Non-excavation Repair Project of Micro-Surface Grouting for Cracks in Semi-Rigid Base

The semi-rigid base course is a structure type commonly used in my country’s high-grade highways. Under the action of factors such as material drying shrinkage, temperature shrinkage, and driving loads, a large number of cracks will occur, which not only destroys the integrity and strength of the pavement structure, but also seriously reduces the quality and quality of the road. Service life is a major problem plaguing the road maintenance industry.
Since the “Thirteenth Five-Year Plan”, Tianjin Expressway Group has carried out innovative research on the “four new technologies” for the treatment of base cracks based on the expressway maintenance projects in Tianjin in response to the difficult problem of semi-rigid base cracks, and applied and promoted them for the first time. A new technology of minimally invasive grouting and non-excavation repair of semi-rigid base cracks with moderate cost, good fluidity, high curing strength and convenient construction has achieved remarkable results.
The raw material index system, construction control method, quality acceptance standard and other contents of this technology are put forward through experimental research, and a construction technical guideline is formed. The test results show that this technology can effectively fill and block deep cracks in the pavement with minimally invasive grouting of polymer materials, bond the loose aggregates of the base layer, and form a certain strength, thereby restoring the structural integrity of the pavement and improving the bearing capacity of the pavement structure , to achieve the purpose of minimally invasive repair of pavement structure cracks and diseases, and the relevant research results have reached the international advanced level.
A large number of engineering promotion and application practices have shown that this technology can prolong the service life of the base layer through minimally invasive repair of cracks in the base layer, thereby greatly delaying the overhaul time limit of the expressway, saving a lot of maintenance costs throughout the life cycle, and realizing rapid maintenance of pavement cracks. The overall strength recovery rate of the base is high, the durability is good, the process is convenient, the civilized construction has little interference with the surrounding traffic and the environment, no waste is generated, and natural resources are saved. The economic, social and environmental benefits are very significant, and the application prospects are broad. Tianjin The improvement of regional expressway maintenance technology and the sustainable development of the industry have played an important role in promoting.

Technical ideas:

Minimally invasive grouting non-excavation repair technology for semi-rigid base cracks. Using pressure grouting equipment, self-developed water-resistant polymer materials are injected into cracks on the road surface. After the two-component polymer is fully mixed at the tip of the gun, a violent reaction occurs , under the pressure of the equipment, the water-resistant polymer material is squeezed into the depth of the cracks, fully penetrates the cracks, and produces high bond strength with the cracks, so as to achieve the purpose of repairing hidden diseases such as base cracks, voids, and looseness.

Key technical solutions:

1. Based on the demand for deep grouting repair of semi-rigid base cracks, the active group capping technology is used to reduce the activity of the active group and water reaction, and a micro-expansion water-resistant foaming ratio of 1.1% to 1.5% has been developed. Modified polyurethane crack grouting material, and based on laboratory tests, an index system for evaluating the mechanical properties, construction performance and road performance of grouting materials was proposed.
2. Through the implementation of the test section, the inverted tapered threaded metal connecting pipe and flower hole PVC drainage pipe were developed as the grouting conduit, and the “GPR seam exploration-hole layout-drilling-hole cleaning-embedding-grouting- Restoring the pavement” standardized process, forming a minimally invasive grouting construction process for semi-rigid bases from bottom to top.
3. Developed the ground-push direct shear strength test method, and proposed a post-construction detection method that combines the ground-penetrating radar to judge the grouting diffusion range, the core sample integrity rate and the indoor ground-push direct shear strength index, and established the on-site and indoor Acceptance evaluation criteria combined with testing.
Implementation Effect:
1. The complete set of minimally invasive grouting equipment and technology for semi-rigid base cracks solves the problems of efficiency, insufficient pressure, and road surface uplift during the grouting process.
2. The grouting effect was systematically evaluated from the perspective of strength and integrity. The integrity rate of coring was over 85%, and the strength recovery rate was over 80%.
3. Compared with traditional conventional treatment technology, this technology can reduce carbon emissions by 99.93% and save construction time by more than 30%.
4. This technology does not need to excavate the old pavement, and the utilization rate of the old pavement structure is 100%.

Production, application and promotion:

Since 2019, this technology has been widely used in major and medium repair and maintenance projects of Beijing-Shanghai, Rongwu, Changshen, Jinji, Binbao, Jinjin and other expressways in Tianjin, with a cumulative length of 60KM.

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