Experimental Study On Rapid Repair Technology Of Precast Concrete Pavement

In the conventional repair technology,the cast-in-place concrete repair is mostly used,which often takes 5-7 days to open to traffic.For the road with large traffic demand,closing of traffic for a long time may cause greater traffic inconvenience.For this reason,the research on the rapid repair technology of precast and assembled cement concrete pavement is very important,it is a kind of repair technology that can open to traffic in a short time,and has good durability and its construction is not affected by climatic conditions.However,the technology still remains to be improved,such as the fast hardening time of the grouting material,the treatment of the interface between the new and old concrete in the trough of the dowel bar,and the cracking of the precast slabs.On the basis of the existing technology,this paper has done the following experiments on this technology,the main contents and conclusions are as follows:In view of the grouting at the bottom of precast slab,grouting material was studied.According to the requirements of grouting material,several groups of cement paste ratio are selected.Then the test specimens of these groups were tested for fluidity and slump diameter,compressive and flexural strength.Through the above experiments,a group of optimum ratio was selected.The polypropylene fiber was considered in the test because of the brittleness properties of the cement paste specimen.All tests showed,under the same condition:1)that the higher the water cement ratio is,the better the flow degree is and the longer the larger the slump diameter is,and the lower the compressive strength and flexural strength of the test specimens are,2)that the difference of fiber content has little effect on the compressive and flexural strength of the test specimens,and the higher the fiber content is,the smaller the test specimens’water expansibility is.In terms of compressive strength,the ratio of this test can reach the strength of 3.5 MPa at 3 hours.This test greatly shortens the time required by the grouting material to meet the traffic requirements.The grouting increases the time to repair the road,therefore,this paper starts with the improvement of the surface evenness of the old road base.The leveling layer between the old base and the precast plate was considered,in order to avoid the inaccessible space between the precast slab and the old road base,thus this paper has a preliminary discussion on the leveling layer.According to the ratio of roller compacted concrete,several groups of ratio with different fly ash content were selected.By testing the flexural and compressive strength of the test specimens,several groups of dry shrinkage tests with multi age period were selected.The test showed that the more the amount of fly ash which takes the place of the cement is,the lower the specimens’compressive and flxual strength,and shrinkage are.At the same time,the ratio of the test can reach the strength requirement of the expressway and the first class highway in heavy traffic at 6 hours.As to the slot interface of the dowel steel,the inter facial agent was studied.In this paper,the mixture of polymer and cement used as an inter facial agent was tested.At the same time,the ratio without inter facial agent was also tested as a contrast.The test showed that under the same condition,the longer the age of the test specimens are,the higher the strength of the test specimens are,and the strength remain stable at last,and that in several groups of ratio,the best mass ratio of polymer to cement is 1:1.5.In order to strengthen road slab’s capacity of bearing vehicle loads,In this paper,the road slabs with fiber reinforced plastic(FRP)were studied and a preliminary Abaqus simulation was also carried out,at the same time.Among them,the beam bearing capacity,fracture toughness and fracture energy,and crack propagation rule are obtained.The influence of different FRP modulus and different bonding interface stiffness on crack stress intensity factor were simulated by Abaqus.The results show that the peak load of the composite pavement bonded with FRP is higher than that of the pavement without FRP,and the fracture toughness and fracture energy of the composite pavement is also improved.The Abauqs simulation shows that the stress intensity factor of crack is inversely proportional to the modulus of FRP and the stiffness of bonding interface.FRP can delay or prevent crack propagation.FRP materials with high modulus and high tensile strength and excellent adhesive paste is recommended.