This paper presents a study of the flexural strength of geopolymer concrete beam using high calcium content fly ash (FA) in marine environment, without high heat curing. Two series of beam specimens were loaded to failure to study the effect of chloride environment on the flexural strength of geopolymer concrete beams. Series I specimens were subjected to sea environment, whereas series II were kept at room temperature. Tests performed on concrete cylinders show that the sea water has no effect on compressive and splitting tensile stress of high calcium content FA based geopolymer concrete. However, the ratio of splitting and compressive strength for both series was approximately 44%, almost double than that of normal concrete. In addition, the flexural test of concrete beams shows that the average cracking load for series I specimens was 275% higher than that of series II. However, the ultimate load, crack pattern and deflection characteristic for both series were very similar.

This study is conducted to determine the effect of four variables on compressive strength of geopolymer concretes. These four variables are binder/aggregate, Alkalinene/fly ash, effect of superplasticizer (SP) addition and curing system. The compressive strength is important mechanical properties for construction material. Taguchi experimental design method is used to compile the concrete composition of geopolymer to achieve the maximum compressive strength. Specimens concrete used is a cylinder with 100 mm diameter and 200 mm height. Compressive strength test is performed at 28 day using SNI 03-6825-2002, Indonesian National Standard. This study concludes that the chloride environment has a beneficial effect on the compressive strength of the concrete. In addition, the Alkalinene/fly ash ratio and binder/aggregate give a significant effect on the compressive strength of geopolymer concretes.

This research is to find out the contribution of waste energy utilization in Indonesia as a binding agent of alkali-activated mortar. In a previous study, researchers investigated mortar made from class F fly ash/GGBFS/micro-silica in Japan. The inclusion of GGBFS is to shorten/normalize the setting time and microsilica is to improve mortar performance. This research is then continued by using abundant waste material in Indonesia, namely class C fly ash, by making cubic mortar specimens. Setting time of class C fly ash paste from Indonesia is very fast, in contrast to that of class F fly ash paste from Japan. Sandblasting as abundant waste material in Indonesia is substituted to class C fly ash to lengthen the setting time of paste and to improve standard deviation of a compressive test of mortar specimens. On the other hand, the addition of sandblasting waste has a negative effect, because it reduces a compressive strength of mortar specimens.

This study is conducted to determine the effect of five variables on mechanical properties of geopolymer binders. These five variables are chloride environment, NaOH molarity, Na2SiO3/NaOH ratio, fly ash/alkaline activator (FA/AA) ratio and superplasticizer (SP) addition. The mechanical properties considered are compressive strength, porosity and density. Taguchi experimental design method is used to compile the binder composition of geopolymer to achieve the maximum compressive strength. Specimens binder used is a cylinder with 25 mm diameter and 50 mm height. Compressive strength test is performed at 28 days using SNI 03-6825-2002 (Indonesian National Standard) and porosity of the binder is determined using vacuum saturation apparatus similar to that developed by RILEM. The density of the binder is measured using Ultrasonic Pulse Velocity (UPV). This study concludes that the chloride environment has a beneficial effect on the compressive strength of the binder. In addition, the FA/AA ratio and NaOH molarity give a significant effect on the compressive strength of geopolymer binders.

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