This study provides the results of an experiment on the possibility of using high-volume ground granulated blast furnace slag (HVGGBFS)-based concrete as mass concrete. In addition to the control concrete, the total weight of the binder was 75% ground granulated blast furnace slag (GGBFS) and 25% ordinary Portland cement (OPC). For the aggregates, both natural and recycled aggregates were used. Three specimens with dimensions of 800 mm × 800 mm × 800 mm were prepared to simulate mass concrete. The workability, temperature aging and strength of the mass concrete were tested. The test results showed that utilizing HVGGBFS concrete as mass concrete can significantly reduce the heat of hydration due to the low heat of hydration of GGBFS, while the heat of hydration of GGBFS and recycled aggregate combination is 11.2% higher than normal concrete, with a slump that is 31.3% lower than that of plain concrete. The results also showed that the use of recycled aggregates in HVGGBFS concrete can significantly reduce workability. However, the compressive strength is higher than when natural aggregates are used due to the alkali activation effect caused by the recycled aggregates. The compressive strength at 7 and 28 days increased by 33.7% and 16.3%, respectively.

The incorporation of circulating fluidized bed (CFB) fly ash into self-leveling cement-based (SLC) paste production presents significant environmental advantages. However, its addition deteriorates the fresh properties of the paste, posing challenges for practical implementation. This research examined the fresh properties of SLC paste blended with CFB fly ash, emphasizing fluidity, rheological characteristics, and bleeding rate. To enhance flowability, polycarboxylate superplasticizer (PCE) was incorporated, with particular emphasis on its interaction with CFB fly ash. The findings reveal that adding CFB fly ash to cement-based paste significantly decreased fluidity while increasing yield stress and plastic viscosity. Incorporating 20 wt.% CFB fly ash reduced paste fluidity by 51.4%, while plastic viscosity and yield stress increased by factors of 2.3 and 73, respectively. While PCE enhanced the fluidity of the blended paste, its water-reducing efficiency diminished, and the bleeding rate of the paste increased with higher CFB fly ash dosage. The water-reducing capability of PCE in the CFB fly ash-blended cement paste with 20 wt.% CFB fly ash decreased by 40.0%, and the bleeding rate of the paste increased from 0.6% to 6.7%. This effect was primarily attributed to the poor compatibility between PCE and CFB fly ash. The decline in PCE efficiency with higher CFB fly ash content, along with its lower adsorption capacity on CFB fly ash compared to cement particles, further confirmed this incompatibility.

This study addresses the recycling of construction waste wood and the development of thermal insulation materials by developing a high-belite sulfoaluminate cement-based recycled wood powder thermal insulation mortar (HRTM). High-belite sulfoaluminate cement (HBSC) and building gypsum (GY) were used as hydraulic binders, and recycled wood powder (RWP) was used as a full substitute for natural fine aggregate. The effects of the RWP-to-binder ratio (R/B) and GY replacement ratio on workability, mechanical properties, thermal insulation performance, water resistance, and drying shrinkage behavior were systematically investigated. The hydration products, pore structure, and microstructural evolution were characterized by thermogravimetry-differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and low-field nuclear magnetic resonance. Increasing R/B reduced dry density and thermal conductivity while improving water retention. The maximum water retention rate was 99.22% at R/B = 1/6 and 15% GY. The mechanical properties and drying shrinkage behaviour varied across the GY series and were influenced by GY replacement, water content, and PCE dosage. At R/B = 1/9 with 10% GY, HRTM exhibited a dry density of 992.19 kg/m³, a thermal conductivity of 0.253 W/(m·K), and a 28 d compressive strength of 23.8 MPa. The microstructural results showed corresponding changes in water-bearing hydration products, matrix continuity, and the RWP–matrix interface. These findings support the use of recycled wood powder in lightweight thermal insulation mortar.