A Study on Permeation Grouting and Quantity of Injection with Microfine Cement Grout
Date Issued
2008
Date
2008
Author(s)
Sze, Kuo-Lang
Abstract
In this study, microfine cement grout with different water-to-cement (w/c) ratios was injected using a low-pressure permeation grouting technique into sand columns composed of sands having two different grain-size distributions (namely, a medium grain-size sand and a fine sand, or more specifically, Ottawa sands Nos.250 and 403) to determine grout injection amounts needed to reach a predetermined height of the sand columns and study the fluidity of grout in the columns. The grout was prepared and injected with a high speed vortex colloidal mixer and pneumatic grouting equipment designed and fabricated for the study. The experiment results show that the necessary injection amounts of grout having different w/c ratios for reaching the predetermined height were 1.16 to 1.63 times the volume of pores in the sand columns, wherein the necessary injection amounts became smaller and grout fluidity became lower as the w/c ratio decreased. It is also found that, whatever the w/c ratio, the injection amounts for the sand columns having the two grain-size distributions were similar times the volume of pores. Moreover, since the sand columns of the medium grain-size sand had larger pores, grout fluidity was higher in such columns.n order to evaluate the improvement of grouted samples, porosity and compressive strength were tested at different grouting distances within the samples on the seventh and 28th day after grouting. It is found that samples having a lower porosity and injected with a grout having a lower w/c ratio had higher compressive strength. Furthermore, regardless of the w/c ratio of the microfine cement grout, the sand columns composed of the medium grain-size sand showed relatively low compressive strength. This is probably because the particle and pore sizes in such columns were larger and therefore resulted in a relatively smaller cementing area between the particles and grout in a unit volume, and relatively poor grain-size distributions. This phenomenon became more apparent in sand columns injected with a high w/c ratio grout, probably because, as the w/c ratio of the grout rose, segregation increased and stability deteriorated, so that larger pores were left in the sand columns composed of the medium grain-size sand after cementing, which lowered the compressive strength still further. In addition, grout having a lower w/c ratio showed more significant filtration during grouting. As a result, the first sections of the samples which were closer to the injection point had higher uniaxial compressive strength on the seventh day. However, due to the pozzolanic reaction and hydration, the second sections of the samples exhibited higher uniaxial compressive strength on the 28th day. Besides, porosity lowered as the distance to the injection point decreased.This study also examined the effects of different slag contents (i.e., 50% and 70%) on grouting when the w/c ratio was 2. The experiment results show that, while the necessary injection amounts for reaching the predetermined height were similar for sand columns having the same grouting condition, grout fluidity was improved and the injection time shortened as the slag content increased.
Subjects
high speed vortex colloidal mixer
low-pressure permeation grouting
microfine cement
porosity and compressive strength.
Type
thesis
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