Faculty of Engineering, Technology, Applied Design & FineArt (FETADFA)

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Browsing Faculty of Engineering, Technology, Applied Design & FineArt (FETADFA) by Subject "Aggregate Size"

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    Modeling the Relationship of Concrete Strength with Aggregate Size Using Quarry Dust as Fine Aggregates for Rigid Pavements.
    (Kabale University, 2024) Ahebwa, Chrispus
    An experiment was conducted to determine the effect of different sizes of machine-crushed aggregates used for concrete production on the strength of concrete when stone dust is used as fine aggregates and to develop a model that can be used to predict compressive strength provided MSA and concrete grade is available. Coarse aggregate samples of maximum sizes of 10mm, 14mm, and 20mm were used to produce concrete of grade 20Mpa, 25Mpa, and 30Mpa at constant water/cement ratios of 0.48, 0.46, and 0.43 for every concrete grade respectively. In all the experiments, the concreting procedures and materials were kept constant while the maximum coarse aggregate sizes were varied. A total of 81 concrete cubes of dimension 150mmx150mmx150mm were crushed at 7, 14, and 28 days to determine their compressive strengths at grades 20,25 and 30Mpa. The results show that the smallest coarse aggregate size gave the highest compressive strength in all concrete grades due to better packing and increased bond strength at a constant water/cement ratio. Results also show that the slump increases with increasing aggregate size. At high concrete grades, there is a reduction in the water-cement ratio in order to increase concrete strength (from ACI 211.1). A regression analysis also shows that the relationship between the maximum coarse aggregate size and the compressive strength follows a linear equation with R2 = 0.990308; indicating that the model is reliable. An equation Strength(fc) = 5.883772 - 0.33855MSA + 0.919C from this study was developed for predicting concrete strength at 28 days given aggregate size and grade of concrete. This linearity suggests a constant rate of change in compressive strength concerning changes in MSA and C. Specifically, for each unit increase in C at constant maximum aggregate size, fc increases by approximately 0.919 MPa, while for each unit increase in MSA at a constant grade of concrete, fc decreases by approximately 0.33855 MPa.