Abstract
Although studies have been performed on the recycled aggregate made of waste concrete for the production of new concrete, the new concrete with 100% recycled coarse aggregate and manufactured sand (abbreviated as RAMC) still needs to be researched for structural applications. In this paper, an experimental study was performed on seven groups, including fourteen reinforced RAMC beams under the simply supported four-point loading test, considering the factors of the strength of RAMC and the reinforcement ratio of longitudinal tensile rebars. Based on the test results, the cracking resistance, the bearing capacity, the crack width, the flexural stiffness and the mid-span deflection of reinforced RAMC beams in bending are discussed and examined by using the formulas of conventional reinforced concrete beams. Results show that an obvious effect of reinforcement ratio was present, while less so was that of the strength of RAMC. With the comparison of predicted values by the formulas of conventional reinforced concrete beams, the reinforced RAMC beams decreased cracking resistance by about 20%, increased crack width by about 15% and increased mid-span deflection by about 10%, although the same bearing capacity can be reached. The results directly relate to the lower tensile strength of RAMC which should be further improved.
Highlights
Solid wastes from construction of urban and other infrastructures need to be urgently recycled to eliminate secondary pollution in the abandonment process and protect the environment
The conventional concrete made of natural aggregates calls for a fundamental change to be produced with recycled aggregates and manufactured sand
Many studies have been performed on the properties of concrete with recycled aggregate and/or manufactured sand at the materials level, with a view to ensure the equivalent properties of conventional concrete or determine the difference from conventional concrete [2,4,5,6]
Summary
Solid wastes from construction of urban and other infrastructures need to be urgently recycled to eliminate secondary pollution in the abandonment process and protect the environment. Satisfactory strength of concrete and reliable loading performance of reinforced concrete beams can be provided by using the composite recycled aggregate [19,20,21] Another attempt was to produce concrete with 100% recycled coarse aggregate and manufactured sand (abbreviated as RAMC). The benefits include the micro-aggregate filling effect on density, the activity effect and crystal nuclei effect on cement hydration, and the enhancement effect on the interface of the aggregate to set cement [4,22,23] This gives the concrete satisfactory performances in terms of good workability of fresh mix, reasonable basic mechanical properties with long-term development and acceptable durability for the structural application [24,25,26]. Test results are compared to the results predicted by formulas specified in current design codes for conventional reinforced concrete beams, the differences and similarities are discussed in detail as they inhere in the combination of the features of RAMC and the bond performance of rebars and revisions are proposed for the correct prediction of reinforced RAMC beam
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