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Primary factors affecting the performance of ground glass used as a pozzolan in portland cement concrete include chemical composition, particle size distribution, and replacement level. Eighteen different waste glass streams from across the United States were analyzed for composition and ground to a consistent size distribution. The compressive strength of mortar cubes made with 20 and 30% glass replacement by mass was measured over 6 months. The flexural capacity of conventional reinforced concrete beams was measured with 0, 10, 20, and 30% soda-lime glass replacement. Compressive strength variation was observed between the different types of glasses tested; however, only a subtle correlation between elemental chemical composition and compressive strength was detected. Few mixtures containing glass surpassed the control mixture (0% glass) compressive strength, and most mixtures containing 20% glass reached higher compressive strengths than those with 30%. The beams with 30% replacement had similarflexural capacity compared to the control mixture.
Keywords: beams; composition; compressive strength; cubes; flexural capacity; ground glass; mortars; pozzolan; reinforced concrete.
INTRODUCTION
The use of pozzolans in portland cement concrete is a beneficial practice due mainly to the decreased permeability and increased long-term strength that comes from the pozzolanic conversion of calcium hydroxide to calcium silicate hydrate (C-S-H). In addition, replacing a portion of portland cement with a pozzolan typically reduces the carbon footprint of the mixture1-3 and provides strong markets for many waste materials and industrial by-products. For these reasons, as well as others, traditional pozzolans such as fly ash and silica fume are in high demand. Recent concern over the long-term availability of these valuable materials, however, has led researchers to investigate the feasibility of using other nontraditional materials as pozzolans. Ground glass possesses a high amorphous silica content and is available nearly everywhere in the world, making it a promising alternative supplementary cementitious material.4
Approximately 90% of the glass produced in the United States is soda-lime glass,5 which can be broken down into container glass (bottles and jars) and plate glass (flat or plate). Other types of glass are produced for specific applications and include vitreous silica glasses, borosilicate glasses, glass fibers (including E-glass), aluminosilicate glasses, television tube glasses, glass-ceramics, and other specialty glasses.6-8 The composition of any given glass is dictated by its application and requirements in...