Evaluation of natural rubber latex as film forming additive in cementitious mortar

•Addition of 2 wt% natural rubber latex (NRL) dispersion to mortar.•NRL produces slightly higher compressive and tensile strengths than synthetic EVA.•Deproteinized NRL shows same effect on mortar strengths as untreated NRL.•SEM images show NRL intertwines cement hydrates and bridges pore space like EVA.•Natural rubber latex can be an alternative film forming agent to industrial latex. The utilization of natural rubber latex (NRL), untreated and treated, to improve the tensile strength of cementitious mortar was studied. Two NRL samples, a commercial NRL and a laboratory–treated, deproteinized NRL sample, were compared with a commercial synthetic ethylene–vinylacetate (EVA) copolymer with respect to their particle size distribution, minimum film forming temperature (MFFT) and surface charge. Furthermore, cement mortars containing 2 wt% of the latexes were tested for their compressive and tensile strength development after 3–14 days. Both NRL samples increased tensile strength as much as the synthetic EVA latex. Thus, deproteinisation of NRL is not required.