Raw fly ash (RFA) was modified by a self-developed new dry energy-saving vertical grinding mill. This was beneficial to improve the particle morphology and distribution of RFA and enhanced its practical applicability in cement and concrete. The physical modification mechanism of RFA was elucidated by simulating the grinding process, and the physical properties and the application performance of modified fly ash (MFA) were characterized. The results demonstrated that the new grinder can effectively realize the physical modification of RFA and significantly improve its properties because the porous structure and the intactness of glass beads of RFA are preserved without being destroyed. The fineness of MFA was improved to the standard of Class I or II fly ash, the 28 d strength activity index of which was increased by 7% to 17%. The fluidity of mortar was also improved by 15 to 34 mm. In addition, the water requirement ratio can be significantly reduced when MFA is used to prepare C30 and C45 concrete. The 28 d strength of concrete with 50% content of MFA was increased by 23.76% and 15.84%, respectively. These results suggest that the grinding process studied here is a novel method for improving the performance of MFA.

Reinforced concrete shear walls are commonly used in buildings to resist lateral loads due to wind and seismic action. They are typically either cast-in-place or precast, with the latter solution used to achieve high construction speed and quality control. At the same time, the main challenge with precast solutions is to ensure appropriate connections between the adjacent walls, as well as the anchorage of the walls in the foundations. A hybrid structural system combining precast and cast-in-place concrete can provide the advantages of both methods such as faster construction, better quality control, improved structural performance, and durability. This study focuses on investigating the shear behaviour of squat hybrid shear walls through full-scale experimental testing. The tests include one conventional cast-in-place wall and one hybrid wall with a pre-wall system (two precast walls) and cast-in-place concrete core. Detailed measurements and kinematic-based modelling are used to develop comprehensive understanding of the behaviour of the test specimens. It is shown that the hybrid method of construction does not affect the stiffness of the walls and results in a slight reduction of shear strength. It is also shown that the three-parameter kinematic theory can be used to predict the shear strength and key deformation components of the tested walls.