Polymer modified mortars using either recycled waste concrete fine aggregate (WCFA) or artificial marble waste fine aggregate (AMWFA) were prepared and investigated for the purpose of feasibility of recycling. The replacement ratio of recycled materials also changed to investigate the effect of it on mechanical and physical properties. The water–cement ratio was increased as the replacement ratio of either AMWFA or WCFA in mortar in the absence of styrene-butadiene rubber (SBR) latex. The presence of SBR for both WCFA and AMWFA gave the increase of the air content. The compressive strength decreased in the presence of SBR. The higher replacement ratio of WCFA and AMWFA lowered the compressive strengths significantly. The compressive strength of AMWFAwas significantly lowered after the hot water resistance test, whereas that of WCFA was slightly increased after the hot water resistance test. As the replacement ratio of either WCFA or AMWFA increased, the flexural strength decreased as well as compressive strength.
Trang 1Comparison of mechanical and physical properties of SBR-polymer
modified mortars using recycled waste materials
Department of Chemical Engineering, Kongju National University, 275 Budae-dong, Cheonan, Chungnam-do 330-717, Republic of Korea
Received 24 December 2007; accepted 17 February 2008
Abstract
Polymer modified mortars using either recycled waste concrete fine aggregate (WCFA) or artificial marble waste fine aggregate (AMWFA) were prepared and investigated for the purpose of feasibility of recycling The replacement ratio of recycled materials also changed to investigate the effect of it on mechanical and physical properties The water–cement ratio was increased as the replacement ratio of either AMWFA or WCFA
in mortar in the absence of styrene-butadiene rubber (SBR) latex The presence of SBR for both WCFA and AMWFA gave the increase of the air content The compressive strength decreased in the presence of SBR The higher replacement ratio of WCFA and AMWFA lowered the compressive strengths significantly The compressive strength of AMWFA was significantly lowered after the hot water resistance test, whereas that
of WCFA was slightly increased after the hot water resistance test As the replacement ratio of either WCFA or AMWFA increased, the flexural strength decreased as well as compressive strength
# 2008 The Korean Society of Industrial and Engineering Chemistry Published by Elsevier B.V All rights reserved
Keywords: Polymer-modified mortar; Recycled waste materials; Recycling; Polymer–cement ratio
1 Introduction
It has been significantly important to develop the technology
to treat or recycle the various waste materials from artificial
marble waste, concrete waste, and plastics waste due to the their
enormous production 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 drawbacks in economic, technical and environmental
manners[10,13–15] Material recycling is expected to be more
feasible in the ways 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 expected to be higher quality
and more ornamental than the past, making use of a huge amount
of acrylic artificial marble as construction material
Conse-quently, this links to the huge amount of waste artificial marble, causing the environmental issue in our society Furthermore, the waste artificial marble is categorized as industrial waste It means
it should be disposed or burned to destroy, resulting in the air and environmental pollution[13,14]
On the other hand, with the growing of construction industry, the demand for aggregates is rapidly increasing River sand, river gravel, and even ocean sand are currently being exhausted and the natural environment of the land is being destroyed as a result of aggregates collecting works to obtain crushed aggregates Because the demand for aggregates steadily increases, while the supply is absolutely limited, the use of recycled aggregates obtained by crushing waste concretes is inevitable when attempting to balance demand and supply [17,18]
The importance of how to recycle or reuse waste artificial marble and waste concrete became an important technological issue recently, and a countermeasure was usage of them as an aggregate in the production of mortar [19] However, the recycling of waste artificial marble and waste concrete fine aggregate could cause lowering the performance or mechanical properties of the final mortar[19]
An organic polymer or resin, so-called polymer-modifier is expected to overcome the problems described above because
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Journal of Industrial and Engineering Chemistry 14 (2008) 644–650
* Corresponding author Tel.: +82 41 521 9356.
E-mail address: ehhwang@kongju.ac.kr (E.-H Hwang).
1226-086X/$ – see front matter # 2008 The Korean Society of Industrial and Engineering Chemistry Published by Elsevier B.V All rights reserved doi: 10.1016/j.jiec.2008.02.009
Trang 2the 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[20–30]
In this study the polymer-modified mortars using recycled
artificial marble and concrete waste fine aggregates were
investigated in detail with styrene-butadiene rubber (SBR) latex
polymer-modifier to overcome the drawbacks such as losing
mechanical and physical properties of the mortar consisted of
recycled waste materials The effects of composition of
recycled waste materials on the mechanical and physical
properties were also investigated
2 Experimentals
2.1 Materials
Conventional Portland cement (OPC, type 1) and standard
sand were used throughout this study Waste concrete fine
aggregate (WCFA) were prepared by crushing waste concrete
and collecting it in the range of 0.1–1.2 mm in diameter 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 latex was utilized
without any further treatment Table 1 shows the physical
properties of polymer modifier, SBR
2.2 Preparation of specimens
The contents of polymer modifier in polymer–cement
mixture were 0, 10 and 20 wt% as shown inTables 2 and 3
The replacement ratios of AMWFA and WCFA 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 [31,32]
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 cured for 28 days 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 either artificial marble waste fine aggregate (AMWFA) or waste concrete fine aggregate (WCFA) in mortar without polymer modifier However,
Table 1 Physical properties of polymer cement modifiers, SBR.
