An experimental study of cementing paste backfill

[Truncated abstract] This thesis focuses on experimental element testing of cementing paste backfill (CPB) to examine and improve on existing laboratory testing techniques. Specifically, the work focuses on developing a framework to account for differences in curing conditions between in situ and laboratory environments, given the recognised improvement in mechanical properties of in situ cured CPB. This has been explored within the effective stress framework by making use of a hydration cell testing apparatus.

The existing hydration cell set-up was modified to allow control over the rate of temperature increase and final temperature of specimens during curing, to replicate in situ curing conditions. The combination of elevated curing temperature and effective stress generation was found to significantly increase the mechanical properties of CPB compared with curing at elevated effective stress and ambient temperatures.

The current procedure for curing under effective stress can be expensive and time consuming. As such, the standard test method for chemical shrinkage of hydraulic cement paste (ASTM C1608-07) was investigated as a potential index/screening test for use in the design of CPB mixes through comparison of the chemical shrinkage-induced strain generated in both the ASTM and hydration cell tests. The appropriate use of this ASTM standard with CPB was validated despite the high w/c ratio of typical CPB mixes.