How to handle cracking in grouting material?

Plastic Shrinkage Cracks

Irregular shapes with varying lengths and discontinuous surfaces resembling dried mud are observed on the structural surface. These typically occur during the early stages of grout pouring (approximately 4 hours post-pouring), when there is a significant temperature difference between the grout itself and the external air temperature, or when the grout temperature remains excessively high for a prolonged period in a very dry climate. These cracks, known as plastic cracks or alligator cracks, are strictly speaking dry shrinkage cracks and are quite common.

Reason:

After grouting material is poured, if the surface is not covered promptly, it is exposed to wind and sun. The surface free water evaporates too quickly, causing rapid volume shrinkage. At this stage, the early strength of the grouting material is low and cannot withstand this deformation stress, leading to cracking.

2) Utilizing cement with high shrinkage rates, excessive cement usage, or an overabundance of fine sand.

3) Excessive water-cement ratio in the grouting material, and the formwork is overly dry.