The technical route of epoxy asphalt and its application

1 The chemical mechanism of epoxy asphalt: epoxy asphalt is a two-component material, a component is epoxy resin, and B component is a uniform and stable multi-component mixture The base asphalt is chemically modified, and functional groups with crosslinking reaction with epoxy resin are introduced into the asphalt molecule to ensure that the asphalt can participate in the curing reaction with epoxy resin, and then the B-component of epoxy asphalt is prepared by combining with the optimized resin When the B-component reacts with A-component, a three-dimensional interpenetrating network structure polymer is formed, which fundamentally changes the thermoplastic property of ordinary asphalt At the same time, the adhesion, tensile strength, elongation at break and low temperature properties of the material were improved The chemical equation of curing reaction is shown in Figure 1 Fig 1 curing reaction of epoxy asphalt Fig 2 physical and mechanical properties of epoxy asphalt epoxy asphalt is neither asphalt material nor epoxy resin material, but a new type of road and bridge construction material with high strength, high adhesion and high elongation, which has both advantages The basic characteristics of epoxy asphalt are as follows: after the mixture of a and B components of 0.1 epoxy asphalt, the physical and chemical effects of the two components increase with time, the viscosity of the system increases gradually, and the higher the temperature is, the faster the viscosity increases Curing of 0.02 epoxy asphalt is a chemical reaction, so the curing process has a great relationship with temperature Curing can be basically completed at 120oc for 4H If the temperature decreases, the curing time will be prolonged accordingly Generally, the standard strength is the degree of curing at 120oc for 4H The 0.03 epoxy asphalt is solidified to form a thermosetting material which is insoluble and immiscible The curing process is irreversible, even if the temperature rises again (for example, to more than 300oC), the material is still in solid form, which ensures that the epoxy asphalt can still maintain good mechanical properties at high temperature The bonding force of 04 epoxy asphalt is produced by physical and chemical actions, not only the usual physical bonding force, so its bonding force is very large (the bonding force with steel plate can reach 6-9mpa) The 0.05 epoxy asphalt has special molecular structure, so it can keep good flexibility even at - 10 ℃, and its fracture elongation is up to 120% (only 20% of SBS modified asphalt) 3 The preparation and process requirements of epoxy asphalt 3.1 selection of epoxy resin epoxy resin is a kind of oligomer containing epoxy group and taking aliphatic, alicyclic or aromatic organic compounds as the skeleton It is usually a viscous liquid at room temperature When it is mixed with hardener at corresponding temperature, it can form a network polymer with three-dimensional structure The product has the characteristics of high adhesive strength, small shrinkage, heat resistance, chemical resistance, excellent mechanical and electrical properties However, in the process of using epoxy resin, its brittleness, poor weather resistance and low ductility also greatly limit the scope of use of epoxy resin In general, to improve the brittleness and ductility of the hardened products of epoxy resin, the molecular structure of the cured products can be changed by selecting or setting up appropriate curing agent to improve the service performance to a certain extent Epoxy resin can be classified into glycidyl ether, glycidyl ester, glycidyl amine, alicyclic epoxy resin and epoxyene hydrocarbon according to its structural characteristics Among them, bisphenol A epoxy resin in glycidyl ether is a widely used product in epoxy resin family At present, it is formed by the condensation of bisphenol-A and epichlorohydrin under the action of basic catalyst The general formula of linear epoxy resin with epoxy end group as condensation product is: the molecular structure of bisphenol A epoxy resin contains epoxy group with strong reaction ability, and there are many ether bonds on the main chain It is a linear polyether structure There are many hydroxyl groups in the molecular chain, which is a long chain polyol The main chain is also in the amount of benzene ring, methylene and isopropyl These characteristics can play the following role: epoxy group and hydroxyl group make the resin have reaction activity, and make the hardener have strong cohesion and adhesion Ether bond and hydroxyl group are polar genes, which help to improve infiltration and adhesion Ether bond and C-C bond make macromolecules have certain flexibility Benzene ring makes the solidified products have heat resistance and rigidity The bond energy of the bond is high, thus improving the basicity The results of Ames showed that bisphenol A epoxy resin had no carcinogenicity, teratogenicity and mutagenicity, so it can be used safely Based on the above advantages of bisphenol-A epoxy resin, it was used as the conventional modified resin in epoxy modified asphalt in this experiment 3.2 selection of curing agent because the selection of curing agent has a great influence on epoxy asphalt, the following requirements shall be met in the selection: after 0.1 epoxy resin and curing agent are mixed, under a certain curing temperature, the curing time of initial mixture shall meet the time required for mixing, transportation, paving and rolling of asphalt concrete 0.2 curing agent should not only cure the epoxy resin at high temperature, but also slowly cure it at normal temperature, because the epoxy asphalt mixture still needs to be further cured at normal temperature after paving, so that the strength of the mixture can be continuously increased In practical application, 0 3 curing agent should have the preconditions of large output, low value, no poison and easy control, which make the use of epoxy asphalt easy to spread and popularize Therefore, the curing agent generally chooses anhydrides (Methyltetrahydrophthalic anhydride or methylhexahydrophthalic anhydride, etc.) as the curing agent of epoxy asphalt Because of its low toxicity and volatility, it not only saves cost, but also benefits the curing of epoxy asphalt 3.3 the preparation process of epoxy asphalt requires that epoxy resin react with asphalt to form an irreversible solidified substance, which fundamentally changes the thermoplastic properties of asphalt However, because epoxy asphalt makes thermosetting