Abstract

This study investigated the underwater abrasion resistance of recycled aggregate concrete according to ASTM C1138 using recycled aggregates obtained from demolished concrete as a 100% replacement of natural aggregates. The objective was to reduce the consumption of natural resources and minimize construction and demolition waste. In addition, ground granulated blast furnace slag (BFS) was used as a supplementary cementitious material at replacement ratios of 25% and 50%. Three BFS products with Blaine fineness values of 3000, 4000, and 6000 cm2/g were used to investigate their effects on the compressive strength and underwater abrasion resistance of recycled aggregate concrete. The experimental results showed that the compressive strength of recycled aggregate concrete was approximately 7% lower than that of natural aggregate concrete. However, the underwater abrasion test according to ASTM C1138 showed that the abrasion depth of recycled aggregate concrete was comparable to that of natural aggregate concrete. After 72 h of testing, the abrasion depth of recycled aggregate concrete was only slightly higher than that of natural aggregate concrete. In contrast, recycled aggregate concrete exhibited a higher weight loss, with an average value of 2.10% compared with 1.77% for natural aggregate concrete. Among the BFS mixtures, increasing the Blaine fineness of BFS resulted in lower abrasion depth and lower mass loss. Concrete containing BFS6000 exhibited the best underwater abrasion resistance within the BFS mixtures, although all BFS mixtures showed higher abrasion depth and mass loss than recycled aggregate concrete without BFS. At the 25% replacement ratio, concrete containing BFS6000 exhibited the lowest abrasion depth (3.11 mm) and weight loss (3.37%), whereas concrete containing BFS3000 showed higher values. A similar trend was observed at the 50% replacement ratio, although both abrasion depth and weight loss slightly increased compared with the corresponding 25% mixtures. The results demonstrate that recycled aggregate concrete combined with BFS has good potential for hydraulic structures and other concrete structures exposed to underwater abrasion. Although a slight reduction in compressive strength was observed, the underwater abrasion resistance can be improved by using BFS with higher Blaine fineness together with quality-controlled recycled aggregates. These findings provide useful information for the development of sustainable recycled aggregate concrete and support the efficient utilization of recycled materials in hydraulic engineering applications.

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