Type Density (20 8C) Viscosity (20 8C, cP) pH (20 8C) Total solids (wt%)
Table 2
Mix proportions of SBR polymer-modified mortars containing waste concrete fine aggregate.
Cement: (sand + WCFAa)
(by weight)
WCFA/(WCFA + sand) (wt%)
P/C ratio (wt%)
W/C ratio (%)
Unit weight (g/ml)
Air content (%)
Flow value
a
WCFA, waste concrete fine aggregate.
E.-H Hwang, Y.S Ko / Journal of Industrial and Engineering Chemistry 14 (2008) 644–650 645
Trang 3adding polymer modifier into mortar reduced water–cement
ratio significantly
The water–cement ratio of WCFA was shown to be much
higher than that of AMWFA The higher water absorption of
cement paste in WCFA compared to that of AMWFA could be
a reason for the increase of water–cement ratio with higher
replacement ratio As the replacement ratio of WCFA
increased, the water–cement ratio was increased dramatically,
resulting from the higher water absorption of the cement
paste
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 both AMWFA and WCFA The air content was decreased as
the replacement ratio of WCFA increased, whereas it was
increased in the case of AMWFA The presence of SBR for both
WCFA and AMWFA gave the increase of the air content excessively Generally, adding around 1% of antifoaming agent
is common way to reduce the excessively entrained air content and improve the properties of mortar In this study, it is determined to be needed to add appropriate amount of antifoaming agent into polymer cement modifier in accordance with the properties of the purposed product
The change in the unit weight of the fresh mortars was dependent on the replacement ratio of either AMWFA or WCFA as shown in Fig 3 Regardless of the absence and presence of SBR, the unit weight decreased significantly with increasing the replacement ratio of AMWFA However, in the case of WCFA, the unit weight increased slightly with increasing the replacement ratio of waste fine aggregate in the presence of SBR It should be considered that the specific gravities of AMWFA and WCFA are lower than that of standard sand and that the presence of polymer cement modifier increased the air content entrained
Fig 1 Variation of water/cement ratios vs replacement ratios of recycled fine
aggregates.
Fig 2 Variation of air contents vs replacement ratios of recycled fine aggregates.
Table 3
Mix proportion of SBR polymer-modified mortars containing artificial marble waste fine aggregate.
Cement: (sand + AMWFAa)
(by weight)
AMWFA/(AMWFA + sand) (wt%)
P/C ratio (wt%)
W/C ratio (%)
Unit weight (g/ml)
Air content (%)
Flow value
a
AMWFA, artificial marble waste fine aggregate.
E.-H Hwang, Y.S Ko / Journal of Industrial and Engineering Chemistry 14 (2008) 644–650 646
Trang 43.3 Water absorption
Water absorption was measured after the curing steps
described in Experimental part There was little difference in
water absorption between no SBR latex and 10% SBR as shown
inFig 4, and it was decreased drastically at 20% of polymer–
cement ratio, resulting from a very good water-resistant bond
between the polymer cement modifier and the cement
components Both AMWFA and WCFA showed a quite similar
trend in water absorption, and the higher water absorption was
observed at the higher replacement ratios of the recycled
materials
3.4 Mechanical strength
Compressive strengths and flexural strengths were
mea-sured and shown in Figs 5 and 6, respectively The
compressive strength decreased in the presence of polymer
cement modifier compared to that of no polymer cement
modifiers, resulting from the excessive increase of air content entrained by SBR-polymer cement modifier The replacement ratio of WCFA and AMWFA affected the compressive strengths significantly, resulting in the lowering the values with the higher replacement ratio Cement hydrate–polymer bonds are weaker in compressive strength than cement hydrate-cement hydrate bonds However, the higher propor-tion of polymer modifier, the higher sealing effect is shown, resulting in improvement of compressive strength The flexural strengths of WCFA increased significantly in the presence of polymer cement modifiers generally except the SBR addition
of 10% in mortar The effect of the increase of the additive amount of polymer cement modifier is higher on flexural strength than compressive strength It seems to be because the compressive strength is mostly influenced by the bonding forces generated by the hydration reaction of cements but the flexural strength is mostly influenced by the bonding forces
of polymer cement modifier adhering to the surfaces of aggregates
Fig 6 Variation of flexural strengths of polymer-modified mortars vs replace-ment ratios of recycled fine aggregates.
