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
• 来源期刊: 岩石力学与岩土工程学报（英文版）
• 年，卷（期）: 2021,（4）
• 页码范围: 875-884
• 页数: 10页
• 语种: 英文

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 en-gineering 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 freezing-thawing (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 un-confined compression tests.Besides,a series of micro tests on MgO-carbonated specimens was per-formed 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 above 0.8 after F-T cycles.There is no visible transformation between nesquehonite and dypingite/hydro-magnesite,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.