If the whole slab is used to repair the local pavement damage, it will not only take a long time to open to traffic, but also be uneconomical, so it is necessary to study and develop special repair materials for the local pavement damage. According to the characteristics of local damage of cement concrete, combined with relevant literature, the performance requirements of local rapid repair materials are studied, and specific indicators are put forward.
(1) choose epoxy mortar and unsaturated polyester mortar, study the influence of aggregate gradation and dosage, types and composition of cementitious materials in the two mortars on their early performance, optimize the composition of mortar, and obtain the formula of quick repair materials suitable for local damage of cement concrete pavement. The comprehensive properties of epoxy mortar and unsaturated polyester mortar, such as strength development law, new and old interface bonding, shrinkage and wear resistance, were tested. According to the performance characteristics of epoxy mortar and unsaturated polyester mortar, the application scope of local repair is studied, and the corresponding construction technology is put forward.
The research results show that (1) aggregate gradation and sand-binder ratio have significant effects on strength, and should be selected in consideration of strength, construction operability and economy. (2) When different curing agents are used in 2)EP mortar, the early strength and workability are quite different, and the workability is shortened with the increase of curing agent content; EP mortar has high bond strength, long operation time and small shrinkage, but its strength develops slowly. It is suitable for local repair with large repair area and high bond strength requirements (such as thin layer repair). Its open traffic time is about 3-5 hours at normal temperature, and the traffic time is correspondingly extended at low temperature in winter. (3) Two main unsaturated polyester agents and two accelerators with different properties were selected. Considering the factors such as operation time, strength, adhesion and shrinkage, the main agent A and the accelerator dimethylaniline are more suitable. UP mortar has high early strength, moderate operation time, large reaction heat release, suitable for local repair, small repair area, short open traffic time and low construction temperature. Its opening time is only 1 hour, which can achieve the purpose of instant paving.
(two) the rapid repair technology of cement concrete pavement damage, including rapid repair materials and corresponding technologies.
Engineering practice shows that it can meet the technical requirements of rapid repair of concrete pavement, and has the characteristics of high early strength, convenient repair, rapid molding and little traffic interference, and has remarkable economic and social benefits.
During repair construction, water reducing agent and sodium sulfate (or sodium sulfate) should be mixed into cement, and triethanolamine solution should be dissolved in water first, and then mixed with water to form Kunming compound. Concrete pouring operation. Pour the evenly stirred Kunming concrete mixture into the repair tank, spread it, compact and level it with vibrator, then plaster it manually to collect the light, and finally nap it with a napping machine. Vibration must be sufficient, especially at the joints between old and new concrete. Pavement maintenance after maintenance. After concrete pouring, it should be cured.
According to the concrete mixture ratio, temperature and the actual situation in the repair process, traffic can be opened after L2 ~ 24h.
Problems needing attention in rapid repair of damaged cement concrete pavement
(1) The amount of raw materials should be accurately weighed, especially additives. Because the dosage of admixture is very small, such as the dosage of triethanolamine is less than 0.07% of the dosage of cement, and the dosage of admixture has a great influence on the early strength of Kunming concrete, so it is very important to accurately weigh the admixture.
(2) The concrete mixture should be stirred evenly. The mixing time of the mixture mixed with additives should be appropriately increased to make the mixture fully and evenly mixed.
(3) Each working procedure should be closely linked. Because the ultra-early strength concrete mixture sets faster, especially in summer construction, the setting time is shorter. The whole construction process, from adding water and stirring to the end of molding and napping, should be controlled at about 45 rain, and the longest rain should not exceed 60 rain. In summer construction, it should be strictly controlled within 20 rain to reduce water evaporation.
(4) Strengthen maintenance. Maintenance of ultra-early strength concrete after paving is an important part of rapid repair. Different curing conditions have great influence on the early strength of concrete. We should not only pay attention to the health care in the early stage of Kunning soil, but also strengthen the health care after opening to traffic, and should not neglect health care when opening to traffic. In addition, concrete should avoid exposure to high temperature to avoid excessive shrinkage due to excessive water loss, and keep warm at low temperature.
(5) According to the temperature during the repair period and the time limit of opening traffic, choose the appropriate concrete mixture ratio, admixture type and dosage. When the weather is hot in summer, the water in cement concrete is easy to evaporate. In the process of mixing, transportation and paving, too much water is lost, which affects the hydration of cement in Kunming concrete. In addition, cement concrete may have false condensation due to excessive temperature. Therefore, while strengthening maintenance, water consumption can be appropriately increased. When the temperature is too high during construction, it will affect the normal progress of each repair process. When necessary, retarder can be added to the ultra-early strength concrete mixture, and the dosage is generally about L% of the cement dosage, so as to adjust the setting and hardening time of concrete, make the quick-repair materials meet the use requirements during and after construction, and achieve the purpose of rapid repair. If the temperature is low during the repair, the time of opening traffic should be appropriately delayed to ensure the quality and use effect of concrete repair.
(6) Ensure the engineering quality of raw materials. Quick repair materials shall meet the requirements of relevant technical standards, and shall be tested according to corresponding test procedures and methods before use. It is forbidden to use materials that do not meet the quality standards. The engineering application shows that the rapid repair effect of concrete pavement slab is ideal, the road performance is good, the purpose of rapid repair and early opening to traffic is achieved, and it has good practical value and can be widely used.
The joint treatment of joint modified asphalt and pavement is more difficult than ordinary mixture. If the joint is treated the next day, the modified asphalt A mixture is very hard, and it is difficult not only to plane with a pick, but also to cut the joint with a cutting machine. So no matter what, we must find ways to prevent cold joints. If two pavers are used for step paving, the longitudinal distance should not be too far, and the longitudinal hot joint should be maintained. If the paving width of the paver can't meet the requirements, cold joints will appear. In this case, when paving, baffles should be set on the side, so that cold joints do not need to be treated separately. The transverse joint adopts the method of longitudinal joint. After coating modified asphalt layer A every day, stop for a period of time, especially before it cools, cut it open and rinse the joints with water. On the second day of construction, apply viscous oil, and then spread a new mixture. Joints should be controlled with a 3m ruler, and the flatness of joints should be checked to prevent the bad joints from affecting the flatness.