Ceramsite vegetated concrete with water and fertilizer conservation and light weight: Effect of w/c and fertilizer on basic physical performances of concrete and physiological characteristics of festuca arundinacea

In this study, vegetated concrete is prepared with ceramsite as aggregate, and urea and diammonium hydrogen phosphate (DAP) as fertilizer to treat soil and water loss in ecologically-imbalanced slopes. The effects of water-cement ratio (w/c) and fertilizer on these properties are studied. The results demonstrate that the w/c causes compressive strength and porosity to increase and then decrease. When the w/c is 0.25, the 28-day compressive strength and connected porosity reach the highest values of 5.69 MPa and 33.66%, respectively. When exposure time reaches 240 h, the water release rate with the w/c of 0.25 is the lowest, at 79.02%. The dry density remains at approximately 708 kg/m3. Urea causes the compressive strength, porosity, and water permeation coefficient to rise slightly, and the alkalinity to reduce sharply. As urea increases the paste porosity by inhibiting ettringite formation and consuming calcium hydroxide crystals, the 56-day total nitrogen (TN) cumulative release rate is 86.12% with 3.5 wt% urea. DAP is not suitable as fertilizer in vegetated concrete, because the PO43- from DAP dissolution can react with Ca2+ and Mg2+ from the cement to generate a phosphate precipitate. The 56-day total phosphorus (TP) cumulative release rate is only 0.25%, with 3.5 wt% DAP.