| Description |
Millions of tons of generated glass are wasted each year and being added to landfills where it takes one million years to decompose. For companies that collect and recycle used glass, contamination from brown or multicolored-glass is more difficult to recycle than the clear glass form. Even among the collected glass, the less-demanded combined colored-glass is still often dumped into landfills. One alternate way to reduce the volume of waste materials being added to landfills is by using waste glass as a supplementary cementitious material (SCM). This alternative may also help in sustainability of the concrete industry by reducing the amount of cement needed in concrete, and thus reducing the amount of carbon emissions produced due to cement production. One challenge to using this waste glass in concrete is that sand-size glass or cullet when added to concrete will cause a cracking-causing expansive reaction referred to as "alkali-silica reaction" (ASR). However, glass also contains a significant amount of silica, which is a main component in many other supplementary cementitious materials that can improve the strength and durability of concrete. It is hypothesized that a finer particle size of the waste glass will drive the reactivity of the silica from the glass to occur earlier in concrete hydration rather than at the later ages when the detrimental reaction in concrete could occur. This research focuses on determining the quantity and particle size at which waste glass powder can be effective in mortar against ASR. The probability of alkali-silica reaction is tested for mortar samples corresponding to ASTM C1567. Additional testing to verify the effect of the glass powder as a SCM on the compressive strength will be measured for mortar using ASTM C109/C109M. A separate common supplementary cementitious material called fly ash was also blended with the glass to examine whether it could provide beneficial combined effects on ASR and strength. It was found that the crushed mixed-colored glass, collected glass dust, or fly ash, when added alone or in combination, but equating to 40% replacement of cement was found to reduce the ASR expansion to the acceptable limits. However, at 10-40% waste glass dust percent replacements of cement, the 7-day compressive strength dropped by 68 to 42% compared to a mortar without any SCMs. The research also found that glass powder collected from the vacuum dust system at a crushing plant acts more effectively to reduce the effects of ASR as compared to the additionally crushed glass powder. |
