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Jian Chu - One of the best experts on this subject based on the ideXlab platform.
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Stress–dilatancy behavior of cemented sand: comparison between bonding provided by cement and Biocement
Acta Geotechnica, 2021Co-Authors: Lei Wang, Jian Chu, Hao WangAbstract:Biocement as an alternative to cement for soil improvement has been studied for the past decade. A comparative study on the cementation effect on the mechanical behavior of sand by Biocement and Portland cement is presented. Drained triaxial tests were carried out on both cement- and Biocement-treated sand. The yielding of cemented sand is largely associated with the breakage of bonding. Bonding ratio is defined in this paper to quantify the bonding effect. The bonding provided by Biocement is stronger than that by cement, and as a result, the stress ratio at yielding for Biocement-treated sand is higher than that for cement-treated sand given the other conditions the same. The shear resistance of cemented sand consists of bonding, dilation and friction. The stress–dilatancy relationship of Biocement-treated sand is different from that of cement-treated sand or the Rowe’s stress–dilatancy equation. The increase in stress ratio with dilatancy ratio (1 − δε _v/ δε _1) is higher for Biocement-treated sand.
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Stress–dilatancy behavior of cemented sand: comparison between bonding provided by cement and Biocement
Acta Geotechnica, 2021Co-Authors: Lei Wang, Jian Chu, Hao WangAbstract:Biocement as an alternative to cement for soil improvement has been studied for the past decade. A comparative study on the cementation effect on the mechanical behavior of sand by Biocement and Portland cement is presented. Drained triaxial tests were carried out on both cement- and Biocement-treated sand. The yielding of cemented sand is largely associated with the breakage of bonding. Bonding ratio is defined in this paper to quantify the bonding effect. The bonding provided by Biocement is stronger than that by cement, and as a result, the stress ratio at yielding for Biocement-treated sand is higher than that for cement-treated sand given the other conditions the same. The shear resistance of cemented sand consists of bonding, dilation and friction. The stress–dilatancy relationship of Biocement-treated sand is different from that of cement-treated sand or the Rowe’s stress–dilatancy equation. The increase in stress ratio with dilatancy ratio (1 − δev/δe1) is higher for Biocement-treated sand.
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stress dilatancy behavior of cemented sand comparison between bonding provided by cement and Biocement
Acta Geotechnica, 2021Co-Authors: Lei Wang, Jian Chu, Hao WangAbstract:Biocement as an alternative to cement for soil improvement has been studied for the past decade. A comparative study on the cementation effect on the mechanical behavior of sand by Biocement and Portland cement is presented. Drained triaxial tests were carried out on both cement- and Biocement-treated sand. The yielding of cemented sand is largely associated with the breakage of bonding. Bonding ratio is defined in this paper to quantify the bonding effect. The bonding provided by Biocement is stronger than that by cement, and as a result, the stress ratio at yielding for Biocement-treated sand is higher than that for cement-treated sand given the other conditions the same. The shear resistance of cemented sand consists of bonding, dilation and friction. The stress–dilatancy relationship of Biocement-treated sand is different from that of cement-treated sand or the Rowe’s stress–dilatancy equation. The increase in stress ratio with dilatancy ratio (1 − δev/δe1) is higher for Biocement-treated sand.
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Biocementation of soil using non-sterile enriched urease-producing bacteria from activated sludge
Journal of Cleaner Production, 2020Co-Authors: Yang Yang, Jian Chu, Bin Cao, Hanlong Liu, Liang ChengAbstract:Abstract Biocement based on microbially induced carbonate precipitation has become a new construction material for soil cementation. One of the key elements of Biocement is urease-producing bacteria (UPB). This paper presents a new method to enrich UPB from waste activated sludge (WAS) under a non-sterile condition so the cultivation of bacteria can be carried out in large-scale for field applications. Using this method, the cost of bacteria cultivation can be reduced by up to 30%. The UPB culture enriched using this method is highly urease active and capable of hydrolyzing urea for calcium carbonate precipitation. After treating sand columns using Biocement made of this type of UPB via equal molar cementation solution of 2 M, the unconfined compressive strength of the sand increased to 2.7 MPa and the permeability reduced to a level of 10−6 m/s. These results are comparable with those obtained for biotreatment using pure UPB. Thus, the UPB cultivating method introduced in this paper has the potential to reduce the cost of soil improvement without compromising the performance.
