Both coarse aggregates and fine aggregates are the main constituents of concrete because they not only give the body to the concrete, it also have a significant effect on the fresh concrete based on aggregate's shape, size, texture, grading and crushing type. Moreover it is proved that aggregate's types has the severe effect on physicmechanical properties of concrete as aggregate covered almost 70 to 80 percent of the total volume of concrete. This paper investigates the effects on properties of concrete due to types of crushed aggregates alone. To observe the effects of crushed aggregates sharply, all other components like water cement ratio kept constant for each type and two types of crushed aggregates were used. 'Impact Crushed' and 'Vertically Shafted' aggregates type have been used to prepare five different groups of concrete blocks and these five groups have different water-cement (w/c) ratio. Source of these two aggregates, density and water absorption also kept constant to identify the effects on properties of concrete only for crushing type. Finally after 1 week and after 4 weeks slump values (consistency of the concrete) and compressive strength were measured without mixing any admixture or superplasticiser to the concrete. Compressive strength difference for all groups at 1 week and 4 weeks also analysed at the end of the study.
In recent decade's world's energy demands are fulfilled by coal, natural gas as well as petroleum though the price of oil is skyrocketing. Moreover, geopolitical tensions around the world may push it higher and demand also increasing as well. The world is faced two new problems severely like energy crisis and environmental degradation. If this continues, global recession is unavoidable and depletion of world reserve accelerates undoubtedly. To produce more fuels and energy more environmental hamper is done by the world that's why many investigations have been done to find out an environment friendly, economically competitive and technically feasible alternative source of energy. Very recently, Biodiesel is found to be more sustainable, non toxic and energy efficient technology which is biodegradable. Around 350 oil bearing crops rapeseed, soybean, jatropha, sunflower, linseed and coconut are the main sources of Biodiesel. But these edible material sources were proved to be unfeasible where demand is much higher than the production. But non-edible materials like algae is acceptable source of biodiesel not only in research but also many recently developed countries like China, Malaysia and India are accepted this technology in production and export. This paper provides an overview of algal biodiesel production at Bangladesh where fuel (oil, gas, coal) is too expensive day by day and to ensure a degradation free environment, alternative source of fuel (Biodiesel) is the time demanding decision for Bangladesh. Both mechanical and chemical methods of biodiesel production are analysed. In China, fundamental research on microalgae energy has a strong engineering and technological base. Several projects were taken from 2005 and algal biodiesel would be the giant source of energy within few years at China. National Biofuel policy of Malaysia increasing productivity and maximising returns in the sector of second generation biofuel technology like biodiesel from algae. In India, they started with jatropha based biodiesel and finally carried out extensive work to find out hydrocarbon at Indian water from hydrocarbon producing algae. For Bangladesh in fostering the development of biofuels industries, government have to play important role to adapt the technologies for their own condition, which raises issues of technology transfer. For both sustainable development and environmental protection, advanced technologies of biodiesel production is imperative for Bangladesh.
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