Effects of calcium leaching from high volume fly ash cement paste and mortar

Calcium leaching is a deterioration problem of concrete that has long been in contact with water such as dam or reservoir. This paper investigated the effects of calcium leach out on high volume fly ash mixtures of paste and mortar. The samples, composed of fly ash to cement ratio, of 100: 90 (by weight), were immersed in 6 M ammonium nitrate solution for 1-28 days. Then, the leaching depths of samples were investigated and characterized by several techniques for porosity and microstructural studies namely; scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDS), mercury intrusion porosimetry (MIP) and Vickers hardness test. The results from SEM/EDS showed that the calcium ion was leached out as high as 42% and 36% for paste and mortar, respectively. The hardness of leaching zone was reduced by 27 % for paste and 22 % for mortar. It was found that pore diameter and pore volume of both paste and mortar were significantly increased. The results indicated significant changes in porosity and microstructure. (C) 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of The 10th Thailand International Metallurgy Conference.