Causes of cracking in cement concrete pavements and preventive measures

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I. Quality issues and phenomena: The surface of the concrete pavement develops network-like, shallow and fine crack patterns in the form of small hexagonal shapes, with a depth of 5–10 mm. II. Cause analysis: 1. After the concrete is poured, its surface is not covered in a timely manner; in hot or windy weather, the free water on the surface evaporates rapidly, causing the concrete to shrink sharply and resulting in cracks. 2. The water-cement ratio is too high during concrete mixing ； The formwork and cushion layer are too dry, resulting in high water absorption. 3. The concrete mix ratio is unreasonable, with excessive amounts of cement and sand ratio. 4. Excessive vibration or smoothing of the concrete surface causes excessive cement and fine aggregates to rise to the surface, leading to shrinkage cracks. III. Preventive measures: 1. After the concrete pavement is poured, cover it promptly with damp materials and water it regularly to prevent strong winds and exposure to direct sunlight. During the hot season, construction should be carried out under a shelter if necessary. 2. When preparing concrete, the water-cement ratio and cement dosage should be strictly controlled, and an appropriate grading of coarse aggregates and sand ratio should be selected. 3. When pouring the concrete pavement, wet the base layer and formwork thoroughly to prevent them from absorbing moisture from the concrete. 4. When using a vibratory screed for dry-hard concrete, prevent excessive vibration so that mortar does not accumulate on the surface. The thickness of the mortar layer should be kept within the range of 2 to 5 mm. There’s no need to over-smooth when troweling. IV. Treatment Methods 1. If cracks appear in the concrete before it starts to set, these can be eliminated by repeatedly pressing and smoothing the area with a trowel or by vibrating it again, followed by enhanced moist covering for curing. 2. Generally, it has little to no effect on structural strength; thus, no treatment is required. 3. When necessary, grouting should be used for surface coating to seal cracks.