Synergetic effect of MEA and SAP on the deformation and mechanical properties of concrete

This paper presents an experimental investigation on the synergetic effect of magnesium oxide expansion additive (MEA) and superabsorbent polymer (SAP) on the long-term drying shrinkage, autogenous shrinkage, internal humidity and mechanical strength of concrete. Concrete with varying dosages of MEA (0, 4, 6, 8 and 10%) and SAP dosage (0, 0·2, 0·4 and 0·8%) was studied to assess the synergetic effect of MEA and SAP on concrete. The results revealed that the long-term drying shrinkage of concrete could be effectively inhibited by a hybrid system based on SAP and MEA addition. SAP had a significant effect on maintaining the internal relative humidity of concrete. The hybrid system of 0·4% SAP and 6% MEA not only eliminated autogenous shrinkage but also controlled the deformation of expansion to a minimum. The addition of SAP and MEA generally resulted in a reduction in the cube strength of concrete. Scanning electron microscopy and stereomicroscopy results showed that larger voids were formed by desorbed SAP, which had a negative effect on the cube strength of concrete.