-modified mortars using recycled artificial marble waste fine aggregate (AMWFA) were prepared and investigated for the purpose of feasibility of recycling. Styrene–butadiene rubber (SBR) latex and polyacrylic ester (PAE) emulsion were employed as polymer modifier, and compared each other. The replacement ratio of AMWFA was also changed to investigate the effect of it on physical properties. Adding polymer cement modifier into mortar reduced water–cement ratio, and PAE was the more effective polymer cement modifier to reduce water–cement ratio than SBR. PAE emulsion-modified mortar increased the air content entrained as the proportion of PAE was increased. There was little difference in water absorption between SBR latex and PAE emulsion. The compressive strength decreased in the presence of polymer cement modifiers compared to that of no polymer cement modifiers, but the compressive strength of 20% of polymer–cement ratio was higher than that of 10%. After the hot water resistance test, both compressive strength and flexural strength were decreased.

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Department of Chemical Engineering, Kongju National University, 275 Budae-dong, Cheonan, Chungnam-do 330-717, Republic of Korea

Received 29 October 2007; accepted 11 November 2007

Abstract

Various polymer-modified mortars using recycled artificial marble waste fine aggregate (AMWFA) were prepared and investigated for the purpose of feasibility of recycling Styrene–butadiene rubber (SBR) latex and polyacrylic ester (PAE) emulsion were employed as polymer modifier, and compared each other The replacement ratio of AMWFA was also changed to investigate the effect of it on physical properties Adding polymer cement modifier into mortar reduced water–cement ratio, and PAE was the more effective polymer cement modifier to reduce water–cement ratio than SBR PAE emulsion-modified mortar increased the air content entrained as the proportion of PAE was increased There was little difference in water absorption between SBR latex and PAE emulsion The compressive strength decreased in the presence of polymer cement modifiers compared to that of no polymer cement modifiers, but the compressive strength of 20% of polymer–cement ratio was higher than that of 10% After the hot water resistance test, both compressive strength and flexural strength were decreased

Keywords: Polymer cement modifier; Polymer-modified mortar; Recycling; Recycled waste material

1 Introduction

It has been significantly important to develop the technology

to treat or recycle the waste from organic materials such as

plastics, vehicle tires, and artificial marble due to the enormous

production of them as the industry and economy of the world

are growing[1–3]

There have been several ways to treat the wastes such as

landfill, incineration, chemical recycling, material recycling

and the utilization of energy from combustion [4–12] Most

methods excluding material recycling are known to have

critical limitations in economic, technical and environmental

manners[10,13–15] Material recycling is expected to be more

feasible in a way that the simplicity of pretreatment, and the

reduction of energy consumption and environment pollution

can be satisfied[1,10,14,16]

A recent trend and preference of the interior decoration or

housing construction material is known to be of higher quality

and more ornamental than the past, making use of a huge amount of acrylic artificial marble as construction material Consequently, this links to the huge amount of waste artificial marble, causing the environmental issue in our society Furthermore, the waste artificial marble is categorized and treated as industrial wastes It means it should be disposed or burned to destroy, resulting in the air pollution and environ-mental pollution[13,14] The importance of how to recycle or reuse waste artificial marble became an important technological issue recently, and a countermeasure was usage of the waste artificial marble as an aggregate in the production of mortar

[17] However, the recycling of waste artificial marble could cause lowering of the performance or mechanical properties of the final mortar[17]

An organic polymer or resin, so-called polymer modifier is expected to overcome the problems described above because the polymer-modifier is well known to offer to the final mortar the improvement of higher strength, durability, good resistance

to corrosion, and strong resistance to damage from freeze-thaw cycles [18–28]

In this study the polymer-modified mortars using recycled artificial marble waste fine aggregate (AMWFA) were

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Journal of Industrial and Engineering Chemistry 14 (2008) 265–271

* Corresponding author.

E-mail address: ehhwang@kongju.ac.kr (E.-H Hwang).

