Construction and demolition (C&D) waste has seriously affected the ecological environment. The utilization of C&D waste resources can greatly alleviate this problem, and it is an important way to help achieve the goal of zero carbon in 2050. In this study, insulation concrete blocks were developed with recycled aggregates, cement, fly ash as main raw materials, expanded polystyrene (EPS) insulation boards as block insulation filling material, and selfdeveloped construction waste composite activator, interface enhancer, surface modifier and other additives. Through experimental research and performance test analysis, the best mix ratio of the product and the mechanism of each additive were proved. The experimental results showed that the insulation concrete block prepared under the conditions of recycled aggregates sand ratio of 45%, active activator Na 2 SO 4 content of 0.15% and fly ash content of 30% has the best performance and meets the relevant standards.

The cyclic plastic characteristics of metal materials are different from the deformation characteristics under monotonic loading, which has an important effect on the safety of structures in service under cyclic loading. However, GS-20Mn5, which is commonly used in large hydraulic machine beams, offshore platforms and large Bridges, is still lacking the studies of mechanical response characteristics under cyclic loading. In this study, the cyclic softening/hardening characteristics of GS-20Mn5 are studied by a series of cyclic loading tests under uniaxial strain control. Combined with transmission electron microscope (TEM) analysis of cyclic loading tests under typical strain levels, the microscopic mechanism of cyclic softening/hardening is discussed. The results show that the cyclic softening/hardening properties of GS-20Mn5 cast steel are sensitive to amplitudes and cycles. At smaller strain amplitudes (0.16%,0.2% and 0.3%), the cyclic hardening properties of GS-20Mn5 cast steel are rapid at the beginning of the cycle, followed by cyclic softening and then slow secondary cyclic hardening at the end. However, under larger strain amplitudes (0.4% and 0.5%), the cyclic hardening continues during the cyclic loading, and the hardening rate is bigger at the beginning of the cyclic loading and smaller at the later cyclic stage. The cyclic softening/hardening characteristics of GS-20Mn5 cast steel are related to the dislocation structure of ferrite and pearlite. Taking the strain amplitude of 0.2% as an example, the initial cyclic hardening is mainly caused by the proliferation and interaction of dislocations in ferrite. Dislocation spots and cell walls in ferrite grains are mainly caused cyclic softening at the initial stage, the secondary cyclic hardening is directly related to dislocation proliferation and entanglement in pearlite.