Abstract
The adhered mortars in recycled aggregates (RA) may lower the performance of the concrete, by for instance reducing its strength and durability, and by cracking. In the present study, the effect of nylon fiber (NF) on the permeability as well as on the mechanical properties of concrete incorporating 100% RA was experimentally investigated. Concrete was produced by adding 0, 0.6 and 1.2 kg/m3 of NF and then cured in water for a predetermined period. Measurements of compressive and split tensile strengths, ultrasonic pulse velocity and total charge passed through concrete were carried out, and the corresponding test results were compared to those of concrete incorporating crushed stone aggregate (CA). In addition, the microstructures of 28-day concretes were examined by using the FE-SEM technique. The test results indicated that recycled coarse aggregate concrete (RAC) showed a lower performance than crushed stone aggregate concrete (CAC) because of the adhered mortars in RA. However, it was obvious that the addition of NF in RAC mixes was much more effective in enhancing the performance of the concretes due to the crack bridging effect from NF. In particular, a high content of NF (1.2 kg/m3) led to a beneficial effect on concrete properties compared to a low content of NF (0.6 kg/m3) with respect to mechanical properties and permeability, especially for RAC mixes.
Highlights
A lack of natural aggregates with a high quality has set up the alarm to find alternative uses for recycled aggregate
At 91 days, the maximum strength value obtained in the case of the crushed stone aggregate concrete (CAC) mixes was mixes was 6.3 MPa for3 1.2 kg/m3 nylon fibers (NF) content, an increase of 23.5% over the CAC1 mix
CACExperimental and recycled coarse aggregate concrete (RAC) mixes in order highlight effect
Summary
A lack of natural aggregates with a high quality has set up the alarm to find alternative uses for recycled aggregate. There have been many reports on the properties of concrete made with recycled aggregate [3,4,5,6,7,8,9,10,11], but most of them resulted in a lower level of concrete strengths. In order to enhance the performance of recycled aggregate concrete, researchers have come up with several advanced techniques These techniques include the surface treatment [12], the use of mineral admixtures [13,14] and the addition of fibers [4,15,16], which can improve the performance of recycled aggregate concrete. One needs to examine the applicability of NF for the purpose of the enhanced mechanical properties and the reduced micro-cracks in recycle aggregate concrete. The microstructures of 28-day concretes were examined by using the FE-SEM technique
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