Effect of partial replacement of the cement by glass waste on cementitious pastes

Utilization of ground glass waste as supplementary cementitious material can be environmentally and sometimes economically advantageous as it converts large amounts of waste materials into value-added products and reduces the need for transportation by providing a local material resource. The research reported here aimed at developing a sustainable cementitious paste by using ground glass waste to replace Portland cement. For this, the glass waste was ground in a ball mill in different grinding times, 6 h, 24 h, and 48 h. The ground glass waste was then used to replace different proportions, 10 and 20 wt% of the cement, in pastes with water to binder ratio of 0.33. The effect of ground-glass residues on the fresh and hardened state properties were investigated In the fresh state, in general, the glass incorporation resulted in enhancement of entrapped air (from 0.8% in REF to 2.4% in 24 h-10% series) and lower cement consumption (from 1527 in REF to 1232 kg/m3 in 48 h-20%). In hydration kinetics, the glass waste improved the cement efficiency in terms that the waste added-series presented higher heat of hydration (from 4.49 in REF to 5.77 mW/g of cement in 48 h-20%). Also, for later ages, was possible to note by thermogravimetry that the waste added-series presented lower portlandite (Ca(OH)2) amount in comparison with reference (in 90 days from 3.14 to 2.11% in 48 h-20%), indicating the pozzolanic reaction of the glass waste. In a hardened state, the cement replacement by glass waste did not improve the mechanical strength. However, the binder index (associated with cement efficiency) was considerably lower than the reference (on average the binder index of the glass waste added-samples were 6.5, 10.6, and 8.5% at 7, 28, and 90 days, respectively, lower), indicating a higher efficiency cement replacement. (C) 2020 Elsevier Ltd. All rights reserved.