The response surface regression model of plant-growing ecological concrete is established based on the factors of the water–binder ratio, fly ash content, and design porosity, with 28-day compressive strength, connectivity porosity, and pH value as response variables. Based on optimizing the mix proportion with the regression model, different dosages of acetic acid are used as excitation agents to increase the compressive strength and reduce the alkalinity of plant-growing ecological concrete to enhance its service life and vegetation performance. The results show that the compressive strength of plant-growing ecological concrete with a water–binder ratio of 0.3, a fly ash content of 26%, and a design porosity of 22% was 10.32 MPa, the connectivity porosity was 20.00%, and the pH value was 11. After the addition of acetic acid at 0.4% of the mass of the cementitious material, the compressive strength increased by 40.29%, and the pH value decreased by 6.33%. This study proposes a cost-effective means and provides data support for the engineering application of plant-growing ecological concrete.

In this study, CT scanning technology was combined with ImageJ 1.54r and Avizo 3D 2022 professional image analysis software to quantify porosity. The aim was to reveal the intrinsic correlation between the pore structure characteristics and the macroscopic properties of vegetated concrete. A combination of 3D reconstruction, fractal analysis and multi-parameter regression modelling techniques was utilised to quantify the association between pore parameters and material properties. The mechanistic role of pore structure in regulating the strength–permeability trade-off relationship was elucidated. The results show that: (1) aggregate particle size and porosity are significantly negatively correlated with the compressive strength of vegetated concrete and strongly positively correlated with the water permeability coefficient, while the effects of both of them on the pH value of the material are negligible; (2) the porosity obtained by the image analysis method meets the design requirements of the target porosity, and the deviation between the computed 3D porosity from CT scanning and the 2D sliced porosity is less than 1%. The image analysis porosity is slightly lower than the measured value, a deviation within a reasonable range. (3) There is a robust positive correlation between the fractal dimension of the vegetated concrete structural surface and porosity. With increasing aggregate size, porosity gradually increases, pore network connectivity is significantly enhanced, and the fractal dimension increases correspondingly. (4) Function fitting analysis confirms that the correlation between the connected porosity and the compressive strength and permeability coefficient is more significant than that of the cross-sectional porosity. Specifically, compressive strength is significantly negatively correlated with equivalent pore size and fractal dimension, and the water permeability coefficient is strongly positively correlated with these two parameters. This study can provide important theoretical support and engineering reference for the optimization of the mix proportion and performance control of vegetated concrete.