Common problems and preventive measures of the hot

Common faults and preventive measures of cement concrete pavement

(1) disease phenomenon and causes

cracks, damages and pits appear on the slab surfaces on both sides of the expansion joint after a period of operation due to the deflection of the expansion joint plate, insufficient length, long expansion joint spacing, misalignment between the lower expansion joint plate and the upper expansion joint, poor expansion joint materials or improper filling and pouring technology. In serious cases, the adjacent two plates are staggered or arched. The filler in the expansion joint is extruded out of the road and taken away by the driving car

(2) preventive measures

① the expansion joint plate should be placed correctly. A pouring section should be made between the two expansion joints, and the expansion joint plate should be added with formwork to control the correct position of the joint plate; The length of the joint plate shall run through the whole joint length, and the concrete in the expansion joint shall be strictly controlled so that it cannot be connected. Carefully clean and fill the expansion joints

② the joint filler should choose materials with good heat and cold resistance, good adhesion and not easy to fall off. 3 Gear deceleration and acceleration system of Jinan experimental machine factory

③ the expansion joint filler is not to be filled once and for all, but to be maintained regularly. Generally, when the spacing between expansion joints is the largest in winter, the invalid filler and sundries in the joint are removed, and new materials are filled again to keep the expansion joints often effective

④ the strength of soil foundation and base course shall be uniform

⑤ if dowel bar is set at the expansion joint, the dowel bar must be parallel to the plate surface and center line

⑥ when the crushed area of the joint is small, and there is only 1-3cm gnawing edge, the sundries in the joint can be removed, and the asphalt sand or dense graded asphalt concrete can be used for leveling and tamping. When the crushing is serious, the cutting machine can be used to cut the crushed part into regular and straight wall grooves, then the sundries in the groove can be cleaned and dried, and the asphalt sand or dense graded asphalt concrete can be used for tamping and flattening

⑦ when the joint part or crack part has a slight dislocation, sweep the road surface, and use asphalt sand or dense graded asphalt concrete for smooth connection. If the dislocation is serious, and the adjacent two slabs are smooth and scratched, use a cutting machine to cut the scratched part and pour the concrete pavement again

2. The crack data information of concrete plate will be displayed in the form of word table

(1) disease phenomenon and causes

① due to insufficient curing, the surface air dried and contracted, resulting in hairline cracks of shape, shallow and fine

② because the contact area of the angle couple at the base is small, the pressure on the unit area is large, and the relative settlement of the base is large, resulting in the fall under the plate, loss of support, and local cracks at the angle couple

③ the cutting time is too late, resulting in shrinkage cracks and plate fracture caused by the subsidence of the pavement base after the opening of traffic

④ cracks due to construction operation errors or raw material problems

(2) preventive measures

① after the concrete slab is poured, it must be covered and cured in time according to the specifications. During the curing period, it must be kept moist frequently, and it must not be exposed to the sun and completely true and false, good and evil, beauty and ugliness, air drying. Generally, the curing time should not be less than 14 days

② the construction joint of concrete should not be set in the middle of the plate, but at the expansion joint

③ joint cutting time: when the concrete reaches 25% - 30% of the design strength, joints can be cut. From the perspective of appearance, it is appropriate that no stubble more than 5mm appears on both sides of the cutting saw blade

④ the synchronous technology of cement concrete pavement and road oil cylinder also costs money. Various settlements are sensitive, and even a small deformation will break the plate. Therefore, the compactness, stability, uniformity of subgrade and base should be changed strictly

⑤ pay attention to the vibration of concrete at the corner couple. If necessary, the corner couple reinforcement can be added. In the soft soil road base section, the reinforcement design can be made to make a reinforced concrete road slab

⑥ control the technical indicators of raw materials used in mixing concrete, especially cement, to meet the requirements of corresponding standards

⑦ during concrete vibration, pay attention to the vibration of those parts that are easy to produce unconsolidated parts to prevent concrete layering caused by excessive vibration

⑧ pay attention to deal with special problems such as vacuum water absorption lap joint and preventing concrete vibration cracking during half width road construction pouring