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investigated in detail with two different polymer-modifiers to

overcome the drawbacks like losing mechanical properties of

the mortar using AMWFA Styrene–butadiene rubber (SBR)

latex and polyacrylic ester (PAE) emulsion were employed as

polymer modifier, and compared each other The effect of

replacement ratio of AMWFA on the physical properties and

mechanical properties were also investigated and reported in

this article

2 Experimental

2.1 Materials

Conventional Portland cement (OPC, type 1) and standard

sand were used throughout this study Waste artificial marble

fine aggregate was acquired from the production process of

acrylic artificial marble, and it was crushed to get the fine

aggregate SBR and PAE were purchased and utilized in the

form of latex and emulsion, respectively without any further

treatment.Table 1shows the physical properties of two polymer

cement modifiers

2.2 Preparation of specimens

The contents of polymer modifiers in polymer–cement

mixture were 0, 10 and 20 wt% as shown inTables 2 and 3 The

replacement ratios of AMWFA for the sand were 0, 25, 50, 75

and 100% Water–cement ratio was adjusted specimen by

specimen so that the flow values of final mortar were fixed at

170 5 mm following KS F 2476 The specimens were prepared using the mold in the dimension of 40 mm

40 mm 160 mm Those were cured in a humid condition

at 20 2 8C and 90% of relative humidity for 2 days, cured again in water at 20 8C for 5 days, and then cured in air at

20 2 8C and 60 10% of relative humidity for 21 days in a thermo-hygrostat consecutively[29,30]

2.3 Test of air content, unit weight and flow value The air content and unit weight of fresh polymer-modified mortars were tested in accordance with JIS A 1174 and flow value of fresh polymer-modified mortars was tested in accordance with KS L 2476

2.4 Test of hot water resistance and pore diameter distribution

Specimens were cured in water at 90 8C for 28 days, and then were measured for compressive and flexural strengths The pore distribution was measured with mercury porosimeter for the particle from specimen which had particle diameter of 2.5–

5 mm after washed with acetone and dried for 48 h

3 Results and discussion 3.1 Variation of water–cement ratio

As shown inFig 1, water–cement ratio was increased as the replacement ratio of AMWFA in mortar increased without polymer modifier However, adding polymer modifier into mortar reduced water–cement ratio significantly In case of SBR latex and PAE emulsion, the content of 20 wt% results in decrease in water–cement ratio by 28% and 55%, respectively, meaning PAE was the more effective polymer modifier to reduce water–cement ratio in this mortar system than SBR

Table 1

Physical properties of polymer cement modifiers

Type Specific

gravity

(20 8C)

Viscosity (20 8C, cP)

pH (20 8C)

Total solids (wt%)

Table 2

Mix proportion of SBR polymer-modified mortars containing artificial marble waste fine aggregate

Cement:(sand + AMWFA)

(by weight)

AMWFA/

(AMWFA + sand) (wt%)

P/C ratio (wt%)

W/C ratio (%)

Unit weight (g/ml)

Air content (%)

Flow value

AMWFA: artificial marble waste fine aggregate.

E.-H Hwang et al / Journal of Industrial and Engineering Chemistry 14 (2008) 265–271 266

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The water absorption of cement paste in AMWFA could be a

reason for the increase in water–cement ratio with higher

replacement ratio Polymer modifier is known to improve

flowability, water resistance, and ball-bearing effect due to the

better dispersion of antifoaming agent and air-entrainment

during forming admixture [29], resulting in the decrease in

water–cement ratio for the mortar with polymer-modifier PAE

emulsion is more air-entrainment than SBR latex, suggesting

that PAE emulsion is more effective to reduce water–cement

ratio in mortar

3.2 Air content and unit weight

Fig 2 exhibits the change in air contents in the fresh

polymer-modified mortar in a function of the replacement ratio

of AMWFA SBR latex-modified mortar increase air content

entrained as the proportion of SBR latex was increased from 0

to 20 wt%, whereas PAE emulsion showed no significant

difference in air content entrained between 10 and 20 wt% In

case that the AMWFA replace ratio was 50%, the air content of SBR-modified mortar were 16.4, 25.0 and 31.5 for the SBR proportion of 0, 10 and 20%, respectively, whereas those PAE-modified mortar were 16.4, 40.4, and 41.2% for the PAE proportion of 0, 10 and 20%

