Physico-mechanical and microstructural properties of an eco-friendly limestone mortar modified with styrene-polyacrylic latex

Sustainable rehabilitation of stone architectural heritage and repair of cracks in concrete require the development of new compatible repair mortars. In addition, recycling industrial waste has become an attractive solution to environmental problems. In this context, the aim of this paper is to study the influence of addition of a new polymer latex (styrene-polyacrylic latex (SPA)), on the physico-mechanical properties and microstructure of limestone mortars mainly based on crushing waste as aggregate. Four SPA latex modified mortars were prepared with different mass “Polymer/Cement” ratios (P/C), 2.5%, 5%, 7.5% and 10%, and compared with ordinary limestone mortar. The tested parameters are: workability, mechanical strength, water absorption, and microstructure. The objective is to search the best composition which may be suitable for the uses mentioned above. The obtained results show that the addition of SPA latex significantly improves the workability and reduces the ‘W/C’ ratio. An increase in SPA latex dosage from 7.5% to 10% significantly increases the flexural tensile strength at 90days. However, the compressive strength is almost inversely proportional to the ‘P/C’ ratio. The XRD analysis reveals that the SPA latex increases the intensities of the cement hydrates such as ettringite. In addition, the SEM analysis shows that the structure of the modified mortars appears more compact and their hydrates are more attached, in comparison with that of the control mortar, which seems to be loose. Finally, it should be noted that 7.5% of SPA latex seems to constitute the best compromise between the studied properties. Consequently, the use of PMM7.5% as repair, finishing and rehabilitation materials for civil engineering works is very useful. •SPA latex reduces the mixing water of limestone mortar.•SPA latex delays the kinetics of hydration and reduces the amount of portlandite.•SPA latex increases its tensile strength, but decreases its compressive strength.•Optimal content of SPA improves the waterproofing of composite.•Thanks to SPA latex, the hydrates structure of the composite is denser and more connected.