Performance of fly ash-based geopolymer mortars with waste cathode ray tubes glass fine aggregate: A comparative study with cement mortars

Abstract

Utilization of waste cathode ray tubes (CRT) glass as aggregates in the production of ordinary Portland cement (PC) concretes is a sustainable recycling method. However, the high potential of alkali-silica reaction (ASR) degradation puts a limit on the recycling rate of CRT glass. Accelerated mortar bar ASTM C1260 test was employed in this study to differentiate the performance of PC and fly ash-based geopolymer mortars with CRT glass fine aggregate. The results showed that sharp ASR expansion occurred in the PC mortars resulted in great damage to the structure integrity, and consequently a distinct compressive strength loss from 45.1 MPa to 20.6 MPa over time of curing up to 28 days. In comparison, the geopolymer mortars were less susceptible to the ASR degradation, which even exhibited slight shrinkage (−0.057%) at the tested age of 14 days. Due to the deficiency of calcium in the matrix, more flowable ASR gel was formed in the mortar without causing destructive expansion. The lead (Pb) leaching and radiation shielding properties of geopolymer mortars were also tested. The compact pore structure was helpful in restricting the Pb leaching from the CRT glass. The Pb immobilized in mortars effectively enhanced the capacity of radiation shielding. This highlights the potential applications of geopolymer mortars in various radiation shielding constructions.