First, the significance of controlling the broken slab of concrete pavement
The broken slab of concrete pavement is generally divided into two types: early broken slab and late broken slab, and the broken slab forms are divided into two types: transverse broken slab and longitudinal broken slab, and the broken slab degree is divided into two types: full penetration type and semi-penetration type.
After the cement concrete pavement is damaged, it will have a great impact on the pavement quality and the safety and comfort of driving. The number of broken slabs is the main basis for evaluating pavement. Once the concrete slab breaks, other diseases will follow, such as dislocation, void, crack, arching and so on. For the broken slab with wide cracks, if it is not treated in time, the cement concrete slab will develop into a broken slab, which will seriously damage the pavement and make the pavement lose its bearing capacity.
Second, the main reason for the broken plate
(A) early broken board
Early slab breaking refers to the rapid fracture of pavement within 24 hours after the completion of construction and pouring. This kind of broken slab is generally caused by insufficient maintenance in the early stage, especially in the hot summer construction season. Because the initial setting stage of concrete needs a lot of water, and hot summer weather is easy to cause the distribution of water. Due to lack of water, the strength of concrete can't meet the design requirements, which leads to fracture. This kind of broken board is semi-permeable, and a large number of small cracks are formed on the surface, like a spider web.
Another reason for the early plate breaking is the late slotting. When pouring large area concrete, it is necessary to cut at the best time because of the large internal stress. If the cutting time is late, it is easy to break the board. Therefore, the cutting time should be strictly controlled. However, due to the different geographical location and construction environment, the' temperature hour method' specified in the specification can only be used as reference data, especially in mountainous areas, where the temperature difference between morning and evening is large and the cutting time is more difficult to control. After a long period of experience, you can scrape its surface with your thumb nail, and you can draw a slight dent, which is white and the edge is neat without slag to determine the best sewing time.
(2) Late plate fracture
The reason of plate fracture in the later period is 10.
The basement construction is unqualified. In the process of grass-roots construction, its quality requirements did not reach the specified value, such as insufficient compaction or broken layer at the grass-roots level. After the completion of concrete pavement construction, broken slabs will not be found in a short time, but often appear after opening to traffic, with a large area of continuous broken blocks or longitudinal cracks, which is particularly serious.
Premature opening and loading. When the pavement does not reach the 28-day maintenance period, it is caused by the development of traffic for the convenience of construction or other reasons. The reason for premature opening to traffic is often that the vehicle will drive slowly on the road surface, which will make the load uniform and will not damage the road surface. In fact, the vehicle will vibrate when walking, and the instantaneous pressure of the * * * vibration force is extremely great, which is easy to cause fractures, so it is necessary to avoid opening the traffic prematurely.
Fracture due to temperature. In a certain area, the temperature difference between day and night is very large, and the hydration heat generated in the process of concrete solidification is affected by extreme temperature changes, which directly leads to insufficient strength. Therefore, when constructing in areas with large temperature difference between day and night, covering insulation should be adopted to reduce the changes caused by temperature difference.
The raw materials of concrete are unqualified. This situation caused a lot of broken boards. First, the gradation of raw materials is poor, and the workability and slump of concrete can not meet the requirements when mixing. When pouring concrete, it is easy to cause aggregate separation, incomplete dissolution of cement or insufficient sand and gravel retention; Second, the purity of raw materials is insufficient, and there are many impurities such as sand, stone and water, which affect the workability of concrete and dissolve some cement, thus affecting the overall quality of concrete.
The mix proportion of concrete is unreasonable. There is a certain gap between indoor mix design and production mix design. In indoor mix design, raw materials are often inadvertently selected, while cement concrete is produced by machinery according to the set mix ratio, and raw materials cannot be selected. Therefore, in the process of producing cement concrete, indoor mix design should be verified and adjusted in time.
Transportation and pouring of concrete. If the initial setting time of cement concrete exceeds due to mechanical failure, it should be resolutely scrapped. Because in continuous casting, the problem of concrete in a single part directly affects the overall strength and is easy to break.
Improper use of additives. Because of the development of modern science and technology, the simple early strength agent and water reducer in the past have already developed into multi-purpose composite products. So be sure to read the instructions carefully before use, especially when the temperature is low or high, and the operation should be managed by a special person.
Improper joint cutting and attachment embedding. In addition to grasping the best opportunity, the depth of kerf should also be guaranteed. When it is necessary to bury accessories, such as seepage wells, marks, expansion joints, contraction joints, etc., construction should be carried out seriously according to the requirements of technical specifications to avoid unnecessary broken plates.
Third, measures to prevent plate breakage
The requirements for roadbed paving are strict, and the compaction degree 100% is qualified, and the deflection meets the design requirements.
The elevation, flatness, cross slope and thickness should be strictly controlled in base construction to meet the strength requirements, and the interval between base construction and pavement construction should not be too long.
The materials used in cement concrete are strictly selected and fed from qualified manufacturers, and all indicators meet the specified requirements. The concrete mixture ratio should be verified according to the batch of incoming materials, so as to improve the mixing quality of concrete and try to avoid the influence of human factors on concrete quality.
The vibrating process of concrete should be uniform and moderate in strength, and the bleeding phenomenon should be eliminated in time.
Ensure the seam cutting depth, master the seam cutting time, and avoid staggered joints during construction.
Cement concrete panels are always exposed to the atmosphere during construction and maintenance, and the wind speed has a great influence on the shrinkage of concrete, so corresponding measures should be taken, such as covering the wind shed.
Strengthen concrete curing. The traditional pickling method is to cover the wine with straw bags and sacks. The straw bags can't leak and spray water evenly every day. At present, a new curing agent is used for pavement maintenance, which is simple in process and convenient to operate, and is conducive to civilized construction.
Put an end to premature opening to traffic. In the process of construction, it is necessary to organize and plan the construction project, form an effective flow process, and put an end to the situation that traffic is blocked and traffic has to be opened in advance.
Four, common methods to deal with broken boards
Draw a line along the seam according to a certain width, cut out the interior neatly, and check whether there is any problem with the basement at the crack. Drill holes with a diameter of 4cm, a depth of about 10cm and a horizontal spacing of 30-40 cm in concrete, bury secondary steel bars with a diameter of 18-20mm and a length of about 20cm, plug the holes, wet the whole cutting groove, and cast with ultra-dry strong micro-expansive cement concrete or rapid-setting concrete for surface treatment.
In the case of irregular and large cracks, a certain range can be drawn, and the concrete panel can be cut to a depth of 5-8cm, cleaned up and equipped with a layer of steel mesh. Steel mesh must cover the cracks and leave a certain width on each side. After wetting, concrete is poured for surface treatment.
When there is a big crack, the whole broken plate will be cut off, with double-layer steel mesh, and concrete will be poured again.
Concluding remarks
According to many years of construction practice, it is proved that as long as the correct preventive measures are taken for cement concrete pavement, the broken slab rate of concrete pavement will be greatly reduced. This will be very important to ensure the construction quality of cement concrete pavement and extend the service life of concrete pavement.
For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd