Innovative solutions for alkalinity control in styrene acrylic latex and polyvinyl alcohol modified cement mortar

High alkalinity in cementitious systems may impair polymer stability and film formation, limiting the benefits of modification using polymers. An alkalinity-control approach for cement mortars modified with styrene acrylic latex (SAL) and polyvinyl alcohol (PVA) was investigated by targeting a fresh-mix pH of ∼11 at controlled times after mixing (0, 10 and 30 min). A reference mortar (400 kg/m3 cement) and polymer-modified mixtures with SAL solids/cement ratios of 5–20% and a fixed PVA solids/cement ratio of 2% were prepared. Mechanical performance (compressive and flexural strength, pull-off bond strength), abrasion depth and drying shrinkage were evaluated, and microstructural characteristics of the mortars were examined using scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The results showed that, compared with the corresponding mixtures without pH control, pH control implemented at mixing reduced the 28-day abrasion depth by ∼23% for mixes without PVA and by ∼11% for mixes with PVA, and reduced the 28-day drying shrinkage strain by ∼22% (without PVA) and ∼18% (with PVA).