Surface modified used rubber tyre aggregates: effect on recycled concrete performance

Abstract

Although research has found that using rubber in concrete will enhance its resilience and reduce its density, the significant loss of strength owing to lack of bonding has remained unresolved. This study considers how to minimise the loss of strength of concrete with used rubber tyre crumb aggregates and investigates the improvement of water permeability resistance that may consequentially develop. A surface of rubber crumb was modified by soaking in the saturated sodium hydroxide solution or silane coupling agent (SCA) before using. Up to 20% of natural fine aggregate was volumetrically replaced with treated rubber crumb. Experimental results show higher compressive and flexural strengths, Young's modulus and water permeability resistance from the samples with SCA-treated rubber than with as-received or sodium-hydroxide-treated rubber. X-ray diffraction pattern analyses indicate almost no change in crystalline phase for the rubber surface modification. Microscopic inspections show an enhanced rubber-matrix adhesion with the use of SCA. Results of mercury intrusion porosimetry reveal that concrete with SCAtreated rubber has a similar pore size distribution to the other three mixes, but achieves the lowest porosity and highest tortuosity, resulting in the best water permeability resistance. A brief cost analysis suggests that this method of surface modification is economically viable.

Impact of Chemically Treated Waste Rubber Tire Aggregates on Mechanical, Durability and Thermal Properties of Concrete

“…The observed improvement of compressive strength as a result of the surface treatment of rubber aggregates is in accordance with previously reported findings (Albano et al, 2005). However, the improvement of compressive strength was relatively minor, as also reported previously (Su et al, 2015).…”

“…It is worth noting that the permeability of R8-C72h was even lower than the REF concrete, by 22.6%. Similar results were reported previously by Su et al (2015). All mixtures in this study can be classified as having medium-range permeability according to DIN 1048, except mixture R8-C72h, which has a low-range permeability.…”

“…Other studies showed that treatment using NaOH increases the compressive strength (Su et al, 2015;Youssf et al, 2016). A treatment with SCA has shown to result in a more drastic increase in compressive strength of more than 6.5% (Su et al, 2015). In terms of solvents, acetone was found to be more effective than ethanol (Rivas-Vázquez et al, 2015).…”

“…Another study showed a significant increase of strength after soaking of rubber aggregates in water for 24 h (Mohammadi and Khabbaz, 2015). Other studies showed that treatment using NaOH increases the compressive strength (Su et al, 2015;Youssf et al, 2016). A treatment with SCA has shown to result in a more drastic increase in compressive strength of more than 6.5% (Su et al, 2015).…”

Editorial: Aggregate – a question of responsible use

“…Lye et al (2015) provide the outcome of their state-of-the-art review of the use of copper slag (CS) and washed copper slag (WCS) with systematic analysis and evaluation of the massive data assembled, showing how CS/WCS as a component of sand can be used and, in so doing, make other recycled and secondary materials more acceptable for their use in concrete. The study by Su et al (2015) describes their development work undertaken to improve, through surface treatment, the bond between the used tyre rubber crumb fine aggregates and the cement matrix, which resulted in minimising strength losses of concrete. Such a concrete has been shown to develop improved engineering and permeation properties of concrete.…”