A ternary blended binder incorporating alum sludge to efficiently resist alkali-silica reaction of recycled glass aggregates

Abstract

Recycled glass has been widely used as aggregates in cement-based materials. However, it may lead to a severe alkali-silica reaction (ASR) due to high reactive silica content in glass, causing cracks and failures in concrete structures. Our previous research indicated that utilization of alum-based drinking water treatment sludge (DWTS) as partial cement replacement could mitigate ASR. However, such mitigation only occurred when a high volume of DWTS was used and resulted in significant mechanical property deterioration. This study developed ternary blends containing ground granulated blast furnace slag (GGBFS) and DWTS content to overcome the strength loss. Up to 30% of the cement were replaced with DWTS and GGBFS at a mass ratio of 1:1. The results showed that the mortar made with the ternary blends had considerable compressive strength (37 MPa) compared with reference (34 MPa) when 30% cement by mass was replaced, and this replacement proportion could effectively control the ASR expansion under 0.1% in samples. The microstructural analysis was conducted using X-ray diffraction (XRD) patterns, X-ray fluorescence (XRF), and backscattered electron (BSE) coupled with energy-dispersive X-ray spectroscopy (EDS) techniques. The results indicated that the Al in the DWTS could limit the precipitation of the detrimental ASR gels by promoting the generation of calcium aluminum silicate hydrate (C-A-S-H), binding alkaline and preventing ASR gels from transforming into low-flowable gels.