【摘要】：碳化固化技術(shù)是近年來提出的一種低碳攪拌處理軟弱土的創(chuàng)新技術(shù)。本文以國(guó)家自然科學(xué)基金項(xiàng)目(51279032)、十二五國(guó)家科技支撐計(jì)劃項(xiàng)目(2012BAJ01B02-01)為依托。選用武漢軟土、南京軟土和宿遷粉土作為加固對(duì)象,活性MgO作為固化劑,采用三軸碳化裝置通入CO2氣體對(duì)靜壓法制成試樣進(jìn)行碳化固化,結(jié)合目前已有研究成果,運(yùn)用室內(nèi)試驗(yàn)、微觀實(shí)驗(yàn)和理論分析相結(jié)合的方法,進(jìn)行了干濕循環(huán)、凍融循環(huán)和硫酸鹽侵蝕三種試驗(yàn),以分析碳化固化土的耐久性,并與相同水泥摻量標(biāo)準(zhǔn)養(yǎng)護(hù)28天的水泥固化土進(jìn)行了對(duì)比,主要研究成果如下：(1)干濕循環(huán)試驗(yàn)結(jié)果表明：不同碳化固化土之間的抗干濕循環(huán)性能存在差異,武漢軟土碳化試樣、南京軟土碳化試樣和宿遷粉土碳化試樣經(jīng)過6次干濕循環(huán)后的殘余強(qiáng)度分別為35%、85%和90%,而三種土體中的黏粒含量分別為20%、10%和5%,存在黏粒含量越高,其碳化固化土抗干濕循環(huán)性能越差的規(guī)律。并且由于碳化固化土滲透性高于水泥固化土,因此抗干濕循環(huán)性能不如相同配比水泥固化土。微觀分析表明,干濕循環(huán)對(duì)宿遷粉土碳化試樣和南京軟土碳化試樣的累計(jì)孔隙影響不大,因此具有較大密實(shí)度來保證試樣強(qiáng)度：而武漢軟土碳化試樣孔隙增加明顯,武漢軟土試樣變得疏松,因此強(qiáng)度顯著降低。(2)凍融循環(huán)試驗(yàn)結(jié)果表明：碳化固化土經(jīng)多次(6次)凍融循環(huán)后,其強(qiáng)度由5MPa左右降低到4.5MPa左右,而水泥固化土經(jīng)4次凍融循環(huán)后其強(qiáng)度由1.6MPa降低到1.4MPa左右,二者均具有較高的強(qiáng)度。微觀機(jī)理分析表明,凍融循環(huán)對(duì)碳化固化土物質(zhì)成分和微觀結(jié)構(gòu)沒有明顯的影響,只是凍融循環(huán)使碳化固化土試樣的0.1-1μm的孔隙有所減少,而1-30μm的孔隙有所增加,但累計(jì)孔隙變化不大,這與試樣內(nèi)部的水分凍結(jié)膨脹有關(guān),也是導(dǎo)致強(qiáng)度略有降低的原因。總體來講,碳化固化土與水泥固化土相似,具有較好的抗凍融性能。(3)硫酸鹽侵蝕試驗(yàn)結(jié)果表明：經(jīng)硫酸鹽溶液浸泡28天的宿遷粉土碳化試樣無側(cè)限抗壓強(qiáng)度基本保持不變,南京軟土碳化試樣有稍許下降,但南京軟土碳化試樣與蒸餾水浸泡溶液相比變化不大；南京軟土水泥硫酸鹽浸泡試樣強(qiáng)度與蒸餾水試樣相比下降明顯,試樣隨齡期增長(zhǎng)膨脹破壞明顯,粉土水泥試樣則表現(xiàn)出早期(7天)有一定增長(zhǎng),隨齡期增長(zhǎng)則由于試樣膨脹,導(dǎo)致強(qiáng)度大大降低；微觀機(jī)理分析表明,碳化固化土經(jīng)碳化生成的鎂的碳酸化合物經(jīng)硫酸鹽侵蝕后不會(huì)發(fā)生明顯變化,孔隙結(jié)構(gòu)不會(huì)明顯改變,從而保證其強(qiáng)度穩(wěn)定。因此,碳化固化土具有比水泥固化土更強(qiáng)的抗硫酸鹽侵蝕能力。
[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.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU472

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