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soil bio cementation using a new one phase low ph injection method
Acta Geotechnica, 2019Co-Authors: Mohamed A Shahin, Liang Cheng, Jian ChuAbstract:Soil bio-cementation via microbially induced carbonate precipitation (MICP) has been extensively studied as a promising alternative technique to traditional chemical cementing agents for ground improvement. The multiple-phase injection methods are currently well adopted for MICP treatment, but it is rather complex and requires excessive number of injections. This paper presents a novel one-phase injection method using low-pH all-in-one Biocement solution (i.e. a mixture of bacterial culture, urea, and CaCl2). The key feature of this method is that the lag period of the bio-cementation process can be controlled by adjusting the biomass concentration, urease activity, and pH. This process prevents the clogging of bio-flocs formation and thus allows the Biocement solution to be well distributed inside the soil matrix before bio-cementation takes effect, allowing a relatively uniform MICP treatment to be achieved. Furthermore, the ammonia gas release would be reduced by more than 90%, which represents a significant improvement in the environmental friendliness of the technology. The new one-phase method is also effective in terms of the mechanical property of MICP-treated soil; an unconfined compressive strength of 2.5 MPa was achieved for sand after six treatments.
Hao Wang - One of the best experts on this subject based on the ideXlab platform.
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Stress–dilatancy behavior of cemented sand: comparison between bonding provided by cement and Biocement
Acta Geotechnica, 2021Co-Authors: Lei Wang, Jian Chu, Hao WangAbstract:Biocement as an alternative to cement for soil improvement has been studied for the past decade. A comparative study on the cementation effect on the mechanical behavior of sand by Biocement and Portland cement is presented. Drained triaxial tests were carried out on both cement- and Biocement-treated sand. The yielding of cemented sand is largely associated with the breakage of bonding. Bonding ratio is defined in this paper to quantify the bonding effect. The bonding provided by Biocement is stronger than that by cement, and as a result, the stress ratio at yielding for Biocement-treated sand is higher than that for cement-treated sand given the other conditions the same. The shear resistance of cemented sand consists of bonding, dilation and friction. The stress–dilatancy relationship of Biocement-treated sand is different from that of cement-treated sand or the Rowe’s stress–dilatancy equation. The increase in stress ratio with dilatancy ratio (1 − δε _v/ δε _1) is higher for Biocement-treated sand.
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Stress–dilatancy behavior of cemented sand: comparison between bonding provided by cement and Biocement
Acta Geotechnica, 2021Co-Authors: Lei Wang, Jian Chu, Hao WangAbstract:Biocement as an alternative to cement for soil improvement has been studied for the past decade. A comparative study on the cementation effect on the mechanical behavior of sand by Biocement and Portland cement is presented. Drained triaxial tests were carried out on both cement- and Biocement-treated sand. The yielding of cemented sand is largely associated with the breakage of bonding. Bonding ratio is defined in this paper to quantify the bonding effect. The bonding provided by Biocement is stronger than that by cement, and as a result, the stress ratio at yielding for Biocement-treated sand is higher than that for cement-treated sand given the other conditions the same. The shear resistance of cemented sand consists of bonding, dilation and friction. The stress–dilatancy relationship of Biocement-treated sand is different from that of cement-treated sand or the Rowe’s stress–dilatancy equation. The increase in stress ratio with dilatancy ratio (1 − δev/δe1) is higher for Biocement-treated sand.
