Effect of ground granulated blast furnace slag and fly ash ratio and the curing conditions on the mechanical properties of geopolymer concrete

摘要

Geopolymer concrete (GPC) is an innovative and eco-friendly construction material. In the experimental investigation, examine the effect of ground granulated blast furnace slag (GGBFS) in the GPC by replacing the fly ash in the various ratios in the different mix design. Fly ash/GGBFS as 100/0, 75/25, 50/50, and 25/75 respectively rate by weight percentage taken in the mix design. All the mix designs specimens cured in two types are ambient-cured and oven-cured at 80℃ for 24 h after the demolding of the samples, and both types samples tests at 7,14, 28, 42 and 56 days for strength (compressive, splitting tensile, flexural strength) and non-destructive (rebound strength and ultrasonic pulse velocity UPV). Examine the density, Poisson ratio and modulus of elasticity of the all mix designs samples of both types of cured specimens at 28 days after the casting. Geopolymer bonding formation is amorphous or crystalline in the bonding mineral components analyzed by the X-ray diffraction test. Examine the thermal stability of the geopolymer bond paste after the gaining strength up to the 850℃ by increases the temperature 10℃ per minute gradually in the thermogravimetric analysis after the 28 days of casting after the experimental investigation results indicate that the ambient-cured samples got less engineering strength as compared to the oven-cured samples. However, in both cured samples, the mix has a ratio of 75/25 of fly ash/GGBFS as binding material got higher mechanical strength than other mixes. In the GPC mix design, the GGBFS 25 by weight of binder with fly ash has instantly increased the strength. However, after the increase of replacement of GGBFS with the flyash slightly decreases the strength of the mix designs. The rebound hammer test strength was marginally higher than the same mix designs specimens destructive compressive strength. UPV shows the similar trends of the graph of ambient-cured and oven cured to the rebound strength. The oven-cured specimens show a higher UPV compared to the ambient-cured specimens. The ambient-cured sample has a higher density compared to the oven-cured GPC specimens of different mix designs. Still, in both cured samples, mix design samples of 75/25 fly ash/GGBFS ratio got the average maximum density. The Poisson ratio of the ambient-cured GPC specimens is slightly excessive than oven-cured specimens. Still, the modulus of elasticity of the GPC mix designs is higher for the oven-cured samples. Weight loss of the specimens occurs at the elevation of temperature with the rise in the content of GGBFS in the mix gradually up to the 850℃, but in oven-cured samples, the weight loss was slightly excessive compared to the ambient-cured samples. After the experimental results of mechanical properties, propose the relationship equations among the mechanical properties. Relationship between flexural strength and compressive strength, splitting tensile and compressive strength, and modulus of elasticity compressive strength. Proposed equations are f_(fs)=0.25f_c~(0.85),f_(st)=0.25f_c~(0.73),E_c=3622f_c~(0.537), respectively.