Strength, Microhardness, and Modulus of Elasticity

Early strength development of Jet Set mortars is generally obtained (up to 15 MPa) within six hours. The strength-time curves for mortars (Fig. 12) indicate slow strength gain between six hours and one day followed by a second period of rapid strength development. 

The curing of Reg Set in air results in low strengths because the large amounts of heat created in the reaction result in the drying out ofthe material, which slows down the hydration reaction. 

The compressive strengths for Reg Set cement during the first 24 hours are higher than those for ultra-rapid hardening portland cement. The strength characteristics of the cements are similar beyond 24 hours. 

Reg Set cement mortar with a citric acid retarder has greater strength than Reg Set cement regulated with calcium sulfate hemihydrate. The increased strength in Reg Set cement paste or mortar made with the addition of citric acid is usually a result of an increased degree of hydration, increased amount of ettringite, increased volume concentration of small pores, and lower total porosity. 

Calcium lignosulfonate or calcium chloride can be used as alternatives to calcium sulfate hemihydrate in order to control the setting time of Reg Set cement. Calcium lignosulfonate (2.2 ml/kg) increases the compressive strength of Reg Set cement paste by approximately 70% at 14 days. Also, 

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