Extraction of Ca(OH)₂ from portland cement and 3CaO.SiO₂ pastes

Abstract

Abstract A procedure for extracting free lime from mature pastes of Portland cement and tricalcium silicate is described. It involves exposure of thin discs of paste to an aqueous solution of Ca(OH) 2 in such a way that the concentration of the solution remains in the range 9.5–12 mmol CaO dm −3 throughout the extraction period. Calcium hydroxide remaining in the solid is estimated by differential scanning calorimetry and that in the extractant is estimated by atomic absorption spectrophotometry. Investigations of the extracted samples by scanning electron microscope, helium pycnometry, X‐ray diffraction, mercury porosimetry and thermogravimetry indicate that the extraction procedure has no significant influence on the C‐S‐H phase.