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stress dilatancy behavior of cemented sand comparison between bonding provided by cement and Biocement
Acta Geotechnica, 2021Co-Authors: Lei Wang, Jian Chu, Hao WangAbstract:Biocement as an alternative to cement for soil improvement has been studied for the past decade. A comparative study on the cementation effect on the mechanical behavior of sand by Biocement and Portland cement is presented. Drained triaxial tests were carried out on both cement- and Biocement-treated sand. The yielding of cemented sand is largely associated with the breakage of bonding. Bonding ratio is defined in this paper to quantify the bonding effect. The bonding provided by Biocement is stronger than that by cement, and as a result, the stress ratio at yielding for Biocement-treated sand is higher than that for cement-treated sand given the other conditions the same. The shear resistance of cemented sand consists of bonding, dilation and friction. The stress–dilatancy relationship of Biocement-treated sand is different from that of cement-treated sand or the Rowe’s stress–dilatancy equation. The increase in stress ratio with dilatancy ratio (1 − δev/δe1) is higher for Biocement-treated sand.
Tibor Sopcak - One of the best experts on this subject based on the ideXlab platform.
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Injectable Enzymatically Hardened Calcium Phosphate Biocement
Journal of functional biomaterials, 2020Co-Authors: Lubomir Medvecky, R. Štulajterová, Maria Giretova, Lenka Luptakova, Tibor SopcakAbstract:(1) Background: The preparation and characterization of novel fully injectable enzymatically hardened tetracalcium phosphate/monetite cements (CXI cements) using phytic acid/phytase (PHYT/F3P) hardening liquid with a small addition of polyacrylic acid/carboxymethyl cellulose anionic polyelectrolyte (PAA/CMC) and enhanced bioactivity. (2) Methods: Composite cements were prepared by mixing of calcium phosphate powder mixture with hardening liquid containing anionic polyelectrolyte. Phase and microstructural analysis, compressive strength, release of ions and in vitro testing were used for the evaluation of cement properties. (3) Results: The simple possibility to control the setting time of self-setting CXI cements was shown (7–28 min) by the change in P/L ratio or PHYT/F3P reaction time. The wet compressive strength of cements (up to 15 MPa) was close to cancellous bone. The increase in PAA content to 1 wt% caused refinement and change in the morphology of hydroxyapatite particles. Cement pastes had a high resistance to wash-out in a short time after cement mixing. The noncytotoxic character of CX cement extracts was verified. Moreover, PHYT supported the formation of Ca deposits, and the additional synergistic effect of PAA and CMC on enhanced ALP activity was found, along with the strong up-regulation of osteogenic gene expressions for osteopontin, osteocalcin and IGF1 growth factor evaluated by the RT-qPCR analysis in osteogenic αMEM 50% CXI extracts. (4) Conclusions: The fully injectable composite calcium phosphate bicements with anionic polyelectrolyte addition showed good mechanical and physico-chemical properties and enhanced osteogenic bioactivity which is a promising assumption for their application in bone defect regeneration.
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Enzymatically hardened calcium phosphate Biocement with phytic acid addition
Journal of Materials Science: Materials in Medicine, 2020Co-Authors: Lubomir Medvecky, Maria Giretova, Tibor Sopcak, Radoslava Stulajterova, Zuzana Molcanova, Karol KovalAbstract:Novel enzymatically hardened tetracalcium phosphate/monetite cements were prepared applying phytic acid/phytase (PHYT/F3P) mixture as hardening liquid after dissolving in acetic acid solution (CX cement). Properties of the cements were compared with classic cement hardened with 2% NaH_2PO_4 (C cement) and cement hardened with acetic acid solution (CAC cement) only. In the microstructure of CX cement, columnar growth of hydroxyapatite particles was found in the form of walls around hydroxyapatite agglomerates originated from tetracalcium phosphate which were mutually separated by a material depleted low density zone. Wet compressive strengths (CS) of all cements were practically identical contrary to about 30% higher dry CS’s of CX and CAC cements due to specific microstructure. It was verified noncytotoxic character of CX cement extracts and positive effect of CX cement on ALP activity and cell behavior during cultivation. The final Ca/P molar ratio and setting time of cement were effectively controlled by the amount of phytic acid and the change in PHYT/F3P mass ratio, or reaction time in hardening liquid, respectively.
