Mechanical performances and microstructural characteristics of reactive MgO-carbonated silt subjected to freezing-thawing cycles  

作　　者：Guanghua Cai Songyu Liu Guangyin Du Zhen Chen Xu Zheng Jiangshan Li 

机构地区：[1]College of Civil Engineering,Nanjing Forestry University,Nanjing,210037,China [2]Institute of Geotechnical Engineering,Southeast University,Nanjing,211189,China [3]State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,430071,China [4]Department of Civil and Environmental Engineering,Washington State University,Pullman,WA99163,USA

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2021年第4期875-884,共10页岩石力学与岩土工程学报（英文版）

基　　金：the support of the National Natural Science Foundation of China(Grant Nos.41902286 and 41972269);Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.Z019026)。

摘　　要：The characteristics of reactive magnesia(MgO)-carbonated silt in respect to long-term stability have not been well understood in severely cold climate despite the usage of reactive MgO in enhancing the engineering performances.Under the binder content of 15%and initial water content of 25%,MgO-admixed silt specimens were carbonized for 3 h and 6 h and then subjected to different numbers of freezingthawing(F-T)cycles.After different F-T cycles,the physico-mechanical properties of MgO-carbonated silt were analyzed in comparison with Portland cement(PC)-stabilized silt through physical and unconfined compression tests.Besides,a series of micro tests on MgO-carbonated specimens was performed including X-ray diffraction(XRD),scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP)tests.The results demonstrate that both mass change ratio and moisture content of carbonated/stabilized silt decrease,and these values of MgO-carbonated silt are significantly lower while the density is higher compared to PC-stabilized silt.The strengths and moduli of MgO-carbonated silt are still two times higher than those of PC-stabilized specimens and the strength change ratio of keeps above0.8 after F-T cycles.There is no visible transformation between nesquehonite and dypingite/hydromagnesite,although the XRD peaks of nesquehonite decrease and the bonding and filling effects weaken slightly.After 6 and 10 F-T cycles,the pore-size characteristics changed from a unimodal distribution to a three-peak and bimodal distribution,respectively.The total,macro and large pore volumes increase obviously while the medium and small pore volumes decrease except for intra-aggregate pore.The findings show better F-T durability of MgO-carbonated silt,which would be helpful for facilitating the application of MgO carbonation in the soil treatment.

关 键 词：Reactive magnesia(MgO) Freezing-thawing(F-T)cycle Carbonated/stabilized silt Engineering performance Microstructural characteristics 

分 类 号：TU43[建筑科学—岩土工程]