Effect of clay content on concrete properties

The presence of clay in aggregate is frequently associated with the deterioration of concrete properties. The objective of this study was to investigate the effects of varying clay contents on the mechanical properties, freeze-thaw resistance, permeability and water absorption behavior of concrete. Additionally, the differences in the permeability, and water absorption behavior of the surface layer and interior of concrete were comparatively analyzed using self-designed tests. The results indicate that the presence of a minimal quantity of clay did not diminish the compressive strength and static compressive modulus of elasticity of concrete. However, it did result in a reduction in the tensile properties and durability of concrete. Furthermore, the mechanical properties, freeze-thaw resistance, and anti-permeability of concrete were significantly diminished when the clay content reached 1.6%. Furthermore, this study proposed an innovative evaluation method for dividing the water absorption behavior of concrete into three stages, which more accurately reflected the trend of water absorption behavior in concrete. It was found that the sorptivity and permeable porosity of concrete in the three stages exhibited a strong correlation. The presence of clay increased the sorptivity and permeable porosity of concrete, with the most pronounced effect observed in the initial water absorption stage. Moreover, the permeable porosity of the interior of concrete was found to be reduced in comparison to that of the surface layer of concrete at all ages with varying clay contents, with the reduction ranging from 10.7% to 14.7%. In practical engineering construction, it is recommended that the clay content be kept within reasonable limits, and the effect of the clay content on the properties of the surface layer of concrete be given greater attention.