Evaluation of the preparation and fertilizer release performance of planting concrete made with recycled-concrete aggregates from demolition

This paper developed a new generation of planting concrete (PC) made from recycled aggregates of demolished concrete (RADC) to improve the fertilizer retention properties and reduce the cost. By optimizing the fabrication procedures and mix proportions of the planting concrete with RADC (PC-RADC), the interconnected porosity, water permeability coefficient and 28-day compressive strength can be enhanced to 40.9%, 2.88 cm/s and 6.5 MPa, respectively, which laid a fundamental basis for the improved release of fertilizer in the developed planting concrete. The experimental results revealed that with the addition of 4.4 kg/m3 urea fertilizer, not only the 28-day release rate of nitrogen, a key parameter representing the fertilizer release performance, of the PC-RADC was improved by 72.1%, but also a more stable pore fluid alkalinity at approximately 8.20 pH was developed, which provided a suitable environment for plant growth. Moreover, the frost resistance of the urea fertilized PC-RADC was enhanced by 12.4% with the reduction of 150-day drying shrinkage rate by 20.5%. In conclusion, utilization of RADC has a great potential for the sustainable PC development with improved fertilizer release performance.