TXI process turns concrete curing inside out

Source: TXI Expanded Shale & Clay (ES&C), Dallas
Under a “Practical solution to concrete shrinkage” banner, TXI ES&C has branded an internal curing process, intraCure, for portland cement-based products designed with the company’s rotary kiln lightweight aggregate. Concrete curing has traditionally seen use of water from the outside in, TXI notes, yet the substitution of normal-weight aggregate with ES&C provides moisture for internal curing that promotes more complete hydration of various cementitious materials. Due to the surrounding environment’s inherently low permeability, internal curing is particularly beneficial in low-water-cementitious material ratio concrete—where external curing has little effect on internal portion hydration.

With an emphasis on durability, and trend to high performance concrete, TXI engineers contend, internal curing is needed to reduce both autogenous shrinkage and cracking. Regarding high performance concrete, they add, it is difficult to provide curing water from the top surface at the rate required to satisfy the ongoing chemical shrinkage, as the capillary passageways often become clogged with cement hydration products. However, ES&C typically contains between 18–25 percent water by weight; it is released from the lightweight aggregate pores as the concrete cures and replaces a portion of the original mixture water consumed by the hydration process.

Among intraCure field successes are a residential concrete mixture’s blend of aggregate—3/8 in. to No. 8 (9.5) to 2.36mm ES&C—that meets ASTM C 330 and replaces a portion of both the coarse and fine aggregates. The aggregate size enhances cementitious materials hydration and complements total aggregate grading in the concrete. TXI ES&C has lightweight aggregate production in Texas, California and Colorado.   —  www.txiesc.com