Influences of superplasticizer, polymer latexes and asphalt emulsions on the pore structure and impermeability of hardened cementitious materials

• The chemical admixtures affect the pore structure due to their plasticizing effects.
• Superplasticizer enhances the impermeability of mortar due to its plasticizing effect.
• Polymers raise the impermeability due to combined effects of filling and plasticizing.
• Filling effect is dominating the enhancement in impermeability at high P/C value.
• Mortars with latex L1 and anionic asphalt emulsion are superior in impermeability.

Three types of polymers commonly used in concrete and mortar (polycarboxylate superplasticizer, polyacrylate latexes and asphalt emulsions) which differ in molecular/particle size from nanometer to micron were employed to investigate their effects on the pore structure of hardened cement pastes and the impermeability of hardened mortars. The pore structure and the impermeability of the hardened ones cured for 7 days and 28 days were measured by mercury intrusion porosimetry and alternating current impedance, respectively. Results show the incorporation of superplasticizer obviously reduces the average pore size and enhances the impermeability. The polyacrylate latexes also lead to the decline in pore size and consequently the enhanced impermeability at dosage higher than 3%. At the same dosage, latex with smaller polymer particle size is more effective in reducing the average pore size and enhancing the impermeability than that with larger particle size due to its better plasticizing effect. Similarly, asphalt emulsions also facilitate the enhancement in impermeability, and the anionic asphalt emulsion with better plasticizing effects brings about stronger impermeability than the cationic one. It is believed that for superplasticizer, the plasticizing effect is the main controlling factor for the finer pore structure and the enhanced impermeability. In the case of polymer latexes and asphalt emulsions, the plasticizing effect contributes actively at low dosage and the filling effect is dominant at high dosage in terms of declining pore size and augmenting impermeability.