Temperature Control Technology for Construction of Jinsha River Bridge

The key problem of mass concrete temperature control is to effectively control the maximum temperature inside concrete, the temperature difference between inside and outside concrete, and the temperature difference between surface and environment. The size of the main tower cap of No. 3 Jinsha River Bridge is 37 m × 23.5 m × 5.5 m, and the cubic volume of concrete reaches 4782.3 m3, which is poured in two times. In order to ensure construction quality of mass concrete structure, prevent the large mass concrete temperature stress, through the numerical simulation of the temperature control and optimization scheme, by optimizing the mixture ratio design, reducing the temperature of concrete pouring into the mold, cooling water cycling, insulation keeping in good health and a series of measures to effectively achieve the control goal, and eliminating the temperature cracks. The measured data show that the maximum temperature inside concrete, the temperature difference between inside and outside, and the temperature difference between surface and environment are qualified, but the temperature difference control of cooling water inlet and outlet has hysteresis effect, and the temperature difference between inlet and outlet will be greater than 10°C, which should be noticed.

Sensitivity analysis on deformation of woven polyethylene formwork

The use of different material quality and amount can affect formwork performance at the beginning of casting. Practical easy to install formwork such as woven polyethylene with wire mesh reinforcement makes field work easier. Sensitivity analysis on the elastic modulus and the thermal coefficient variables of woven polyethylene, fresh concrete temperature during casting and fresh concrete load model are the objectives of this research. The research is performed by comparing experimental data and the numerical modeling of woven polyethylene formwork using Finite Element Method. The formwork span and width dimension are 1 m x 0.3 m, with a variety of heights namely 0.6 m, 0.45 m, and 0.3 m. The sensitivity value for each variable will be evaluated based on Pearson coefficient or R. The sensitivity analysis of thermal coefficient showed no correlation to changes in formwork deformation. The sensitivity analysis of elastic modulus and fresh concrete temperature showed perfect correlation to changes in formwork deformation although the changes are small (around 0.0003 cm to 0.0006 cm). The fresh concrete load model showed perfect correlation to formwork deformation as well as becoming the determining variable of the changes in the formwork deformation values.

Analysis of Long-Term Durability Monitoring Data of High-Piled Wharf with Anode-Ladder Sensors Embedded in Concrete

The structural durability monitoring (SDM) system for a high-piled wharf in the Tianjin Port of China is devised and deployed with an anode ladder sensor, which provides a means to monitor the state of steel corrosion for the wharf. In this project, the anode-ladder sensors are installed on the reinforced concrete components of the front platforms. After the installation, the monitoring data from the anode-ladder sensor was collected for 40 months. Based on the monitoring data for 40 months, it is proven that the resistance of concrete will be significantly affected by the change in temperature, and the increase in temperature will cause the drop in concrete resistance. Furthermore, the data of the anode-ladder sensor set in the track beam of the front platform shows that the current in anode A1 and A2 relative to the cathode exceeded 15 μA during the four-month period, which is abnormal. The main reason is the influence of concrete temperature and humidity. Therefore, the monitoring data for current, voltage, resistance, and temperature should be combined to determine the activation state of the anode, and cannot be determined simply using the current value.

Combustibility of lightweight foam concrete based on natural protein foaming agent

There is an experimental study of samples of monolithic foam concrete “SOVBI” with a density of 205 kg /m3 (grade D200) for combustibility. The evaluation criteria are the following values of combustion characteristics: temperature increment in the furnace, duration of the stable flame burning, sample mass loss. The experimental results show the following values for foam concrete: temperature increment in the furnace of 2 °C, duration of the stable flame burning of 0 s, and sample mass of 24.4%. Thus, monolithic foam concrete with a density of 205 kg/m3 is noncombustible material. It is proposed to use monolithic foam concrete and other lightweight monolithic cellular foam concrete, as a structural fire protection for lightweight steel concrete structures. It, in turn, can increase the fire resistance of external walls and floor structure with the steel frame of cold-formed zinc-coated profiles.