Abstract
In this paper, the mechanical and fracture properties of fly ash geopolymer concrete (FAGC) mixed with calcium aluminate cement (CAC) were explored. Fly ash was partially replaced by CAC with 2.5%, 5% and 7.5%. The results exhibit that the mechanical and fracture behaviors of FAGC are significantly influenced by CAC content. Based on the formation of more aluminum-rich gels, C-(A)-S-H and C-S-H gels, with the increase of CAC content, the compressive strength, splitting tensile strength and elastic modulus improved. Meanwhile, the peak load and effective fracture toughness show a monotone increasing trend. In addition, because C-S-H gels absorbed more energy, the fracture energy of FAGC increases. The maximal peak load, double-K fracture toughness and fracture energy reached up to1.79 kN, 4.27 MPam0.5, 10.1 MPam0.5 and 85.8 N/m with CAC content of 7.5%, respectively.
Highlights
Concrete is the most widely used building material; the production of one ton of cement will emit 600–800 kg of CO2, which accelerates global warming [1]
The results showed that the former system obtained C-(A)-S-H gel and sulfoaluminate in the medium alkaline medium
The results identified that the optimal replacement rate of calcium aluminate cement (CAC) is 10% on the compressive strength of 7 days and 28 days
Summary
Concrete is the most widely used building material; the production of one ton of cement will emit 600–800 kg of CO2 , which accelerates global warming [1]. It is necessary for concrete to switch over from Portland cement to a greener and environmentally friendly alternative binder with desirable mechanical and durability properties [2]. As one of the novel types of aluminosilicate inorganic polymer materials, geopolymer is produced by the reaction of solid aluminosilicate source materials and high concentration of alkali activator, which was described by Davidovits in the 1970s [3]. Through a large number of studies, fly ash geopolymer was reported to have many superior mechanical performances, such as high compressive strength, negligible shrinkage, good resistance to acid, and thermal stability, etc. In order to expand the application range of fly ash geopolymer, a large number of studies have been conducted to improve the performance of geopolymer by adjusting the chemical composition of the aluminosilicate raw materials. The preferred methods are to incorporate calcium-rich or silica-rich source materials, such as Portland cement, blast furnace slag, silica fume, rice husk ash, metakaolin, and nano-particles etc. [9,10,11,12]
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