Laboratory investigation of permeability properties of cement mortar with different sand-cement ratio

This paper is devoted to the study of the influence of the sand-cement ratio and microstructure of cement mortar on their water permeability. For that purpose, laboratory experiments were carried out to study the influence of sand-cement ratio on the seepage failure of cement mortar. The results show that the contact relationship of aggregate grain can be divided into three types: wrapped-contact, surface-contact and point-contact. The relationships of water permeability with porosity and velocity of cement mortar has also been investigated. It is found that permeability coefficient of cement mortar exponentially increases with the increase of sand-cement ratio. There exists a critical sand-cement ratio of range around 5∼6, at which the porosity and wave velocity change remarkably. After exceeding the critical sand-cement ratio, there exists a threshold value named critical seepage pressure at which the samples will meet with seepage failure. Power function is obtained between the permeability and critical seepage pressure. Highlights: Variation between permeability and sand-cement ratio can be expressed by exponential law; (1)  The permeability, porosity and wave velocity will be significantly changed, once the sand-cement ratio is higher than critical range value of around 5∼6; (2)  (3) The contact relationship of aggregate grains can be divided into three types including wrapped-contact, surface-contact and point-contact. Seepage failure occurs when critical seepage pressure of the cement mortar is reached. Power function relationship exists between permeability coefficient and critical seepage pressure. (4)