The effects of pore size distribution and working techniques on the absorption and water content of concrete floor slab surfaces

•Pore size distribution in the slab surface varies by finishing and curing quality.•The better the quality is, the less the pores of ca. 10−7 to 10−6m in diameter is.•The better the quality is, the more the pores of ca. 10−7 and smaller in diameter is.•The water absorbency is affected by pores with diameters of ca. 10−7m and larger.•The water content is affected by pores with diameters of ca. 10−8m and smaller. Pore size distribution in the surface of a concrete floor slab may vary according to the quality of the finishing work, such as trowelling, or with the curing of the concrete. The pore size distribution also influences the water absorbency and water content that modulates the quality of the finished floor. We examined how working techniques, e.g., floor top finishing and curing and the resulting pore distribution on the concrete floor slab surface related to water absorbency and the water content of study specimens. As a result, the more the surface is smoothed, pressing it with a wood or steel trowel (henceforth, Finishing) and the longer the surface is moisture-cured, the more the volume of pores ranging from 10−7 to 10−6 m (100nm to 1μm) in diameter is reduced, while the volume of pores with diameters of 10−7m (100nm) and smaller tended to increase. Furthermore, the study revealed that the quantity of pores exceeding ca. 10−7m (100nm) in diameter strongly affected the water absorbency, while that of pores smaller than 10−8m (10nm) in diameter affected the water content. Thus, the above results demonstrate that a working technique of better quality decreases the water absorbency and increases the water content of a concrete floor slab.