Mechanical properties of hybrid fiber reinforced lightweight aggregate concrete made with natural pumice

The purpose of this study is to improve the ductility of pumice lightweight aggregate concrete by incorporating hybrid steel and polypropylene fibers. The changes in mechanical properties and also bulk density and workability of pumice lightweight aggregate concrete due to the addition of hybrid steel and polypropylene fibers have been studied. The properties were investigated include bulk density and workability of fresh concrete as well as compressive strength, flexural tensile strength, splitting tensile strength and toughness of hardened concrete. Nine concrete mixtures with different volume fractions of steel and polypropylene fibers were tested. A large increase in compressive and flexural ductility and energy absorption capacity due to the addition of steel fibers was observed. Polypropylene fibers, on the other hand, caused a minor change in mechanical properties of hardened concrete especially in the mixtures made with both steel and polypropylene fibers. These observations provide insight into the benefits of different fiber reinforcement systems to the mechanical performance of pumice lightweight aggregate concrete which is considered to be brittle. These results provide guidance for design of concrete materials with reduced density and enhanced ductility for different applications, including construction of high-rise, earthquake-resistant buildings.

Research highlights
► Steel and PP fibers reduce the risk of segregation in lightweight aggregate concrete.
► PP fiber has minor effect on mechanical properties of concrete at fiber volume less than 0.4%.
► Both PP and steel fibers significantly improve ductility of lightweight concrete.
► Steel fibers increase the flexural strength up to 200%.
► Effect of fibers on flexural strength is more than the improving effect of fibers on tensile strength.