An investigation on the mechanical properties of concrete mixed with crumb rubber and fly ash after exposure to elevated temperature

• Main Authors: Bautista, Denise Riana M., Romanillos, Gerard H., Sales, Kendrick H., Yabut, Ludwig Alain S.
• Format: text
• Language: English
• Published: Animo Repository 2018
• Subjects: Fly ash; Concrete; Cement; Crumb rubber
• Online Access: https://animorepository.dlsu.edu.ph/etd_bachelors/7735
• Institution: De La Salle University

The increasing amount of waste rubber tires has brought detrimental effects to the environment and various health risks. Thus, there is a necessity of finding ways to reuse them in order to reduce waste. The objective of the study is to determine the compressive, tensile, and flexural strength of concrete with 20% fly ash replacement cement while incorporating crumb rubber as partial replacement to fine aggregates after exposure to elevated temperature. The samples were comprised of 0%, 5%, 10%, 15%, and 20% crumb rubber replacement. Other properties determined were the slump, air content and unit weight, as well as the modes of failure that occurred to the concrete samples. It was observed that as the percentage of rubber increased, the strength parameters as well as unit weight decreased. Also, as the time of exposure to elevated temperature increased from 1 to 3 hours, the strength parameters decreased. Based on the results of the samples containing rubber, the samples with 5% rubber replacement to sand obtained the highest compressive, tensile and flexural strength whereas the samples containing 20% rubber obtained the least compressive, tensile and flexural strength. The optimum mix is 5% replacement of crumb rubber to fine aggregates, and 20% replacement of fly ash to cement, as its strength properties may be acceptable for structural use up to 1 hour exposure to elevated temperature. The concrete sample with 20% rubber replacement exposed to 3 hour elevated temperature is not a recommended mix as the samples experienced explosive spalling. It can be noted that the incorporation of rubber caused a decrease in workability, wherein the mix incorporating 20% rubber caused the cement, fly ash, water, sand, and rubber clumped up together forming ball-like shapes. The modes of failure that occurred to the cylinders tested for compressive strength showed mostly type 5 failure, which implies that the strength is relatively high, as the failure only occurred at the outermost tips of the specimen.