Strength behavior and autogenous shrinkage of alkali-activated mortar made from low-calcium fly ash and calcium carbide residue mixture. (20th December 2021)

• Record Type: Journal Article
• Authors: Suttiprapa, Puntana; Tangchirapat, Weerachart; Jaturapitakkul, Chai; Rattanasak, Ubolluk; Jitsangiam, Peerapong
• Is Part Of: Construction & building materials. Volume 312(2021)
• Publication Date: 2021-12-20
• Subjects: Alkali-activated mortar -- Autogenous shrinkage -- Calcium carbide residue -- Compressive strength -- Low-calcium fly ash; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2021.125438
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: CR was used as CaO source to produce low-CaO FA-based AAM cured at ambient temperature. Effects of NaOH and ratios of FA to CR on strength and shrinkage of AAM were investigated. Shrinkage of AAM increased with the increased NaOH and decreased with the increased CR. AAM made from FA-CR and cured at ambient temperature had compressive strengths up to 60.2 MPa. Reaction products C–S–H, C–A–S–H, and N–A–S–H were detected by XRD analysis. Abstract: In this study, the effects of sodium hydroxide (NaOH) concentrations, ratios of low-calcium fly ash (FA) to calcium carbide residue (CR), and adding 5% of Portland cement on compressive strength and autogenous shrinkage of alkali-activated mortar made from FA-CR mixtures were investigated and verified by examining the microstructure and morphology of alkali-activated paste. Both FA and CR were improved by grinding a finer powder. The alkali activators were a NaOH solution and a liquid sodium silicate at a constant ratio of 2:1. The results indicated that the utilization of CR partially substituted in FA and activated with a higher NaOH concentration significantly improved the compressive strength of alkali-activated mortars. The autogenous shrinkage of alkali-activated mortars increased with the increased NaOH concentration and decreased significantly when the CR partially replaced in FA. An alkali-activated mortar made from an FA-CR mixture (without cement) achieved compressive strengths up to 60.2 MPa and had an autogenous shrinkage of less than 100 × 10 −6 mm/mm. Moreover, the XRD patterns of alkali-activated pastes showed that the reaction products of C–S–H, C–A–S–H, and N–A–S–H were related to the dense structure and the Si, Al, Ca, and Na detected in SEM/EDS results.