The effects of waste glass aggregate on the strength and durability of Portland Cement Concrete

Abstract

Waste glass has been heavily targeted for recycling efforts by various municipalities. Not all waste glass can be recycled into new glass, however, and alternative methods must be found for utilization of this waste glass; one possible use for this glass is as aggregate in portland cement concrete. An experimental research program was conducted to identlfy characteristics of waste glass that produce satisfactory concrete for pavement applications, to document the alkah-silica reactivity (ASR) of waste glass aggregate and determine means of mitigating this ASR, and to determine the effects of waste glass aggregate and powdered waste glass on the strength and durability of concrete. The performance of waste glass/fly ash concrete was evaluated, and experimental work conducted by the author, results of others at the University of Wisconsin, and other researchers' pubhhed results were used to synthesize conclusions about the processes and mecbms of ASR and strength development in waste glass/fly ash concrete. The research was conducted in several distinct phases: a study of the interaction of coarse and fine glass with fly ash and their effect on strength and durability, a field trial to study several of the most promising mixes under field conditions, a laboratory test of the possible use of finely ground glass as a cement supplement, and a series of accelerated ASR expansion mortar bar tests. Evaluation of the experimental mixes included consideration of compressive strength, fr-eezdthaw resistance, and resistance to ASR deterioration at ages fiom one month to three years. Some study of the interactions between the experimental materials and air-entraining admixtures, water-reducing admixtures, fly ash and fine powdered waste glass was included to aid application of the conclusions to pavement trials. It w& determined that the effects of glass aggregate on strength may be divided into three separate effects: (1) water demand of glass aggregate; (2) interaction with strength developmnt by fly ash;and (3) intrinsic effects of glass aggregate, including particle strength and paste-aggregate. bond. The combined effect may range between an 80% loss in strength and a slight (=I% - 5%) gain in strength as compared to the control, dependmg on the form and gradation of the glass and the type of cemnt used. Freeze-thaw durability was found to be promising; ASR is demonstrated, mitigation can be provided by judicious use of fly ash.