Airport runway ground subsidence void grouting cement geopolymer micro-expansion cement

There are three main forms of interlayer voiding defects in cement concrete pavement structures: ① Interlayer voiding between the subgrade and base course (cushion course) caused by uneven settlement of the subgrade. ② Interlayer voiding between the subbase (cushion course) and base course caused by traffic loads and water action at cracks and joints. ③ Interlayer voiding between the slab and base course.

Airport pavement grouting reinforcement technology is used to address more severe defects such as foundation voiding, sinking, displacement, and step faults. The geopolymer material selected for this technology is a mixture composed of polymer materials, micro-expansion agents, mineral admixtures, inorganic cementitious materials, and other components. After rapid mixing with water, it is used as a grouting material for subgrade reinforcement and filling.

General construction process:

1. Hole Layout: Based on the detection positioning marked by void detection and deflection testing, locate the hole positions on each defective slab and mark them clearly.

2. Drilling: Use a 16mm diameter drill bit to drill holes, with the drilling depth penetrating the cement slab and base course, reaching the top surface of the roadbed (i.e., drilling through the entire rigid structural layer).

3. Hole Cleaning: Promptly clean the dust and powder brought out by the drill rod around the holes using cleaning tools; use an air compressor to seal the hole channel and blow away dust inside and around the hole.

4. Grout Preparation: The geopolymer grouting material must be strictly mixed according to the water-cement ratio. For this experimental section, the water-cement ratio of the geopolymer grouting mixture is 0.33. Mark the water level inside the mixing tank during grout preparation. After daily construction, the mixing tank should be cleaned promptly.

5. Grouting: Start the grouting equipment, adjust the pressure to the designed grouting pressure (1.5 MPa), and conduct a trial grouting observation. Begin grouting, maintain stable pressure during grouting, and stop immediately when the grouting pressure exceeds the designed pressure of 1.5 MPa or when the grouting equipment piston stops for more than 5 seconds. Withdraw the grouting head and move to the next hole.

6. Hole Sealing: After grouting operations, promptly seal the grout overflow holes with wooden plugs and use geotextile to wipe off any grout overflow around the grouting holes.

7. Curing: The curing time for slabs grouted with ordinary geopolymer grouting material should not be less than 24 hours. For fast-setting geopolymer grouting material, traffic can be opened 2-4 hours after curing. Aircraft traffic is prohibited during the curing period.