Cement concrete pavement with high strength, durability, and can also make full use of local building materials, in promoting regional economic development at the same time, can significantly reduce the cost of the project, which is increasingly used in the construction of various grades of roads.
This paper first analyzes the causes of the emergence of the concrete concrete pavement, and then puts forward the prevention method. Finally, the treatment method of the broken plate is discussed.
"Eleventh Five-Year" period, the implementation of the province through the village cement road construction projects, the county to seize this historical opportunity, big and fast, in the county set off a village through the road construction boom, as the county through the village project management Personnel, after several years of practical experience and access to relevant information, I Tongcun highway construction in the cement concrete pavement construction problems often occur in the problem and approach to the following discussion.
First, the reasons for the emergence of broken plate
1, raw materials, cement concrete pavement of the main materials: cement, gravel (broken) stone, in the coarse sand, water, cement label is not enough, poor stability, lack of strength; aggregate harmful substances or mud content exceeded.
Improper control of concrete mix. Construction of the aggregate due to dry or large quantity, absorption of mixed water and construction measurement are not allowed, thus affecting the initial strength of concrete. Above will lead to the emergence of broken board.
In order to ensure the quality of concrete pavement construction, the county through the village to do the raw materials of cement, sand, gravel are clear the origin, specifications, cement using the three companies on the road production of Portland cement, , Jingyang River, gravel requires the maximum particle size of not more than 4 cm, and sand, gravel (broken) stone, cement, water must be qualified.
Cement requirements are factory inspection certificate, to meet the design of the label. Sand to control the amount of mud. Mixing must pay attention to the mix of various materials, must be mechanical mixing.
2, the construction process
Cement concrete pavement works in the construction organization to consider the design of the mixing station to set the supply distance, generally not more than 10km. It is best to use a mixer. The construction of the village road is generally less than 5 km.
Pay attention to vibration, especially the pavement of the pavement of the requirements of more stringent, in strict accordance with the specification requirements, vibrator in each position of the duration of vibration, should be the concrete gypsum prevail, and should not be too , With flat vibrator vibrator, not less than 15s, with plug-in vibrator vibrator, not less than 20s.
Concrete pavement construction process control improper, stirring time is not enough, vibrating is not dense; mixing concrete composition material temperature is too high, in the cooling, hardening process due to temperature difference increases the bending stress of concrete, resulting in cracking; construction process Improper control (such as the concrete is not done when the construction of sewing joints, the gap is not timely, vacuum suction suction, force bar installed properly, in the adverse season construction, etc.) affect the concrete itself, lack of anti-bending strength, leading to cracking.
Uneven surface of the grassroots and improper humidity of the material. The surface layer is not smooth and the surface thickness is inconsistent, which increases the wear resistance between the base layer and the surface layer, which leads to the difficulty of drawing the tensile stress at the weak road surface. The base material is too dry and absorbs the bottom concrete moisture, so as to reduce the anti- Leading to cracking.
Second, the use of cracking, broken plate reasons
1, early design improper early due to lack of experience in the thickness of concrete panels thin; plate size does not meet the specification requirements; raw material selection and design with improper ratio.
2, roadbed uneven settlement of the wet soft roadbed improper handling, filling and digging at the junction of the compaction standards are inconsistent, bridges and tectonics near the compaction degree is insufficient, road sections of geological changes at the roadbed improper handling, the above situation will produce uneven roadbed settlement Concrete panel cracking.
3, grass-roots instability grassroots construction quality is not good, the surface is not smooth, uneven intensity, resulting in surface layer of concrete plate bending stress increases, resulting in broken plate; surface seams at the joint material failure, Water into a pressurized water, so that seams occur at the mud, empty, resulting in broken plate. Other conditions such as poor road drainage, overload and overruns increased.
Third, the cement concrete pavement prevention plate
Cement concrete pavement is mainly in the construction process and the use of the process, so the prevention of the plate should be based on the emergence of different periods of control.
1, a good combination of structural design can effectively prevent the off-board cement concrete pavement in the use of the process, due to design, over-load factors will lead to cement concrete pavement plate. The impact of design factors is mainly due to structural design, drainage design considerations are not thoughtful.
