Sodium sulfate (SS) is a neutral activator. SS-activated alkali-activated slag cement (AASC) has lower shrinkage. However, it sets slowly, and the mechanical property develops slowly. Slaked lime (SL) is an alkaline substance widely used in industry that can be used as an activator in AASC. In this paper, SL was used alone, and SL and SS were mixed together to prepare AASC. The effects of SL content on the setting time, shrinkage properties and mechanical strength of AASC were investigated. Furthermore, the mechanism was explored with the analysis of microscopic tests. The results showed that SS could not be used as an activator alone, while SL could be used as an activator alone, and SS could be combined with SL to prepare AASC. The setting time of the SL system or the SS-SL mix system decreased with the increase in SL. The mechanical properties of the SL system were poor. The SS-SL system showed the highest mechanical properties when SL was 3%. With the increase in SL, the autogenous and drying shrinkage of the SL system increased, while the former of the SS-SL system increased and the latter decreased. At the same time, due to the different changes in pore structure and mesoporous volume in the two systems, the drying shrinkage showed different changes. Compared with the SL system, ettringite (AFt) with a slight expansion property and more crystal phases were formed in the SS-SL system, which reduced the drying shrinkage.

Pervious planting concrete (PPC) is in line with the concept of ecological environmental protection. However, due to its own porous structure, it is difficult to obtain excellent mechanical properties and water permeability at the same time, which hinders its promotion and application. In this paper, natural gravel (NG), ordinary Portland cement (OPC), polyvinyl alcohol latex powder (PVAP) and polycarboxylate superplasticizer (PS) were used to prepare the PPC, and its mechanical properties and water permeability were studied. Three kinds of plants were planted in the PPC and their planting properties were studied. At the same time, the effect of Bacillus on the planting properties was studied. The results show that when the water–binder ratio (W/B) was 0.28 and the PVAP content was 0.8%, both the mechanical properties and water permeability of the PPC were optimal. The compressive strength and permeability coefficient were 14.2 MPa and 14.48 mm/s, respectively. The mechanical properties and water permeability of PPC prepared with 10~20 mm NG were better than those prepared with 5~10 mm NG. Among the three plants, the germination rate and growth of Elymus dahuricus Turcz (EDT) were the best. The incorporation of Bacillus can optimize its planting properties and promote the effective combination between plants and the PPC substrate.

A large amount of construction waste could be reused if recycled aggregate (RA) is used to prepare pervious planting concrete (PPC). This would reduce the consumption of natural resources and environmental burdens, in line with the concept of sustainable development. The effects of the water/binder ratio (w/b), polyvinyl alcohol powder (PVAP) content and aggregate size on the compressive strength and water permeability of RA-PPC were studied in this work. Elymus dahuricus Turcz (EDT) was planted on the RA-PPC matrix to study its vegetative property and bacillus was used to improve growth. The results showed that the compressive strength and water permeability of the RA-PPC first increased and then decreased with an increase in w/b and PVAP content. The performance of RA-PPC made with larger aggregate (10–20 mm) was superior to that of RA-PPC made with smaller aggregate (5–10 mm). The pore structure characteristics and the paste thickness on the surface of the aggregates were the primary factors influencing the performance of the RA-PPC. The incorporation of bacillus promoted the growth of EDT on the concrete matrix and enhanced the vegetative property of RA-PPC. The water permeability and compressive strength of the RA-PPC decreased slightly after planting.