Geopolymer concrete/mortar is the new development in the field of building constructions in which cement is totally replaced by pozzolanic material like fly ash and activated by alkaline solution. This paper presented the effect of concentration of sodium hydroxide, temperature, and duration of oven heating on compressive strength of fly ash-based geopolymer mortar. Sodium silicate solution containing Na 2 O of 16.45%, SiO 2 of 34.35%, and H 2 O of 49.20% and sodium hydroxide solution of 2. 91, 5.60, 8.10, 11.01, 13.11, and 15.08. Moles concentrations were used as alkaline activators. Geopolymer mortar mixes were prepared by considering solution-to-fly ash ratio of 0.35, 0.40, and 0.45. The temperature of oven curing was maintained at 40, 60, 90, and 120 ∘ C each for a heating period of 24 hours and tested for compressive strength at the age of 3 days as test period after specified degree of heating. Test results show that the workability and compressive strength both increase with increase in concentration of sodium hydroxide solution for all solution-to-fly ash ratios. Degree of heating also plays vital role in accelerating the strength; however there is no large change in compressive strength beyond test period of three days after specified period of oven heating.

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Geopolymer is a new development in the world of concrete in which cement is totally replaced by pozzolanic materials like fly ash and activated by highly alkaline solutions to act as a binder in the concrete mix. For the selection of suitable ingredients of geopolymer concrete to achieve desire strength at required workability, an experimental investigation has been carried out for the gradation of geopolymer concrete and a mix design procedure is proposed on the basis of quantity and fineness of fly ash, quantity of water, grading of fine aggregate, fine to total aggregate ratio. Sodium silicate solution with Na 2 O = 16.37 %, SiO 2 = 34.35 % and H 2 O = 49.28 % and sodium hydroxide solution having 13 M concentration were maintained constant throughout the experiment. Water-to-geopolymer binder ratio of 0.35, alkaline solution-to-fly ash ratio of 0.35 and sodium silicate-to-sodium hydroxide ratio of 1.0 by mass were fixed on the basis of workability and cube compressive strength. Workability of geopolymer concrete was measured by flow table apparatus and cubes of 150 mm side were cast and tested for compressive strength after specified period of oven heating. The temperature of oven heating was maintained at 60°C for 24 h duration and tested 7 days after heating. It is observed that the results of workability and compressive strength are well match with the required degree of workability and compressive strength. So, proposed method is used to design normal and standard geopolymer concrete.

Geopolymer is a new invention in the world of concrete in which cement is totally replaced by pozzolanic material that is rich in silica and alumina like fly ash and activated by alkaline liquids to act as a binder in the concrete. Experimental investigation has been carried out to study the effect of water-to-geopolymer binder ratio on workability in terms of flow and compressive strength tested after heat curing in oven at 900C for 8 hours duration. Activated liquid to fly ash ratio of 0.35 by mass was maintained constant on the basis of past research. Sodium silicate solution with Na2O = 16.37%, SiO2 = 34.35% and H2O = 49.28% and 13 mole concentrated sodium hydroxide solution were used as alkaline activators. Test results show that the flow of geopolymer concrete increases with increase in the water-to-geopolymer binder ratio. But the compressive strength decreases with increase in water-to-geopolymer binder ratio similar to water/cement ratio in cement concrete.

Aggregate characteristics have a significant effect on the properties of concrete in the fresh state and the hardened state. They also influence the quantity of cement paste required to fill the voids between aggregate particles. The manual methods suggested for the measurement of aggregate characteristics are laborious, time consuming and approximate. This paper presents the development of a Digital Image Processing (DIP) based system for the measurement of sphericity, shape factor, elongation ratio and flatness ratio of coarse aggregate particles. The system is calibrated using standard objects such as marbles, coins and then used for the measurement of coarse aggregate particles having varied characteristics. Samples of rounded gravels and crushed aggregates from different crushers are considered for the study. The results indicated that the system can be used for the accurate measurement of aggregate characteristics.

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