The design of the structure should focus on the impact of pavement on the cement concrete panel, that is, the pavement in addition to meet the sufficient strength, stiffness, but also should have good water stability and flatness. Good water stability can effectively avoid the generation of mud, so as to avoid the destruction of the grassroots and the bottom of the bottom of the blank, cement concrete panel to provide a good support to avoid breaking plate; good flatness can effectively avoid the role of load Cement concrete panel stress concentration area, to avoid broken plate.
2, the construction process of the prevention of strict control of cement concrete mix to avoid the water-cement ratio is too large or mixture of segregation to ensure that the concrete mixture has sufficient strength, at the same time, strictly grasp the cutting time, Temperature, to avoid the shrinkage of concrete and produce broken plate, because the temperature, humidity and wind changes, will cause a large concrete shrinkage.
3, the use of the process of prevention of the prevention of cement concrete pavement in the course of the use of excessive load, a variety of ground water into the cement concrete pavement gap, the formation of mud mud, and thus produce broken plate, which should strictly control the overload load, Timely cement concrete pavement of various cracks in the irrigation joints to prevent a variety of ground water into the cement concrete pavement structure, the elimination of mud source, to avoid broken plate.
Fourth, the cement concrete pavement treatment method
Broken plate processing should be based on the different extent of the use of the corresponding method to deal with. The shape of the seam appears: ¢Ù more straight seam; ¢Ú smaller slope of the narrow; ¢Û corners at the corners; ¢Ü large slope of the fracture. The first three cases are more common, the fourth case is rare.
There are many ways to deal with the broken panel (broken plate), after a number of works of the treatment of broken plate experience, I think concave filling concrete is simple, easy to learn, the treatment effect is better. The main construction process is:
1, concave excavation According to the location of the seam, the cement concrete panel chiseled into a rectangular groove, through the entire thickness of the groove wall chisel 1: 0.15 slope is the best, so that the repair of concrete and the panel more fully Common support driving load. The right side of the groove is parallel to the shrinkage and longitudinal seam. For the more straight seam, the two sides of the seam on both sides of the width of not less than 20cm, the total width of not less than 40cm; if the seam is slightly inclined or curvature, the time to dig from the crevice protruding position or end Less than 10cm, the groove cut the total width of not less than 40cm; if the seam in the vicinity of the shrinkage, and cut the edge from the shrinkage is not greater than 40cm, the original shrinkage as a groove of the edge.
For the corners of the corners, according to the requirements of the above cut size, the seam (broken plate) around the concrete chisel can be cut out. For the larger slope of the seam, can be broken around the concrete is divided into two pieces of chisel digging.
Before the excavation according to the situation of the seam, according to the size of the requirements of the ink bucket in the cement on the concrete pavement on the road to play ink lines, and then cut along the cutting machine, and then need to dig out the concrete pavement cut with a cutting machine , The smaller the area of the grid easier to digging digging. And then use the hexagonal steel brazing and sledgehammer (eight pounds hammer) to dig out the concrete chisel, dug after, to be around the groove with signs to facilitate safety.
2, filling the expansion of concrete filled with the groove, we pour the road is higher than the original level of the label of the panel surface, through the village of cement road design design for the 30 #, to deal with the use of concrete to promote the expansion of concrete alumina On the sale of aluminum powder, content of 0.3%). The mix ratio is cement: concrete: sand: gravel: water: alumina = 100: 158: 275: 62: 0.3.
Fill the groove is completed, to be surrounded by signs or obstacles, not to be in its traffic, to be expelled concrete to the final setting time (usually 8h), can be in the concrete on the thickness of not less than 15cm fine soil, health, soil Always keep wet. To be healthy two weeks later, you can remove the Xu signs or obstacles, transport traffic.
Five, concluding remarks
Filled with expansive concrete method to deal with broken plate, after several years of traffic observation, the expansion of concrete within the groove and the original road panels between the close, no gaps, and even asphalt waterproof material did not smear, indicating that the expansion of concrete as a road The treatment of the filling material is feasible, and thus in the county through the village of cement road construction has been recognized and promoted.
From:mobile concrete batching plant