Abstract
Concrete is an important construction material. Its characteristics depend on the environmental conditions, construction methods, and mix factors. Working with concrete is particularly tricky in a hot climate. This study predicts the properties of concrete in hot conditions using the case study of Rawalpindi, Pakistan. In this research, variable casting temperatures, design factors, and curing conditions are investigated for their effects on concrete characteristics. For this purpose, water–cement ratio (w/c), in-situ concrete temperature (T), and curing methods of the concrete are varied, and their effects on pulse velocity (PV), compressive strength (fc), depth of water penetration (WP), and split tensile strength (ft) were studied for up to 180 days. Quadratic regression and artificial neural network (ANN) models have been formulated to forecast the properties of concrete in the current study. The results show that T, curing period, and moist curing strongly influence fc, ft, and PV, while WP is adversely affected by T and moist curing. The ANN model shows better results compared to the quadratic regression model. Furthermore, a combined ANN model of fc, ft, and PV was also developed that displayed higher accuracy than the individual ANN models. These models can help construction site engineers select the appropriate concrete parameters when concreting under hot climates to produce durable and long-lasting concrete.
Highlights
Introduction andBackground published maps and institutional affil-In the era of globalization and immense focus on the construction of critical facilities, various construction materials and their properties are investigated by researchers worldwide
Compressive strength: according to British Standards (BS) 1881−116, the fc of concrete was determined using a 100 mm cube sample; Split tensile strength: by following the procedure stated by ASTM C 496, the ft was determined using cylindrical concrete specimens with a 75 mm diameter and a height of 150 mm; Ultrasonic pulse velocity (PV): similar to fc, the ultrasonic pulse velocity of concrete was determined using 100 mm cube specimens following ASTM C 597; Depth of water penetration (WP): following the procedure reported in DIN 1048, a water pressure (5 bar) was applied to the sample for 72 h to determine WP depth
WP was not included in the combined artificial neural network (ANN) model because the tests needed to be carried out after days of curing
Summary
Various studies considered the effect of placement, distribution, and mixing on the characteristics of fresh concrete [33,34,35,36]. These studies revealed that maintaining the evaporation rate of mix water under 0.2 kg/m2 controlled the development of plastic shrinkage cracks. Kim et al [38] prepared concrete samples using different types of cement and checked the effect of curing temperature on the samples. ACI 318 recommends using lower w/c with a proper quantity of admixture to achieve the optimum workability and strength conditions Curing is another significant parameter to be considered when concreting under hot weather conditions. Different curing methods, supplemented with additional steps on a case-to-case basis, can be used when curing concrete under different conditions
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