Effect of calcium sulfoaluminate and MgO expansive agent on the mechanical strength and crack resistance of concrete

Abstract This work explored effects of calcium sulfoaluminate (CSA) and MgO blended expansive agent on the mechanical strength and deformation of concrete. What’s more, the mechanism was investigated using SEM and XRD analysis. Results show that the addition of MgO is beneficial to improve the later strength of concrete. When the MgO content exceeds 2%, the mechanical strength of concrete at the later stage increases significantly; however, it begins to reduce when the MgO content is more than 5%. All results illustrate that the optimum mass ratio of CSA and MgO is 2:1, and the concrete shows a certain expansion at all stages, which also reduces the drying shrinkage at the later stage. Meanwhile, with the optimum mass ratio of CSA and MgO, the crack resistance of concrete can be improved by 97–127 % compared with a single expansive agent.