Air content and size distribution of air voids in hardened cement pastes using the section-analysis method

The section-analysis method was used to determine the air-void parameters of hardened cement pastes. The results are compared to those obtained using the point-count method. Five series of air-entrained cement pastes with different water-to-cement ratios were prepared. The point-count method was conducted using a stereoscopic microscope at 50x and the section-analysis method was applied by taking photographs at 80x and reproducing the surface under study. The air content, specific surface, and spacing factor were determined using the point count method. The air content and the air-void size distributions were obtained using the section-analysis method. For the size of surface area examined and for the air content tested in this study, the results show that the air contents determined using the section-analysis method are lower than the air contents determined using the point-count method by 1.4% to 34.3%. The air-void size distributions obtained using different calculation procedures compare well to each other for all series. (C) 1999 Elsevier Science Ltd. All rights reserved.