Abstract
Abstract In this study, the effects of steel fibers on the mechanical properties of the geopolymer concrete – compressive, splitting tensile, and flexural strength; compressive elastic modulus; and fracture properties – were evaluated. Milling steel fibers were incorporated into the geopolymer concrete, and the volume fraction of the steel fibers was varied from 0 to 2.5%. Fly ash and metakaolin were chosen as the geopolymer precursors. Fracture parameters – critical effective crack length, initial fracture toughness, and unstable fracture toughness – were measured by a three-point bending test. The results indicated that all the mechanical properties of the geopolymer concrete are remarkably improved by the steel fibers with the optimum dosage. When the steel fiber content was under 2%, the cubic and axial compressive strength and the compressive elastic modulus increased. The inclusion of 2% steel fibers enhanced the cubic and axial compressive strength and the compressive elastic modulus by 27.6, 23.7, and 47.7%, respectively. When the steel fiber content exceeded 2%, the cubic and axial compressive strength and the compressive elastic modulus decreased, having values still higher than those of the geopolymer concrete without steel fibers. The splitting tensile strength and flexural strength of the concrete were enhanced with increasing steel fiber content. When the steel fiber content was 2.5%, the increment of the splitting tensile strength was 39.8%, whereas that of the flexural strength was 134.6%. The addition of steel fibers effectively improved the fracture toughness of the geopolymer concrete. With 2.5% steel fibers, the initial fracture toughness had an increase of 27.8%, and the unstable fracture toughness increased by 12.74 times compared to that of the geopolymer concrete without the steel fibers.
Highlights
Cement concrete has been extensively used in construction worldwide because it is a low-cost raw material and can be formed into any shape or size
The variation in the cubic compressive strength of the reinforced geopolymer concrete with the steel fiber content is shown in Figure 6, and it can be described by the following formula: y = −3.6x4 + 16.7x3 − 24.1x2 + 16.0x + 43.3, (13) R2 = 0.96
The addition of the steel fibers assists in maintaining the integrity of specimens, and when their volume fraction is 2.0%, they have the maximum effect on the integrity of the geopolymer concrete
Summary
Cement concrete has been extensively used in construction worldwide because it is a low-cost raw material and can be formed into any shape or size. Ordinary Portland cement, as one of the major raw materials of cement concrete, requires various natural sources and substantial energy, and will produce massive amounts of greenhouse gases during the production. Based on studies, producing 1 ton of cement requires approximately 1.6 ton of raw materials; it utilizes approximately 1,300 kW h of embodied energy and releases approximately 0.8 ton of the greenhouse gas, CO2 [1,2,3,4]. The amount of CO2 produced during the production of concrete accounts for 7–10% of the total global CO2 emission in accordance with the studies [5]. It is in conflict with the concept of sustainable development to abuse cement concrete. Considering the above factors, it is imperative to identify other construction materials for replacing cement concrete
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