Role of cement alkali content in acid attack: A pore-solution and pore-size-distribution study

The behavior of hydrated portland cement pastes in an acid-buffered solutio n of acetic acid/sodium acetate (HAc/NaAc) (pH 4.5) during a period of 90 d ays at a temperature of 21 degrees C has been studied. The changes that wer e caused by the acid ingress were monitored via analysis of the extracted p ore solution. The evolution of the porosity and pore-size-distribution chan ges were evaluated by using intrusion mercury porosimetry, and those of cry stalline compounds were evaluated by using X-ray diffractometry. A similar study was conducted with an equivalent series of samples that were immersed in distilled water. The results showed the important role that cement alka li content (1.03 % K2O, 0.2% Na2O) has in the mechanism of the acid attack, Interesting correlations were established between pore-solution and porosi ty data.