INTERACTION BETWEEN ACCELERATING ADMIXTURES AND PORTLAND-CEMENT FOR SHOTCRETE - THE INFLUENCE OF THE ADMIXTURES CHEMICAL BASE AND THE CORRELATION BETWEEN PASTE TESTS AND SHOTCRETE PERFORMANCE

This study analyzes the correspondence between initial and final setti ng times measured using Gillmore needles (commonly specified for shotc rete) with shooting stiffness-measured Proctor needles and compressive strength at early ages (evaluated using nondestructive penetration te sts). Two different types of accelerating admixtures (carbonate and al uminate-based) and two different types of portland cements were used i n the tests on cement paste and shotcrete. Results indicate a differen ce in performance between the different types of accelerating admixtur es tested. Also, it was found that although tests on cement paste show adequate sensitivity to accelerator type and addition rate, the corre spondence with setting lime and early strength gain in shotcrete is st ill very poor.