Thermal and Mechanical Properties of Concrete Incorporating Silica Fume and Waste Rubber Powder

Abstract

Using waste rubber tires for concrete production will reduce the demand for natural aggregate and help to reduce environmental pollution. The main challenge of using waste rubber tires in concrete is the deterioration of mechanical properties, due to poor bonding between rubber and cement matrix. This research aims to evaluate the mechanical and thermal properties of rubberised concrete produced by using different proportions of rubber powder and silica fume. Ordinary Portland cement was partially replaced with silica fume by amounts of 5%, 10%, 15% and 20%, while sand was replaced by 10%, 20% and 30% with waste rubber powder. Tests were carried out in order to determine workability, density, compressive strength, splitting tensile strength, elastic modulus, thermal properties, water absorption and shrinkage of rubberised concrete. The compressive strength and splitting tensile strength of concrete produced using waste rubber powder were reduced by 10-52% and 9-57%, respectively. However, the reduction in modulus of elasticity was 2-36%, less severe than compressive and splitting tensile strengths. An optimum silica fume content of 15% was observed based on the results of mechanical properties. The average shrinkage of concrete containing 15% silica fume increased from -0.051% to -0.085% at 28 days, as the content of waste rubber powder increased from 10% to 30%. While the thermal conductivity of rubberised concrete was reduced by 9-35% compared to the control sample. Linear equations were found to correlate the density, splitting tensile strength, modulus of elasticity and thermal conductivity of concrete with silica fume and waste rubber powder.

Keywords: mechanical properties; silica fume; thermal properties; waste rubber powder.

Figure 1

The particle size of sand, waste rubber powder and coarse aggregate distribution of aggregates.

Figure 2

(a) Silica fume and waste rubber powder (b) mesh 40 and (c) mesh 80.

Figure 3

The testing of waste rubber powder concrete (a) splitting tensile strength, (b) modulus of elasticity and (c) thermal conductivity.

Figure 4

The workability of concrete with different proportions of waste rubber and silica fume.

Figure 5

The density of concrete with different proportions of waste rubber and silica fume.

Figure 6

The water absorption of concrete with different proportions of waste rubber and silica fume.

Figure 7

The microstructure of concrete with silica fume and waste rubber powder (a) 10SF-20R and (b) 10SF-30R.

Figure 7

The microstructure of concrete with silica fume and waste rubber powder (a) 10SF-20R and (b) 10SF-30R.

Figure 8

The compressive strength of concrete with different proportions of waste rubber and silica fume.

Figure 9

The splitting tensile strength of concrete with different proportions of waste rubber and silica fume.

Figure 10

The modulus of elasticity of concrete with different proportions of waste rubber and silica fume.

Figure 11

The shrinkage of concrete with different proportions of waste rubber and silica fume.

Figure 12

The thermal properties of concrete with different proportions of waste rubber and silica fume (a) thermal conductivity and (b) specific heat.

Figure 13

SEM images of concrete with different silica fume and waste rubber powder content (a) 5SF-20R and (b) 15SF-20R.

Figure 14

The linear relationships of rubberised concrete (a) compressive strength vs. density, (b) splitting tensile strength vs. compressive strength, (c) modulus of elasticity vs. compressive strength, (d) thermal conductivity vs. density, and (e) thermal conductivity vs. compressive strength images of concrete with different silica fume and waste rubber powder content.

Figure 14

The linear relationships of rubberised concrete (a) compressive strength vs. density, (b) splitting tensile strength vs. compressive strength, (c) modulus of elasticity vs. compressive strength, (d) thermal conductivity vs. density, and (e) thermal conductivity vs. compressive strength images of concrete with different silica fume and waste rubber powder content.

Figure 14

The linear relationships of rubberised concrete (a) compressive strength vs. density, (b) splitting tensile strength vs. compressive strength, (c) modulus of elasticity vs. compressive strength, (d) thermal conductivity vs. density, and (e) thermal conductivity vs. compressive strength images of concrete with different silica fume and waste rubber powder content.