碳化固化土的耐久性能试验研究

发布时间：2018-10-12 15:34

【摘要】：碳化固化技术是近年来提出的一种低碳搅拌处理软弱土的创新技术。本文以国家自然科学基金项目(51279032)、十二五国家科技支撑计划项目(2012BAJ01B02-01)为依托。选用武汉软土、南京软土和宿迁粉土作为加固对象,活性MgO作为固化剂,采用三轴碳化装置通入CO2气体对静压法制成试样进行碳化固化,结合目前已有研究成果,运用室内试验、微观实验和理论分析相结合的方法,进行了干湿循环、冻融循环和硫酸盐侵蚀三种试验,以分析碳化固化土的耐久性,并与相同水泥掺量标准养护28天的水泥固化土进行了对比,主要研究成果如下：(1)干湿循环试验结果表明：不同碳化固化土之间的抗干湿循环性能存在差异,武汉软土碳化试样、南京软土碳化试样和宿迁粉土碳化试样经过6次干湿循环后的残余强度分别为35%、85%和90%,而三种土体中的黏粒含量分别为20%、10%和5%,存在黏粒含量越高,其碳化固化土抗干湿循环性能越差的规律。并且由于碳化固化土渗透性高于水泥固化土,因此抗干湿循环性能不如相同配比水泥固化土。微观分析表明,干湿循环对宿迁粉土碳化试样和南京软土碳化试样的累计孔隙影响不大,因此具有较大密实度来保证试样强度：而武汉软土碳化试样孔隙增加明显,武汉软土试样变得疏松,因此强度显著降低。(2)冻融循环试验结果表明：碳化固化土经多次(6次)冻融循环后,其强度由5MPa左右降低到4.5MPa左右,而水泥固化土经4次冻融循环后其强度由1.6MPa降低到1.4MPa左右,二者均具有较高的强度。微观机理分析表明,冻融循环对碳化固化土物质成分和微观结构没有明显的影响,只是冻融循环使碳化固化土试样的0.1-1μm的孔隙有所减少,而1-30μm的孔隙有所增加,但累计孔隙变化不大,这与试样内部的水分冻结膨胀有关,也是导致强度略有降低的原因。总体来讲,碳化固化土与水泥固化土相似,具有较好的抗冻融性能。(3)硫酸盐侵蚀试验结果表明：经硫酸盐溶液浸泡28天的宿迁粉土碳化试样无侧限抗压强度基本保持不变,南京软土碳化试样有稍许下降,但南京软土碳化试样与蒸馏水浸泡溶液相比变化不大；南京软土水泥硫酸盐浸泡试样强度与蒸馏水试样相比下降明显,试样随龄期增长膨胀破坏明显,粉土水泥试样则表现出早期(7天)有一定增长,随龄期增长则由于试样膨胀,导致强度大大降低；微观机理分析表明,碳化固化土经碳化生成的镁的碳酸化合物经硫酸盐侵蚀后不会发生明显变化,孔隙结构不会明显改变,从而保证其强度稳定。因此,碳化固化土具有比水泥固化土更强的抗硫酸盐侵蚀能力。
[Abstract]:Carbonation curing technology is an innovative technology for treating soft soil by low carbon agitation in recent years. This paper is based on the National Natural Science Foundation (51279032) and the National Science and Technology support Program (2012BAJ01B02-01). Wuhan soft soil, Nanjing soft soil and Suqian silt were selected as reinforcement objects, active MgO was used as curing agent, and CO2 gas was used to carbonize and solidify the sample made by hydrostatic pressure. In order to analyze the durability of carbonized solidified soil, the dry and wet cycle, freeze-thaw cycle and sulfate erosion were carried out by the methods of laboratory test, microscopic experiment and theoretical analysis. The main results are as follows: (1) the dry and wet cycle test results show that the dry and wet cycle resistance of different carbonized cured soils is different. The residual strength of Wuhan soft soil carbonization sample, Nanjing soft soil carbonization sample and Suqian silty soil carbonization sample after 6 dry and wet cycles is 35% and 90%, respectively, while the clay content in the three soils is 20% and 5%, respectively. The higher the clay content is, the higher the content of clay is. The worse the resistance to dry and wet circulation of carbonized solidified soil is. And because the permeability of carbonized solidified soil is higher than that of cement-cured soil, the dry-wet cycle resistance of cement-cured soil is inferior to that of cement-cured soil with the same ratio. The microcosmic analysis shows that dry and wet cycles have little effect on the accumulative porosity of Suqian silt carbonization sample and Nanjing soft soil carbonization sample, so they have a large compactness to ensure the strength of the sample, while Wuhan soft soil carbonization sample has a significant increase in pore size. The results of freeze-thaw cycle test show that the strength of carbonized solidified soil decreases from 5MPa to 4.5MPa after several (6) freeze-thaw cycles. The strength of cement-cured soil decreased from 1.6MPa to 1.4MPa after four freeze-thaw cycles, and both of them had high strength. The micromechanism analysis shows that the freezing and thawing cycle has no obvious effect on the composition and microstructure of carbonized solidified soil, but the freezing and thawing cycles decrease the porosity of the carbonized soil at 0.1 ~ 1 渭 m, but increase the porosity of 1-30 渭 m. But the accumulative pore has little change, which is related to the freezing expansion of water inside the sample, and it is also the reason of the slight decrease of the strength. As a whole, carbonized soil is similar to cement solidified soil and has good freeze-thaw resistance. (3) Sulfate erosion test results show that the unconfined compressive strength of carbonized soaking silt samples soaked in sulfate solution for 28 days remains basically unchanged. The carbonation sample of Nanjing soft soil decreased slightly, but the carbonation sample of Nanjing soft soil did not change much compared with distilled water soaking solution, and the strength of cement sulphate soaking sample of Nanjing soft soil decreased obviously compared with distilled water sample. The expansion and destruction of the sample with the increase of age is obvious, the cement sample of silty soil shows a certain increase in the early stage (7 days), and the strength decreases greatly with the increase of the age, and the microscopic mechanism analysis shows that, The carbonated magnesium carbonates of carbonized solidified soil will not change obviously and pore structure will not change obviously after sulfate erosion, thus ensuring its strength stability. Therefore, carbonized soil has stronger sulfate corrosion resistance than cement solidified soil.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU472

【相似文献】