To explore the modification effect of CO2
foam on the properties of cementbased grout, the
cementbased grout modified by CO2 foam is used to replace the original grout with the same watercement ratio. Then, a range analysis is conducted for the ratios of
waterbinder, fly ashcement,
bindersand, and bentonitewater
of the slurry to comprehensively determine the main factors affecting the
performance of the modified slurry and optimal mixing proportions. In addition,
the performance parameters of the modified slurry are compared with those of
the synchronous grouting slurry currently being used in the shield tunneling of
the Nanjing metro line 7. Further, microscopic mechanism tests are performed
using the scanning electron microscope and Xray
diffraction. The test results show that: (1) For the slurryfoam ratio of 1∶4.5, watercement ratio of 1∶2.4, foaming pressure of
0.02 MPa, and rotational speed of 70 r/s, the compressive strength of the
slurry is high, and the density, water separation rate, specific gravity, and
other properties can meet the actual site requirements. (2) The carbonation of
CO2 reduces the time for foamed grout to achieve a
higher strength. In addition, the results of the range analysis show that the
optimal waterbinder, fly ashcement,
bindersand, and bentonitewater
ratios are 0.8, 2.0, 0.5, and 0.16, respectively. The setting time of the
slurry increases with the increasing waterbinder and
bentonitewater ratios. In addition, the bentonitewater ratio has a significant effect on the consistency, initial
fluidity, and water separation rate of the slurry. Compared with the
synchronous grouting slurry currently being used in the shield tunneling of the
Nanjing metro line 7, the modified slurry has lower fluidity and density,
higher consistency, initial fluidity, density, stone rate properties, and
strength, as well as a shorter setting time under the action of carbonization
by the CO2 foam.
LIU Gongxun
,
XIE Kang
,
ZHANG Jian
,
LIANG Xin
. Properties and Influencing Factors of CementBased Grout Modified by CO2 Foam[J]. Tunnel Construction, 2023
, 43(6)
: 995
-1002
.
DOI: 10.3973/j.issn.2096-4498.2023.06.010
