Hydration and Microstructure of Cement Pastes with Calcined Hwangtoh Clay

Abstract

Calcined Hwangtoh (HT) clay is a very promising supplementary cementitious material (SCM). In this work, the development of the mechanical properties and microstructures of HT-blended cement paste was studied after substituting the binder with HT powder calcined at 800 °C. The water-to-binder (w/b) ratios of the paste used were 0.2 and 0.5, and the quantities of HT powder added to the mixture were 0, 10, and 20%. The compressive strength test indicates that the addition of the HT powder increases the compressive strength of the paste after seven days of curing, and the highest compressive strength is obtained with the 10% HT substitution, regardless of whether the w/b ratio is 0.5 or 0.2. X-ray fluorescence (XRF), X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), isothermal calorimetry, thermogravimetric analysis (TGA), and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) analysis show that the HT powder not only has a physical effect (i.e., nucleation effect and dilution effect) on cement hydration but also has a chemical effect (i.e., chemical reaction of HT). The results of scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) analysis show that the paste has more ettringite during the early stage, and the microstructure is refined after the addition of the HT powder. In addition, the relationships between chemically bound water, hydration heat, and compressive strength are presented.

Effect of Pre-Wetted Zeolite Sands on the Autogenous Shrinkage and Strength of Ultra-High-Performance Concrete

“…The sample surface area and thickness was large enough to avoid beam overflow and sample transparency aberrations [36]. XRD was carried out using a Panalytical X'pert-pro MPD diffractometer (Panalytical, Almelo, The Netherlands), with CuKα radiation (λ = 1.5404 Å) [37]. The measurements were conducted in the 2θ range of 5 • -70 • , with a 2θ scan rate of 0.1 • /min.…”

Evaluation of Strength Development in Concrete with Ground Granulated Blast Furnace Slag Using Apparent Activation Energy

“…The hydration degree of Portland cement can be derived by the weight ratio of reaction products. The weight ratio of reaction products can be determined by non-hydrated cement using an electron microscope or X-ray diffraction analysis [29][30][31][32]. Also, the degree of hydration can be measured by the amount of water, as well as heat generation, and the compressive strength in an indirect way.…”

The influence of alkaline activator concentration on the apparent activation energy of alkali-activated materials

“…The degree of hydration of Portland cement can be derived by the weight ratio of reaction products. The weight ratio of reaction products can be determined by non-hydrated cement using an electron microscope or X-ray diffraction analysis [27][28][29][30]. The reaction rate constant is an indicator of the initial gradient for the degree of hydration.…”

“…It is believed that exothermic effects mainly result from the dissolution of solid fly ash components in a strongly alkaline aqueous solution and the disintegration of fly ash particles together with the formation of oligomeric compounds in the aqueous phase in combination with the formation of alumina / silica-hydroxy type. Polymerisation / condensation reactions can be attributed to a small share of heat evolution, which means that the process of network consolidation is a rather thermally stable state [3,29,35]. Fig.…”