Strength and Quality Assessment of Recycled Aggregate and Crumb Rubber Concrete Using the Ultra Pulse Velocity Method

This study focuses on the strength and quality of concrete incorporated with recycled aggregate and crumb rubber through the compressive strength test and the Ultra Pulse Velocity (UPV) test. RA was used to replace coarse aggregate while CR was used to replace fine aggregate in concrete production. A total of 36 specimens consisting of cubes (100 mm 100 mm 100 mm) with partial replacements of 50% RA and 0, 1, 2, 3, 4, and 5% CR were prepared, subjected to water curing for 7 and 28 days and tested in terms of compressive strength and quality using the compressive strength test and the UPV method. The UPV test and the compressive strength test were conducted at day 7 and day 28. The results show that the compressive strength of concrete decreased slightly with the increase of rubber content. Additionally, the quality of concrete slightly decreased as the percentage of rubber content increased. Finally, the optimum percentages for partial replacement of concrete suggested based on the results are 3% CR and 50% RA as this concrete mix achieved the highest velocity in the UPV test and the highest compressive strength compared to the control mix

Thermal Conductivity of Crumb Rubber as Partial Sand Replacement and Recycled Aggregates as Partial Coarse Aggregate Replacement in Concrete

Disposal of waste tire rubber has become a major environmental issue worldwide and is increasing day by day, especially in Malaysia where carbon emission is among the highest in the world. Therefore, recycled waste materials are being used as construction materials in order to create new innovative products that are able to mitigate environmental pollution, reduce the cost of construction and improve the properties of concrete. This study discusses the utilisation of crumb rubber and recycled aggregates in concrete construction and the objective of this study is to determine the thermal conductivity of crumb rubber and compare the optimum strength of concrete materials. 12 cube samples measuring 200 200 100 mm containing different percentages of crumb rubber (0, 1, 2, 3, 4, and 5%) as fine aggregate substitute and 50% of recycled aggregates as coarse aggregate substitute were produced. The concrete grade used for these specimens is grade 35. The curing process was conducted on the samples to achieve the standard strength of concrete in 7 and 28 days. Therefore, the real strength of concrete was measured after the curing process. A slump test was conducted to determine the properties of crumb rubber. In addition, the samples were examined using the guarded hot box method to obtain the optimum percentage of crumb rubber as partial sand replacement in concrete for thermal conductivity. The results show that thermal conductivity (k-value) decreased slightly with the increase in crumb rubber content. However, the quality of concrete also slightly increased as the percentage of crumb rubber content increased. Lastly, based on the results, 5% of crumb rubber and 50% of recycled aggregates were suggested as the optimum percentages to be used in concrete as it achieved the lowest thermal conductivity compared to conventional concrete