The change in the unit weight of the fresh mortars was dependent on the replacement ratio of AMWFA as shown in

Fig 3 Regardless of the absence and presence of polymer cement modifier, the unit weight decreased significantly with increasing the replacement ratio of AMWFA It should be considered that the specific gravity of AMWFA is lower than that of standard sand and that the presence of polymer cement modifier increased the air content entrained

3.3 Water absorption Water absorption was measured after the curing steps described in Section 2 There was little difference in water absorption between SBR latex and PAE emulsion as shown in

Table 3

Mix proportion of PAE polymer-modified mortars containing artificial marble waste fine aggregate

Cement:(sand + AMWFA)

(by weight)

AMWFA/

(AMWFA + sand) (wt%)

P/C ratio (wt%)

W/C ratio (%)

Unit weight (g/ml)

Air content (%)

Flow value

Fig 2 Variation of air contents vs contents of artificial marble waste fine aggregate.

Fig 1 Variation of water–cement ratios vs replacement ratios of artificial

marble waste fine aggregate.

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Fig 4, and it was decreased drastically at 20% of polymer–

cement ratio for both SBR and PAE, resulting from a very good

water-resistant bond between the polymer cement modifier and

the cement components AMWFA having the property of high

water absorption resulted in higher water absorption with

higher replacement ratios

3.4 Mechanical strength

Compressive strengths and flexural strengths were measured

and summarized inFigs 5 and 6, respectively The compressive

strength decreased in the presence of polymer cement modifier

compared to that of no polymer cement modifiers, but the

compressive strength of 20% of polymer–cement ratio was

higher than that of 10% The polymer-modified mortar has

cement hydrate–cement hydrate bond and cement hydrate–

polymer bond[29] Cement hydrate–polymer bonds are weaker

in compressive strength than cement hydrate–cement hydrate

bonds However, the higher proportion of polymer modifier, the

higher sealing effect is shown, resulting in the improvement of

compressive strength The flexural strengths of mortar

increased significantly in the presence of polymer cement modifiers, whereas it decreased as the replacement ratio increased The improvement of flexural strength is linked to the nature of polymer that is known to be flexible than cement hydrate and other inorganic materials [29] The flexural strength of SBR-modified mortar with 20% of polymer–cement ratio was about 47% higher than that of no polymer modification at the replacement ratio of AMWFA of 50% 3.5 Mechanical strength after hot water resistance test

As shown in Fig 7, the compressive strength after immersing the specimen in hot water of 90 8C was lower than

it was before the immersion The compressive strength was lowered significantly after the hot water resistance test, suggesting that the deterioration or decomposition of polymer cement modifier at high temperature causes the change in strength There was little difference between SBR latex and PAE emulsion in hot water resistance, but as the replacement ratio of AMFWA increased, the compressive strength decreased The increase rate of compressive strength of 20%

Fig 5 Compressive strengths of polymer-modified mortars vs contents of artificial marble waste fine aggregate.

Fig 6 Flexural strengths of polymer-modified mortars vs contents of artificial marble waste fine aggregate.

Fig 4 Variation of water absorption vs contents of artificial marble waste fine

aggregate (before hot water immersion).

Fig 3 Variation of unit weight ratios vs contents of artificial marble waste fine

aggregate.

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of polymer–cement ratio had a lower value than that of 10% for

both SBR and PAE, resulting from the higher proportion of

polymer which was deteriorated or decomposed at high

temperature

The flexural strength was measured after immersing the

specimen in hot water of 90 8C, and shown inFig 8 The rate of

decrease in flexural strength was similar between PAE-modified

mortar and SBR-modification As the replacement ratio of WCFA

increased, the flexural strength as well as compressive strength

decreased The flexural strength is closely affected by the bonding

strength of polymer itself and an overall improvement in cement

hydrate–aggregate bond[29,30–33], and the hot water resistance

test leads to the weakening of this bonding due to the deterioration

or decomposition of polymer[29,34]

3.6 Pore volume and density

The pore volumes of the specimen before and after hot

water resistance test were measured as depicted in Fig 9

Fig 9 Comparison of total pore volume vs contents of artificial marble waste fine aggregate before/after hot water immersion test (PAE polymer–cement ratio: 20 wt%).

