Use of Crumb Rubber and Cementitious Materials for Concrete Pavement Application

Abstract

The challenge that has aroused in front of us is the discarding of the scrap rubber tires. The discarding process till now generally followed the burning of the rubber tires or disposing them into the ground and has resulted into a global environmental issue. The burning of tires creates toxic gases which not only harms the atmosphere, but is hazardous for human life. On the other hand, the increase in use of natural river sand for concrete construction has created its shortage. Thus, the researchers have been exploring the use of scrap rubber tires as the replacement of fine and coarse aggregates as per the required application in concrete construction.

Here, the present investigation is based on developing the crumb rubber concrete of M30 grade for concrete pavement application. Three sizes of crumb rubber (Mesh 30 powder as 40%, 0.8mm -2mm as 35%, 2mm - 4mm as 25%) are explored in the study. Total 27 mixes are cast with three types of crumb rubber content (0%, 7.5%, and 12.5%) as partial replacement by weight of fine aggregate. Cementitious materials such as GGBFS (40%, 50%), silica fume (5%, 10%) and metakaolin (7.5%, 12.5%) are explored as partial replacement by weight of cement. The 7 day compressive strength is evaluated of all concrete mixes and the results are compared with control mix.

From the results obtained, final 7concrete mixes are selected and further tested for mechanical properties such as compressive strength at 7, 28 days, flexural strength at 28 days and split tensile strength at 28 days respectively. From the results explored, the 7.5% crumb rubber mix showed better performance as compared to that for 12.5% crumb rubber mix for the above mechanical properties. Based on the results, concrete mixes are further classified in to two categories. The concrete mix with 7.5% crumb rubber along with 5% silica fume and 12.5% Metakaolin is selected for cast-in-place crumb rubber concrete. On the other hand, mix with 12.5% crumb rubber along with 5% silica fume and 12.5% metakaolin is selected for crumb rubber concrete paver blocks. 3 crumb rubber concrete mixes with 7.5% crumb rubber along with control mix is evaluated for mechanical properties such as modulus of elasticity, abrasion resistance and impact resistance at 28 days respectively. The durability properties namely sulphate attack at 42 days and rapid chloride penetration test at 28 days are evaluated for the said concrete mix.

For crumb rubber concrete paver block of M35 grade, 10 trials concrete mixes are cast with 0.5, 0.53, 0.6 and 0.63 w\c ratio respectively. 7 days compressive strength is evaluated and based on the results, the mix with 0.5 w/c ratios along with 5% silica fume and 7.5% Metakaolin is selected .The mechanical properties such as compressive strength at 7 and 28 days, flexural strength at 28 days are evaluated of crumb rubber concrete paver blocks is explored and the results are compared with control mix. Based on test results, the paver blocks for light traffic as well as for medium traffic conditions are suggested.