A Brief Analysis of the Causes of Asphalt Concrete Cracks

1. The proportion of asphalt concrete is unreasonable or the finished products produced by the mixing plant are substandard

Asphalt concrete is an asphalt mixture made by blending coarse aggregates, fine aggregates and fillers in appropriate proportions with asphalt under strictly controlled conditions. If the asphalt is insufficient or substandard, the bonding capacity will decrease, leading to the formation of cracks. When the coarse aggregate exceeds 200% of the specified proportion, the fine aggregate will not be sufficient to fill the voids, and cracks will also occur during compaction, causing premature damage to the pavement.

The emulsified asphalt in the slurry seal has a low viscosity and a small quantity

Emulsified asphalt accounts for 10% to 20% of the slurry seal material and is an important component. The quality of its performance directly affects the quality of the seal material. Emulsified asphalt is composed of paste asphalt, water and emulsifiers. Paste asphalt that is relatively hard and meets national standards should be selected. The penetration of the ointment asphalt is relatively large, making it convenient to prepare emulsified asphalt. However, if the asphalt does not meet the national standards, has a small penetration or a small proportion, it will cause a decrease in adhesion. During the compaction process, it will slide in the direction of the roller's travel, and the upper and lower layers will not bond, resulting in cracks or a scruple. The remedial method is to sprinkle another layer of emulsified asphalt on the emulsified asphalt seal layer.

The compaction speed of the road roller

Practical experience has shown that when the compaction speed of a roller increases, the degree of compaction achieved only improves slowly. However, on the other hand, if the compaction speed is too fast at a certain vibration frequency, it will also increase the impact distance, which may lead to unevenness of the road surface, the formation of ripples or scrubbing phenomena, and a decrease in compaction quality. To increase the compaction speed, the vibration frequency must be increased.

Segregation occurs when the paver is laying

When the paver is laying, segregation is inevitable. The longer the screed is joined, the more severe the segregation becomes. Coarse aggregates are concentrated on both sides, and during compaction, cracks occur on both sides.

5. The weather or the working surface is too dirty

When paving, if it rains and the working surface gets wet, it will cause the upper and lower layers to fail to bond, resulting in cracks. Water will be trapped between the upper and lower layers, causing early damage to the road surface. If the working surface is too dirty, it will also isolate the connection between the upper and lower layers, causing cracks. Therefore, before paving, the working surface should be cleaned thoroughly and paving must be stopped on cloudy days.

6. The temperature is low during paving

Due to the low temperature, the tensile strength of the asphalt mixture is insufficient or its deformation capacity is poor, resulting in cracks. During construction, pay attention to insulation, spread and compact in a timely manner to reduce the impact on the quality of the road surface due to low temperatures.