Abstract.A damage case of light weight brick's production approximately at 6-7% of total production was found daily in one industry in East Jawa, Indonesia. The physical damage of product always occured. This paper investigates some factors that affect the lost in laboratory analysis. The analysis includes the chemical analysis of raw materials, reactivity of pozzolanic materials, and observation of strength based upon the position of light-weight bricks during autoclaving process. In addition, fly ash is introduced as mineral additive as one of the alternatives to improve the product's quality. It is also concluded that grinding the silica sands particles is the optimum way to improve the quality, but the adding class F of fly ash to five percent in mixture is the most effective solution. Furthermore, maintaining quality of raw materials, curing process, and maintaining the machine will either reduce the product damage that occurred during the fabrication process in industry.

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Specific microbial agents such as bacteria are often used in concrete to improve its performance. Some microbes act as self-healing agents to close cracks in concrete, and to increase concrete strength. This paper presents a study to observe the effects of microbe addition to two types of concrete mixtures the fly ash-based, as geopolymer paste, and portland cement paste containing fly ash. Furthermore, the investigation was conducted to compare the properties of each paste, such as its compressive strengths, specific gravities, porosity, microstructures, and XRay diffracting properties. The results indicate that microbial activities positively affected the properties of both, portland cement paste and geopolymer paste. The result reported here strongly suggests that fly ash can be used to produce a high quality, but environmental friendly construction material when it’s mixed together with useful microbes.

There are many concrete constructions in marine environments. Due to its salinity content, seawater is aggressive, both towards concrete and reinforcement. Concrete interacts with seawater which causes deterioration. The chemical attack occurs at least through 3 common mechanisms: sulfate-attack, carbonation, and chloride-induced corrosion of reinforcement. The chemical resistance of concrete is determined by the porosity and chemical composition of the concrete. Partly subsitution of cement with supplementary cementitious materials (SCM) known as an effective way to create the less permeable concrete. Concrete with fly ash as SCM has excellent potential to be applied to marine construction in Indonesia because the abundant availability of fly ash in Indonesia and the presence of aluminum species in fly ash provide an opportunity to increase binding capacity to chloride.

Abstract. Komba E, Lusambo LP. 2019. Socio-economic influences of Pangani river basin on community’s livelihoods in Korogwe, Tanga Region, Tanzania. Bonorowo Wetlands 10: 41-51. River basin`s resources are vital to basic livelihoods improvement and to the economy growth of the world. Although river basins played a significant role to Tanzania`s economic growth, little information is known on the socio-economic effects of river basin in the urban areas. To address the information gap between urban and rural areas, this study was conducted to: identify socio-economic activities undertaken by urban community along Pangani river basin, analyse gross profit from identified socio-economic activities and analyse factors influencing urban community`s dependency on river basin. Purposive sampling was used to select three wards among seven wards crossed by river basin. A cross-sectional research design was employed involving 90 respondents were randomly selected and interviewed using household questionnaire. Key informant’s informations were collected and three focus group discussions comprising 6-10 people were carried out using a developed checklist. Data were analysed using statistical package for social science (SPSS), gross margin analysis and multiple regression model. The findings revealed that, 33.3% of the respondents were conducting gardening activities, 26.7% crop cultivation, 26.7% brick making, 8.9% sand mining and 4.4% car wash activity. The overall gross profit was found to be TZS 5 263 736.00 per household/year which is higher than that recorded in previous researches conducted in rural areas. Soil fertility, land availability, water availability, access to market, conducive climatic condition and vicinity to new construction area were found to be significant factors influencing urban community to depend on river basin. The result prevail that, there is high utilisation of river basin resources in urban than in rural areas. The study recommends strengthening of community participation and awareness in conserving the sustainable river resources and further study on investigating economic efficiency of socio-economic activities.