A. Allahverdi
E. Najafi Kani
M. Fazlinejhad

Abstract: The linear expansion, early-age compressive strength and setting times of the binary mixtures of gypsum and Portland cement clinkers of relatively low C۳A-contents were investigated. For this reason, type ۱, ۲, and ۵ of Portland cement-clinkers were selected and a number of binary mixtures were designed. At relatively lower percentages of gypsum (about ۵%), the early strength behavior is improved. Results obtained for compressive strength of mixtures with ۵% gypsum confirm the possibility of achieving ۲۸- and ۹۰-day compressive strengths up to values higher than ۱۰۰ MPa and ۱۳۰ MPa, respectively. At relatively higher percentages of gypsum (more than ۲۵%), excessive expansion caused by ettringite formation results in the formation of micro-cracks effectively weakening the strength behavior. The work suggests that type S expansive cements could be produced from Portland cement clinkers of relatively low C۳Acontents.

Portland cement; Gypsum; Linear expansion; Compressive strength