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.
Available online at www.sciencedirect.com Journal of Industrial and Engineering Chemistry 14 (2008) 644–650 www.elsevier.com/locate/jiec Comparison of mechanical and physical properties of SBR-polymer modified mortars using recycled waste materials Eui-Hwan Hwang *, Young Soo Ko 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 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- * Corresponding author Tel.: +82 41 521 9356 E-mail address: ehhwang@kongju.ac.kr (E.-H Hwang) 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 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 E.-H Hwang, Y.S Ko / Journal of Industrial and Engineering Chemistry 14 (2008) 644–650 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 [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 645 Table Physical properties of polymer cement modifiers, SBR Type Density (20 8C) Viscosity (20 8C, cP) pH (20 8C) Total solids (wt%) SBR 1.020 171 9.2 49.1 in a humid condition at 20 Ỉ 8C and 90% of relative humidity for days, cured again in water at 20 8C for days, and then cured in air at 20 Ỉ 8C and 60 Ỉ 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 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 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 in Tables and 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 Ỉ 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 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 Results and discussion 3.1 Variation of water–cement ratio As shown in Fig 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 Mix proportions of SBR polymer-modified mortars containing waste concrete fine aggregate Cement: (sand + WCFAa) (by weight) WCFA/(WCFA + sand) (wt%) 1: 3.0 25 50 75 100 1: 3.0 1: 3.0 a W/C ratio (%) Unit weight (g/ml) 70.1 75.7 93.0 108.7 117.4 1.961 1.940 1.925 1.913 1.899 8.5 7.5 3.0 1.8 1.5 170 175 174 175 165 25 50 75 100 10 61.6 74.4 92.6 106.5 115.3 1.605 1.599 1.628 1.650 1.683 24.6 22.6 15.6 12.2 8.0 175 173 175 172 167 25 50 75 100 20 42.3 70.1 83.8 97.5 110.2 1.577 1.616 1.642 1.683 1.710 26.1 19.0 13.3 7.2 5.3 168 170 167 165 169 WCFA, waste concrete fine aggregate P/C ratio (wt%) Air content (%) Flow value 646 E.-H Hwang, Y.S Ko / Journal of Industrial and Engineering Chemistry 14 (2008) 644–650 Table Mix proportion of SBR polymer-modified mortars containing artificial marble waste fine aggregate Cement: (sand + AMWFAa) (by weight) AMWFA/(AMWFA + sand) (wt%) 1: 1: 1: 1: 1: 3.00 2.75 2.50 2.25 2.00 25 50 75 100 1: 1: 1: 1: 1: 3.00 2.75 2.50 2.25 2.00 1: 1: 1: 1: 1: 3.00 2.75 2.50 2.25 2.00 a P/C ratio (wt%) W/C ratio (%) Unit weight (g/ml) Air content (%) Flow value 70.1 73.6 77.3 79.8 82.6 1.961 1.709 1.541 1.434 1.364 8.5 14.9 16.4 18.0 19.5 170 168 165 173 169 25 50 75 100 10 61.6 67.3 71.0 75.1 77.3 1.605 1.479 1.395 1.291 1.151 24.6 25.0 25.0 25.6 26.2 168 169 168 170 175 25 50 75 100 20 42.3 48.5 49.5 50.0 51.0 1.577 1.384 1.199 1.115 1.053 26.1 29.6 31.5 32.7 34.2 174 165 175 175 170 AMWFA, artificial marble waste fine aggregate Fig 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 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 Variation of water/cement ratios vs replacement ratios of recycled fine aggregates Fig Variation of air contents vs replacement ratios of recycled fine aggregates adding 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 E.-H Hwang, Y.S Ko / Journal of Industrial and Engineering Chemistry 14 (2008) 644–650 Fig Variation of unit weight ratios vs replacement ratios of recycled fine aggregates 647 Fig Variation of compressive strengths of polymer-modified mortars vs replacement ratios of recycled fine aggregates Compressive strengths and flexural strengths were measured and shown in Figs 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 proportion 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 Variation of water absorption vs replacement ratios of recycled fine aggregates Fig Variation of flexural strengths of polymer-modified mortars vs replacement ratios of recycled fine aggregates 3.3 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 in Fig 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 648 E.-H Hwang, Y.S Ko / Journal of Industrial and Engineering Chemistry 14 (2008) 644–650 Fig Variation of compressive strengths of polymer-modified mortars vs replacement ratios of recycled fine aggregates (—, before hot water immersion; , after hot water immersion) Fig Variation of total pore volume vs replacement ratios of recycled fine aggregates before/after hot water immersion test (—, before hot water immersion; , after hot water immersion) It 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 The hot water resistance test leads to the weakening of the bonding between cement hydrate-polymer due to the deterioration or decomposition of polymer [31,33–36] 3.5 Mechanical strength after hot water resistance test 3.6 Pore volume and density 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 As the replacement ratio of either WCFA or AMWFA increased, the flexural strength decreased as well as compressive strength The pore volumes of the specimen before and after hot water resistance test were measured as depicted in Fig 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 in Fig 10 AMWFA and WCFA had lower density than the standard sand, Fig Variation of flexural strengths of polymer-modified mortars vs replacement ratios of recycled fine aggregates (—, before hot water immersion; , 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 immersion; , after hot water immersion) E.-H Hwang, Y.S Ko / Journal of Industrial and Engineering Chemistry 14 (2008) 644–650 649 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% suggesting 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 in Fig 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 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 650 E.-H Hwang, Y.S Ko / Journal of Industrial and Engineering Chemistry 14 (2008) 644–650 resistance test.As the replacement ratio of either WCFA or AMWFA increased, the flexural strength 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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