Punching Behavior Of Self-Compacting Concrete Slabs Incorporating Coarse Recycled Concrete Aggregates

Abstract

This paper presents an experimental investigation on the effects of incorporating coarse recycled concrete aggregates (RCA) on the punching and flexural behaviour of reinforced concrete two-way slabs. For this purpose, four concrete mixes were designed with various substitution ratios of natural coarse aggregates (NCA) by RCA 0% (reference mix), 25, 50 and 75%. Subsequently, fourteen 800 × 800 mm × variable thickness reinforced concrete slabs (two per concrete type) were cast and subjected to punching and flexural tests. Different parameters that affect the behavior of two-way slabs were studied including type of failure, replacement ratios of NCA by RCA, amount of main reinforcement, thickness and loading patch size. In order to investigate the effect of RCA incorporation on hardened concrete properties (compressive strength Fcu, tensile Ft strength, flexural Fr strength and modulus of elasticity Ec), different replacement ratios were considered, while the quantity of cement was kept equaled for all the mixes (with and without RCA). Hardened concrete samples results showed that Fcu, Ft, Fr and Ec were decreased by (8.62, 13.54 and 19.12%), (13.08, 17.63 and 25.46%), (10.02, 21.67%, and 34.30%) and (9.69, 15.65 and 16.62%) respectively, for the (25, 50 and 75%) replacement ratios compared with samples made from SCC without RCA. The experimental results of slabs showed that the cracking and ultimate load (11% maximum reduction ratio) and moment (19.5% maximum reduction ratio) capacities of slabs were decreased compared with slabs made from SCC without RCA. Moreover, the load deflection curves were almost identical with proportional increase to the RCA content. From the general behavior, ultimate capacity, deflections, failure angle and crack pattern results, it can be concluded that the recycled concrete aggregate can be used as a partial replacement of natural coarse aggregate to produce self-compacting concrete mixes, where the behavior of two-way slabs cast with SCC containing RCA can considered acceptable.