① Chlorine salts, chlorine salt rust inhibitors, and inorganic chlorine salt antifreeze can be used in concrete projects.
② Chloride salt antifreeze can be used in concrete projects, and chloride salt rust-inhibiting antifreeze can be used in reinforced concrete projects. The application engineering scope is not allowed to be the same as that of early strength agent.
③ Chloride-free antifreeze, can be used in reinforced concrete projects and prestressed concrete projects. However, nitrate, nitrite, and carbonate admixtures shall not be used in prestressed projects and reinforced concrete projects in contact with galvanized steel or aluminum and iron.
④ Contains toxic antifreezes such as hexavalent complex salts and nitrites. It is strictly prohibited to be used in waterproofing projects and parts in contact with food.
⑤ For concrete projects that have special requirements for hydraulic engineering, bridges and frost resistance, the choice of antifreeze type and dosage should be determined through experiments.
⑥ The selection of antifreeze should be based on the lowest daily humidity, and antifreeze with antifreeze performance of -5℃, -10℃, and -15℃ should be selected.
⑦ Portland or ordinary Portland cement should be used for concrete mixed with antifreeze. The cement grade should not be less than 32.5Mpa. The use of high alumina cement is strictly prohibited. Expired cement can only be used after passing the re-inspection.
⑧ The coarse and fine aggregates must be clean and free of ice, snow and minerals that are easily cracked by freezing. Antifreeze with high potassium and sodium ion content must not use active aggregates.
⑨ For the mix ratio of antifreeze, the water-cement ratio of C20 concrete should be 0.5-0.6, C40 should be 0.35-0.45, and the amount of C20 cement should not be less than 300kg .m3, C40 should not be less than 450kg/m3. For thin-walled concrete, it can be increased by 10%. Using antifreeze with air-entraining components, the sand rate can be reduced by 1-3%.
⑩ The preparation of antifreeze should be calculated based on the solid content. If there is crystal precipitation when preparing liquid antifreeze, it should be prepared separately and added separately. When calcium chloride and air-entraining agent are used in combination, the air-entraining agent or air-entraining water-reducing agent should be added first, and then the calcium chloride solution is added after stirring. When calcium salt and air-entraining agent are used in combination, the air-entraining agent or air-entraining water-reducing agent should be added first, and then the calcium chloride solution should be added after stirring. When calcium salt and sulfuric acid are used in combination, first add the calcium salt solution and stir, then add the sulfate solution. Powdered antifreeze that has agglomerates should be passed through a 0.63mm sieve before use.
⑾ When the temperature is lower than -5℃, the water temperature should not be higher than 65℃. The moisture brought in by steam heating should be deducted from the mixing water.
⑿ The preparation and blending of antifreeze should be controlled by dedicated personnel who strictly control the preparation process and mixing amount. Before mixing, clean the mixer with hot water and extend the mixing time by 50% compared to normal temperature.
⒀ The temperature of fresh concrete when leaving the machine shall not be lower than 10℃, and the temperature when entering the concrete shall not be lower than 5℃. When the concrete is transported to the pouring site, it should be poured within 15 minutes, and the exposed surface should be covered with plastic wax and insulation materials.
⒁ Do not water during maintenance under negative temperature conditions. The temperature at the initial stage of maintenance must not be lower than the temperature specified by the antifreeze, otherwise heat preservation measures should be taken. When the concrete temperature drops below the specified temperature, the concrete strength must reach 3.5Mpa. When the difference between the concrete surface temperature after disassembly and the ambient temperature is greater than 15°C, insulation materials should be used for covering and curing.
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