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A shortage of natural fine aggregates has occurred worldwide, especially due to excessive consumption of them in construction activities. For this, the availability of sustainable alternative materials for natural fine aggregate is researched. Fly ash is identified as one such material that can partially replace fine aggregate in concrete. The current study demonstrates the feasibility of using fly ash as a partial fine aggregate replacing material in concrete and its effects on the compressive strength and some significant durability properties when cured under different curing temperatures. Fine aggregate and cement were partially replaced with Class F fly ash in different percentages. The curing methods (used in this study) were isothermal heat curing at 30ºC, 50ºC, and 70ºC, and one-day accelerated heat curing. The compressive strength test, carbonation depth test, rapid chloride penetration test, and surface resistivity test were performed for concrete mixtures with different fly ash replacement levels and curing temperatures. Test results reveal that the use of fly ash as a partial fine aggregate replacing material in concrete gives higher compressive strength than that of concrete with fly ash as a partial cement replacing material at both an early age and a later age. One-day accelerated curing is the most beneficial curing method, regarding the compressive strength at all the tested ages. Moreover, concrete with fine aggregate replacement gives better results for carbonation resistance, chloride penetration resistance, and surface resistivity when compared with the control mixture and mixtures with fly ash as a partial cement replacing material.

Chloride induced corrosion of reinforcing steel is a significant problem. Thermograph is one of the Non-Destructive Testing methods which may be useful for detecting corroded bar in reinforced concrete. This study aims to investigate the thermal behavior of concrete influenced by chloride and corrosion of reinforcing steel. The results of this thermal behavior are useful for determining the detectability of corrosion by thermograph. Different mix proportions of concrete and level of corrosion were studied. The results of temperature profiles obtained from experimental work proved that when there is presence of dense rust confined between concrete and steel, thermal behavior of concrete around steel bar changed. When applying heat source on top surface of the specimen, there was a slight change of temperature on top of corroded bar while there was more signification change of temperature below it. This is because dense rust with low porosity is a better heat conductor when compared to concrete. The temperature history obtained from simulation and experiment are in a good agreement. Numerical simulation provides quite good results in the area closing to the concrete top surface (depth 0.5cm and 1.5cm) and the accuracy of the estimated temperature is within 2%-5% of the experimental results.