Potential expansion of cement mortars in the presence of K2SO4 and pozzolan

• Published in: Cement and concrete research Vol. 24; no. 4; pp. 728 - 734
• Main Authors: LUXAN, M. P, FRIAS, M, DORREGO, F
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Science 1994
• Subjects: Applied sciences; Buildings. Public works; Concretes. Mortars. Grouts; Exact sciences and technology; General (composition, classification, performance, standards, patents, etc.); Materials; Cement mortar; Material composition; Pozzolana; Hydration; Sodium Carbonates; Potassium Sulfates; Properties of materials; Experimental study; Portland cement; Expansion
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/0008-8846(94)90198-8

Hydration of cements is a very complex process, and the presence of alkalis influences the hydration reactions, thereby modifying its properties. The effect of incorporating Na2CO3 and K2SO4 on Portland cement expansion was studied. Potential expansion tests were carried out according to ASTM C452. It was found that incorporation of alkali salts (1 and 2% Na2CO3; 1, 2 and 3% K2SO4) reduces the expansion of Portland cement mortars, mainly when the C3A content is low. The amount of added alkali salts has an optimum value for each Portland cement. The expansion remains stable for samples cured at 40 C instead of 23 C after 28 days. The presence of a natural pozzolan reduces the alkali effect in the potential expansion test, due to their retention by the solid phase. Incorporation of K2SO4 generally decreased compressive strength development, both at early and late ages. 10 refs.