The effect of waste rubber particles and silica fume on the mechanical properties of Roller Compacted Concrete Pavement

The current investigation discusses the potential use of recycled tire rubbers in roller compacted concrete pavement with the purpose of both improving its performance and reducing its environmental impacts. The main focus was on the basic properties of the roller compacted concrete, including the unit weight, the compressive strength, the flexural strength, and the water absorption of samples; thus, the particles of used tires were utilized as a replacement for the sand aggregate by 0, 5%, 10% … and 35%. Also, the silica fume additive was used as a replacement for the cement material in eight mixes. The main point is that fresh specimens were compacted by a hammer, not a vibrator, in order to reach a homogeneous concrete. The results of the study showed an increase in the compressive strength of 28 days for different rubber contents 5% and 10%, without silica fume, and 5%, 10%, 15% and 20%, with silica fume; however, the compressive strength was reduced for the other samples in comparison with the control specimen. Correspondingly, there was an increase in the flexural strength of 28 days for samples containing of 5% crumb rubber, with and without silica fume, although the flexural strength decreased for the other mixtures. Furthermore, the findings of the present investigation showed that the replacement of the sand by the used tire particles reduces water absorption, and this decrease was more obvious for samples with silica fume. In the final analysis, a regression model was defined to find a relationship between compressive and flexural strengths.