Experimental studies on hydration–strength–durability of limestone-cement-calcined Hwangtoh clay ternary composite

Abstract

Hwangtoh clay is a type of kaolin clay, which is used as an environment-friendly material in constructions. This study presents multiple experimental studies on the hydration, strength, and durability properties of ternary or binary composites, with calcined Hwangtoh clay and limestone powder. The replacement levels of calcined Hwangtoh clay and limestone powder in the composite were in the ranges of 0%–30%, and 0%–15%, respectively. Multiple experimental studies involving compressive strength tests, isothermal calorimetry, thermogravimetric analysis, X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, electrical resistivity, and carbonation were performed. The corresponding experimental results indicated the following: 1) among all the mixtures, the ternary composite with a 15% replacement level provided the most optimal mixture, and 30% replacement level was the threshold level for achieving a similar strength as that of plain concrete; 2) for all the mixtures aged 3–270 days, there was a linear relationship between the strength and combined water; 3) for the ternary composite, the contents of hemicarboaluminate (Hc) became more evident as the amount of Hwangtoh was increased, which showed a synergic relation between the calcined clay and limestone; 4) for the ternary composite, as the replacement levels of limestone and Hwangtoh were increased, the electrical resistivity increased significantly, and so did the carbonation degree; and finally, (5) compared to strength, the combined water was a better indicator for judging the carbonation resistance of the blended concrete.