Influence of compaction techniques and cement paste thickness on porous concrete performance

This study investigates the influence of compaction mechanisms and corresponding cement paste thickness on the properties of porous concrete. Using Proctor and Marshall hammers, cylindrical specimens were compacted in both 3-layer and 5-layer configurations with 25 blows per layer. Two aggregate size ranges, 4.75-8.0 mm and 8.0-12.5 mm, were utilized. Experimental evaluations using the both compaction methods demonstrated their effectiveness in producing a uniform mix, as evidenced by consistent measurements of compressive strength, density, porosity, and permeability. While compaction energy influences void structure, cement content has a more significant effect on compressive strength, indicating that optimizing cement content is key to achieving desired strength. MATLAB image analysis showed effective cement paste thickness (d50) ranged from 0.485 mm (Marshall 5-layer) to 0.605 mm (Proctor 3-layer), with over 50% of values below 0.6 mm and a peak at 0.1 mm. Cement paste thickness is primarily controlled by cement content rather than compaction energy and shows a positive correlation with compressive strength. Overall, increasing cement paste thickness enhances strength. Furthermore, a two-factor ANOVA was performed to statistically evaluate the effects of aggregate size and compaction method, confirming that compaction method significantly influences compressive strength, while both factors significantly affect permeability. These results highlight the importance of managing compaction technique, cement paste distribution and aggregate size to balance mechanical performance and permeability in porous concrete design.