The Experimental Study For Cohesive Property Of Polyurethane Sealing Material In Expansion Seam Of Channel Under The Special Construction Environment

The polyurethane sealant is widely used as the water sealing material of hydraulic expansion joint. But under the special environment and conditions, due to the construction environment temperature, damp expansion joint interface with dirt and so on, which will to reduce the bonding performance of polyurethane sealing material. Therefore, aiming at the existing problem of the polyurethane sealing material in construction, we start the test and research of the polyurethane sealing material bonding performance in channel expansion joint under the special construction environment, we can get the following conclusion through the experimental study:(1)The double polyurethane sealing material bonding performance, which are greatly influenced by the mixing time and environmental temperature in the mix process before construction, the results found that: The double polyurethane sealing material bonding performance will promote with the increase of mixing time; If the environment temperature is more lower, the mixing difficulty of the double polyurethane sealing material is bigger, its construction is more difficult, its mixing uniformity and sticking performance are more worse. When the environment temperature is from 15 ?to 25?, the fully mixing time should be ? 5 min, then can ensure the double polyurethane sealing material with sufficient bond strength; When the environment temperature is ? 2?, even if the fully mixing time go up to 10 min, it is also difficult to guarantee the adhesive strength and quality of the double polyurethane sealing material; We choose the method of adding diesel under the low temperature environment, although can dilute the double polyurethane sealing material mixture to some extent and be convenient for stirring and mixing, but the bond strength of polyurethane sealing material will be significantly reduced after construction.(2)If the concrete expansion jointing interface have dust, dry soil, damp earth, and oil pollution, which will reduce the bonding strength of polyurethane material, the reduced degree is respectively 21.71%, 16.82%, 43.43% and 33.15%. For the interface with dust, adopt “brushing interface agent”, “brushing treatment”, “brushing treatment + interface agent” and “blower”, the four kinds of treatment method can improve the interface bonding performance effectively, in which the treatment effects of “brush treatment 5 times + interface agent” are best; For the interface with dry soil, adopt“ steel brush + hair dryer + interface agent”, “ steel brush + hair dryer ”, these two methods can effectively improve the interface bonding performance.(3)By using the measures of “brushing interface agent”, witch have obvious effect for the interface with dust, but have no obvious effect for the interface with soil.(4)The moisture bonding interface will obviously reduce the bonding strength of polyurethane materials, the reduced degree is mainly depend on the moisture content of the interface, if the moisture content is higher, the reduced degree is bigger. The interface moisture content is in 2.074% ~ 4.197%, the adhesive strength of polyurethane materials decline 15.32% ~ 28.76%. For the wet concrete expansion joint interface, before construction, when the environment temperature is ? 20?, adopting natural drying 5h or spray and bake for 20 times for the expansion joint interface can reduce the moisture content of interface, improve the bonding strength of polyurethane materials.(5)The curing environment also influence the bonding performance of polyurethane materials. Under the same construction conditions, the bonding performance of polyurethane materials in the wet curing environment is significantly lower than the dry curing environment after construction.(6)The bonding strength of polyurethane materials will increase with the drying curing time. The polyurethane materials will undertake the task of water conveyance after different drying curing time, the polyurethane materials performance will decline, the falling degree decreases with the extension of drying curing time.