Zhuojin Pipe Fitting Co., LtdGiant Steel Tube High Strength Concrete Hydration Heat Temperature Field Analysis
Hydration Heat Findings
This paper studies the hydration heat temperature field of giant steel tube members filled with C70 high strength concrete. The work is important because large diameter steel tube columns and concrete filled members are used in high rise buildings, bridges, and heavy industrial structures. The hydration heat of high strength concrete can generate significant internal temperature rise, and the steel tube affects heat transfer and thermal stress development.
The study combines physical temperature monitoring with finite element simulation using MIDAS FEA. The temperature field development is examined, and the concrete casting quality is evaluated. The results indicate that some temperature control indicators do not fully satisfy the requirements of GB 50496-2018, but the concrete casting quality still meets construction quality requirements. This distinction is valuable because code limits are often written for mass concrete and may not directly reflect the behavior of steel tube confined concrete.
| Factor | Effect | Practice implication |
|---|---|---|
| high strength concrete | higher hydration heat and thermal gradient | adjust mix design and curing |
| steel tube | changes heat transfer and restraint | include steel in thermal analysis |
| internal steel members | alter local temperature distribution | model embedded elements |
| thermal parameter theory | may not match measured values | verify with field data |
| casting quality | can remain acceptable despite temperature deviations | focus on integrity and defect control |
The table shows that temperature control in giant steel tube members should not be treated as a simple mass concrete problem. The steel tube is not just a formwork, but an active participant in the thermal and mechanical response.
Internal Steel Members and Thermal Coupling
The study emphasizes that internal steel members must be included in the thermal analysis. These members change heat conduction paths, create local thermal bridges, and influence the restraint condition of the concrete. If the analysis ignores steel members, the predicted temperature field may differ significantly from measured values. This is a practical warning for engineers who use simplified thermal models.
The steel tube also restrains the concrete as it expands and contracts during heating and cooling. This restraint can produce cracking if external temperature differences are large or if cooling is too rapid. However, confinement may also reduce crack opening because the steel tube limits radial expansion and supports the concrete core. The net effect depends on wall thickness, diameter, concrete mix, and curing regime.
The finding that theoretical thermal parameters do not always produce accurate simulation results is important. The heat of hydration, thermal conductivity, and heat release rate are sensitive to cement type, mineral admixtures, aggregate temperature, and ambient conditions. For giant members, the cooling boundary condition is complex because the steel tube exchanges heat with air, formwork, and surrounding concrete. Field calibration is therefore essential.
Construction and Material Control
For concrete mix design, the study suggests reducing the hydration reaction rate to improve the temperature field. This can be achieved through cement replacement, temperature control of materials, delayed placement, or controlled curing. The goal is not merely to reduce peak temperature, but to reduce thermal gradients and cooling rate. A lower peak temperature with high gradient may still cause cracking.
The conclusion that temperature control indicators may be appropriately relaxed for C70 high strength concrete should be interpreted carefully. Relaxation should be based on demonstrated cracking resistance, structural integrity, and inspection results, not simply on code exemption. Engineers should define acceptance criteria based on crack width, core quality, interface bonding, and long term durability.
From a steel pipe perspective, the hydration heat process can affect the steel concrete interface. Excessive temperature may influence residual stress, local buckling, or bond condition. The steel tube should be inspected for deformation, weld integrity, and internal cleanliness before casting. The paper is valuable because it connects thermal analysis with real construction quality and reminds engineers that temperature control must consider the coupled steel concrete system.