Fig 4 Variation of water absorption vs replacement ratios of recycled fine
aggregates.
Fig 5 Variation of compressive strengths of polymer-modified mortars vs replacement ratios of recycled fine aggregates.
Fig 3 Variation of unit weight ratios vs replacement ratios of recycled fine
aggregates.
E.-H Hwang, Y.S Ko / Journal of Industrial and Engineering Chemistry 14 (2008) 644–650 647
Trang 5It was decreased in general as the replacement ratio
increased, and the higher replacement ratio of WCFA
with 20%-SBR showed significant decrease in the flexural
strength
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 changed
and it was dependent on the kind of the recycled materials The
compressive strength of AMWFA was significantly lowered
after the hot water resistance test, whereas that of WCFA was
slightly increased after the hot water resistance test However,
as the replacement ratio of AMWFA increased, the compressive
strength decreased in general
The flexural strength was measured after immersing the
specimen in hot water of 90 8C, and shown in Fig 8 As
the replacement ratio of either WCFA or AMWFA increased,
the flexural strength decreased as well as compressive strength
The hot water resistance test leads to the weakening of the bonding between cement hydrate-polymer due to the deteriora-tion or decomposideteriora-tion of polymer[31,33–36]
3.6 Pore volume and density The pore volumes of the specimen before and after hot water resistance test were measured as depicted inFig 9 The total pore volume increased as the replacement ratio of either AMWFA or WCFA increased significantly, resulting from that the higher amount of the recycled materials, the higher the amount of air entrained during the mixing process
The reason for the 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 inFig 10 AMWFA and WCFA had lower density than the standard sand,
Fig 7 Variation of compressive strengths of polymer-modified mortars vs.
replacement ratios of recycled fine aggregates (—, before hot water
immer-sion; , after hot water immersion).
Fig 8 Variation of flexural strengths of polymer-modified mortars vs
replace-ment ratios of recycled fine aggregates (—, before hot water immersion;
, after hot water immersion).
Fig 9 Variation of total pore volume vs replacement ratios of recycled fine aggregates before/after hot water immersion test (—, before hot water immer-sion; , after hot water immersion).
Fig 10 Variation of bulk density vs replacement ratios of recycled fine aggregates before/after hot water immersion test (—, before hot water immer-sion; , after hot water immersion).
E.-H Hwang, Y.S Ko / Journal of Industrial and Engineering Chemistry 14 (2008) 644–650 648
Trang 6suggesting the higher replacement ratio caused the lower
density value
3.7 Microstructure of the mortars
The microstructures of two specimens having SBR cement
modifier of 10% with the replacement ratio of either AMWFA
or WCFA of 50% were observed by SEM prior to and after the
hot water resistance test as shown inFig 11 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 to present in the same co-matrix phase
[31,37,38] 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 physical properties of SBR-polymer modified mortar with either WCFA or AMWFA were investigated and can be summarized as follows:The water–cement ratio was increased
as the replacement ratio of either AMWFA or WCFA in mortar without polymer modifier.The air content was decreased as the replacement ratio of WCFA increased, whereas it was increased
in the case of AMWFA The presence of SBR for both WCFA and AMWFA gave the increase of the air content.The compressive strength decreased in the presence of SBR compared to the absence of SBR The higher replacement ratio of WCFA and AMWFA lowered the compressive strengths significantly.The compressive strength of AMWFA was significantly lowered after the hot water resistance test, whereas that of WCFA was slightly increased after the hot water
Fig 11 SEM photographs of the specimens having the replacement ratio of recycled fine aggregates of 50% prior to (a, b, d and e) and after (c and f) the hot water resistance test: (a) SBR = 0%, WCFA = 50%; (b) SBR = 10%, WCFA = 50%; (c) SBR = 10%, WCFA = 50%; (d) SBR = 0%, AMWFA = 50%; (e) SBR = 10%, AMWFA = 50%; (f) SBR = 10%, AMWFA = 50%.
E.-H Hwang, Y.S Ko / Journal of Industrial and Engineering Chemistry 14 (2008) 644–650 649
Trang 7resistance test.As the replacement ratio of either WCFA or
AMWFA increased, the flexural strength decreased as well as
compressive strength
Acknowledgement
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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