Concrete Filled Tube Using PCM-Impregnated Fine Aggregate and Method for Manufacturing Concrete

Square CFT Column with Enhanced Thermal Storage and Conductivity Using Sol-Gel Coated PCM Fine Aggregate and Through-Reinforcement

This technology is a Concrete Filled Tube (CFT) featuring a square metal pipe filled with PCM concrete, which is made from fine aggregate impregnated with Phase Change Material (PCM). The interior of the metal pipe includes multiple protruding shear plates along its length, along with reinforcing steel bars that pass through the pipe. The fine aggregate is vacuum-impregnated and then coated with a silica layer using a sol-gel process to prevent PCM leakage.

Construction materials using PCM offer excellent thermal storage and heat dissipation, helping to reduce heating and cooling energy. However, simply mixing PCM into cement often leads to stability issues, as the volume changes during phase transitions cause the concrete to repeatedly expand and contract. Previous methods, such as filling lightweight aggregate with PCM and applying a double coating, struggled with inconsistent shapes, complex structures, and poor heat transfer to the core of large concrete members, limiting their ability to respond effectively to temperature changes.

This technology involves drying fine aggregate at 105°C for 24 hours, vacuum-impregnating it with PCM for 4 hours, and coating it with a sol-gel solution—a mixture of ethyl silicate, ethanol, distilled water, hydrochloric acid, and ammonia water at specific molar ratios and temperatures—to prevent PCM leakage. Shear plates with vertical and diagonal sections are positioned toward the corners to enhance shear strength, while reinforcing bars with surface-protruding support members facilitate heat exchange between the concrete core and the outside air. Waste concrete powder can also be used as a cement raw material. Applicable to high-rise CFT columns, energy-efficient apartment frames, and low-carbon eco-friendly structures, this design allows the structural members themselves to act as thermal storage bodies that absorb indoor temperature fluctuations while maintaining flexural strength without cracking from PCM volume changes.

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Key Features:

• PCM concrete formed by including fine aggregate impregnated with phase change material inside a square metal pipe
• Multiple shear plates protruding inside the metal pipe along its longitudinal direction, including vertical sections and diagonal sections at a predetermined angle
• Multiple reinforcing steel bars passing through the metal pipe, with both ends penetrating a pair of opposing plates
• A coating layer on the fine aggregate, applied via a sol-gel process after PCM impregnation to prevent leakage

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This invention was developed with support from the Ministry of Trade, Industry and Energy for the development of low-heat cement manufacturing and utilization technology that replaces more than 5 wt.% of limestone using non-carbonate raw materials.

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