To estimate a compressive strength from existing concrete structures by core drilling are usually gathered with a diameter specimen of 100 mm or three times of maximum coarse aggregate size and examined by uniaxial co...To estimate a compressive strength from existing concrete structures by core drilling are usually gathered with a diameter specimen of 100 mm or three times of maximum coarse aggregate size and examined by uniaxial compressive strength （UCS）. It is relatively difficult to gather a large sized core, and a pit place will be limited by main members. To get an alternative solution with smaller specimen, point load test （PLT） has been sele,：ted which is a simple test and widely accepted in rock materials research, but relatively new in concrete. The reliability of PLT is evaluated by extracting a lot of core drilled specimen from ready mixed concrete blocks with maximum coarse aggregate size, G of 20 mm in representative of architectural structures and 40 mm in representative of civil structures on the range of concrete grade from 16 to 50. Compressive strengths were classified into general categories, conversion factors were determined, and scattering characteristics were also investigated. The relationship between point load index （Is） and compressive strength of concrete core specimen （fcc） can be written as linear approximation as fcc = k.Is- C.展开更多
Enzyme induced carbonate precipitation(EICP)is a promising technique in the field of biocementation due to its efficiency and controllability.Although many studies have proved its reliability in different environment,...Enzyme induced carbonate precipitation(EICP)is a promising technique in the field of biocementation due to its efficiency and controllability.Although many studies have proved its reliability in different environment,little attention has been paid to the influence of humic substances on the EICP.Humic substances cover most of the surface soil across the world land with vegetation,which varies according to the density of vegetation and climate.To understand the compatibility of this technique to distinct problematic soils,it is important to figure out how humic substances could affect the carbonate precipitation process induced by urease enzyme.Therefore,this study aims to investigate the effects of humic acid(HA),one type of humic substance,on the soil solidification through EICP.For this purpose,HA was added to natural soil with varying addition amounts(0%,1%,2%,4%,8%,16%)in soil column solidification tests.The results found that the cementation effectiveness was enhanced by a small amount of HA addition(<4%),while an addition up to 8%greatly inhibited the formation of calcium carbonate.At the same time,soil samples were buffered by HA in a weak acidic condition,thus preventing the emission of undesirable by-product ammonia in the ureolysis process.Therefore,this study makes a contribution to research on enzymatic biocementation by demonstrating the effects of HA on the cementation effectiveness of EICP technique.展开更多
文摘To estimate a compressive strength from existing concrete structures by core drilling are usually gathered with a diameter specimen of 100 mm or three times of maximum coarse aggregate size and examined by uniaxial compressive strength （UCS）. It is relatively difficult to gather a large sized core, and a pit place will be limited by main members. To get an alternative solution with smaller specimen, point load test （PLT） has been sele,：ted which is a simple test and widely accepted in rock materials research, but relatively new in concrete. The reliability of PLT is evaluated by extracting a lot of core drilled specimen from ready mixed concrete blocks with maximum coarse aggregate size, G of 20 mm in representative of architectural structures and 40 mm in representative of civil structures on the range of concrete grade from 16 to 50. Compressive strengths were classified into general categories, conversion factors were determined, and scattering characteristics were also investigated. The relationship between point load index （Is） and compressive strength of concrete core specimen （fcc） can be written as linear approximation as fcc = k.Is- C.
基金JST SPRING,Grant Number JPMJSP2119Japan Society for the Promotion of Science(JSPS)KAKENHI Grant Number JP22H01581。
文摘Enzyme induced carbonate precipitation(EICP)is a promising technique in the field of biocementation due to its efficiency and controllability.Although many studies have proved its reliability in different environment,little attention has been paid to the influence of humic substances on the EICP.Humic substances cover most of the surface soil across the world land with vegetation,which varies according to the density of vegetation and climate.To understand the compatibility of this technique to distinct problematic soils,it is important to figure out how humic substances could affect the carbonate precipitation process induced by urease enzyme.Therefore,this study aims to investigate the effects of humic acid(HA),one type of humic substance,on the soil solidification through EICP.For this purpose,HA was added to natural soil with varying addition amounts(0%,1%,2%,4%,8%,16%)in soil column solidification tests.The results found that the cementation effectiveness was enhanced by a small amount of HA addition(<4%),while an addition up to 8%greatly inhibited the formation of calcium carbonate.At the same time,soil samples were buffered by HA in a weak acidic condition,thus preventing the emission of undesirable by-product ammonia in the ureolysis process.Therefore,this study makes a contribution to research on enzymatic biocementation by demonstrating the effects of HA on the cementation effectiveness of EICP technique.
