Both shrinkage reducing admixtures (SRA) and expansive admixture (EXP) can be used to reduce the risk of cracking in concrete. Synergistic effect of using both of those admixtures simultaneously was a was found, however little information can be found on the effects of using both EXP and SRA on the properties of mortars and concrete other than shrinkage. Therefore in this paper, effect of adding both EXP and SRA on properties of mortars outside of their effect on shrinkage is researched. Mortars with Portland cement CEM I were modified by adding EXP and SRA in amount of full dose recommended by the producer, and half of the recommended dose. Research consisted of tests of properties of fresh mortars (consistency, initial setting time, hydration heat) and hardened mortars (compressive strength and drying shrinkage). It has been found that using both SRA and EXP admixtures leads to maintaining the same setting time which can be prolonged if only SRA is used, decreased compressive strength, possibility of increased consistency. Synergistic effect on shrinkage was also confirmed.

Calcium Sulfoaluminate cements (CSA) may be an alternative to Portland cements due to their very high early strength and more environmentally friendly production technology, however they are characterized by a short setting time and high cost. A possible solution to these problems is to mix CSA cement with other binders or additives. In order to test this possibility, CSA cement was mixed with Portland cement and limestone in the amount of 10, 20 and 30 wt. %. A hydration heat test was carried out in the first 72 hours after the components were mixed, measured were compressive and flexural strength after 1, 2, 7 and 28 days, and rheological properties, including early shrinkage. A negative interaction between CSA and CEM I 42.5R was observed, leading to deterioration of mechanical properties of the mortars. The study did not indicate a similar negative interaction between CSA cement and limestone.