Study on green restoration of exposed mountain: Effect of isobutylidene diurea on slow-release of total nitrogen and physiological characteristics of euonymus fortune in planted eco-concrete

Planted eco-concrete with drought-enduring and barren-resistant Euonymus fortunei (EF) and slow-release isobutylidene diurea (IBDU) was prepared to regreen poor soil or rocky slope. The effects of different IBDU content on the pore structure, water permeability coefficient (WPC), compressive strength, and alkalinity of eco-concrete were studied, and investigated the compatibility between eco-concrete and EF. Experimental results revealed that the TN release content in eco-concrete gradually rose with the increase of IBDU content, especially in the early days because TN existed in free water. IBDU could decrease the 28 days (28 d) pH value to 8.23 due to the hydrolysis of IBDU to produce carbonic acid. Although IBDU had a tendency to reduce the total porosity (TP) and connected porosity (CP), the lowest TP and CP were still up to 32.41 % and 29.71 % which were suitable for plant roots. The 28 d compressive strength of concrete with 3.5 wt% IBDU reached the maximum of 8.42 MPa and 10.3 % higher than that of the sample without IBDU. The IBDU significantly promoted the increase of stem length and stem diameter. It was a result that IBDU added the relative water content of leaves (LRWC), nitrogen content, and chlorophyll content of leaves, which had an excellent correlation with the experimental results. The research results provide an environmentally friendly solution for damaged rock slopes and regreen engineering.