Eco-friendly high performance lightweight concrete containing different tires waste materials

In the presented work, eco-friendly High-Performance Lightweight Aggregate Concretes (HPLWAC) are produced by including both tire waste rubber aggregate as volume replacement to aggregate and reinforced with steel fibers recovered from scrap tire waste after preparation. Using recycled materials from local tire waste in the building sector is one way to solve the environmental problems resulting from its disposal and to produce a new type of sustainable concrete. A critical research gap exists in utilizing this local aggregate in non-traditional building materials. Addressing this gap, our research investigates the durability and mechanical properties of lightweight concrete by waste rubber tires; they are important due to their sustainability and environmental friendliness, especially in high-performance lightweight concrete and concrete applications in various construction. Several trial mixes were prepared with 10,15 and 20% coarse tire rubber waste aggregate (TRWA) and concrete mixtures with 5,10,15% fine TRWA as substitution by volume. Furthermore, 0, 0.5, 0.75, and 1% by volume of recycled steel fibers derived from waste tires (RSFs) were utilized to reinforce the samples. Test results for the HPLWAC with 20% coarse and 15% fine rubber tire replacement showed that the compressive, tensile, and flexural strengths, with 1% RSFs, increased by about 24%, 35%, and 56%, respectively. At the same time, the addition of 1% recycled steel fibers leads to an improvement of permeability by about 20% compared to the reference mixture without fiber. These results are very promising in taking into consideration a partial tire rubber waste replacement of 20% coarse rubber tires and 15% fine by the normal coarse and fine aggregate while keeping a competent structural application. Furthermore, SEM analysis was performed to assess the influence of rubber waste and RSFs on the microstructure of high-performance lightweight concrete. The results demonstrated that using specimens including tire rubber aggregate and reinforced with RSFs revealed that the microstructure of the cement paste is dense, homogeneous, and compacted with very small pores and microcracks. Additionally, there are cement paste particles that adhere to the fiber surface, indicating that there is adequate contact between the fiber and the cement matrix.