Review On Geopolymer Concerte With Different Additives
Abstract
The development of new binders, as an alternative to Portland cement (PC), by alkaline activation, is a current researcher’s interest. Geopolymer binder is obtained by a manufacturing process less energy-intensive than Portland cement and involves less greenhouse gases emission and also reducing initial cost of the project. A supplementary material belongs to prospective materials in the field of civil engineering. Researchers have employed Various molecular ratio, temperature and duration, Fibers addition, Superplastizers, Setting time, alkaline activators and alternate binders to modify some properties of Geopolymer system. This paper presents a comprehensive overview of the previous works carried out on using different additives by varying various properties.
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Introduction
The use of alkali materials and aluminosilicates to form a cement is broadly referred to as 'Geopolymer' technology, coined by French researcher Davidovits, but is also known as alkali-activated cement and inorganic polymer concrete in various parts of the world. Geopolymer technology provides comparable performance to traditional cementitious binders, but with the added advantage of significantly reduced Greenhouse emissions, increased fire and chemical resistance and waste utilization. The use of Geopolymer in modern industrial applications is a recent development, becoming increasingly popular due to its intrinsic environmental and technical benefits.
Conclusion
General conclusions of this literature review can be summarized as following:
Compressive strength increases with S/A and N/A and decreases with H/N (Optimum level S/A=3-3.3 and N/A =0.85-1.0).
Optimal characteristics of alkali-activated binder related to the following chemical composition of the binding gel: Ca/Si=0.34–0.50, Al/Si=0.15–0.24, Mg/Si=0.07–0.16 and Na/Si=0.21–0.37.
In term of molar ratios, optimum was achieved at Al2O3/Na2O of 1.09 and SiO2/Na2O molar ratios of 3.58.
Increase in Al (low SiO2/Al2O3) leads to products of low strengths, accompanied by microstructures with increased Na–Al–Si grains rather than amorphous Na– Al–Si-containing geopolymers.
Highest compressive strength was obtained at the temperature and duration of curing of 120°C and 20 hours (33 MPa) at 7 days.
At the temperatures higher than 800C, the strength of all tests is not found to increase. Hence, 800C can be thought of as an optimum temperature for curing the geopolymer samples.
Fly ash based geopolymer and shows that the compressive strength is increased with a higher molar concentration of NaOH. Mix of sodium silicate and NaOH(mix ratio 1:1and SiO2/Na2O = 8).
Higher Na2SiO3/NaOH ratio than 0.32, it was believed that the high amount of waterglass liquid may inhibit the geopolymerization process.
Alkali fusion process used to enhance the reactivity of the volcanic ash. Various amount of Metakaolin up to 60% was used to consume the excess alkali needed for the fusion. The amount of reactive phase in natural volcanic ash is equal to 29%.
Addition of 6% nano silica shows appreciable improvement in compressive, flexural and tensile strength at 28 days under ambient temperature curing.
Mixtures having 10% slag, 40% alkaline activator and SS/SH ratio 1.5–2.5 with no extra water can be considered as the optimum mixture for reasonable compressive strength in ambient curing condition with a setting time comparable to that of OPC concrete.
Modified Polycarboxylate based SPs(latest generation) was the most efficient type which increased the relative slump of the paste upto 45% with reference to the paste without using any SP.
This paper has presented about the geopolymer concrete with various researches based on strength properties and other criteria related to improve the Strength of geopolymer concrete. This will be useful for developing eco-friendly concrete in all the aspects.