دانلود رایگان مقاله انگلیسی گزینش بازیافت برای فرآورده فرعی متالورژیکی در بتن سبز برای سازه پایدار و مقاوم - الزویر 2018

Abstract

Reuse of waste materials as construction material is very much essential to achieve sustainable construction. Utilization of waste materials as construction material not only help in protection of environment but also result in monetary savings. Spent Foundry Sand (SFS) is the waste material generated by metal casting industry. This paper presents study on economic and environmental benefits of recycling of SFS in concrete as sand replacement. Strength and durability properties of green concrete made with SFS as sand replacement are also presented. Natural sand in concrete was replaced with SFS at 0, 5, 10, 15 and 20% replacement levels by weight. To assess the performance of green concrete made with SFS, compressive strength, splitting tensile strength, deicing salt resistance and chloride permeability tests were performed. At age of 28 days, green concrete mixtures containing SFS as sand replacement displayed up to 26% and 12.87% improvement in compressive strength and splitting tensile strength over that of control concrete, respectively. Similarly, concrete mixtures made with SFS exhibited 7.2 to 17.7% lower chloride ion penetration and 6.6 to 26.42% improvement in salt scaling resistance on use of SFS. The green concrete mixtures showed very slight scaling after 50 cycles of freezing and thawing in the presence of deicing salt compared to slight to moderate scaling shown by control concrete. The incorporation of up to 20% SFS as sand replacement results improvement in strength and durability properties of green concrete over those of control concrete. Green concrete made with SFS is economical and reduces negative impact on environment by reducing CO2 emissions.

 Conclusions

Most of the published studies are based the concept of reducing CO2 emissions by using supplementary cementitious materials as cement replacement in concrete but the published literature lacks in studies on CO2 emissions and monetary benefits due to replacement of natural materials with SFS in concrete. In this study, the significance of use of SFS in concrete in terms of improvement in properties and microstructure of green concrete, monetary and environment benefits was examined. From the present study following conclusions can be drawn.

1. Strength and durability properties of concrete improved on use of up to 20% SFS as partial replacement of sand. The use of finer SFS material resulted in denser concrete matrix. At the age of 28 days, SFS concrete mixtures exhibited up to 26% and 12.87% higher compressive strength and splitting tensile strength compared to that of control concrete, respectively. Similarly, SFS concrete mixtures displayed 7.2 to 17.7% lower chloride ion penetration and 6.6 to 26.42% improvement in salt scaling resistance on use of SFS.

2. Concrete mixture containing 15% SFS as sand replacement displayed optimum percentage improvement in strength and durability properties. On further increase in replacement level up to 20%, percentage improvement in strength and durability properties of SFS concrete with reference to that of control concrete started decreasing.

3. SFS is a potential material to be used as partial replacement of natural sand in concrete for achieving the sustainable construction. On recycling of SFS in concrete, reduction in CO2 emissions as well as saving in disposal cost can be achieved.

4. Green concrete made with fly ash based cement and SFS lessens negative impact on environment by reducing CO2 emissions. Green concrete made with SFS as sand replacement consumes less energy and is more economical compared to conventional concrete.