Size Effect on Compressive Strength of Alkali-activated Slag/Fly Ash-based Concrete

In order to analyze the size effect of alkali-activated recycled aggregate concrete（AARAC）, a total of 72 AARAC cubes with four specimen sizes of 70.7 mm, 100 mm, 150 mm and 200 mm were tested to obtain the compressive strength. The effect of recycled aggregate（RA） substitute rate on the compressive strength and its size effect was analyzed. The results show that the compressive strength of AARAC decreases with increasing RA substitute rates due to the increased amount of defects, with the decreasing amplitudes of about 4.0%～30.4%, except that their size effect becomes more apparent. Based on Bazant′s size effect law（SEL）, analytical model for SEL of compressive strength of AARAC was established, and the critical size and critical strength of AARAC were further proposed. Finally, conversion factors were suggested for the transformation of the compressive strength measurements of AARAC.