The effect of latex on macrodefect-free cement

The effect of adding latex to macrodefect-free cement was studied. The porosity of the modified pastes was smaller than the normal macrodefect system but the pore size was not significantly changed. The traditional relationship between strength and flaw size in the cement system was found to be inadequate to explain the observed mechanical behaviour of the latex-modified systems. Scanning electron microscopy of the fracture surfaces of the normal and latex-modified pastes revealed that the use of different polymers resulted in different fracture paths through the cement composite. This was due to the difference in chemical nature of the polymer. The results demonstrated that the modulus (E) and fracture energy (R) terms in the traditional Griffith equation become limiting factors for strength determination in low-porosity cement systems.