Biochars are, amongst other available amendment materials, considered as an attractive tool in agriculture for carbon sequestration and improvement of soil functions. The latter is widely discussed as a consequence of...Biochars are, amongst other available amendment materials, considered as an attractive tool in agriculture for carbon sequestration and improvement of soil functions. The latter is widely discussed as a consequence of improved physical quality of the amended soil.However, the mechanisms for this improvement are still poorly understood. This study investigated the effect of woodchip biochar amendment on micro-structural development, micro-and macro-structural stability, and resilience of two differently textured soils,fine sand(FS) and sandy loam(SL). Test substrates were prepared by adding 50 or 100 g kg^(-1) biochar to FS or SL. Total porosity and plant available water were significantly increased in both soils. Moreover, compressive strength of the aggregates was significantly decreased when biochar amount was doubled. Mechanical resilience of the aggregates at both micro-and macro-scale was improved in the biochar-amended soils, impacting the cohesion and compressive behavior. A combination of these effects will result in an improved pore structure and aeration. Consequently, the physicochemical environment for plants and microbes is improved. Furthermore, the improved stability properties will result in better capacity of the biochar-amended soil to recover from the myriad of mechanical stresses imposed under arable systems, including vehicle traffic, to the weight of overburden soil. However, it was noted that doubling the amendment rate did not in any case offer any remarkable additional improvement in these properties, suggesting a further need to investigate the optimal amendment rate.展开更多
This study investigates the influence of waste characteristics,especially zeta potential,on the properties of cement pastes and solutions.The focus is to evaluate the impact of the zeta potential of cement particles a...This study investigates the influence of waste characteristics,especially zeta potential,on the properties of cement pastes and solutions.The focus is to evaluate the impact of the zeta potential of cement particles and waste materials on the sedimentation speed,rheology,and hardening time of stabilized cement pastes.Portland Cement II F 40,retarder additive,silica,and fly ash were used in the research.The pastes were prepared,and during the stabilization period,their rheological properties and pH were evaluated.The zeta potential and sedimentation speed of the cement and waste particles were measured at the pH that the pastes presented during the entire stabilization period.After the stabilization period,the pastes were subjected to the hardening time test.The zeta potential analyses revealed diverse values for the different powder types,with the cement particles exhibiting a zeta potential of−3.0 mV,the silica particles exhibiting−10.5 mV,and the fly ash particles exhibiting−20.3 mV.The influence of the high zeta potential modulus was observed on the sedimentation speed,with the solution containing fly ash exhibiting a speed of 40.01μm/s,whereas the solution containing only cement exhibited a speed of 99.38μm/s.In the pastes,the results indicate that the presence of fly ash particles with a significantly negative zeta potential led to a 16%reduction in hardening time compared to particles with a lower modulus of zeta potential.Rheometry tests showed that the inclusion of fly ash particles prevented the formation of agglomerates.Although the zeta potential influenced agglomerate formation and hardening time,it was found to have no effect on yield stress or viscosity.展开更多
Whilst caking occurs via several different mechanisms,absorption and migration of moisture is frequently the most dominant mechanism within the food and pharmaceutical industry.Fully understanding the propensity to ca...Whilst caking occurs via several different mechanisms,absorption and migration of moisture is frequently the most dominant mechanism within the food and pharmaceutical industry.Fully understanding the propensity to cake is important for minimising down-stream process issues,however most characterisation techniques assume that moisture induced caking occurs homogenously through the sample resulting in a uniformly caked powder bed.In this study,the effect of moisture induced caking on powder flowability was investigated using powder rheology.Several materials,including skimmed milk powder(SMP)and sulphated methyl ester(SME)were stored for several days under controlled humidity conditions.The flow energies,a measure of the resistance to flow,were measured at 24 h intervals using an FT4 Powder Rheometer.As the energy is measured as a function of the bed height,variations in the powder bed are also captured.The results demonstrated that caking does not always occur uniformly,instead a caked region(or crust)forms at the air-powder interface and then progresses through the powder bed.Furthermore,the strength of this caked region was shown to increase over several days before stabilising.展开更多
基金the George Foster Research Fellowship provided by Alexander yon Humboldt Fellowship of Germany.
