Mechanical properties of synthetic aggregate pelletized by waste concrete fines in Vietnam

Due to rapid industrialization and economic growth, the generation of construction and demolition waste (CDW) from the activities of demolishing buildings is increasing in Vietnam. The Vietnamese Government has regulations on recycling and collecting CDW for reuse, recycling to environmental protection through Circular No. 08/2017/TT-BXD in 2017, and Directive 41/CT-TTg in 2020. Waste concrete fines (WCF) are generated during demolishing process or crushing of CDW materials. To save natural resources and increase the recycling rate, a disc pelleting technology has been used to recycle WCF. The pellet machine has a disk with 1.5m of diameter and 0.3m of depth; tilted at an angle of 55 degrees and the rotation speed from 15 to 22 rpm; the capacity is 0.5 to 0.8 tons per hour. This paper presents the results of pelletizing WCF research to produce synthetic aggregate (SA). The SA pelletized by WCF and cement had an apparent specific gravity of 2.45 – 2.55 g/cm3, a dry bulk specific gravity of 1.85 – 1.95 g/cm3, a crushing value of 19.2 – 29.9%, a LA (Los Angeles) value of 23 – 33% and water absorption around 13.2%. The mechanical properties of SA meet the requirement of TCVN 11969:2018, recycled aggregate type II for concrete.