A REVIEW ON GEOPOLYMER CONCRETE WITH COPPER SLAG AS A PARTIAL REPLACEMENT FOR FINE AGGREGATE

1K.Mahendran, 2N.Arunachelam1Associate professor,2Research Scholar, Rural Technology Centre, Gandhigram Rural Institute,

Gandhigram.Mahendran_gri@rediffmail.com,arunachelam.gri@gmail.com

ABSTRACT

The use of industrial wastes in concrete production is environment friendly because of its reduction in consumption of the natural resources like sand and course aggregate and also reduces the Co2 emission during the cement manufacturing process. Geopolymer an innovative binder material which was invented by Davidovits in 1978 can be synthesized from alkali activation of materials like Fly ash, Rice Husk ash which are rich in Silicon and Aluminium. This paper presents the future study of utilizing the copper slag as partial replacement for fine aggregates. Geopolymer concrete batches will be made with varying the percentage of copper slag as partial replacement for fine aggregate with varying molarity of sodium hydroxide solution and properties such as compressive strength , Flexural strength, Splitting Tensile strength, and durability characteristics will be studied for this concrete cured under ambient condition and also in elevated temperatures.

INTRODUCTION

Cement is the major constituents of the concrete. The worlds yearly production of cement is about 1.6 billion tons accounts for about 7% of global loading of carbon dioxide in to atmosphere. Ordinary Cement concrete typically contains 12% of cement and 80% of aggregates by mass, globally concrete making consumes sand, gravel and crushed rock. Utilizing these natural resources causes several environmental impacts like depletion of Ground water, loosing water retaining sand strata, affecting the bank side vegetation and aquatic life are few impacts due to sand mining in river bed.in order to overcome the above problem “Geopolymer” which was developed by Davidovits, that can be used as a binder which is alternate to the cement. The binder is produced by the reaction of an alkaline liquid with a source material that is rich in silica and alumina. Wide range of research related to geoplymers, with some reporting on chemical composition aspects or reaction process and few of them related to mechanical properties and durability. Fly Ash can be used as a binder in Geopolymer which has a high amount of silica and alumina which is solid waste generated in thermal power plants. Hence Fly ash based geoplymers concrete is a good alternative to ordinary Portland cement concrete.

Copper slag is an industrial by-product material produced from the process of manufacturing copper. It has been estimated that for manufacturing 1 tonne of copper an amount of 1.5 tonnes of copper slag is produced. Copper slag possesses mechanical and chemical characteristics that qualify the material that can be used geopolymeric concrete as partial replacement/substitute for the fine aggregate. Also copper slag contains Al2o3, SiO2 and Fe2O3 which may react with the alkaline solution.

Literature Review

The chemical composition of the Geopolymer resembles similar to the natural zeolite mineral and amorphous in microstructure[1], Geopolymer are synthesised by polymerization process involves a substantially fast chemical reaction under alkaline condition on Si-Al minerals that results in a three dimensional polymeric chain and ring structure consisting of Si-O-Al-O bonds as follows

Mn [-(SiO2) z-AlO2] n. wH2O

Where M = the alkaline element or cation such as potassium, sodium or calcium; the symbol – indicates the presence of a bond, n is the degree of polycondensation or polymerisation; z is 1,2,3, or higher.[2], Unlike ordinary Portland cement, Geopolymer do not form

calcium silicate- hydrates(CSHs) gel for matrix formation and strength, these Geopolymer are sometime referred to as alkali activated alumina silicate binders[4]. Low-calcium fly ash-based Geopolymer concrete has excellent compressive strength, suffers very little drying shrinkage and low creep, excellent resistance to sulphate attack, and good acid resistance [3]. The concentration of NaOH greatly influence strength of Geopolymer concrete[18] The Geopolymer concrete beam exhibit increased flexural strength, the deflection at different stages including service load and peak load stage are higher for Geopolymer concrete beams[5].Mixing of time of the Geopolymer concrete influence strength and workability of the Geopolymer concrete. Longer mixing time yielded lower sump value and higher compressive strength and higher density of concrete[13]. The compressive strength of Geopolymer increases with increase in duration of curing time and also the temperature of the oven curing[6], the effect of treatment time on the compressive strength of Geopolymeric pastes can not be generalised for 5 and 6 hours , however it seems that the extremely higher durations such as 21 hours are very effective for the development of compressive strength[7], The optimum mix ratio for the Geopolymer is 1:1.5:3.3 with a solution (NaoH & Na2SiO3 combined together) to fly ash ratio of 0.35 [12], Addition of silicia fume up to 7% greatly enhances the geopolymerization process, while further increase of silica fume leads to decrease in the mechanical characteristics[14] the modulus of elasticity of the fly ash based Geopolymer concrete is observed as on par strength when compared to conventional concrete[16],the flextural capacity of the beams is influenced by the concrete compressive strength and the tensile reinforcement ratio[17]. also apart from curing temperature and time few other parameters also influence the strength of the Geoploymer concrete such as alkaline liquid to Fly Ash ratio, molarity of Na OH, ratio between Sodium silicate and sodium hydroxide.

On the other hand utilization of copper slag in cement concrete an alternative for the partial natural sand Copper Slag an industrial by product which is produced during the manufacturing of copper. For each ton of

copper slag manufacture it generates 2.5 tonnes of copper slag. In India 8 lakh tons of copper slag is generated every year, it has been widely used for abrasive tools, roof granules, cutting tools, abrasive, tiles, glass, road base construction, rail road ballast and cement and concrete industries [8]. Addition of copper slag increases the density thereby the self-weight of the concrete [9]. Compressive strength of the cement concrete increased by 55% at 40% replacement of the fine aggregate by copper slag and upto 75% concrete gain more strength than control mix concrete strength [10]. Marginal increase in the flexural strength of cement concrete specimen with 40% replacement of copper slag for sand [11].

RESEARCH SIGNIFICANCE

Cement concrete place an vital role in the construction industry and they are the higher utilizes of the natural resources. In terms of reducing the utilization of natural resources and global warming, Geopolymer concrete with copper slag as replacement for aggregates could reduce the CO2 emission to the atmosphere during the manufacturing process and utilization of copper slag in Geopolymer concrete may reduce the environment problems caused by the sand mining.

MATERIALS

The materials needed to manufacture the fly ash based Geopolymer concrete are fly ash, alkaline solution and aggregates.

Fly ash to be used in making the Geopolymer concrete is obtained from the Neyveli Thermal Power Station and the chemical composition is shown in the table 1.

Alkaline liquid are also required to activate the fly ash in the geopolymerisation process. The most common alkali activator used is combination of sodium silicate (Na2Sio2) and sodium hydroxide will be used in making of Geopolymer concrete. The role of alkaline solution is to dissolve the reactive portion of source material Si and Al present in fly ash and provide a high alkaline liquid medium for condensation polymerisation reaction [15]

Aggergates

Fine aggregate locally available river sand having a specific gravity of 2.64 and confirming to Zone III will be used as a fine aggregate

Coarse aggregate will be a crushed granite metal having a specific gravity of 2.70, passing through 20 mm and retained in 4.75 mm and having a water absorption of 0.89%.

REFERENCES

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