CHLORIDE PENETRATION RESISTANCE OF CONCRETE MIXTURES WITH RECYCLED CONCRETE AGGREGATES

摘要

Disposal of aged concrete pavements involves great cost and (due to volumes involved) can be detrimental to environment when all of this material is deposited in landfills. It is therefore cost-effective to recycle crushed concrete as coarse aggregates (referred hereafter as RCA) to replace natural aggregates (NA) during construction of new concrete pavements. This approach reduces the need for quarrying of natural aggregates and saves space in the landfills. The main focus of this study was on determining the chloride penetration resistance of pavement concretes containing various levels (0, 30 and 100%) of RCA as a replacement for NA. All concrete mixtures used in this study were designed to meet the fresh properties and flexural strength requirements specified for pavements by the Indiana Department of Transportation (INDOT). The resistance to chloride ion penetration was determined using two electrical migration tests:rapid chloride permeability (RCP) test (as per ASTM Cl202) and non-steady state migration test (as per NT BUILD 492). Before the initiation of the RCP test, all specimens were first subjected to 250 mV AC potential scan using Solartron~(TM) 1260 gain-phase impedance analyzer. The impedance spectra (collected over a frequency range of 0.1 Hz to 10 MHz) were used to obtain bulk resistance (R_b) of the concrete. The steady state diffusion coefficients were calculated using RCP test data in Nernst-Plank and empirical equations. The general trends obtained from the chloride penetration resistance results indicate that initial current values from RCP test can be used to predict the performance of concretes containing RCA. Mixtures with 30% RCA performed similar to 0% RCA mixture while the resistance to chloride penetration of concrete with 100% RCA was somewhat reduced.