Abstract: The aim of this research is to study the influence of grain size distribution of shale ceramsite on the bulk density, compressive strength, void ratio and pH value in the internal voids of porous concrete for plant growing. First of all, we set up two groups of grain size distribution of shale ceramsite, and measured the basic physical properties such as stack density, apparent density, void ratio and bibulous rate for mixture proportion design. Furthermore, we added fly ash, compound fertilizer, FeSO₄ and vinyl acetate emulsion into yellow brown loam to prepare modified soil, which was further mixed with humus and vermiculite powder in a proportion of 2∶2∶1 to obtain planting substrate flurry of a fluidity of 210-240 mm. Then we carried out planting tests with two planting structures: a. seeds in humus overhead the porous concrete; b. seeds in substrate among voids of the porous concrete. Test results showed that with the changes of grain size distribution and target void ratio, the bulk density of 12 groups of porous concrete varied between 600-800 kg/m³; compressive strength of the porous concrete at the age of 28-day was above 5 MPa; and the pH value of internal voids between 11 to 12. Under necessary maintenance and management conditions, plants could completely grow well in the porous concrete, indicating that the mixture proportion of planting substrate is good.

Key words: shale ceramsite, porous concrete, bulk density, pH value, compressive strength, void fraction, vegetating