Hardening process of cement-based materials monitored by the instrumented penetration test Part 1: Neat cement paste and mortar

摘要

Little fundamental understanding of hardening of cement-based materials can be derived from the standard tests, such as the Vicat needle (ASTM C191-82) and penetration resistance (ASTM 403) tests. A new instrumented penetration test has been developed which continuously monitors the hardness development during early hydration and enables greater understanding of details of the hardening process. The test was designed to measure hardening in situ under ambient temperature or during microwave heating. Descriptive models of the hardening response to selected processing variables for paste as well as mortar were established using statistical experimental designs. The water/cement (w/c) ratio and temperature significantly influenced hardening, while the effect of the amount of sand on hardening was negligible. Several interactions among processing variables were observed to affect hardening. Rheological as well as chemical effects were observed.