Design and performance of fiber-reinforced shrinkage compensating eco-friendly concrete

Abstract

Eco-Crete is an ecological and economical concrete that benefits from high packing density of solid materials and reduced paste. Eco-Crete can enhance the service life of structures by reducing the risk of shrinkage cracking. In this study, shrinkage mitigating materials included an expansive agent (EA), a shrinkage reducing admixture (SRA), and a lightweight sand (LWS), as well as steel and synthetic fibers were used to minimize the risk of cracking. A total of 35 fiber-reinforced Eco-Crete mixtures were prepared with 350 kg/m3 of cementitious materials and 55 % substitution of fly ash and slag. Key fresh and mechanical properties in addition to plastic, restrained, and drying shrinkage were evaluated. Results showed that 32-week drying shrinkage of Eco-Crete made with shrinkage mitigating strategies was limited to 400 µstrain, and none of the selected Eco-Crete mixtures experienced cracking up to 112 d under restrained shrinkage testing. Mixtures incorporating only EA and synthetic fibers exhibited excessive initial expansion and minor plastic shrinkage cracking. Eco-Crete mixtures developed at least 40 MPa compressive strength after 56 d. Mixtures made with EA and SRA presented the highest flowability and mechanical properties and the lowest drying shrinkage. The use of synthetic fibers exhibited a better flexural pre-cracking performance than steel fibers. However, steel fiber-reinforced mixtures showed 250 % greater flexural toughness. The use of steel fibers was more effective than synthetic fibers in reducing long-term shrinkage and limiting initial expansion caused by the high content of EA. Statistical analysis and embodied carbon assessment revealed the advantages of using Eco-Crete made with 5 % EA and 0.5 % SRA and 0.5 % synthetic fibers to secure low-shrinkage Eco-Crete.