Nondestructive Evaluation for Hydration and Setting Time of Gypsum Modified Calcium Sulfoaluminate Cement Paste.

Calcium sulfoaluminate (CSA) cement is a promising solution for reducing CO emissions. While previous studies have attempted to investigate the usefulness of CSA cement via various approaches, early age nondestructive evaluations for the setting and hydration of CSA cement mixtures have not been reported. In this study, we measured the ultrasonic pulse velocity and electrical resistivity of early age CSA cement paste.

CO Curing Efficiency for Cement Paste and Mortars Produced by a Low Water-to-Cement Ratio.

Curing by CO is a way to utilize CO to reduce greenhouse gas emissions. Placing early-age cement paste in a CO chamber or pressure vessel accelerates its strength development. Cement carbonation is attributed to the quickened strength development, and CO uptake can be quantitatively evaluated by measuring CO gas pressure loss in the pressure vessel.

Alkali-Activated Slag Paste with Different Mixing Water: A Comparison Study of Early-Age Paste Using Electrical Resistivity.

This paper reports the electrical resistivity measurements on KOH-activated ground-granulated blast-furnace slag, which was mixed with deionized water or natural seawater at three different activator-to-binder ratios (0.4, 0.45, and 0.

Effects of CO Curing on Alkali-Activated Slag Paste Cured in Different Curing Conditions.

The effect of CO curing on alkali-activated slag paste activated by a mixture of sodium hydroxide and sodium silicate solutions is reported in this paper. The paste samples after demolding were cured in three different curing environments as follows: (1) environmental chamber maintained at 85% relative humidity (RH) and 25 °C; (2) 3-bar CO pressure vessel; and (3) CO chamber maintained at 20% CO concentration, 70% RH and 25 °C. The hardened samples were then subjected to compressive strength measurement, X-ray diffraction analysis, and thermogravimetry.

Properties of Alkali-Activated Slag Paste Using New Colloidal Nano-Silica Mixing Method.

Previous studies of alkali-activated slag cement (AASC) using nano-silica have mentioned mostly powdered nano-silica and binder weight replacement methods, which have a rapid decrease in fluidity, a short setting time and a low nano-silica replacement rate (< 5%). In this study, colloidal nano-silica (CNS) was used and the mixing-water weight substitution method was applied. The substitution method was newly applied to improve the dispersibility of nano-silica and to increase the substitution rate.

Phase Changes of Monosulfoaluminate in NaCl Aqueous Solution.

Monosulfoaluminate (Ca₄Al₂(SO₄)(OH)∙6H₂O) plays an important role in anion binding in Portland cement by exchanging its original interlayer ions (SO₄ and OH) with chloride ions. In this study, scanning transmission X-ray microscope (STXM), X-ray absorption near edge structure (XANES) spectroscopy, and X-ray diffraction (XRD) were used to investigate the phase change of monosulfoaluminate due to its interaction with chloride ions. Pure monosulfoaluminate was synthesized and its powder samples were suspended in 0, 0.