Effect of under water storage on bridge formation by water-soluble polymers in cement mortars

Polymer film formation in cement mortars modified with small amounts of water-soluble polymers (1% of the cement mass) is studied. A major contribution of the polymer films to the mechanical strength is found. Polymer bridges are detected between the layered Ca(OH)(2) crystals, on top of the cement hydrates at the air void surfaces and intermingled with the cement hydrates. Because water-soluble polymer films are highly sensitive to moisture and water, the effect of under water storage on the bridge formation is important towards the practical applications. A serious decrease of the flexural and splitting tensile strength is observed during intensive storage at high relative humidity or under water. The polymer bridges are leached under water and deposed in free spaces of the cement matrix upon subsequent drying. (C) 2009 Elsevier Ltd. All rights reserved.