Study On Bonding Property Of Threaded Polypropylene Bar In Concrete

Underground granary has become the ideal warehouse type of green grain storage because of its advantages such as low temperature,excellent sealing and energy saving.However,the continuous erosion and penetration of groundwater is one of the key technical problems encountered by underground granary in the process of construction and use.If the degree of leakage is lighter,it will affect the quality of storage in the warehouse,thus reducing the functionality of underground granary.When it happens,remedial measures need to be used immediately at a later stage to repair the leakage problem,which will be easy to cause the results of wasting time and labor;If the leakage is serious,the whole project may be scrapped.Therefore,in the process of design and construction of underground granary,the quality of waterproofing system is the key to eliminate the corrosion caused by groundwater.At present,the commonly used waterproof materials include coils and coatings.However,the service life of the coil is short,the quality of the coil after construction is easy to decompose with the change of the external environment,resulting in the destruction of the waterproof system,but also improve maintenance and labor costs.In the continuous development of underground granary,the waterproofing system with high standards and demands plays an increasingly important role in the whole project.Polypropylene plate was selected as a new waterproof material for underground granary waterproofing system;This study is based on a waterproof scheme of polypropylene waterproof plate lined with concrete silo wall plate.In this scenario,a new type of polypropylene rod(PP rod)with threaded surface as a connector between the lining Polypropylene plate and the concrete silo wall plate is proposed.If the groundwater seeps from the outside of the concrete silo to the concrete silo wall and the PP waterproof plate,the groundwater will produce water pressure on the PP waterproof plate,while the bonding performance between the PP rod welded to the PP waterproof plate and the concrete determines whether the PP rod will be destroyed by the action of the water pressure.The bonding between PP rod connectors and concrete is the basis on which they can work together,and the bonding properties also fundamentally affect the anti-pulling performance of PP rods in concrete and many other mechanical properties.Therefore,it is of great significance toexplore and analyze the bonding slip characteristics between PP rod and concrete to establish the waterproofing system of underground granary and ensure the effectiveness of waterproofing system.In this paper,a new type of circular rod-shaped PP connector is proposed,The central drawing test is designed and implemented to explore the bonding characteristics of PP rods in concrete,By analyzing the variation characteristics of the strain along the anchorage length,the distribution law of the bonding stress between PP rod and concrete in the anchorage length is investigated by means of setting the groove inside the PP rod and pasting the strain gauge in the groove.During the experiment,the bonding stress-slip relation of PP rod in concrete is obtained by collecting and analyzed the anti-pulling capacity of the loading end of the specimen,the slip value of the free end,the slip value of the loading end.Furthermore,the corresponding curve is drawn and the development law of the curve is also discussed.Meantime and the segmented expression of the curve and the selection value of the curve feature parameter are suggested.The effects of different surface formation of PP rod(smooth surface and threaded surface),different diameter of PP rod(25mm and 30mm)and different concrete strength(C35 and C55)on the bonding stress-slip relationship of PP rods in concrete are considered.The results of each influencing factor are also compared,analyzed and summarized.The data obtained from the drawing test are applied to the finite element model of the finite element software ABAQUS to establish the PP-concrete drawing specimen,The results show that the finite element simulation results are slightly smaller than the test results and the difference is only 14.3% at most,which is in the acceptable range.The compatibility between the two is high,which verifies the correctness of the bonding slip constitutive relationship between the PP rod and the concrete used in this model.The results show that the finite element model of PP-concrete bonding slip established in this paper is effective and provides a basic reference for the design of waterproofing system in practical engineering.