CO_(2)泡沫改性水泥基浆液性能及影响因素研究

Properties and Influencing Factors of Cement-Based Grout Modified by CO_(2) Foam

为探究CO_(2)泡沫对水泥基浆液性能的改进作用,利用CO_(2)泡沫水泥浆替换相同水灰比的原始水泥浆,对影响浆液性能的因素进行正交试验,对浆液的水胶比、粉灰比、胶砂比和膨水比进行极差分析,综合确定影响改性浆液性能的主要因素,并确定浆液最佳配比。此外,将改性浆液与南京地铁7号线盾构施工中所使用的同步注浆浆液各项性能参数进行对比分析,并进行SEM和XRD微观机制分析。试验结果表明:1)当浆泡比为1∶4.5,水灰比为1∶2.4,发泡气压为0.02 MPa,转速为70 r/s时,浆液抗压强度较高,且密度、析水率、相对密度等性能满足实际现场要求。2)相比非加气浆液,CO_(2)的碳化作用使得泡沫水泥浆在较短养护时间内达到了较高的强度。极差分析结果表明:1)浆液最佳配比为水胶比0.8,粉灰比2.0,胶砂比0.5,膨水比0.16。2)浆液凝结时间随水胶比和膨水比的增大而增加;膨水比对浆液稠度、初始流动度和析水率的影响显著。与南京地铁7号线盾构施工中所使用的同步注浆浆液相比,改性浆液具有较低的流动性和较小的密度,稠度、初始流动度性能得以改善,凝结时间缩短,强度有较大的提高。

To explore the modification effect of CO_(2) foam on the properties of cement-based grout,the cement-based grout modified by CO_(2) foam is used to replace the original grout with the same water-cement ratio.Then,a range analysis is conducted for the ratios of water-binder,fly ash-cement,binder-sand,and bentonite-water 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 X-ray diffraction.The test results show that:(1)For the slurry-foam ratio of 1∶4.5,water-cement 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 CO_(2) reduces the time for foamed grout to achieve a higher strength.In addition,the results of the range analysis show that the optimal water-binder,fly ash-cement,binder-sand,and bentonite-water ratios are 0.8,2.0,0.5,and 0.16,respectively.The setting time of the slurry increases with the increasing water-binder and bentonite-water ratios.In addition,the bentonite-water 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 CO_(2) foam.