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Abstract: The effect of different quantities of admixed superabsorbent polymers (SAP) on durability and strength properties of normal strength mortars containing various binary cement blends was investigated. Addition of SAP did not significantly affect compressive strength, although a slight retardation of strength development was observed in mortars with higher w/b ratio. Tensile strength values were generally slightly improved with the use of SAP. Durability was assessed by measuring porosity, oxygen permeability, chloride conductivity, accelerated carbonation, and bulk diffusion. The generally improved durability properties, especially for mortars containing silica fume, indicates the potential to use SAP to design high quality concrete repair mortars. [Copyright &y& Elsevier]

Abstract: The use of superabsorbent polymers (SAP) was found to significantly improve cracking characteristics of normal strength bonded mortar overlays containing silica fume. Mortars were designed with two water/binder ratios and three different SAP contents and tested for relevant material properties such as tensile strength, tensile relaxation, elastic modulus and drying shrinkage. With respect to overlay cracking, SAP addition generally resulted in an improvement in all tested properties, especially with respect to increasing relaxation and reduced elastic modulus. To observe cracking in real bonded overlays, mortars were cast on a rigid substrate and their cracking behavior observed for a period of approximately 7weeks. The results indicate that SAP additions of 0.4% and 0.6% are very effective in reducing cracking in bonded mortar overlays with water/binder ratios of 0.45 and 0.55, respectively. [Copyright &y& Elsevier]

Abstract: Restraint of shrinkage deformations is the main factor influencing the serviceability and durability of bonded concrete overlays. Failure mechanisms associated with differential shrinkage stresses are cracking and debonding. Tensile overlay relaxation may release a considerable amount of the imposed stresses and is therefore of major importance for the performance of the overlay. Composite specimens were used for the identification of fundamental characteristics of strain development of bonded concrete overlays, with regard to different interface textures and overlay materials. The development of overlay strains and material parameters in relation to the observed mechanisms of overlay failure allowed an estimation of the magnitude of tensile relaxation. A simplified approach to tensile stress relaxation in bonded overlays is introduced. [Copyright &y& Elsevier]