Impact of anhydrite proportion in a calcium sulfoaluminate cement and Portland cement blend

Abstract

Calcium sulfoaluminate (CSA) cement and ordinary Portland cement (OPC) blends are innovative binders. In comparison with OPC, these mixtures can reduce the environmental impact of cement production as well as increase the hardening speed. This article deals with the effects of calcium sulfate (anhydrite) percentage on hydration mechanisms, compressive strength and dimensional stability of binders containing 40% OPC. Calcium sulfate quantity is an essential parameter that can be used to control the hardening speed and dimensional stability. Mortars with 6 . 5% and 10% anhydrite present moderate compressive strength and expansion, whereas higher compressive strength and expansion are obtained with blends containing 17% and 20 . 5% anhydrite. These anhydrite proportions slow down the OPC and CSA clinker hydration kinetics but increase the ettringite proportion and stability.

A critical review of the role of ettringite in binders composed of CAC–PC–C$ and CSA–PC–C$

“…The hydration mechanisms of the CSA–PC–C$ binder incorporate some aspects of the neat PC and neat CSA hydration, but not all, and also include new reactions unique to the ternary system. Figure 2 shows the chemical reactions from each component of the CSA–PC–C$ system 12,57–59 . Here, reaction pathways (routes 1, 2, 3, etc.)…”

“…Binders that rapidly hydrate to form ettringite as the major hydration product (∼24 h) are commonly referred to as ettringite‐accelerated binders. Examples of ettringite‐accelerated binders in the literature include CSA–C$ (calcium sulfoaluminate cement with calcium sulfate), CSA–PC (calcium sulfoaluminate cement blended with Portland cement), CSA–C 2 S (calcium sulfoaluminate belite), CSA–PC–C$, CAC–PC–C$, CAC–C$ (calcium aluminate cement blended with calcium sulfate), and LSG (ladle slag and gypsum) 9–13 . Among these binders, blended types of cement composed of CSA–PC–C$ and CAC–PC–C$ have shown the potential for a wide range of applications and comprise materials that are already produced commercially.…”

Synthesis and Hydration of Ye’elimite

“…In fact, ye'elimite hydration proceeds through dissolution and precipitation [142], leading to the precipitation of various hydrates. In the presence of anhydrite (calcium sulfate), ye'elimite hydrates to form ettringite as well as gibbsite (Reaction R1') [18,107,143,144]:…”

“…In the absence of calcium sulfate, the hydration of ye'elimite can lead to the formation of monosulfoaluminate and gibbsite (Reaction R2') [18,107,143,144]:…”

Factors Influencing the Hydration, Dimensional Stability, and Strength Development of the OPC-CSA-Anhydrite Ternary System

“…By contrast, there was rather less effect on dimensional stability in ternary blends. Trauchessec [40] explored the effect of different anhydrite contents on the performance of ternary binders containing fixed OPC proportions and concluded that blends with 40% OPC, 46.5% CSA, and 13.5% anhydrite had optimal properties (in terms of strength and shrinkage).…”