High-plastic clays with significant volume change due to moisture variations present critical challenges to civil engineering structures.Limestone calcined clay cement(LC3),an innovative and sustainable hydraulic bind...High-plastic clays with significant volume change due to moisture variations present critical challenges to civil engineering structures.Limestone calcined clay cement(LC3),an innovative and sustainable hydraulic binder,demonstrates significant potential for improving the engineering characteristics of such soils.Nevertheless,the impact of LC3 on the physico-mechanical characteristics of treated soil under a cyclic wet-dry environment remains unclear.This study for the first time investigates LC3's impact on the long-term durability of treated high-plastic clays through comprehensive macro-micro testing including physical,mechanical,mineralogical,and microstructural investigations with an emphasis on wet-dry cycles.The results revealed that LC3 treatment exhibits significant resistance to wet-dry cycles by completely mitigating the swelling potential,and a considerable reduction in plasticity resulting in enhanced workability.The compressibility and shear strength parameters have been significantly improved to several orders of magnitude.However,after six wet-dry cycles,a slight to modest reduction is observed,but overall durability remains superior to untreated soil.Cohesive and structural bonding ratios quantitatively assessed the impact of wet-dry cycles emphasizing the advantage of LC3 treatment.According to mineralogical and microstructural evaluation,the mechanism behind the adverse effects of wet-dry cycles on the compressibility and strength behavior of LC3-treated soil is mainly attributed to:(1)weakening of CSH/C(A)SH and ettringite(AFt)phases by exhibiting lower peak intensities;and(2)larger pore spaces due to repeated wet-dry cycles.These findings highlight LC3's performance in enhancing the long-term behavior and resilience of treated soils in real-world scenarios,providing durable solutions for infrastructure challenges.展开更多
Limestone calcined clay cement(LC^3),consisting of ordinary Portland cement(OPC)clinker,calcined clay,limestone powder,and gypsum,has been considered a promising solution to current challenges in the cement and concre...Limestone calcined clay cement(LC^3),consisting of ordinary Portland cement(OPC)clinker,calcined clay,limestone powder,and gypsum,has been considered a promising solution to current challenges in the cement and concrete industry,such as high carbon emissions,high energy consumption,and resource shortages.This study carries out a series of experimental investigations of LC^3-based paste,mortar,and concrete,including microstructural analyses(e.g.hydration product characterization and pore structure analysis)and macro-scale testing(e.g.workability and mechanical properties),using raw materials from south China.The results show that,in LC^3 paste,the replacement of clinker by calcined clay and limestone leads to an increased volume of small pores but decreased total volume of pores.The workability of LC^3 mortar and concrete can be readily tailored using conventional superplasticizers.When designed for comparable 28-d compressive strength,the LC^3 mortar and concrete tend to have lower early-age compressive strength,but comparable compressive strength and higher flexural strength than those of the OPC counterparts at late ages.This study also examines the bond-slip behavior between LC^3 concrete and steel bars and finds that the bond strength is comparable to that of OPC concrete with the same 28-d compressive strength,but that the LC^3 concrete-rebar interface exhibits higher bond-slip stiffness.These findings on LC^3 concrete provide fundamental information and guidance for furthering the application of LC^3 binder in structural concrete in the near future.展开更多
Limestone calcined clay cement(LC3)is an environment-friendly and sustainable cementitious material.It has recently gained considerable attention for the stabilization/solidification(S/S)of soils contaminated by heavy...Limestone calcined clay cement(LC3)is an environment-friendly and sustainable cementitious material.It has recently gained considerable attention for the stabilization/solidification(S/S)of soils contaminated by heavy metals.However,the existing studies on S/S of Zn-contaminated soils using LC3 in terms of hydraulic conductivity and microstructural properties as compared to ordinary Portland cement(OPC)are limited.This study focuses on the evaluation of the mechanical,leaching,and microstructural characteristics of Zn-contaminated soils treated with different contents(0%,4%,6%,8%,and 10%)of low-carbon LC3.The engineering performance of the treated Zn-contaminated soils is assessed over time using unconfined compressive strength(UCS),hydraulic conductivity(k),toxicity characteristic leaching procedure(TCLP),and synthetic precipitation leaching procedure(SPLP)tests.Experimental results show that the UCS of Zn-contaminated soils treated with LC3 ranged from 1.47 to 2.49 MPa,which is higher than 1.63%–13.07%for those treated with OPC.The k of Zn-contaminated soils treated with LC3 ranged from 1.16×10^(−8)to 5.18×10^(−8)cm/s as compared to the