Metakaolin additions to autoclaved cement—quartz pastes: evaluation of the acid-insoluble residue

Metakaolin (MK) is an important source of reactive aluminous material which accelerates the crystallization rate 11 Å tobermorite (C₆S₅H₅) in autoclaved cement-quartz and lime-quartz based building materials. The acid-insoluble residue (AIR) provides a measure of unreacted MK when excessive additions of MK are made. This paper reports the findings of our evaluation of the AIR, for autoclaved cement-quartz pastes with MK additions of up to 30·5% and autoclaved cement-MK paste, by using a combination of analytical techniques such as X-ray fluorescence and X-ray diffraction spectrometry, scanning electron microscopy and differential thermal analysis and thermal gravimetric analysis.