In a chloride environment, taking reinforced concrete structures as the research object, the corrosion rate of reinforcement determines its corrosion expansion because multiple coupling parameters will affect the corrosion rate of reinforcement, which is extremely difficult to effectively predict. In this paper, 144 sets of experimental data were collected and sorted out by reading the relevant literature, and six empirical models for predicting the corrosion rate of steel bars were compared and analyzed based on these experimental data. Based on the investigations, a new empirical model is proposed for predicting the corrosion rate of reinforcement, and the relevant influencing factors are considered in the new model. By comparing the 144 sets of experimental data and 90 experimental data for this paper, the new prediction model can well predict the corrosion rate of reinforcement. Furthermore, the time variability of the new prediction model is verified. The probability distribution characteristics of seven prediction models are obtained through model error analysis, which provides a theoretical basis for the next step of concrete cover cracking and reliability analysis.

This paper investigates the influence of metakaolin (MK) as well as various early-age curing regimes on late-age hydration of ultrahigh-performance concrete (UHPC) immersed in hot water. To reduce the consumption of cement, we partially substitute cement by limestone (LS) in the UHPC mixture. After 24 h of hardening, UHPC specimens are demolded and exposed to different curing regimes, including standard water curing at 20°C for up to 28 days as well as steam curing at 55°C or 90°C for 24 or 48 h followed by standard water curing for up to 28 days. Afterward, the UHPC mortar and paste specimens are transferred into the water at 80°C and left for predesigned testing ages (7, 14, 21, and 28 d). We evaluate the compressive strength of UHPC mortar as well as hydration and microstructural properties of UHPC paste with the analysis of chemically bound water, differential thermal analysis, and mercury intrusion porosimetry. The results indicate that the compressive strength of the UHPC has an increasing tendency from 28 to 42 days and then a decreasing tendency. The addition of MK alleviates the late-age strength development tendency of the steam-cured UHPC specimens compared with the control mixtures without MK. The hydration results verify this strength development tendency of UHPC from 28–56 days. The ternary MK- and LS-blended UHPC exhibits similar strength development tendency and microstructure with binary paste incorporated with MK at later ages.

To study the mechanical performance of bolted connections with different structural forms of reinforced rings, based on the results of monotonic loading tests on two bolted connections between a concrete-filled steel tubular column and a steel beam with an outer reinforcing ring, this article uses ABAQUS v.2020 software to establish a three-dimensional refined finite element analysis model of such connections using appropriate constitutive models for concrete and steel. Subsequently, the effect of the dimensions of the steel beam, reinforcing ring, and cover plate on the load-bearing properties and the failure mechanism of the connections is investigated, and the numerical model is consistent with the verification test results. Then, the numerical simulations comparing bolted exterior reinforced rings under seven different construction measures (i.e., number of bolts, stiffeners) based on a conventional welded exterior reinforced rings with rigid connections (i.e., CGJ) are standardized. The research results indicate that when four rows of bolts are introduced on exterior reinforced rings, the web of steel beam is welded with stiffeners, and the top and bottom reinforced rings are also added with stiffeners; this bolted connection with an external reinforcing ring (i.e., GZ-7) can achieve the rigidity and load-bearing capacity of a fully welded external reinforcing ring rigid connection. At the same time, the reinforcing ring plate is bolted to the flange of the steel beam, and the force transmission path at the connection is changed to avoid the brittle fracture easily caused by the welded flange joints. It is also in line with the development trend of sustainable construction of “assembly” and “disassembly”.