OPC treated samples.For the leaching properties,the leached Zn from TCLP and SPLP is 1.58–321.10 mg/L and 0.52–284.65 mg/L as the LC3 contents ranged from 4%to 10%.Further,the corresponding pH modeling results indicate that LC3 promotes a relatively suitable dynamic equilibrium condition to immobilize the higher-level Zn contamination.In addition,microscopic analyses demonstrate that the formations of hydration products,i.e.,Zn(OH)_(2),Zn_(2)SiO_(4),calcium silicate hydrate(C–S–H),calcium silicate aluminate hydrate(C–A–S–H)gel,ettringite,and CaZn(SiO_(4))(H_(2)O),are the primary mechanisms for the immobilization of Zn.This study also provides an empirical formula between the UCS and k to support the application of LC3-solidified Zn-contaminated soils in practical engineering in the field.展开更多
Limestone Calcined Clay Cement(LC^(3)) is a newly proposed low-carbon cement,which can effectively reduce energy consumption and carbon emissions of the traditional cement industry without changing the basic mechanica...Limestone Calcined Clay Cement(LC^(3)) is a newly proposed low-carbon cement,which can effectively reduce energy consumption and carbon emissions of the traditional cement industry without changing the basic mechanical properties of cement-based materials.In this study,the degradation process of mortar samples of limestone and calcined clay cementitious material under sulfate attack is studied by both macroscopic and microscopic analysis.The results show that compared with pure Portland cement,the addition of calcined clay and limestone can significantly reduce the expansion rate,loss of dynamic modulus and mass loss of mortar specimens under sulfate attack.The addition of calcined clay and limestone will refine the pore size distribution of mortar specimens,then inhibiting the diffusion of sulfate and formation of corrosive products,therefore leading to a significant improvement of the sulfate resistance.展开更多
This study aims to investigate the impact of various water-to-binder(w/b)ratios by mass(0.3–2.0)on the performance of limestone calcined clay cement(LC^(3))pastes.The flowability,setting time,density,unconfined compr...This study aims to investigate the impact of various water-to-binder(w/b)ratios by mass(0.3–2.0)on the performance of limestone calcined clay cement(LC^(3))pastes.The flowability,setting time,density,unconfined compressive strength,hydration,and microstructure of LC^(3) pastes under different w/b ratios were thoroughly investigated.The results show that increasing the w/b ratio extends the flowability and setting time while significantly reducing the unconfined compressive strength of LC^(3) pastes.LC^(3) pastes with w/b ratios above 0.6 exhibited a final flow diameter surpassing 167 mm,indicating good flowability.The 28-d unconfined compressive strength decreased from 82.3 to 1.3 MPa as the w/b ratio increased from 0.3 to 2.0.This study confirmed that the relationship between unconfined compressive strength and the w/b ratio of LC^(3) follows Abram’s law.Furthermore,a modified gel/space ratio was proposed to reflect the concentration of solid products,effectively explaining the influence of the w/b ratio on strength,with an R2of 0.96.展开更多
基金The financial support of the National Natural Science Foundation of China(Grant No.42030714)the National Key R&D Program of China(Grant No.2019YFC1509900)is greatly acknowledged.
文摘High-plastic clays with significant volume change due to moisture variations present critical challenges to civil engineering structures.Limestone calcined clay cement(LC3),an innovative and sustainable hydraulic binder,demonstrates significant potential for improving the engineering characteristics of such soils.Nevertheless,the impact of LC3 on the physico-mechanical characteristics of treated soil under a cyclic wet-dry environment remains unclear.This study for the first time investigates LC3's impact on the long-term durability of treated high-plastic clays through comprehensive macro-micro testing including physical,mechanical,mineralogical,and microstructural investigations with an emphasis on wet-dry cycles.The results revealed that LC3 treatment exhibits significant resistance to wet-dry cycles by completely mitigating the swelling potential,and a considerable reduction in plasticity resulting in enhanced workability.The compressibility and shear strength parameters have been significantly improved to several orders of magnitude.However,after six wet-dry cycles,a slight to modest reduction is observed,but overall durability remains superior to untreated soil.Cohesive and structural bonding ratios quantitatively assessed the impact of wet-dry cycles emphasizing the advantage of LC3 treatment.According to mineralogical and microstructural evaluation,the mechanism behind the adverse effects of wet-dry cycles on the compressibility and strength behavior of LC3-treated soil is mainly attributed to:(1)weakening of CSH/C(A)SH and ettringite(AFt)phases by exhibiting lower peak intensities;and(2)larger pore spaces due to repeated wet-dry cycles.These findings highlight LC3's performance in enhancing the long-term behavior and resilience of treated soils in real-world scenarios,providing durable solutions for infrastructure challenges.
