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Abstract: The aim of the present paper was to investigate the efficiency of polyether polyol as shrinkage-reducing admixture on pastes and mortars prepared with calcium sulfoaluminate cement (CSA). CSA was prepared by mixing CSA clinker and re-crystallized gypsum in different proportions. Three types of polyether polyol were added at a dosage of 1.5wt% of CSA when hydrating pure pastes and standard mortars. The engineering properties of mortars (compressive strength, drying shrinkage) and the microstructure of pastes were investigated. The results show that polyol reduces drying shrinkage of CSA-based mortars without affecting the nature of hydrates formed. The effect of polyol mainly depends on its molecular weight. [Copyright &y& Elsevier]

Highlights • Calcium Carbide method is a classical field technic for residual water evaluation. • Study focuses on residual water evaluation on model materials for SLU applications. • Comparison of residual water measurements techniques evidence biases. • Residual water evaluation is highly dependents of hydrates microstructure. • New evaluation techniques are proposed for material with weakly bound water. Abstract A self-leveling underlayment is a thin layer used to smooth floors and has to contain a very low level of residual water prior to covering with the final coating. Therefore, the evaluation of residual water is a key point. The aim of this study is to compare two residual water evaluation techniques: the calcium carbide method (CCM) and oven drying at 40 °C. The following model materials are investigated: silica, gypsum, plaster, and ettringite. The CCM measurements provide an effective indicator of free water for silica and gypsum. Although not a field measurement, oven drying offers a reliable and truly representative measure of the residual water, regardless of the material used. [ABSTRACT FROM AUTHOR]

Abstract: The water resistance of plaster of Paris is limited due to the high solubility of calcium sulphate hemihydrate. In order to improve this resistance, calcium sulphoaluminate clinker was added to plaster at different contents: 30, 50, and 70%. Mortars were cast using these new binders and subjected to the Soxhlet extraction test. The presence of calcium sulphoaluminate clinker considerably reduced the quantity of sulphate extracted per day and after 5days: from 78.9% to 89.1%. The analysis of microstructure showed the stability of ettringite during the leaching test and the refinement of the porosity. [Copyright &y& Elsevier]

Abstract: Phosphogypsum (calcium sulfate) is a naturally occurring part of the process of creating phosphoric acid (H3PO4), an essential component of many modern fertilizers. For every tonne of phosphoric acid made, from the reaction of phosphate rock with acid, commonly sulfuric acid, about 3t of phosphogypsum are created. There are three options for managing phosphogypsum: (i) disposal or dumping, (ii) stacking, (iii) use-in, for example, agriculture, construction, or landfill. This paper presents the valorization of two Tunisian phosphogypsums (referred as G and S) in calcium sulfoaluminate cement in the following proportions: 70% phosphogypsum–30% calcium sulfoaluminate clinker. The use of sample G leads to the production of a hydraulic binder which means that it is not destroyed when immersed in water. The binder including sample S performs very well when cured in air but is not resistant in water. Formation of massive ettringite in a rigid body leads to cracking and strength loss. [Copyright &y& Elsevier]

Abstract: Gypsum based binders are cheap but their development in the building industry is limited to inside applications due to their bad water resistance. In order to improve this resistance, calcium sulphoaluminate clinker was added to 3 types of calcium sulphate at a content of 30%. Mortars were cast using these new binders and subjected to the Soxhlet extraction test. The results obtained show that the presence of calcium sulphoaluminate clinker drastically reduces the quantity of sulphate extracted per day and after 5 days: from 78.9% to 89.1%. The microstructural analysis pointed out the stability of ettringite during the leaching test and the refinement of the porosity. [Copyright &y& Elsevier]