Early-Age Shrinkage of Ordinary Concrete and a Strain-Hardening Cement-Based Composite (SHCC) in the Conditions of Hot Weather Casting

摘要

The early-age shrinkage of concrete has a pronounced influence on the performance of the material during the whole service life. The casting of concrete in hot climatic conditions, which are harsh for early-age concrete, often lead to cracking which subsequently has an negative impact on various properties of the structural element, especially on its durability. The article at hand provides some additional insights on plastic and early-age shrinkage of two very different types of concrete: an ordinary concrete and a relatively new type of fiber-reinforced concrete - a strain-hardening cement-based composite (SHCC). These materials were produced and tested both without and with addition of a superabsorbent polymer (SAP), which was used as an internal curing agent for mitigating early-age shrinkage. Three climatic parameters were varied in a certain range: temperature of the surrounding air, its relative humidity and the wind velocity. The addition of SAP clearly reduces the capillary pressure within fresh concrete, which indicates the efficiency of its action as internal curing agent. The SHCC is able to successfully withstand the early-age shrinkage in the hot climatic conditions under investigation. In contrary, in the most cases a major crack developed in the ordinary through the entire height of the specimen and separated it in two parts.