Environmental Greening Through Utilization of Glass Waste for Production of Concrete
14 Pages Posted: 21 Jan 2014
Date Written: January 20, 2014
The amount of glass waste generated by glass manufacturing and recycling companies creates serious environmental challenges. The utilization of glass waste in concrete to mitigate such challenges involved the adaptation of the material with respect to the fundamental requirements. This research involved the beneficial use of two types of soda-lime glass wastes in concrete, as partial replacement of cement and fine aggregate, in order to enhance the greening of the environment. The glass wastes were produced in large quantities by glass recycling companies in Gauteng, South Africa. Low alkali cement, CEM V/A 32.5N, a composite cement with 25% Fly Ash (FA) and 18% Ground Granulated Blast-furnace Slag (GGBS) was used. The two types of glass waste, namely, Superfine Waste Glass Sand (SGW), a fine residue of glass recycling processes and Ceramic Stone and Porcelain (CSP) glass waste, cullet contaminated with ceramics, stones and porcelain; were respectively used as sand and cement replacements. As collected, SGW was sieved and blended with fine sand in line with the recommendations of the South African National Standard (SANS) for sieve analysis. CSP was sorted from contaminations, through decantation, dried in the oven at 104 oC for 24 hours, grounded into powder with rod and ball mills successively; and sieved through 75µm mesh. The tests conducted include sieve analysis, particle relative densities, compacted bulk densities and loose bulk densities; in accordance with the Cement and Concrete Institute (C&CI) mix design protocol. Twenty mix proportions were designed with water-to-cement ratio of 0.7 and 75 mm slump. The first set of mixes consisted of 20%, 40%, 50% and 60% SGW replacement of sand; the second set consisted of 10%, 20% and 30% of glass powder (GLP) replacement of cement; the third set consisted of 10% GLP in combination with 20%, 40%, 50% and 60% of SGW, respectively; the fourth set consisted of 20% GLP in combination with 20%, 40%, 50% and 60% of SGW, respectively; and the fifth set consisted of 30% GLP in combination with 20%, 40%, 50% and 60% of SGW, respectively. Subsequently, cube specimens were tested at 3, 7 and 28 days for compressive strength, according to the SANS recommendations. It was found that, the glass waste were effectively adapted in concrete. SGW was adequate for blending with fine aggregates as it improved the gradation of the blend. SGW and GLP increased the workability of the fresh concretes and significantly reduced the weight of the hardened concrete by 6.5%. Glass powder reacted as early reactive pozzolanic material, as it enhanced the 3 days compressive strength of the concrete by 14% when compared to the control mix with natural aggregates. Compressive strengths obtained from the laboratory tests ranged between 18.8 MPa and 32.7 MPa, which were 65% above that of the control mix. Up to 30% of glass wastes used as cement and fine aggregate replacement, respectively, did not impair the 28-day compressive strength of the concrete. The blend with 20% GLP and 40% SGW exhibited the same 28-day compressive strength as that of the control mix value with a value of 25.86 MPa. The mix with 20% GLP and 20% SWGS exhibited the highest strength at 28 days with a value of 32.7 MPa which represented an increase of 26.5% of the compressive strength of the control mix. The research demonstrated the beneficial use of glass waste as partial replacement for cement and sand in concrete. This will appreciably reduce the amount of glass waste dumped to the landfill sites and enhance the greening of the environment, with the added advantage of preservation of virgin materials for posterity.
Keywords: Compressive strength, control mix, environmental greening, glass waste, virgin materials.
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