Published Online: 16 September 2011
Page Count: 12
Ni, James C.
Associate Professor, Dept. of Civil Engineering, National Taipei Univ. of Technology, Taipei,
National Taipei Univ. of Technology, Taipei,
(Received 29 January 2011; accepted 18 August 2011)
A trial pressure grouting program is conducted to restore the load carrying capabilities of Portland cement concrete slabs that have been in service for a number of years and are showing signs of distress. First, a series of laboratory tests are conducted to find a Portland cement grout mix with the appropriate properties of fluidity, viscosity, stability, shrinkage, and strength. Second, ground penetrating radar (GPR) is used to detect the possible voids under the slab before grouting, and falling weight deflectometer (FWD) is concurrently used to evaluate the load bearing capacity from slab deflection. Then trial grouting under the slab is conducted after the grout holes are installed based on the results derived from GPR. The grouting process will be halted if the injection pressure increment over the initial contact pressure is larger than 0.5 kg/cm2 or the slab heave is over 1 mm throughout the trial pressure grouting program. The elevations at various locations of each slab are closely monitored during grouting. Last, the GPR is used again to evaluate the effectiveness of slab stabilization. Then, FWD is also used to evaluate the effectiveness to restore the load carrying capability of the slab from grouting. This program is successfully achieved verifying by a series of laboratory and field tests undertaken before and after grouting.
Paper ID: JTE103776