The optimal pretreatment condition of coconut husk by physicochemical methods for biogas production was investigated. The coconut husk was dried and ground into powder (~0.1 nm) and was then determined for chemical contents such as cellulose hemi-cellulose and lignin respectively. The chemical contents of cellulose hemi-cellulose and lignin were 35.67±2.02 7.41±0.69 and 40.82±0.62 w/w respectively. After pretreatment with 4 different methods the results showed that the pretreatment of sodium hydroxide 30 % (w/w) gave the highest chemical contents of cellulose hemi-cellulose and lignin with 43.30±0.03 33.69±7.48 and 27.36±0.03 w/w respectively. As for the biogas production the result showed that the ratio of coconut husk to cow dung of 1:4 with C:N ratio of 23:1 gave the highest cumulative biogas of 442.6 ml for 30 days. Methane and carbon dioxide contents were 46.1 and 23.1 %. Moreover the removal percentages of the total solids (TS) volatile solid (VS) suspended solids (SS) and COD were 69.3 32.5 50.0 and 58.4 % respectively. The coconut husk could be used as an alternative material for the application of biogas production with cow dung in the near future.

This research aimed to investigate the effect of rice husk ash blended with fly ash on mechanical properties of concrete including compressive and flexural strengths. The studied parameter was the replacement percentages of cement by rice husk ash blended with fly ash at 0 30 and 50 by weight of cementitious materials. The constant ratio of rice husk ash to fly ash of 1:1 by weight was used in this study. The test results showed that the strength of concrete decreased while the replacement percentages of rice husk ash blended fly ash increased. The compressive strength at the age of 7 days of concrete containing rice husk ash blended with fly ash was lower than the control concrete but concrete containing rice husk ash and fly ash at 30% by weight of cementitious materials had comparable compressive and flexural strengths at the age of 28 days to the control concrete. As for the results the mechanical properties of concrete containing rice husk ash blended with fly ash at 30% by weight of cementitious materials were comparable to the control concrete.

This research studies the potential for using waste ash from industrial and agricultural by–products as a geopolymer material. This paper presents a study of the resistance to chloride penetration and resistance to sulfuric acid of geopolymer mortar containing ground rice husk ash (RA) and ground bagasse ash (BA). Geopolymer mortars with constant liquid to ash ratio and similar flow were used for the tests. Compressive strength porosity chloride penetration test Rapid migration test of chloride depth chloride ion diffusion coefficient immersion test of chloride depth and weight loss with impressed sulfuric acid were investigated. Test results show that the workable flow of geopolymer mortar was in the range of 110–115% and was dependent on the ratio by mass of sodium silicate to NaOH and the concentration of NaOH. Extra water was used to improve the workabililty. In case of rice husk ash geopolymer mortar the geopolymer mortars with high strengths were obtained with concentration of NaOH of 15M with the sodium silicate to NaOH ratio by weight of 2.5. However the bagasee ash geopolymer mortars with high strengths were obtained with concentration of NaOH of 10M with the sodium silicate to NaOH ratio by weight of 2.5. The use of rice husk ash and bagasse ash produces geopolymer mixes with good strength and resistance to acid and chloride penetration. The resistance to acid and chloride penetration is higher with an increase in the sodium silicate to NaOH ratio by weight of 2.5.

The effect of grinding on the chemical and physical properties of rice husk ash was studied. Four rice husk ashes with different finenesses i.e. coarse original rice husk ash (RHA0) RHA1 RHA2 and RHA3 were used for the study. Ordinary Portland cement (OPC) was partially replaced with rice husk ash at 20% by weight of binder. The water to binder ratio (W/B) of the mortar was maintained at 110%±5% with flow table test. Specific gravity fineness chemical properties compressive strength and porosity test of mortars were determined. The differences in chemical composition of the rice husk ashes with different finenesses from the same batch are small. The use of RHA3 produces the mortars with good strength and low porosity. The strength of the mortar improves with partial replacement of RHA3 in comparison with normal coarse rice husk ash. The use of RHA3 results in a strong and dense mortar which is due to the better dispersion and filling effect as well as an increase in the pozzolanic reaction.

In this paper the effects of carbonation on pore structure of blended pozzolan cement pastes were investigated. Ordinary Portland cement _OPC_ was partially replaced with ground palm oil fuel ash _POA_ ground rice husk ash _RHA_ and classified fine fly ash _FA_. The strength total porosity specific surface area and pore size distribution were tested. In general incorporation of pozzolans increased the total porosity of blended cement pastes in comparison to that of OPC paste. Carbonation of pastes under 5% CO2 and 50% relative humidity _RH_ for 28 days resulted in filling of the pore voids and possible attack on calcium silicate hydrate _CSH_ depending on the type of pozzolan used. After carbonation total porosity decreased and specific surface areas of the blended pozzolan cement pastes reduced indicating the infilling of voids. Pore size distributions of POA and RHA pastes were different to those of FA pastes. Large pores of the POA and RHA pastes were increased indicating coarsening of pores owing to possible attack on CSH. It is possible that POA and RHA were highly reactive and hence their uses resulting in severe carbonation compared to use of FA.