Fig 10 Comparison of bulk density vs contents of artificial marble waste fine aggregate before/after hot water immersion test (PAE polymer–cement ratio:

20 wt%).

Fig 11 Comparison of average pore diameter vs contents of artificial marble waste fine aggregate before/after hot water immersion test (PAE polymer– cement ratio: 20 wt%).

Fig 7 Compressive strengths of polymer-modified mortars vs contents of

artificial marble waste fine aggregate (—: before hot water immersion, : after

hot water immersion).

Fig 8 Flexural strengths of polymer-modified mortars vs contents of artificial

marble waste fine aggregate (—: before hot water immersion, : after hot

water immersion).

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The total pore volume increased as the replacement ratio of

AMWFA increased significantly, resulting from that the

higher the amount of AMWFA, the higher the amount of air

entrained during the mixing process

The reason for the significant decrease of total pore volume

after the hot water resistance test could be the progress of

hydration reaction of cement paste The decrease of total pore

volume is also closely linked to the slight increase in the density

of the specimen after the hot water resistance test as shown in

Fig 10 AMWFA had lower density than the standard sand, suggesting the higher replacement ratio caused the lower density value

It was shown inFig 11that the average pore diameter is in the range of 0.10–0.14 mm, meaning it consisted of mainly macro-pores regardless of the presence of AMWFA The higher replacement ratio of AMWFA caused increase in pore diameter The larger entraining air content due to the higher AMWFA content could cause a slight increase in the pore diameter

Fig 12 SEM photographs of the specimens having the replacement ratio of AMWFA of 50% prior to (a–e) and after (f and g) the hot water resistance test: (a) polymer cement modifier = 0%; (b) SBR polymer cement modifier = 10%; (c) SBR polymer cement modifier = 20%; (d) PAE polymer cement modifier = 10%; (e) PAE polymer cement modifier = 20%; (f) SBR polymer cement modifier = 10%; (g) PAE polymer cement modifier = 10%.

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However, there was little difference in the average pore

diameter between different proportions of AMWFA after the

hot water resistance test

3.7 Microstructure of the mortars

The microstructures of two specimens having SBR or PAE

polymer cement modifier of 10% and 20% with the replacement

ratio of AMWFA of 50% were observed by SEM prior to and

after the hot water resistance test (10% of polymer cement

modifier only), and shown inFig 12 In the presence of polymer

cement modifier, the components of mortar, cement hydrate,

AMWFA and polymer cement modifier were shown to stick to

each other, and present in the same co-matrix phase[29,35,36]

The remarkable shrinkage of polymer cement modifiers in the

mortar could be observed with the specimens after the hot water

resistance test due to the thermal degradation and deterioration of

polymer cement modifiers

4 Conclusions

The effect of the type of polymer cement modifier in the

mortar using AMWFA was investigated and can be summarized

as follows

(1) Adding polymer modifier into mortar reduced water–

cement ratio significantly PAE was the more effective

polymer modifier to reduce water–cement ratio in this

mortar system than SBR

(2) PAE emulsion-modified mortar increased the air content

entrained as the proportion of PAE was increased

(3) There was little difference in water absorption between

SBR latex and PAE emulsion and it was decreased

drastically at 20% of polymer–cement ratio for both

SBR and PAE

(4) The compressive strengths decreased in the presence of

polymer cement modifiers compared to that of no polymer

cement modifiers, but the compressive strength of 20% of

polymer–cement ratio was higher than that of 10%

(5) After the hot water resistance test, both compressive

strength and flexural strength were decreased

Acknowledgements

This study was supported by Ministry of Commerce,

Industry & Energy (MCIE) and Regional Innovation Center for

New Materials by Recycling (RIC/NMR) at Kongju National

University and here we would like to appreciate their supports

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