Enhancement of early engineering characteristics of modified slag cement paste with alkali silicate and sulfate

• Published in: Construction & building materials 2020-01, Vol.230, p.117013, Article 117013
• Main Authors: Nguyen, Hoang-Anh, Chang, Ta-Peng, Thymotie, Anne
• Format: Article
• Language: English
• Subjects: Commercial chemical agents; Engineering performance; Hydration products; Slag cement
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2019.117013

•Commercial chemical agents enhanced early performance of slag cement binder.•Commercial water glass induced slag cement with reduced strengths.•Commercial sulfate remarkably improved setting times and strengths of slag cement. The current study aims at exploring existing problems of a supplementary cementitious material with slag cement mixture, and distinguishing benefits of using different commercial chemical agents to improve the performance of the binder. Experimental results showed that although slag replacement led to fresh pastes with improved workability and lowered hydration heat liberation, it generally caused impacts of delayed setting times and reduced early compressive strengths of the binder. The sulfate activator of Na2SO4 was more suitable than the sodium silicate solution to enhance the performance of sulfate modified slag cement binder, e.g., to reduce its setting times and increase the early strengths. On the other hand, CaSO4·2H2O could be preferable to prolong heat liberation during hydration. At the very early age, the additions of CaSO4·2H2O and Na2SO4 only changed hydration products of the sulfate modified pastes because of the precipitated secondary gypsum and hydrotalcite, respectively.