This study was conducted with the aim to chemically remove the cement paste attached to the aggregate surface using acidic substances. Sulfuric and hydrochloric acids were used as the acidic substances, and after analyzing the quality characteristics of the aggregates following the acid treatment, a mortar test was performed using the aggregates. The results showed that the acidtreated recycled aggregates were superior to the original aggregates and the recycled aggregates that were manufactured using natural water in terms of density, absorption ratio and solid volume percentage. Based on this, it was determined that acid treatment was effective in improving the quality of recycled fine aggregates. In addition, the results of reviewing the strength characteristics of the mortar obtained using the acid-treated aggregates showed that the residue substances remaining in the recycled fine aggregates after reacting with the cement paste had a negative impact on the concrete strength. Based on this, it was determined that in case of improving the quality of recycled aggregates by acid treatment, there needs to be strict management of the products of the reaction with the acid in order for the aggregates to be used in structural construction.
Abstract:There has been an increasing amount of waste concrete generated in recent years, which has made recycling more important. Waste concrete is generally recycled as recycled aggregates, and many studies have been conducted to seek ways to improve their quality. Such quality improvement processes has led to the generation of byproducts such as waste concrete powder, which needs to be recycled efficiently based on further research. Accordingly, this study was conducted with the aim to use waste concrete powder (WCP) to substitute silica powder in the manufacturing of the extrusion concrete panels in cases where high SiO 2 content is not a requirement. The results of this study showed a negative correlation between flexural strength and silica powder-WCP substitution ratio. For example, 50% substitution resulted in a product that satisfied the required flexural strength over 14 MPa as stipulated by the Korean Industrials Standards, and it gave rise to properties such as specific gravity, absorption ratio, length change, thermal conductivity, and fire-resistance that were similar to those of plain specimens. Based on these results, it was deemed that it would be possible to use WCP as an alternative material in place of siliceous fillers in cases where high-purity is not required.
Carbon dioxide generated from construction materials and construction material industry among the fields of construction is approximately 67 million tons. It is about 30% of the carbon dioxide generated in the fields of construction. In order to reduce carbon dioxide in the fields of construction, it is necessary to control the use of fossil fuel consumed and decrease carbon emission by reducing the secondary and tertiary curing generating carbon dioxide in construction material industry. Therefore, this study manufactured mortar by having cement as the Plain and substituting three binding materials up to 50% and then adopted different curing methods to analyze congelation and strength characteristics. Test results for strength property by changing binding materials showed that specimens with blast furnace slag, CSA 15% and CAMC 5% resulted in positive effect for strength improvement. Especially, specimens with 50% of blast furnace slag, CSA 15% and CAMC 5% showed the most apparent
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