Analysis of the durability of high strength concrete with superabsorvent polymer

The High Strength Concretes (HSC) provided significant advances in civil construction, due its superior strength, efficiency and durability. Due to the high content of cement, low water/cement ratio and mineral additions, it is essential to avoid the emergence of tensile stresses generated autogenous shrinkage and consequently the cracking of structural elements and, therefore, losses in the durability. One strategy to mitigate autogenous shrinkage of HSC is the use of superabsorbent polymers (SAP) as internal curing agent. However, the use of SAP increases the porosity, leaving unconnected voids in the hardened material, which can reduce the durability of it. This research aims to analyse the influence of the addition of superabsorbent polymer on the durability of Portland cement microconcrete. In order to compare the influence of the use of shrinkage mitigation agents in durability, the experimental program consists of two mixtures of high strength microconcretes with water/cement ratio equal to 0.35: one used as reference and another one containing 0.3% of SAP. The behaviour of concrete in the hardened state was evaluated by performing the tests: resistance to simple axial compression, modulus of elasticity, migration of chloride ions and absorption by capillarity. It was verified that the dense microstructure, characteristic of HSC, was preserved even in the presence of pores created by the SAP desorption process, because they are larger and disconnected instead of smaller and continuous pores. In conclusion, the SAP is a promising strategy to mitigate autogenous shrinkage, with a low prejudice to the mechanical properties and even improving the durability