Abstract
Mass concrete has been commonly known for its thermal stresses which arise due to the entrapment of hydration temperature susceptible to thermal cracking. The utilization of mineral additives is a promising and widely adopted technique to mitigate such effects. This paper presents the thermal, physico-chemical, mechanical, and morphological behaviour of mass concrete with blends of bentonite (BT) and fly ash (FA). Apart from the rise in temperature due to hydration, the compressive strength, ultrasonic pulse velocity (UPV), differential thermal analysis (DTA), thermo-gravimetric analysis (TGA), X-ray diffraction (XRD) analysis, and microstructure were studied. The results of this study revealed that the substitution of BT and FA significantly improved the compressive strength and development rate of UPV in the mass concrete samples. The FA concrete (FC) specimen presented the lowest temperature during the peak hours compared to all other concrete mixes studied in this research. Bentonite concrete (BC) was also found to be more effective in controlling the escalation of temperature in mass concrete. Scan electron microscopy (SEM) micrographs presented partially reacted FA particles in a mix. XRD and DTA analysis indicated that the concentration of calcium hydroxide (CH) declined by substituting FA and BT, specifically in ternary blends, which was due to the dilution effect and consumption of CH through the pozzolanic reaction.
Highlights
Thermal stresses in mass concrete often rise due to the hydration of cement
The inclusion of fly ash (FA) and BT in concrete presented a slight reduction of 4% and 6% in compressive strength, respectively, at 28 days
The decrease in strength is mainly attributed to the reduction in the amount of cement content, which resulted in a slow pozzolanic reaction [21]
Summary
Thermal stresses in mass concrete often rise due to the hydration of cement. The temperature differences in mass concrete may vary during its placement [1,2]. FA is the most common material used in the concrete to retard the hydration of OPC at an early age It has been utilized as a replacement of cement in catering environmental deterioration due to the emission of CO2 during the manufacturing process of cement [12]. The heat of hydration in FA concrete is controlled by various factors, i.e., quantity and chemical composition of cement and fly ash in a mix, ambient temperature, finesse of cement, and FA [14]. Memon et al [15] studied the effects of BT on the workability, compressive strength, water absorption, and acid attack resistance of concrete and reported that a higher replacement of BT led to a reduction in the workability. This study was designed to assess the effectiveness of BT as partial replacement to the cement on the aforementioned properties of mass concrete. FA separately and together with BT were prepared to compare the performance of BT with FA and control mix
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