In order to prolong the service life of highway pavement, combined with engineering examples, rubber-modified asphalt concrete is used for pavement maintenance construction in serious disease sections. The properties and requirements of modified asphalt, mineral powder, aggregate and rubber powder in its raw materials are summarized, and its construction technology and construction technology are analyzed from the aspects of mixing, transportation, paving, rolling, joint treatment, etc. . The results show that the application of this construction technology reduces the amount of asphalt, which is beneficial to environmental protection and effectively ensures the quality of the pavement.
Key words: rubber-modified asphalt; pavement; disease; construction technology
1 Project overview
The total length of the highway project is 13.5 kilometers. This section is rich in mineral resources and is the main road for the transportation of mineral resources. There are many heavy vehicles, the traffic flow is large, and the phenomenon of vehicle overloading is extremely common. In addition to the influence of natural factors, the road section is seriously damaged, with potholes, subsidence, and rut diseases. more. In order to ensure the traffic quality of this section, it is decided to carry out road maintenance construction. After analyzing the local geological conditions, combined with previous construction experience, it was decided to use rubber-modified asphalt concrete for road maintenance construction. Before large-scale construction, a representative road section can be selected as a test road section with a length of 1000m. In order from top to bottom, the pavement surface structure is WRAC-13 rubber-modified asphalt mixture (4cm) + WRAC-20 rubber-modified asphalt mixture (5cm), with a total thickness of 9cm.
2 selection of raw materials
2.1 Modified Asphalt
The asphalt selected in this paper is 70# matrix asphalt. In addition, a shear emulsifier was used to prepare rubber powder modified asphalt. First, add 10% rubber powder to the base asphalt preheated to 170°C, and stir at 185°C for 20 minutes. After stopping, stir again with a glass rod to remove air bubbles. Penetration, viscosity and road performance tests were carried out in accordance with the corresponding test procedures in “Technical Specifications for Highway Asphalt Pavement Construction” (JTG F40-2017). The technical indicators are shown in Table 1.
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2.2 Mineral powder
In order to fully fill the excess voids in the rubberized asphalt mixture, mineral powder is selected as its filler. In addition, mineral powder can improve the stability and strength of the mixture. The ore powder involved in this paper has a water content of 0.96%, no agglomeration, a relative apparent density of 2.814, and a particle size of less than 0.075mm. As high as 94%, all meet the specification requirements.
2.3 Aggregation
The surface of the aggregate selected in this paper has the characteristics of dryness, no impurities, hard texture and good weather resistance. Removal of various harmful substances, rough surface, sharp edges and corners, no slender particles, no flat aggregate shape.
2.4 Rubber powder
At present, the main sources of rubber powder are natural rubber and waste rubber tires. The utilization of waste rubber tires is of great significance to save costs and reduce environmental pollution. Therefore, waste rubber tires are selected as the material of rubber-modified asphalt mixture in this road section.
3 Construction Technology of Rubber Modified Asphalt Pavement
3.1 Mixing
The mixing construction process of rubber-modified asphalt mixture is basically the same as that of ordinary SBS-modified asphalt. The difference is that when the asphalt is added to the mixing tower, the material selected is rubber-modified asphalt, and the heating temperature of the rubber-modified asphalt shall not be lower than 180 °C. In addition, due to its high viscosity, in order to ensure uniform mixing, the mixing time must be reasonably controlled to avoid segregation and whitening. According to the construction requirements, the mixing equipment is a batch mixer to ensure that it can be used with mixing. If the storage time is too short, the storage temperature must be controlled within 24 hours, and the storage temperature must not be lower than 100 ℃. In case of segregation, graying, aging, etc., it should not be used.
3.2 Transportation
On the premise that the temperature meets the construction requirements, in order to ensure the paving quality of the rubber-modified asphalt mixture, the transportation distance must be reasonably controlled, and it should not be too far. In the process of transportation, large-tonnage trucks are generally used. In order to reduce the evaporation of water and achieve the effect of heat preservation, the tarpaulin must be well covered