Low CO2 emission cements of waste glass activated by CaO and NaOH

• Published in: Journal of cleaner production 2019-12, Vol.239, p.117992, Article 117992
• Main Authors: Menchaca-Ballinas, L.E., Escalante-Garcia, J.I.
• Format: Article
• Language: English
• Subjects: Alkali-activated cement; CaO; Green cement; Low emissions; Waste glass
• ISSN: 0959-6526; 1879-1786
• DOI: 10.1016/j.jclepro.2019.117992

The recycling of Silica soda lime waste glass (WG) as a precursor of low emissions alkaline cements activated with CaO and NaOH was investigated in pastes and mortars. The experimental factors were the WG surface area, curing temperature, Na2O %wt. and %CaO wt. %, each with 3 levels using an experimental design based on orthogonal arrays. The use of CaO favored the reactivity of the WG in combination with Na2O; the CaO reduced the demand for Na2O to create an alkaline environment that promoted the dissolution of WG and provided Ca2+ for the formation of cementitious hydrated calcium silicates. The mortars showed hydraulic behavior and increasing strengths greater than 15 and 29 MPa after 28 and 180 days, respectively. The formation of the calcium silicate hydrates intermixed with silica gel was evidenced by energy dispersive spectroscopy, with reaction products of Ca/Si ratios of 0.35–0.75 for pastes, while 29Si Nuclear magnetic resonance indicated the formation of chain structures with a predominance of Q2 signals. Waste glass is an abundant promising precursor for new green cements, which creates a sustainable and simpler route to revalorize large volumes of this urban and industrial waste. •Novel cements of recycled waste glass activated with CaO and NaOH were studied.•The CaO propoted the hydraulic behavior and lowered the demand of Na2O.•29Si NMR, DRX and EDS indicated the formation of amorphous C–S–H and silica gel.•Mortars showed hydraulic nature, reached 29 MPa@180 days and had positive trends.•A clean, simple and sustainable route is proposed to revalorize waste glass.