Plastic shrinkage cracking (as shown below) is caused by rapid drying of the concrete surface. They can occur at any time of the year, from cooler low-humidity weather conditions to, in particular, hot weather conditions involving any one or a combination of high temperature, low humidity and wind.

These types of cracks occur while the concrete is bleeding and during the finishing operation. Fresh concrete may be exposed to the elements for a considerable time during these stages, causing the concrete at the surface to dry and shrink before it has any strength to resist the shrinkage forces.

Concrete cracks in much the same way as clay soils.

Methods of Preventing Plastic Shrinkage Cracking of Concrete

1.Erecting Temporary Wind Breaks

Higher wind velocities can greatly affect the rate of evaporation of water from the concrete being placed. This in turn will result is plastic shrinkage cracking of concrete. Therefore erect temporary wind breaks to reduce the wind velocity over the surface of the concrete.

2.Providing Sunshades

In case of construction of concrete slabs, it is very effective to provide sunshades over the concrete slabs and thereby controlling the surface temperature of the slab.

3.Proper Placement Timing

在非常炎热的天气条件下，不应在下午放置混凝土，因为它可能导致塑料收缩裂缝由于水的损失而在混凝土上。因此，在清晨或傍晚安排混凝土放置是一个很好的做法。这样我们就可以更好地控制混凝土温度。

4.使用雾喷雾

In very hot and dry periods the wind is very hot. Therefore use fog sprays to spray fog into the air over the concrete surface and in the direction opposite to the direction the wind is blowing. Using of fog sprays reduce the rate of evaporation from the concrete surface.

5.致电路基

During construction of concrete pavement in hot and dry weather, dampen the subgrade which is liable to water absorption from concrete. But remember the subgrade should not be over dampened. The formwork and the reinforcement should also be dampened.

6.Using Evaporation Retarder

Spray an evaporation retarder such as aliphatic alcohol over the freshly screeded concrete surface. Surfaces can dry prematurely when the rate of evaporation is greater than the rate of bleeding. These products form a film on the surface that reduces the rate of evaporation of water, thus allowing time for all the bleed water to rise to the surface. In extreme conditions, re-application of the evaporation retarder may be necessary both before and during trowelling. These products do not affect the strength or performance of the concrete and can act as a finishing aid.

7。Start Curing Immediately

在完成后尽快开始治疗。用液膜固化化合物喷涂表面，或用湿粗麻布覆盖表面或在混凝土放置后开始水固化。

8。Accelerating Setting Time of Concrete

在混凝土中使用某种形式的化学混合物来加速混凝土的设定时间，避免混凝土和空气温度之间的大温差异。

9.Adding Polypropylene Fibres in Concrete Mix

Polypropylene fibres can be added to the concrete mix to reduce the incidence of plastic shrinkage cracking. Fibres tend to bind the surface of the concrete together and provide some strength to the plastic concrete to resist the shrinkage forces.

10。Be Ready

Have proper manpower, equipment and supplies on hand so that the concrete can be placed and finished promptly.