Use of cupola slag as fine aggregate in concrete

Abstract

The growing scarcity of natural sand and the increasing demand for sustainable construction have driven the search for alternative materials in concrete production. One promising option is cupola slag, an industrial waste by product generated during cast iron production in cupola furnaces operating at temperatures between 1400°C and 1600°C. The disposal of cupola slag is a matter of burden for the manufacturers of casting industry. It is may be mentioned that cupola slag contains only 10.7% CaO which is quite less than Granulated Blast Furnac Slag (GGBFS) . Thus, it is not economically viable to replace the cement partially after grinding. Although it contains substantial amount of amorphous silica, the use of cupola slag as partial cement like fly ash as it requires fine grinding and will generate carbon foot print. Thus, recycling of cupola slag as a partial replacement for aggregate. This requires less energy compared to fine grinding. This will not only help reduce waste but also conserves natural resources. Few researchers have used cupola slag as a coarse aggregate in concrete. Based on the above background, the present study focuses on the use of cupola slag as a fine aggregate replacing the natural sand to develop a practical way of solid waste management. The study is limited to normal grade concrete of grade M25. Cupola based fine aggregate has been prepared from chunks by hand grinding in the laboratory. The grading has been prepared as Zone II (as per IS 383-2017) which is similar to natural sand. It may be mentioned here that this can be made to Zone I and can be suitable used as manufactured sand. The cupola slag is used as fine aggregate (FA), partially replaced by 0–50% (by weight) in the step of 10% (by weight). The experimental results indicate that the dry density of concrete mix increase with the increased weight percent of cupola slag based FA (CS) in concrete. The compressive strength and split tensile strength at 28 day specimens increased with the increase of replacement percentage of Cupola slag up to 40% replacement compared to the control specimen. In such cupola based concrete, the water absorption of concrete is less by about 1.23% for 40% replacement compared to the control specimen. The chloride ions penetration in cupola based concrete decreases with the increase of Cupola slag as fine aggregate in concrete. Field Emission Scanning Electron Microscope (SEM) images revealed that use of Cupola slag modifies the concrete microstructure and fill the small pores. EDS and XRD based microstructure analysis indicates such improvement in microstructure with the development of new compound in the cupola slag based concrete. However more study is needed for other concrete grade and with the mechanically prepared cupola based fine aggregate.