As a critical component of construction and infrastructure development, the concrete industry holds significant potential for future growth while also encountering numerous challenges. One such challenge is the occurrence of concrete cracks, which can be significantly influenced by temperature. Effective temperature control is essential to minimize crack formation, thereby enhancing the structural integrity and durability of concrete.

The impact of temperature control on concrete cracking can be summarized in the following aspects:

1. Thermal Stress Induced by Temperature Variations

During the hydration process of cement, substantial heat is generated, leading to an increase in internal temperature. When the temperature differential between the interior and exterior of the concrete becomes too large, uneven thermal expansion and contraction occur, resulting in thermal stress. If this stress exceeds the tensile strength of the concrete, cracks will form.

2. Influence of Internal-External Temperature Differential

Due to its substantial volume, concrete's internal heat dissipates slowly, creating a significant temperature difference between the inside and outside. Research indicates that when this temperature difference exceeds 25°C, considerable tensile stress develops within the concrete, potentially causing cracks. Therefore, managing this temperature differential is crucial for preventing crack formation.

3. Impact of Temperature Change Rate

Rapid temperature changes can also induce cracks. For instance, if the surface of freshly poured concrete cools too quickly or if inadequate insulation measures are taken during sudden temperature drops, a steep temperature gradient forms, leading to crack formation.

4. Types and Characteristics of Temperature-Induced Cracks

Temperature-induced cracks primarily include thermal expansion cracks, cold contraction cracks, and frost expansion cracks. Thermal expansion cracks typically exhibit wider middles and narrower ends, whereas cold contraction cracks maintain a relatively consistent width. These cracks not only mar the appearance of structures but can also lead to corrosion of reinforcing steel, reducing the structure's durability and impermeability.

5. Preventive Measures for Temperature Control

To mitigate temperature-induced cracking, the following measures are recommended:

- Optimize Concrete Mix Design: Utilize low-heat cements (such as slag cement or fly ash cement), reduce cement content, and incorporate fly ash or high-efficiency water reducers to lower hydration heat.

- Control Pouring Temperature: During summer construction, lower the pouring temperature to avoid high-temperature conditions; during winter construction, increase the pouring temperature to ensure the internal temperature remains above the external ambient temperature.

- Implement Proper Curing Practices: Promptly apply wet curing to prevent surface shrinkage; during the cooling phase, limit the cooling rate to no more than 2°C per day.

- Employ Layered and Segmented Pouring: For large-volume concrete, use layered and segmented pouring methods to facilitate heat dissipation and reduce constraints.

- Apply Insulation Measures: When temperatures drop sharply, insulate the concrete surface to prevent excessive temperature gradients.