WASTE GLASS - A SUPPLEMENTARY CEMENTITIOUS MATERIAL

Abstract

<p>This study investigates the feasibility of using waste glass as a supplementary cementitious material (SCM). By further defining some of the parameters by which waste glass may be incorporated into concrete as a cement replacement, the environmental, economical, and engineering benefits of this material may be realized. Past observations, including the production of alkali silica reaction (ASR) gel, and the lack of pozzolanic reactivity, have limited the acceptance of waste glass as a SCM,</p> <p>Mechanical treatment was used to improve reactivity and provide a particle size at which waste glass performs comparably to ground granulated blast furnace slag and nearly as well as silica fume. At 6.6 µm, the pozzolanic reactivity of waste glass was demonstrated through consumption of Ca(OH)₂ and heat of hydration. Waste glass at a larger particle size (16.5 µm) was as reactive as slag. Use of waste glass at 10% replacement of Portland cement by mass and at a particle size below 100 µm proved useful as a SCM.</p> <p>A relationship between pozzolanic and alkali silica reaction (ASR) was identified with intermediate phases of the reaction present. Calcium silicate hydrates (C-S-H) from the pozzolanic reaction have a Ca/Si ratio of 1.5-2. ASR products generally have a Ca/Si ratio of 0.01-1. The products observed with agglomeration of glass particles had a Ca/Si ratio from 0.5-2. The affects of silica concentration and alkalinity of the solution on the reaction products were explored.</p> <p>A reaction rim was identified around glass agglomerates where fluorescence was observed. The results indicate that ASR can be induced even in low alkalinity cement, and the rate of reaction influences both the characteristics and composition of the reaction product.</p>