Simplex-Lattice Hydration Prediction and Microstructure Verification of Cementitious Systems.

Understanding hydration processes in cementitious systems is essential for predicting material performance. Prior research has shown that hydration products like calcium hydroxide (CH) and non-evaporable water content influence strength and durability. However, the interaction between Portland cement, pulverized fuel ash, and silica fume remains unclear. This gap motivated the need to quantify CH and non-evaporable water content in blended systems. Existing studies have focused on binary blends but not on ternary systems. The role of PFA in delaying hydration is known, but its long-term effects are not well established. SF is recognized for accelerating early hydration, but its impact when combined with PFA is understudied. This paper addresses these uncertainties by analyzing hydration parameters in both binary and ternary systems.

This study aimed to assess how hydration develops in blended cementitious systems over time. The specific problem addressed was the lack of detailed data on CH and non-evaporable water content in PC-PFA and PC-PFA-SF mixtures. The motivation came from the need to better understand how PFA and SF influence hydration dynamics. By using TGA and SEM, the researchers sought to track hydration products and microstructure changes. The study focused on age-dependent behavior from one to 28 days. The goal was to determine how PFA and SF interact in binary and ternary systems. The researchers also aimed to develop predictive models for hydration parameters. This approach allows for better material design and performance prediction.

The researchers used thermo-gravimetric analysis (TGA) to measure CH and non-evaporable water content in blended pastes. Scanning electron microscopy (SEM) was employed to examine microstructural changes. The study involved binary mixtures of PC and PFA as well as ternary mixtures with SF added. Hydration parameters were tracked at various ages, including one, three, seven, and 28 days. The simplex-lattice design was used to create predictive models for hydration behavior. Experimental results were compared with model predictions to validate accuracy. The focus was on quantifying hydration product development and its relation to mix composition. This approach allowed for a detailed analysis of hydration dynamics.

The study found that CH content in PC-PFA binary blends increased up to three days before decreasing. The reduction in CH was proportional to the PFA dosage used. In ternary blends, SF caused an early decrease in CH at one day, with most SF consumed by seven days. The addition of 10% SF altered early hydration rates in PC-PFA pastes. PFA had minimal effect on non-evaporable water content until three days, after which its influence became significant. SF increased non-evaporable water content from early ages up to seven days. Beyond 28 days, SF showed no further pozzolanic activity. Ternary systems significantly increased non-evaporable water content compared to reference pastes.

The authors concluded that PFA delays hydration in blended systems, with CH content decreasing after three days. SF accelerates early hydration but is consumed by seven days. The combination of PC, PFA, and SF creates a system with higher non-evaporable water content early on. The study showed that SF’s pozzolanic activity diminishes after 28 days. The predictive models developed using simplex-lattice design aligned well with experimental results. SEM analysis supported the hydration predictions. The findings suggest that SF improves early hydration in PC-PFA systems. These results can help in designing cementitious systems with controlled hydration behavior.