Investigation of technical and economic desirability of recycled concretes containing pozzolan

Document Type : Research Article

Authors

1 Associate professor, Department of Civil Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran

2 PhD student, pepartment of Civil Eignieerng, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran

Abstract

The present paper investigates the effect of replacement of recycled concrete aggregates (RCA’s) on the mechanical properties and durability of RC’s and their technical and economic desirability. Concretes made to replace RA’s including 25%, 50% and 100% were made. To improve the quality of RC’s, micro-silica, fly ash and natural zeolite pozzolans were replaced separately with partial of cement. A total of 40 mixing designs were made in the form of 1000 standard concrete specimens. In a period of 28 days, tests of compressive strength, splitting tensile strength, static elasticity modulus and ultra-pulse velocity (UPV) and in a period of 180 days, tests of immersion water absorption (IWA), capillary water absorption (CWA), electrical resistivity, electrical conductivity and rapid chloride penetration (RCPT) was applied to the specimens. It was concluded that even with the replacement of pozzolanic materials, the results of IWA and CWA conditions in RC’s are affected by the development of porous and capillary space due to increased replacement of RCA’s. From viewpoint of the results related to electrical resistivity, electrical conductivity and RCPT, due to changes in the chemical structure of the pore flow in RC’s, it is possible to achieve RC’s with similar durability to ordinary concrete. The desirability of RC’s made from both technical and economic perspectives and their interaction were examined. Among the concretes made, 25% RC’s containing 10% and 15% micro-silica and 10% natural zeolite and 50% RC containing 10% micro-silica showed more technical and economic desirability than reference concrete.

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