Influence of micro- and nanoclays on fresh state of concrete

The processing of cement and concrete in its fresh state has become a crucial part of today's construction industry. Concretes such as selfconsolidating concrete, shotcrete, and extruded cement-based materials have found wide application in the national infrastructure. These engineered materials rely on their rheology during the first few hours after casting to achieve superior performance. This paper discusses the use of micro- and nanoclays to tailor the balance between a concrete's ability to consolidate under minimal energy before processing and to achieve shape stability afterwards. A concrete has been developed for use in slipform paving to mitigate durability issues resulting from improper consolidation. This concrete, termed "slipform self-consolidating concrete," is one that consolidates under minimal energy yet retains shape stability after slipforming, thus eliminating internal vibration and associated durability problems. The finished product is a pavement with smooth surfaces and straight edges without the use of formwork. In this investigation, a multiscale approach is used to demonstrate the effects of micro- and nanoclays on the cement microstructure, the concrete's early-age strength properties, and the slipform processing itself. Results show a clear relationship between all levels of analysis, and specifically they show how clays can increase shape stability with only a minimal loss in flowability.