Sprayed planting concrete (SPC) can be used for the ecological restoration of rocky steep slopes. It is a kind of outside-soil material with excellent soil and slope stabilization performance, and plants can grow in SPC, thus achieving harmony between engineering stability and ecological restoration and improving the landscape and ecosystem. The addition of cement is the key to allowing SPC to achieve slope stabilization and prevent soil erosion. However, the addition of cement can cause SPC to have high alkalinity, overheating (cement generates hydration heat), and excessive hardening, which are not conducive to the growth of plants and can lead to poor ecological performance of SPC for slope ecological restoration. We studied the improvement of the ecological performance of SPC by using a polymer composite material composed of a polymer adhesive material and a polymer water-retaining material. This paper studied the improvement effects of the polymer composite material on the ecological performance of SPC used in slope ecological restoration through a laboratory erosion resistance test and a plant growth test. The results showed that SPC with the addition of polymer composite material can reduce its cement content by about 50% while still retaining excellent erosion resistance performance when it is used in slope ecological restoration. Additionally, the plant germination rates and plant heights when using the SPC improved by polymer composite material were increased by 190% and 110%, respectively. These results show that polymer composite material can significantly improve the ecological performance of SPC and effectively improve its slope ecological restoration effects. This study provides theoretical and technical support for the application of SPC in ecological restoration on rocky steep slopes.

Background Ecological protection of slope surfaces by vegetation is one of the effective methods to reduce soil erosion. However, the surface soil of slope often has the problems of poor structure and low water use efficiency, which is not conducive to plant growth. Super absorbent resin (SAR) as a new type of water retention agent can effectively improve the surface soil of slopes. The study was designed to evaluate the effect and mechanism of SAR on aggregate stability, soil water characteristics and mechanical strength by analyzing the aggregate characteristics, moisture characteristics, microstructure and mechanical properties of SAR-treated soil. Results The results show that (1) the volume expansion and shrinkage in the process of water absorption and release of SAR loosened the soil, which improved the microstructure of the soil and increased the aggregate content, while the change of soil pore distribution significantly affected the soil–water characteristics; (2) the fractal dimension and stability of aggregates, the cohesion and internal friction angle of soils all tend to decrease with increasing SAR; and (3) the strong water absorption and retention of SAR increases the water holding capacity of the soil, thus increasing the water availability. Conclusions The above research is conducive to further revealing the good role of SAR in improving the surface soil of slope, promoting plant growth and improving the environmental protection effect. It can provide experimental and data support for the application of polymer water retaining agents. Graphical Abstract

The loose structure and low mechanical strength of the surface soil make it vulnerable to damage under erosion conditions. Slope ecological protection is one of the effective methods to improve the stability of slope soil. Although it has been proved that polymer modified materials can effectively improve the soil properties and the environmental protection effect of slope, so far, the improvement mechanism has not been fully understood, especially the chemical mechanism of the material on the enhancement of soil mechanical properties is not clear. In the present study, the effects of nano-aqueous adhesive (NAA) on unconfined compressive strength, shear strength and aggregate characteristics of soil were studied by a series of laboratory experiments. The results show that NAA can increase the strength, aggregate number and stability of the soil, to effectively improve the stability of surface soil. In addition, through infrared spectroscopy and SEM test, it was found that NAA molecules were mainly distributed in the interlayer position of flaky clay minerals, mainly connected with clay minerals through hydrogen bonds, thereby effectively enhancing the cohesion of soil particles.

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Ecological slope protection projects (such as the reinforcement of low slopes by plants and ecological restorations of the soil of high steep rocky slopes) are essential for restoring the natural environment. In this study, red bed soil and composite polymer adhesive materials were used to develop an ecological membrane for application in slope ecological protection. The basic physical and mechanical properties of the ecological membranes with different material percentages were studied through tensile strength test and viscosity test, the effect of different material percentages on the properties of ecological membranes was studied, and the soil protection performance and ecological restoration performance were studied through anti-erosion and plant growth tests. The results show that the ecological membrane is soft and tough, with high tensile strength. The addition of the red bed soil can enhance the strength of the ecological membrane, and the ecological membrane with 30% red bed soil has the highest tensile strength. The ecological membrane has considerable tensile deformation capability and viscosity, and up to 100% by mass, the more composite polymer adhesive materials added, the greater the tensile deformation capability and viscosity. And the ecological membrane can enhance the anti-erosion performance of the soil. This study clarifies the development and technology of the ecological membrane, reveals the effect of different material percentages on the properties of ecological membrane, and analyzes the slope ecological protection mechanism of the ecological membrane, thereby providing theoretical and data support for its development, improvement, and application.