Abstract

     Curing has a substantial function on the progress of strength and durability of concrete. Previously, researchers focused on the curing of normal concrete. The number of investigations on the curing of concrete under hot weather is quite limited. Regrettably, investigators have not concentrated on curing of high-performance concrete under hot weather. This paper investigates the behavior of eco‐friendly green high-performance concrete casted in hot weather and cured by conventional methods without using high quantity water. Three types of curing were investigated: immersion in water inside the laboratory, curing compounds outside the laboratory and wet sheet outside the laboratory. A comparison between curing methods inside and outside the laboratory under hot weather for mixtures with (0%, 40%) fly ash replacement and with (0%, 30%) palm kernel shells replacement was conducted. High-performance concrete properties were obtained by various tests such as compressive strength, flexural strength and modulus of elasticity at 7, 28, 56, 90 and 180 curing days. Also, air dry density, absorption and length change were investigated at 28 curing days. The results showed a slight decrease in strengths of curing compound concrete compared to immersion in water curing due to fly ash and palm kernel shells replacements. When comparing concrete mixture with 30% palm kernel replacement and 40% fly ash replacement cured by immersion in water (IWP30F40) with that cured using curing compounds (OCP30F40), the decrease ratio in compressive strength and modulus of elasticity were 1,5% and 3.7%, respectively, at 28 days of curing age. The maximum shrinkage value at 28 days of curing was 0.0859 mm/m for mixture cured via wet sheets without fly ash or palm kernel shells replacements (OSP0F0).

Introduction

     In general, the early strength of concrete is positively afected by elevated production and curing temperature, but later-age strength is adversely afected. Concrete durability and deterioration of concrete quality have been a well-confrmed truth. Judgments diverge, however, as to the specifc causes and the deductions to be deduced with respect to concreting in a hot climate.

     Tsui Leung-Cho (Tsui 1971) discovered that due to hot weather circumstances, under 38 C° air curing temperatures and depending on the temperature of mixing (19–۳۳) °C the compressive strength at 7 days of age was 73–۸۲% of strength at 28 days of age. This was extremely higher than at normal (30 C°) air curing temperatures, as the strength at 7 days was around 2/3 of that at 28 days.

Conclusions

     ۱٫ Curing methods are important for high-performance concrete. Given that environmental conditions are diffcult to control. Curing methods should be tested in hot weather to obtain satisfactory results.

۲٫ The best curing method after immersion in water was curing compounds.

۳٫ For concrete with fy ash and date palm shells replacements in areas with a scarcity of freshwater, curing by water immersion can be replaced by other methods, such as curing compounds or wet sheet, since no signifcant diference in mechanical properties was observed when compared with concrete cured by water immersion method.

۴٫ The maximum decrease in percentages due to curing mixtures via wet sheets instead of curing them via immersion in water was 29.2%, 12.6 and 11.6% for fexural strength, compressive strength and modulus of elasticity, respectively, at 28 days of curing age.

۵٫ The maximum decrease in percentages due to curing mixtures via curing compounds instead of curing them via immersion in water was 24.3%, 6.4 and 7.6% for fexural strength, compressive strength and modulus of elasticity, respectively, at 28 days of curing age.

۶٫ The method of partial replacement of concrete components with fy ash and date palm shells is very important in hot weather as it works to increase the strength as well as reduce the cost and contributes to waste disposal.