Siddharth Roy Chowdhury

Personal Information

Title: Geopolymer Concrete as an alternative to Ordinary Portland Cement to reduce CO2 emissions


      Studies have shown a well-known fact that the increase in the level of CO2 (a greenhouse gas) is responsible for increasing the Earth’s overall temperature. Greenhouse gases are mostly responsible for heating the Earth’s surface by trapping the radiation from the Sun. Hence, the concentration of greenhouse gases is directly proportional to the radiation trapped. Without the gases however, the Earth’s surface would remain at a temperature of -18 ⁰C and life threatened.

         The main concern is that the carbon emissions contribute to the atmosphere and less radiation escapes which heats the Earth’s surface more so than required. In the upcoming years, studies have shown that the surface will keep getting hotter and hotter unless measures are taken to reduce the carbon emissions.

One of the sources of these carbon emissions is cement. Research shows that cement releases high amounts of CO2 to the atmosphere. 1 tonne of cement releases 1 tonne of CO2 which contributes to 7% of world CO2 emissions. That might seem like a minuscule portion of the big picture, nonetheless it affects the heating of the Earth’s surface since most of the Earth’s structures are built from Ordinary Portland Cement. The question now is to reduce the vast application of cement and find an alternative.

           One possible alternative is the Geopolymer concrete which is a hardened cement-like paste made from fly-ash and alkaline solutions. Fly-ash is the by-product of combustion reactions, and comprises of fine particles like alumina-silicate that rise with the flue gases. A Combination of sodium hydroxide (NaOH) or potassium hydroxide (KOH) and sodium silicate or potassium silicate can be used as alkaline solutions.

Research Objective


            The research objective to reduce the carbon emission from Ordinary Portland Cement and to replace such cement with Geopolymer concrete which provides better results in various different environments as compared to the Portland cement.

            A brief process to manufacture Geopolymer cement is as follows. The alkaline solutions induce the Si and Al atoms in the source materials, example fly ash, to dissolve. Gel formation is assisted by applying heat. Gel binds the aggregates, and the unreacted source material to form the Geopolymer concrete. The aggregates are prepared in saturated-surface-dry (SSD) condition, and are kept in plastic buckets with lid. The fly ash and the aggregates are first mixed together dry in 80-litre capacity pan mixer. Saturated-surface-dry is the condition of the aggregate in which the pores in each particle of the aggregate particle are filled with water and no excess water is on the particle surface. The liquid component of the mixture is then added to the dry materials and the mixing continued usually for another four minutes. The fresh concrete could be handled up to 120 minutes without any sign of setting and without any degradation in the compressive strength. The workability of the fresh concrete is measured by means of the conventional slump test. Curing is done at 60-90 ⁰C.

          The following are the major advantages of using Geopolymer concrete. It cuts the world’s carbon content. Fly-ash is an unnecessary by-product, and hence easily accessible at a low cost. It shows better compressive strength as compared to ordinary Portland cement. It is fire-proof, eco-friendly, and is resistant to both acid and salt environments. Due to its nature of low permeability, it can also be used for underwater applications or for waste containments to prevent seepage.

       Major hurdles of using Geopolymer cement is that gathering all the different source materials can be problematic. Adding different amounts of alkaline solutions have shown to change the properties of the soluble silicate making it difficult to handle. Contaminants present with the fly-ash cannot be removed and hence adds to possible structural defects. Since Geopolymer concrete is a new material, it is not totally trusted compared to Portland cement. Replacing the cement with polymer based material might take some time; however, it is definitely worth in the long run.

Research Methodology

       To pursue this research, information already existing on the internet shall be collected and a detailed literature survey to be done. Different parameters will be chosen from the already identified studies and further improvement to be made in that particular research section.

            Firstly, different types of aggregate materials for construction as well as fly-ash from suitable sources shall be collected. The materials and alkaline solutions collected should be sufficient to last the length of the project. Using elemental analyzer, the different components in aggregate materials as well as fly-ash should be analyzed and compared and divided into separate batches to perform experiments. Each batch can undergo treatment from different alkaline solutions or other changes in the parameters and the results accordingly compared.

Next alkaline solutions as well as different polymer materials can be selected to provide for different improvement factors in the experiment such as compressive strength, workability, or reaction to the environment. Machines for testing viscosity, compressive strength and several other important factors in cement industries shall be made use of in the research. Slump test to be performed after Geopolymer concrete is formed.

Different tests such as creep test, drying shrinkage test, sulphate resistance test, or acid resistance test shall be performed in order to compare the strength of the Geopolymer to Portland cement. Test parameters and results shall be clearly defined and compared.

          Graphs to identify changes in strengths and viscosity are to be determined, displayed and compared with the Ordinary Portland Cement. Regression analysis, and strength of various samples also compared. 

Research Schedule

In order to assure that the research proceeds smoothly, a particular schedule is to be followed

  • First to sixth month is reserved for lectures, literature surveys, theoretical study and other secondary data collection.
  • Seventh to sixteenth month is reserved for field work and primary data collection.
  • Seventeenth to twenty-fourth months is designed for analysis, writing, and presenting the thesis.

This plan excludes the Japanese language study period. The schedule is subject to change as and when advised by my guiding professor.

Projects Engaged in at Present

             Currently, only the theory portion of this research has been developed and experimental work has yet to be done. However, as the project is economically feasible and not performed in harmful environment as such, research can be performed in depth having suitable alternative and various different parameters controlled.

A project that I am engaged in currently is making of biodiesel from waste cooking oil for which the experiment has already been performed and results achieved. Successful utilization of waste cooking oil which is thrown away to make a biodiesel which is less harmful to the environment is something to aspire to.

Another project is the use of polymers in briquettes to enhance the adhering nature of the material and keep it moisture free so as to ultimately improve the combustion characteristics. Project is still ongoing and results are yet to the achieved.

       I have also extensively involved myself with learning about the efficiency and capacity of multi-effect evaporators and developing a way to increase the feed capacity and the steam economy of a plant during my summer internship for which my idea about inserting a plate type heat exchanger after the multi-effect evaporator in line was considered.

              During my period of summer vacation, I have involved myself with a brief understanding of all the sections of a textile plant including the manufacturing, textile forming, solvent recovery, quality management, dyes, Differential Control Systems, and the marketing department. Knowing the whole process has given me a sense of understanding and achievement. Some aspects to improve in the industry have also shown up when viewing the process as a whole.

Relation of Project to the Technical/Academic/Economical Development of India

          First and foremost, reducing the carbon content is beneficial to any part of the world. Although carbon emissions from building add up to a minute amount of 7%, reducing this factor might benefit people in the long run. Adding different types of polymeric materials, as well as, experimenting with different alkaline solution and aggregate, strength of the new Geopolymer concrete can be enhanced and utilized in different industries accordingly.

            Success of this relatively new concept if spread world-wide can bring about great benefit in cutting down the carbon emissions. Increasing parameters like compressive strength, durability, workability can also help in construction of buildings that are resistant to different environment. It can be used universally. The main concern is probably the replacement of the already existing buildings with Geopolymer concrete. However, in such cases, an overcoat can be developed which assists in providing the same feature as that of the polymer concrete, but without the need to replace the whole building and start anew.

           Hence, I am not only trying to benefit India but the world as a whole, if there is a chance to perform this experiment extensively over the period of two years. It is no doubt that Geopolymer concrete holds a secret to successful reduction of carbon emission in the near future and I would very much like to play an active part in the role of bringing about this change.