substances, there are still many problems compared with ordinary asphalt Therefore, the following problems need to be considered in the preparation of epoxy asphalt: 1 Epoxy resin and asphalt have poor compatibility Epoxy resin is a polar substance, while asphalt is a non-polar substance When they are mixed, the compatibility is poor In order to prepare epoxy asphalt mixture with uniform and stable performance, the dispersion and compatibility of epoxy resin and asphalt should be improved Generally add compatibilizer 2 The flexibility of epoxy asphalt prepared by ordinary epoxy resin is poor The brittleness of ordinary epoxy resin after curing is poor, resulting in poor ductility, which is difficult to meet the requirements of steel bridge pavement on the performance of the mixture 3 Determination of the best proportion of each component of epoxy asphalt Epoxy asphalt is composed of asphalt, epoxy resin, curing agent and other additives First of all, it is necessary to determine the appropriate proportion of them However, in many cases, the relative proportion of each component is a pair of contradictions Therefore, a large number of tests are needed to determine the best proportion and evaluation index 4 Application of epoxy asphalt in engineering 4.1 application of epoxy asphalt in bridge deck pavement theory and engineering practice show that the steel bridge deck pavement should mainly meet the following conditions: 1) The local deformation of steel bridge deck caused by vehicle load is large, and the deflection halo produced by the same wheel load on the steel plate is about three times of that on the general road surface Therefore, the bridge deck pavement must have enough deformation adaptability 2) Steel deck is easy to be affected by climate, so deck pavement should be able to maintain stable performance in a large temperature range 3) Under the action of wheel load, the steel bridge deck pavement is located in the grid stiffener, which will form a large bending tensile stress repeated action, and easily lead to the fatigue cracking of the pavement Therefore, the bridge deck pavement structure should have good anti fatigue cracking performance 4) The steel bridge deck pavement should have a perfect anti drainage and anti-corrosion system to ensure that the steel plate is not eroded 5) It has a good combination of structural layers to ensure the synergistic effect of pavement and bridge deck 6) Good flatness to reduce the impact of driving load In recent years, with the increase of traffic volume and axle load in China, as well as the increasingly harsh climate conditions, the bridge deck pavement in China has generally suffered serious early damage, which has greatly affected the service life of the bridge and caused huge economic losses The practice shows that the maintenance cost of the damaged deck pavement is often several times of the original investment, and the repair time is long, which seriously affects the safety, rapidity and comfort of traffic As a suspension structure, the bridge deck pavement is sensitive to the changes of natural factors, and it is more prone to early disease than the asphalt pavement of subgrade section In hot summer, the temperature of the steel bridge deck is 25 ℃ ~ 35 ℃ higher than that of the ordinary road section, and the possibility of rutting is higher than that of the ordinary road section; the bridge is more sensitive to the low temperature and temperature rise and fall cycle, so it is easier to appear various forms of cracks The deflection of the bridge is large, and it is influenced by the temperature stress Sometimes there is negative bending moment These external force conditions are more severe than the pavement In addition, due to the material performance difference between asphalt mixture pavement and bridge structure, it will lead to the discontinuity of stress and deformation under the action of external force Due to the complex temperature stress, negative bending moment, shear stress, overload and impact force, bridge deck pavement is prone to deformation damage and crack damage The application of epoxy asphalt pavement started from the Second Yangtze River Bridge in Nanjing, China introduced epoxy asphalt as the bridge deck pavement material, and thus launched a new page in the history of bridge deck pavement in China Subsequently, the epoxy asphalt concrete bridge deck pavement has been used in the Runyang Yangtze River Bridge test bridge, Jiangyin Yangtze River Bridge test section, Zhejiang Zhoushan taotianmen bridge, Runyang Yangtze River Bridge, Jiangyin Yangtze River Bridge Bridge Deck Repair, Nanjing Yangtze River Three Bridge and other national key projects According to the bridge deck service condition of Nanjing Second Yangtze River Bridge in more than five years and the construction quality inspection indexes of other bridges, the epoxy asphalt concrete bridge deck pavement has obvious advantages in bridge deck waterproof, interlayer bonding and asphalt layer pavement, and has good pavement performance Epoxy asphalt mixture is an ideal road construction material for steel bridge deck pavement, pavement wearing course and super heavy load traffic road It has a wide application prospect It is an urgent task to research and develop domestic epoxy asphalt The successful development of domestic epoxy asphalt concrete pavement technology will greatly reduce the engineering cost and use cost of bridge deck pavement Meanwhile, it has its own epoxy asphalt Green technology is also convenient to optimize the performance of epoxy asphalt pavement in the future production practice, and its economic and social benefits will be considerable 4.2 the application of epoxy asphalt on high-grade highways and urban main roads causes various damages to the road surface due to the increase of traffic pressure The thermoplastic nature of asphalt itself makes it relatively difficult to repair The thermosetting epoxy asphalt just fills this defect The application of epoxy asphalt in the road is mainly reflected in the following aspects: 1 On the road, especially in the parking station, due to the frequent brake, start-up and long-term parking of the locomotive, the traditional asphalt pavement will have serious rutting damage When using epoxy asphalt as pavement material, it can reduce this problem and improve the performance of pavement 2 epoxy asphalt has good adhesion and high rigidity, so its deformation at high temperature is very small After wearing, the surface will not become smooth due to oil flashing These characteristics make the anti sliding wearing course