基金the National Natural Science Foundation of China(Nos.51708360 and 51978407)the Shenzhen Basic Research Project of China(No.JCYJ20180305124106675)+4 种基金the Key Projects for International Cooperation in ScienceTechnology and Innovation of China(No.2018YFE0125000)the Taipei University of TechnologyShenzhen University Joint Research Program of China(No.2020008)the National Science Foundation of the USA(No.1661609)the Advanced Materials for Sustainable Infrastructure Seed Funding Program at Missouri University of Science and Technology,USA。
文摘Limestone calcined clay cement(LC^3),consisting of ordinary Portland cement(OPC)clinker,calcined clay,limestone powder,and gypsum,has been considered a promising solution to current challenges in the cement and concrete industry,such as high carbon emissions,high energy consumption,and resource shortages.This study carries out a series of experimental investigations of LC^3-based paste,mortar,and concrete,including microstructural analyses(e.g.hydration product characterization and pore structure analysis)and macro-scale testing(e.g.workability and mechanical properties),using raw materials from south China.The results show that,in LC^3 paste,the replacement of clinker by calcined clay and limestone leads to an increased volume of small pores but decreased total volume of pores.The workability of LC^3 mortar and concrete can be readily tailored using conventional superplasticizers.When designed for comparable 28-d compressive strength,the LC^3 mortar and concrete tend to have lower early-age compressive strength,but comparable compressive strength and higher flexural strength than those of the OPC counterparts at late ages.This study also examines the bond-slip behavior between LC^3 concrete and steel bars and finds that the bond strength is comparable to that of OPC concrete with the same 28-d compressive strength,but that the LC^3 concrete-rebar interface exhibits higher bond-slip stiffness.These findings on LC^3 concrete provide fundamental information and guidance for furthering the application of LC^3 binder in structural concrete in the near future.
基金supported by the Scientific Research Foundation from Sun Yat-sen University and the Guangdong Basic and Applied Basic Research Foundation of China(No.2022A1515110443).
文摘Limestone calcined clay cement(LC3)is an environment-friendly and sustainable cementitious material.It has recently gained considerable attention for the stabilization/solidification(S/S)of soils contaminated by heavy metals.However,the existing studies on S/S of Zn-contaminated soils using LC3 in terms of hydraulic conductivity and microstructural properties as compared to ordinary Portland cement(OPC)are limited.This study focuses on the evaluation of the mechanical,leaching,and microstructural characteristics of Zn-contaminated soils treated with different contents(0%,4%,6%,8%,and 10%)of low-carbon LC3.The engineering performance of the treated Zn-contaminated soils is assessed over time using unconfined compressive strength(UCS),hydraulic conductivity(k),toxicity characteristic leaching procedure(TCLP),and synthetic precipitation leaching procedure(SPLP)tests.Experimental results show that the UCS of Zn-contaminated soils treated with LC3 ranged from 1.47 to 2.49 MPa,which is higher than 1.63%–13.07%for those treated with OPC.The k of Zn-contaminated soils treated with LC3 ranged from 1.16×10^(−8)to 5.18×10^(−8)cm/s as compared to the OPC treated samples.For the leaching properties,the leached Zn from TCLP and SPLP is 1.58–321.10 mg/L and 0.52–284.65 mg/L as the LC3 contents ranged from 4%to 10%.Further,the corresponding pH modeling results indicate that LC3 promotes a relatively suitable dynamic equilibrium condition to immobilize the higher-level Zn contamination.In addition,microscopic analyses demonstrate that the formations of hydration products,i.e.,Zn(OH)_(2),Zn_(2)SiO_(4),calcium silicate hydrate(C–S–H),calcium silicate aluminate hydrate(C–A–S–H)gel,ettringite,and CaZn(SiO_(4))(H_(2)O),are the primary mechanisms for the immobilization of Zn.This study also provides an empirical formula between the UCS and k to support the application of LC3-solidified Zn-contaminated soils in practical engineering in the field.
基金supported in part by grants from National Natural Science Foundation of China(52278259).
文摘Limestone Calcined Clay Cement(LC^(3)) is a newly proposed low-carbon cement,which can effectively reduce energy consumption and carbon emissions of the traditional cement industry without changing the basic mechanical properties of cement-based materials.In this study,the degradation process of mortar samples of limestone and calcined clay cementitious material under sulfate attack is studied by both macroscopic and microscopic analysis.The results show that compared with pure Portland cement,the addition of calcined clay and limestone can significantly reduce the expansion rate,loss of dynamic modulus and mass loss of mortar specimens under sulfate attack.The addition of calcined clay and limestone will refine the pore size distribution of mortar specimens,then inhibiting the diffusion of sulfate and formation of corrosive products,therefore leading to a significant improvement of the sulfate resistance.
基金supported by the Natural Sciences and Engineering Research Council of Canada(No.NSERC RGPIN-2017-05537).
文摘This study aims to investigate the impact of various water-to-binder(w/b)ratios by mass(0.3–2.0)on the performance of limestone calcined clay cement(LC^(3))pastes.The flowability,setting time,density,unconfined compressive strength,hydration,and microstructure of LC^(3) pastes under different w/b ratios were thoroughly investigated.The results show that increasing the w/b ratio extends the flowability and setting time while significantly reducing the unconfined compressive strength of LC^(3) pastes.LC^(3) pastes with w/b ratios above 0.6 exhibited a final flow diameter surpassing 167 mm,indicating good flowability.The 28-d unconfined compressive strength decreased from 82.3 to 1.3 MPa as the w/b ratio increased from 0.3 to 2.0.This study confirmed that the relationship between unconfined compressive strength and the w/b ratio of LC^(3) follows Abram’s law.Furthermore,a modified gel/space ratio was proposed to reflect the concentration of solid products,effectively explaining the influence of the w/b ratio on strength,with an R2of 0.96.
