In the present paper different external surface treatments published in the literature as preventive solutions for improving the performance of existing concrete constructions are presented and discussed. They are categorized as repair materials for concrete conservation, protection surface methods against moisture and aggressive agent penetration, injection techniques for crack sealing and preventive repair solutions with smart functionalities. In a final section, the most extended testing methods for evaluating the effectiveness of the different repair solutions are summarized depending on the property to be enhanced: moisture control and resistance against penetration of aggressive agents. The review shows that although several possibilities exist for the repair of the existing constructions, there is a lack of comparative analysis between the different methodologies. SARCOS COST Action CA15202 stablishes as scientific objectives to carry out comparative studies including the most advanced solutions for the external repair of concrete, giving criteria for effectiveness assessment and defining robust and reliable methods for charactering the performance of the repaired structures.@en

The ability of Superabsorbent Polymers (SAP) to block water flow along cracks in cement-based materials has become an attractive feature of these admixtures. The diminution of fl w rates in such composites are attributed to the capacity of the SAPs to absorb water and swell in the crack, but no evidence exists in literature that indicates one or the other cause. On the other hand, the SAPs present in the bulk matrix might act as distributed sinks through which water is absorbed (water that otherwise would have continued its path into the matrix). In this paper a preliminary effort is made to numerically model the effect of SAPs on the water absorption by mortar. A lattice-type model is proposed to predict both the bulk water absorption and the resulting penetration depth of water into the cementitious matrix. The results of the simulations point out the mechanisms of water absorption in mortar containing SAPs.@en