Abstract: Portland Cement-based concretes and mortars exhibit significant reduction in shrinkage cracking when combined with Magnesium Oxide (MgO), Shrinkage Reduction Admixtures (SRA) and Super Absorbent Polymers (SAP). However, MgO is a solid that reacts with water, SRA is a liquid, and SAP if not added properly could pull water out of the system and thus increase shrinkage. Unique admixture blends used as supplementary cementing materials that do not significantly affect concrete or cement strength properties of Portland cement itself address such issues. Proper ratios of MgO, SRA and/or SAP perform better against crack reduction when compared to commonly used Expansive Cements (EC).

Abstract: A high early strength admixture for precast hydraulic cement comprises a calcium salt and a copolymer having a carbon-containing backbone to which are attached cement-anchoring members, such as carboxyl groups, and to which are also attached oxyalkylene pendant groups by linkages selected from the group consisting of amide and imide members. The copolymers used are preferably formed by reacting an acrylic polymer with ammonia or an alkoxylated amine. The calcium salt, preferably calcium nitrite, and the copolymer can be added simultaneously as one admixture, or separately. The invention relates also to methods for enhancing high early strength in concrete, cement, masonry, and mortar mixtures generally, and to precast concrete particarly, and also pertains to such hydraulic mixtures containing the calcium salt and copolymer.

Abstract: A cement admixture composed of a mixture of lower alkyl ether oxyalkylene adducts with a sulfonated organocyclic material to provide cement compositions of mortar and concrete which inhibit drying shrinkage while attaining very high slump and/or increased compressive strength.