Research on Pure Modes I and II and Mixed-Mode (I/II) Fracture Toughness of Geopolymer .

What is it about?

The unsustainable use of resources and the rising demand for traditional concrete have disrupted ecological equilibrium, necessitating the adoption of a more appropriate and long-lasting alternative. One such substitute for cement in concrete production is geopolymer concrete, although this material is prone to cracking and fracturing due to its low tensile strength, leading to costly repairs or even structural collapse. Fiber-reinforced concrete has recently been widely adopted as a construction material to counteract these issues. This research examined the crack proliferation and fracture toughness of geopolymer concrete comprising different fibers using a cracked Brazilian disc. Four different fibers were used, such as polypropylene and steel fiber (short and long), at a dosage of 1.5% by volume. Fracture toughness was computed for various modes (I, II, and I/II) of fractures, and crack propagation from cracked specimens was studied. A different angle of inclination (0, 15, 28, 83, 60, 75, and 90 degrees) was used to conduct the Brazilian disc test on the specimens with respect to the preexisting crack direction. The findings indicate that the increasing loading angle increased the load-carrying capacity. The fracture toughness values of specimens under all three modes ranged from 0.26 to 1.75 MPa.m1/2. Additionally, long polypropylene and steel fibers exhibit higher fracture toughness than short fibers.

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Why is it important?

An excessive amount of carbon dioxide and other greenhouse gases are released due to concrete production. Therefore, scientists have been looking into possible solutions to slow the dramatic rise in atmospheric carbon dioxide levels [1]. Environmentalists and scientists have advocated the utilization of supplemental cementitious materials due to the cement industry’s high carbon footprint (about one kilogram of CO2 is released for every kilogram of cement manufactured) [2]. Cement is often supplemented with cementitious materials, mainly waste materials or industrial by products, to reduce the harmful effects on the ecosystem and natural surroundings. The concrete’s durability was improved by using supplemental cementitious materials in place of some cement, which also helped save natural resources and cut down on carbon dioxide emissions. The improvement was primarily attributable to the pozzolanic properties of supplementary cementitious materials, which caused a change in the microstructure of the cement matrix.

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