Mechanical behaviour of polymer modified mortars

We investigate the mechanical behaviour of a mortar and five polymer (latex styrene–butadiene) modified mortars (PMMs) with different polymer contents. The mechanical characterisation of the materials is based on compression and three-point bending tests. As expected, compression tests reveal a decrease of the PMMs rigidity and compressive strength for increasing polymer content. On the contrary, three-point bending tests show an increase of the flexural strength from a polymer-to-cement weight ratio higher or equal to 10 wt.%. After some considerations on material porosity and cement hydration, we establish that the main cause of the PMMs flexural strength increase is the latex percolation into a continuous network. Finally, analysis on damage initiation and material rigidity seems to indicate that latex addition limits skin and inner material micro-cracking due to sample drying out.