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Coal is a fossil fuel and an important natural resource. Combustion of coal provides high energy production. Total coal production in 2011 was 7678 Mt and lignite production was 1041 Mt. Coal provides 30.3% of the total world primary energy demand and 42% of the world's electricity is produced from the combustion of coal. Coal production will continue to increase and in the 2030's 44% of the world's electricity will be produced from coal (from Data courtesy). Coal combustion is provided in thermal power plants. A significant amount of coal ash is produced burning coal and utilization of ash is an important issue in the world. The sustainable utilization of coal ash could improve production efficiency, reduce production costs and diminish waste product disposal problems. In this research coal combustion product - coal bottom ash - was investigated regarding its application as a micro filler in conventional concrete production. Coal bottom ash was taken from a local boiler house in Latvia and preliminary processing of coal bottom ash was done. Coal bottom ash was ground for 15, 30 and 45 minutes respectively. The grading analysis of obtained microfiller was done with standard sieves and grading curves were obtained. Scanning electron micrographs were obtained and energy-dispersive X-ray spectroscopy was performed. In the current study, conventional concrete mixture with the cement amount of 350kg/m3 and W/C 0.61 was chosen to integrate it with coal bottom ash as a microfiller. The integration ratio of microfiller was chosen 10, 20, 30 and 40% by the mass of cement for each type of prepared coal bottom ashes. Reference concrete mixture consisted of 0% coal bottom ash. The concrete workability was kept constant for all mixtures and the chosen cone slump class was S4 (160-210mm). Fresh and hardened concrete properties were obtained. Compressive strength was determined at the age of 7, 14 and 28 days. Processed coal bottom ash could be used as a microfiller for conventional concrete production. Higher concrete strength class with the same amount of cement could bring economic benefit up to 3.6%. By incorporation of coal bottom ash in concrete environmental benefits could be achieved due to reduced cement consumption and effective disposal of coal bottom ash. The integration level of coal bottom ash could not exceed 30% by the mass of cement. At low rates of incorporation (<20%) coal bottom ash provides the same W/C for concrete and fresh concrete density increases. Mechanical and physical properties of concrete can be improved by choosing appropriate amount of coal bottom ash microfiller. [ABSTRACT FROM AUTHOR]