Workability and Strength Properties of Class C Fly Ash-Based Geopolymer Mortar

Abstract

Fly ash-based geopolymer mortar normally achieves expected properties by heat curing. This becomes one of the obstacles for in-situ applications. The development of high calcium fly ash-based geopolymer mortar, suitable for ambient curing, will gain the applicability of such a material in civil structures. This article reports the results of an experimental study on mortar workability and the increasing of compressive strength of class C fly ash-based geopolymer mortar created in ambient curing condition. The main synthesis parameters such as alkali to the cementitious mass ratio varied from 30% to 40% by an increment of 5% and absolute volume of paste to absolute volume of voids of the aggregate ratio varied from 1 to 2 by an increment of 0.25. These parameters were designed to figure out their individual effects on mortar workability and the mechanical properties for the production of geopolymer mortar. The results suggested that the workability of mortar generally increased by using alkali to the cementitious mass ratio. The compressive strength of 60 MPa and the direct tensile strength of 2.8 MPa, the ratio of alkali to the cementitious mass of 0.35 and absolute volume of paste to absolute volume of voids of the aggregate ratio was 1.5; it was obtained at ambient temperature after 28 days of age. The results will be useful for developing the knowledge for the use of class C fly ash in producing geopolymer concrete, which is currently in progress. Hopefully, this contribution of research will improve the applications of such new binding material in the future.

Effect of the Mortar Volume Ratio on the Mechanical Behavior of Class CI Fly Ash-Based Geopolymer Concrete

“…The high compressive strength of GC4 caused by the amount of paste is sufficient to produce excess thickness, thereby allowing a perfect geopolymer reaction and an adequate amount of binding gel [31]. This is consistent with the previous study that geopolymer paste and mortar compressive strength amounted to 60 MPa after 56 days [32,33]. The condition is slightly different from the OPCC because an increase in the cement paste raises the volume of water needed for the hydration process, resulting in higher workability and lower compressive strength.…”

“…The relationship between workability and mechanical properties at different excess paste levels was observed in detail based on the absolute volume ratio of paste to river sand void, Rm. Some previous research on GM stated that the highest mortar compressive strength is attained if the value of the Rm ratio is 1.5 [32] where Gsfa is the fly ash specific gravity, Gsfa is the SH specific gravity, Gsfa is the SS specific gravity, Wfa is the weight of fly ash in kilograms per cubic meter, Wss is the weight of SS solution in kilograms per cubic meter, Wsh is the weight Assuming the weight ratio of SH to SS (R) and that of fly ash to alkali solution SS + SH (A) are known, like the water-cement ratio in the OPCC system, then Equation 4 is simplified as follows:…”

“…The previous research on geopolymer paste (GP) and geopolymer mortar (GM), has several parameters that resulted in high mechanical strength. These include the molarity of NaOH of 10 M, the ratio of Na2SiO3 to NaOH (R) of 2, the weight ratio of alkaline to fly ash (A) of 0.35, and the volume ratio of paste to sand voids (Rm) of 1.5 [32,33]. Furthermore, the Rc parameter was raised by 0.25 increment from 1 to 1.75 to determine the effect of the volume ratio of mortar to CA void on the GC mechanical properties.…”

The influence of low alkaline activator on the compressive strength and workability of geopolymer concrete

“…According to Harjito et al [9][10], the use of alkaline activator 6% NaOH 14M molarity, fly ash with a treatment temperature of 60 o C, the compressive strength reaches 28-66 MPa. Alkaline activator 6.5% with NaOH 8-10 M molarity, fly ash with room temperature treatment obtained compressive strength of 7.5-45 MPa [11][12][13][14]. The use of alkaline activator of 10.8% NaOH 16M, fly ash with a treatment temperature of 60 o C resulted the compressive strength reached 30-60 MPa [15][16][17][18].…”

Competitive Risaralda, generating research alliances for development

“…Shanmugavel et al (2020) say that the Ordinary Portland Cement product releases a focus six times greater than that of CO2 compared to geopolymer-based concrete. Cornelis et al(2019) believe that a lot of construction waste is generated every second worldwide, which is not used effectively. Many of them are willing to make new land; at the same time, they also cause pollution of construction waste.…”