Properties of fly ash-based lightweight geopolymer concrete prepared using pumice and expanded perlite as aggregates

Abstract

Abstract The present paper aims to utilize the fly ash wastes with lightweight aggregates for geopolymer concrete production process in which sodium hydroxide (NaOH) and sodium metasilicate (Na2SiO3) were used as alkali activators, respectively. The designed experiments were examined by the Yates Analyses and so the productions of geopolymer concrete were investigated depending on curing temperature, solid/liquid rate and concentration of alkali activators. The curing temperature and alkali activator concentration were revealed as effective parameters in geopolymerization. The effects of expanded perlite (EP) and acidic pumice (AP) aggregates were discovered for the production of lightweight geopolymer concretes. The microstructural properties of each produced geopolymer concrete were characterized using SEM, EDS and laser particle size analyses. The specifications of the concrete were evaluated based on their uniaxial compressive strength (UCS), point load strength (PLS), sonic speed (SS), Mohs hardness (MH), and water absorption (WAR) ratio results. In addition, the effects of pre-wetting of EP aggregates, which have hydrophilic nature, were examined. To the best of our knowledge, this is the first time that pre-wetted lightweight EP aggregates were used to produce lightweight GP concretes. As a result of pre-wetting, chemical usage decreased by 32.5%. The UCSs of the lightweight geopolymer concretes were in a range of 10–50 MPa and their unit weights changed between 1250 and 1700 kg/m3. Lighter concretes were obtained by the addition of EP aggregates rather than AP ones.