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 per...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.展开更多
The replacement ratio is an essential factor in evaluating the bearing capacity characteristics of compositefoundations. This study focuses on the bearing capacity of a pervious concrete pile with different replacemen...The replacement ratio is an essential factor in evaluating the bearing capacity characteristics of compositefoundations. This study focuses on the bearing capacity of a pervious concrete pile with different replacementratios. The axial force, skin friction, and settlement were evaluated using a model test to assess the performance ofthe pervious concrete pile composite foundation. When the replacement ratio was reduced from 9.26% to 2.32%,the characteristic bearing capacity value was only 14%. Therefore, it may be unreasonable to use the settlementratio method to evaluate this composite foundation's bearing capacity in a model test. Appropriate loading cansignificantly improve the bearing capacity of a pervious concrete pile composite foundation with a lowreplacement ratio. The pile–soil stress ratio exhibited different decreasing ranges in the later loading stage. As theload increased, the axial force of the pervious concrete piles was small and nonobvious, and the average sidefriction resistance of the piles in the foundation with a lower replacement ratio slowly increased.展开更多
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)。
文摘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.
基金the support from the National Natural Science Foundation of China(Grant No.41977241).
文摘The replacement ratio is an essential factor in evaluating the bearing capacity characteristics of compositefoundations. This study focuses on the bearing capacity of a pervious concrete pile with different replacementratios. The axial force, skin friction, and settlement were evaluated using a model test to assess the performance ofthe pervious concrete pile composite foundation. When the replacement ratio was reduced from 9.26% to 2.32%,the characteristic bearing capacity value was only 14%. Therefore, it may be unreasonable to use the settlementratio method to evaluate this composite foundation's bearing capacity in a model test. Appropriate loading cansignificantly improve the bearing capacity of a pervious concrete pile composite foundation with a lowreplacement ratio. The pile–soil stress ratio exhibited different decreasing ranges in the later loading stage. As theload increased, the axial force of the pervious concrete piles was small and nonobvious, and the average sidefriction resistance of the piles in the foundation with a lower replacement ratio slowly increased.