文摘Biochars are, amongst other available amendment materials, considered as an attractive tool in agriculture for carbon sequestration and improvement of soil functions. The latter is widely discussed as a consequence of improved physical quality of the amended soil.However, the mechanisms for this improvement are still poorly understood. This study investigated the effect of woodchip biochar amendment on micro-structural development, micro-and macro-structural stability, and resilience of two differently textured soils,fine sand(FS) and sandy loam(SL). Test substrates were prepared by adding 50 or 100 g kg^(-1) biochar to FS or SL. Total porosity and plant available water were significantly increased in both soils. Moreover, compressive strength of the aggregates was significantly decreased when biochar amount was doubled. Mechanical resilience of the aggregates at both micro-and macro-scale was improved in the biochar-amended soils, impacting the cohesion and compressive behavior. A combination of these effects will result in an improved pore structure and aeration. Consequently, the physicochemical environment for plants and microbes is improved. Furthermore, the improved stability properties will result in better capacity of the biochar-amended soil to recover from the myriad of mechanical stresses imposed under arable systems, including vehicle traffic, to the weight of overburden soil. However, it was noted that doubling the amendment rate did not in any case offer any remarkable additional improvement in these properties, suggesting a further need to investigate the optimal amendment rate.
文摘This study investigates the influence of waste characteristics,especially zeta potential,on the properties of cement pastes and solutions.The focus is to evaluate the impact of the zeta potential of cement particles and waste materials on the sedimentation speed,rheology,and hardening time of stabilized cement pastes.Portland Cement II F 40,retarder additive,silica,and fly ash were used in the research.The pastes were prepared,and during the stabilization period,their rheological properties and pH were evaluated.The zeta potential and sedimentation speed of the cement and waste particles were measured at the pH that the pastes presented during the entire stabilization period.After the stabilization period,the pastes were subjected to the hardening time test.The zeta potential analyses revealed diverse values for the different powder types,with the cement particles exhibiting a zeta potential of−3.0 mV,the silica particles exhibiting−10.5 mV,and the fly ash particles exhibiting−20.3 mV.The influence of the high zeta potential modulus was observed on the sedimentation speed,with the solution containing fly ash exhibiting a speed of 40.01μm/s,whereas the solution containing only cement exhibited a speed of 99.38μm/s.In the pastes,the results indicate that the presence of fly ash particles with a significantly negative zeta potential led to a 16%reduction in hardening time compared to particles with a lower modulus of zeta potential.Rheometry tests showed that the inclusion of fly ash particles prevented the formation of agglomerates.Although the zeta potential influenced agglomerate formation and hardening time,it was found to have no effect on yield stress or viscosity.
文摘Whilst caking occurs via several different mechanisms,absorption and migration of moisture is frequently the most dominant mechanism within the food and pharmaceutical industry.Fully understanding the propensity to cake is important for minimising down-stream process issues,however most characterisation techniques assume that moisture induced caking occurs homogenously through the sample resulting in a uniformly caked powder bed.In this study,the effect of moisture induced caking on powder flowability was investigated using powder rheology.Several materials,including skimmed milk powder(SMP)and sulphated methyl ester(SME)were stored for several days under controlled humidity conditions.The flow energies,a measure of the resistance to flow,were measured at 24 h intervals using an FT4 Powder Rheometer.As the energy is measured as a function of the bed height,variations in the powder bed are also captured.The results demonstrated that caking does not always occur uniformly,instead a caked region(or crust)forms at the air-powder interface and then progresses through the powder bed.Furthermore,the strength of this caked region was shown to increase over several days before stabilising.
