Top 6 Misunderstandings about Water Curing of Concrete

In the construction site, water curing of concrete is a very common thing. This article will analyze the mechanism and role of water curing of concrete in order to get out of the 6 misunderstandings about it.

Misunderstanding about the purpose of water curing of concrete

The primary purpose of water curing of concrete is to keep the exterior of the concrete structure sufficiently moist for a specified period of time, which is the basis for the heat of hydration of cement. On the other hand, only by controlling the external conditions of water curing of concrete can it be beneficial to the temperature control to avoid cracks. In the specific process of water curing of concrete, operators often misunderstand the purpose of water curing of concrete. It is just wrong to think that the water curing of concrete is understood as a prescribed operation, which does not have much value for the concrete structure itself.

The construction personnel should learn the process and principle of water curing of concrete before it is done, to clarify the purpose of water curing of concrete, to pay more attention to water curing of concrete, and to realize the improvement of work quality of water curing of concrete. 

Misunderstanding about the starting time of water curing of concrete

According to the specifications and acceptance rules related to concrete, concrete should be covered and watered for timely maintenance within 12h after pouring. The actual situation is that some construction personnel including technical personnel misunderstand the time of concrete watering and curing as after 12h, which leads to various concrete problems in the already placed concrete. 

Especially for early-strength cement and high-performance concrete, if the concrete watering maintenance is delayed, it will cause early cracking of concrete and then temperature deformation, and dry shrinkage deformation to form various cracks. 

water curing of concrete

In the process of concrete pouring, we should develop the understanding of the nature of cement and concrete to avoid the possibility of deviation from concrete nature. At the same time, technical training should be carried out for concrete pouring and maintenance personnel. For high-performance concrete and early strength type of cement to carry out targeted watering maintenance of the technical briefing. On the basis of timely determination of the starting time of concrete watering and curing, form effective prevention of early cracking of concrete. To avoid the accumulation of potential problems affecting the quality of the structure in the process of watering and curing concrete, and to improve the effectiveness of concrete construction. 

Misunderstanding about the duration of water curing of concrete

Currently, there is a misunderstanding in the industry that the longer the concrete watering and curing time is, the better it is for the concrete structure. Even some companies blindly extend the process of concrete watering and curing. This practice will not only increase the cost of concrete watering and curing but also bring a serious impact on the strength and quality of the concrete structure itself.

In the usual construction of concrete maintenance is generally divided into 7d or 14d maintenance periods. Excessively long concrete curing will increase the hydrate inside the concrete. This will substantially increase the amount of deformation of concrete from shrinkage to some extent. Neither can reduce the amount of dry shrinkage of concrete, but also will prolong the shrinkage of concrete is not conducive to the formation of the entire concrete structure’s strength and stiffness.

The key technical and design parameters of concrete construction should be based on the ratio, temperature, and humidity factors as the control points to start the regulation of concrete watering and maintenance time. For concrete structures with a low water-cement ratio, watering should be carried out in a timely manner in order to achieve the replenishment of water from the outside. When the water-cement ratio is large, the time of concrete watering and curing should be extended appropriately to prevent the cracks that appear due to poor concrete watering and curing on the basis of the stable concrete structure.

For concrete structures with admixtures and retarders added, the time of concrete watering and curing should be determined according to the design and relevant scientific research, so as to effectively ensure the strength and stiffness of the concrete structure.

Misunderstanding about the final set of concrete

Concrete will form condensation on the surface at the end of the setting. Many concrete watering and maintenance personnel make the judgment that watering and maintenance are not required based on the presence of condensate. This is a misconception without an in-depth understanding of the concrete setting process and technical specifications. The generation of condensate does not mean that the entire concrete structure is not in urgent need of water. It is important to see the complex process before the final set of concrete.

Especially inside the concrete structure, there is still a large demand for water. If timely watering and maintenance are not carried out, the surface condensate will accelerate the dry shrinkage effect on the concrete surface after rapid evaporation. Due to severe water shortage inside the concrete without replenishment, it can lead to dry shrinkage and cracking problems. The simultaneous presence of plastic shrinkage, self-shrinkage, and dry shrinkage in different parts of the concrete seriously affects the performance and safety of the entire concrete structure.

Excessive water curing of concrete

Some concrete watering maintenance personnel are aware of the importance of watering, so as to increase the watering effect and excessive watering. Such watering will bring several problems as follows. 

First, a large amount of watering will cause flooding, forming an increase in the cost of concrete watering and maintenance. 

Second, excessive watering will cause a large amount of heat loss on the surface of the concrete, which will in turn cause temperature steps inside and outside the concrete, leading to the possibility of temperature cracks. 

Third, a large amount of watering will cause an impact effect on the concrete surface, which will cause problems such as pockmarks and holes. The concrete surface temperature should be controlled during the concrete pouring process while avoiding continuous large amounts of water to avoid the occurrence of concrete cracking, and intermittent spraying with a sprayer is recommended.

Wrong timing of insulation coverage

Engineering practice has proven that temperature change is an important and very complex load for concrete structures. The steepness of the temperature gradient can be regarded as the speed of “loading” of concrete and has an important impact on the physical and mechanical properties of concrete. A sudden drop in temperature can be seen as a rapid loading of concrete, which can lead to an increase in the tensile stress and modulus of elasticity of concrete, while the ultimate tensile strength of concrete is reduced and the crack resistance is weakened.

Conversely, a slow drop in temperature can be seen as a slow loading of concrete, which can lead to a reduction in the tensile stress and modulus of elasticity of concrete than a rapid loading, while the ultimate tensile of concrete increases. At the same time, a sudden drop in temperature can also lead to an increase in the degree of internal and external restraint. Whether the structure is predominantly externally restrained or internally restrained, concrete cracking can be avoided and reduced by external insulation and internal slow cooling.

In summary, regardless of the ambient temperature, the thermal insulation maintenance of concrete not only increases the surface temperature of concrete, but also enables the internal temperature of concrete to slow down, and reduces the temperature difference between the internal and external temperature and the temperature difference between the concrete surface and the atmospheric environment, and reduces the possibility of concrete cracking while doing a good job of watering and covering maintenance.

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