Technical Specifications and Management Measures for Winter Construction of Concrete
With the arrival of winter and the continuous drop in temperature, construction projects have officially entered the winter construction phase. The low-temperature environment places higher demands on the quality of concrete construction. As a professional concrete supplier, Asian Construction Equipment Group Co., Ltd. adheres to the philosophy of “quality first, technology leading,” and based on the “Code for Winter Construction of Building Engineering” (JGJ/T 104–2011) and related technical standards, combined with years of winter construction experience, has developed a scientific and systematic winter concrete construction technology solution. This solution aims to comprehensively strengthen quality control in all aspects, from raw material control, mix design, production and transportation to on-site construction coordination, to ensure the construction quality and long-term durability of concrete projects in low-temperature environments.
I. Mechanism of the Influence of Low Temperatures on Concrete Performance in Winter
When the ambient temperature is between 0 and 4°C, the cement hydration rate decreases significantly, and the strength development of concrete is slow, making it difficult to achieve the strength growth requirements under standard curing conditions. When the temperature drops below 0°C, free water in the concrete begins to freeze, expanding in volume by approximately 9%, which may damage the bond interface between the cement paste and aggregates, affecting the integrity of the concrete’s microstructure. Furthermore, water freezing reduces the amount of liquid water available for cement hydration, essentially halting strength development. Therefore, taking effective antifreeze and insulation measures in the early stages of concrete setting and hardening is crucial.
II. Winter Concrete Production Technical Measures
According to specifications, winter construction begins when the average daily outdoor temperature remains consistently below 5℃ for five consecutive days. To ensure the workability and mechanical properties of concrete under low-temperature conditions, our company has adopted the following key technical control measures:
(1). Optimization of Cementitious Materials and Mix Proportion
1.1. Use early-strength or ordinary Portland cement, controlling the cement content to be no less than 300 kg/m³ and the water-cement ratio to be no greater than 0.60, to improve the early strength and frost resistance of concrete.
1.2. Add an appropriate amount of antifreeze water-reducing agent to reduce the amount of mixing water while ensuring workability, thereby increasing the critical frost resistance strength of concrete.
Note: (If necessary, written procedures must be completed in advance according to regulations.)
(2). Raw Material Temperature Control and Thermal Management
2.1. Heat the mixing water. When the air temperature is below 0℃, use steam heating to ensure the water temperature is not lower than 50℃, guaranteeing that the concrete outlet temperature meets the specifications.
2.2. Strictly control aggregate quality. The use of aggregates containing ice, snow, or frozen lumps is strictly prohibited. If necessary, preheat or cover the aggregates for insulation.
(3). Mixing Process Adjustment
3.1. Appropriately extend the mixing time. For concrete with antifreeze additives, extend the mixing time by 10–15 seconds compared to normal temperature conditions to ensure the homogeneity of the mixture and the full dispersion of admixtures.
(4). Strengthen Factory Inspection and Transportation Scheduling
4.1. Strengthen the testing of slump, air content, and temperature before leaving the factory to ensure that the concrete quality meets design requirements.
4.2. Rationally plan transportation routes and departure frequencies to shorten the time from concrete leaving the factory to placement in the formwork and control temperature loss.
III. Key Technical Coordination Requirements at the Construction Site
To ensure that the concrete is not damaged by frost during the pouring and curing stages, the client is requested to cooperate in implementing the following construction measures:
(1)Concrete Arrival Inspection
1.1. Upon arrival of each truckload of concrete, the construction unit’s quality inspection personnel should verify the delivery note information, including the project name, strength grade, mix proportion number, etc., and conduct a visual inspection.
1.2. If any abnormal setting, segregation, or temperature discrepancies are found in the concrete, unloading should be immediately suspended, and our on-site technical personnel should be notified for assistance.
(2)Pouring Process Control
2.1. It is strictly forbidden to mix concrete provided by Asian Construction Equipment Group Co., Ltd. with concrete from other manufacturers, nor is it permitted to add water or unapproved admixtures during the pouring process.
2.2. Concrete should be poured within one hour of leaving the factory. If slump loss occurs due to construction delays, adjustments should be made using a special admixture under our guidance, and the concrete should be mixed at high speed in the mixer truck for no less than 3 minutes.
2.3. The formwork should have tight joints and be firmly supported to prevent leakage or deformation from affecting the dimensions and appearance of the components.
2.4. During pouring, the concrete should be poured in layers, with each layer not exceeding 1.25 times the length of the vibrator’s working section to avoid cold joints. Vibration should be uniform, ideally until the concrete surface is covered with grout and there is no obvious settling, preventing over-vibration or under-vibration.
(3)Finishing and Thermal Curing
3.1. Any bleed water on the concrete surface should be removed, and laitance should be pressed into the interior. Roughening with a wooden trowel should be performed at least twice before and after initial setting to improve surface density and crack resistance.
3.2. Immediately after pouring, the concrete should be covered with plastic film, and thermal insulation measures (such as insulation felt, heated sheds, etc.) should be taken according to thermal calculations to ensure the concrete does not freeze before reaching its critical strength.
3.3. No personnel should work on the concrete or apply any load before the concrete strength reaches 1.2 MPa. The strength of the formwork should be sufficient to prevent damage to the edges and corners of the components when removing the side formwork.
(4)Formwork Removal Control
4.1. When removing formwork, the order of “removing the last support first, and the first support last” should be followed. Impact loads on the floor surface are strictly prohibited. The removed formwork and support system should be promptly dispersed and transported to designated storage areas, and should not be piled up on floors to avoid localized overloading.
4.2. When removing side formwork, the concrete strength should be sufficient to ensure that its surface and edges are not damaged. Generally, the strength should not be lower than 5.0 MPa. Under winter construction conditions, the specific removal time should be determined based on the strength of test blocks cured under the same conditions to avoid edge damage due to insufficient strength.
4.3. The concrete strength at the time of removal of the bottom formwork and its supports shall meet the design requirements and relevant specifications; if the design does not specify requirements, it shall meet the relevant requirements of the “Code for Construction of Concrete Structures” (GB 50666).
(5)Construction of Large-Volume Concrete and Special Structures
5.1. For large-volume concrete or vertical structures (such as columns and walls), a specific temperature control and insulation plan should be developed to control the internal and external temperature differences and prevent temperature cracks.
5.2. For structures exceeding 3m in height, auxiliary feeding devices such as chutes or conveyors should be used to avoid concrete segregation.
IV. Conclusion
Asian Construction Equipment Group Co., Ltd. will continue to provide reliable and high-quality concrete products for all projects, and will cooperate with construction units to ensure quality control during winter construction. We are willing to work closely with all parties to strictly implement winter construction technical plans, implement various anti-freezing and insulation measures, and ensure that the construction quality of concrete structures meets design and specification requirements, jointly creating high-quality projects.
The above information is for reference only.
