Abstract
Replacement of natural aggregates (NAs) with recycled concrete aggregates (RCAs) in complex reinforced concrete (RC) structural elements, such as deep beams with openings, supports environmental sustainability in the construction industry. This research investigates the shear response of RC deep beams with openings made with 100% RCAs. It also examines the effectiveness of using steel fibers as a replacement to the minimum conventional steel stirrups in RCA-based deep beams with web openings. A total of seven RC deep beams with a shear span-to-depth ratio (a/h) of 0.8 were constructed and tested. A circular opening with an opening height-to-depth ratio (h0/h) of 0.3 was placed in the middle of each shear span. Test parameters included the type of the coarse aggregate (NAs and RCAs), steel fiber volume fraction (vf = 1, 2, and 3%), and presence of the minimum conventional steel stirrups. The deep beam specimens with web openings made with 100% RCAs exhibited 13 to 18% reductions in the shear capacity relative to those of their counterparts made with NAs. The inclusion of conventional steel stirrups in RC deep beams with openings was less effective in improving the shear response when 100% RCAs was used. The addition of steel fibers remarkably improved the shear response of the tested RCA-based beams. The gain in the shear capacity of the RCA-based beams caused by the inclusion of steel fibers was in the range of 39 to 84%, whereas the use of conventional steel stirrups resulted in 18% strength gain. The use of 1% steel fiber volume fraction in the RCA-based beam with openings without steel stirrups was sufficient to restore 96% of the original shear capacity of the NA-based beam with conventional steel stirrups. The shear capacities obtained from the tests were compared with predictions of published analytical models. The predicted-to-measured shear capacity was in the range of 0.71 to 1.49.
Highlights
At the end of their service lives, aged concrete structures are demolished creating massive amounts of construction and demolition waste (CDW)
The shear behavior of recycled concrete aggregates (RCAs) deep beams with and without conventional steel stirrups is compared to that of similar beams made with natural aggregates (NAs)
Experimental results of the current study indicated that the use of 1% steel fiber volume fraction in a deep beam with openings made with 100% RCAs without conventional steel stirrups was sufficient to offset the strength reduction caused by full replacement of NAs with RCAs and restore 96%
Summary
At the end of their service lives, aged concrete structures are demolished creating massive amounts of construction and demolition waste (CDW). This CDW is mostly disposed of in stockpiles or landfills, causing serious environmental hazards [1]. A sustainable solution to the problem of CDW and the scarcity of natural resources for natural aggregates (NAs) is the concept of recycling this waste in the form of recycled concrete aggregates (RCAs). The potential substitute of NAs by RCAs is considered a promising approach to promote the use of sustainable materials in construction. Its positive environmental impact has driven researchers to investigate the effect of its usage in structural applications such as reinforced concrete (RC) beams. The shear behavior of RC beams with RCAs is an important aspect that requires investigation and experimental evidence prior to using RCAs routinely in structural applications [5,6,7,8,9]
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