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preparation and properties of tetracalcium phosphate monetite Biocement
Materials Letters, 2013Co-Authors: Lubomir Medvecky, Maria Giretova, Tibor SopcakAbstract:Abstract The tetracalcium phosphate–monetite cement mixture was prepared by reaction milling of tetracalcium phosphate with the orthophosphoric acid ethanol solution. The presence of nanomonetite phase caused significant lowering of the pH value in cement paste during hardening. The agglomerates of nanomonetite phase homogeneously distributed in powder cement mixture were observed by TEM. The compressive strength and setting times of cement were 35 MPa and 4–9 min respectively.
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Preparation and properties of tetracalcium phosphate–monetite Biocement
Materials Letters, 2013Co-Authors: Lubomir Medvecky, Maria Giretova, Tibor SopcakAbstract:Abstract The tetracalcium phosphate–monetite cement mixture was prepared by reaction milling of tetracalcium phosphate with the orthophosphoric acid ethanol solution. The presence of nanomonetite phase caused significant lowering of the pH value in cement paste during hardening. The agglomerates of nanomonetite phase homogeneously distributed in powder cement mixture were observed by TEM. The compressive strength and setting times of cement were 35 MPa and 4–9 min respectively.
Lei Wang - One of the best experts on this subject based on the ideXlab platform.
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Stress–dilatancy behavior of cemented sand: comparison between bonding provided by cement and Biocement
Acta Geotechnica, 2021Co-Authors: Lei Wang, Jian Chu, Hao WangAbstract:Biocement as an alternative to cement for soil improvement has been studied for the past decade. A comparative study on the cementation effect on the mechanical behavior of sand by Biocement and Portland cement is presented. Drained triaxial tests were carried out on both cement- and Biocement-treated sand. The yielding of cemented sand is largely associated with the breakage of bonding. Bonding ratio is defined in this paper to quantify the bonding effect. The bonding provided by Biocement is stronger than that by cement, and as a result, the stress ratio at yielding for Biocement-treated sand is higher than that for cement-treated sand given the other conditions the same. The shear resistance of cemented sand consists of bonding, dilation and friction. The stress–dilatancy relationship of Biocement-treated sand is different from that of cement-treated sand or the Rowe’s stress–dilatancy equation. The increase in stress ratio with dilatancy ratio (1 − δε _v/ δε _1) is higher for Biocement-treated sand.
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Stress–dilatancy behavior of cemented sand: comparison between bonding provided by cement and Biocement
Acta Geotechnica, 2021Co-Authors: Lei Wang, Jian Chu, Hao WangAbstract:Biocement as an alternative to cement for soil improvement has been studied for the past decade. A comparative study on the cementation effect on the mechanical behavior of sand by Biocement and Portland cement is presented. Drained triaxial tests were carried out on both cement- and Biocement-treated sand. The yielding of cemented sand is largely associated with the breakage of bonding. Bonding ratio is defined in this paper to quantify the bonding effect. The bonding provided by Biocement is stronger than that by cement, and as a result, the stress ratio at yielding for Biocement-treated sand is higher than that for cement-treated sand given the other conditions the same. The shear resistance of cemented sand consists of bonding, dilation and friction. The stress–dilatancy relationship of Biocement-treated sand is different from that of cement-treated sand or the Rowe’s stress–dilatancy equation. The increase in stress ratio with dilatancy ratio (1 − δev/δe1) is higher for Biocement-treated sand.
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stress dilatancy behavior of cemented sand comparison between bonding provided by cement and Biocement
Acta Geotechnica, 2021Co-Authors: Lei Wang, Jian Chu, Hao WangAbstract:Biocement as an alternative to cement for soil improvement has been studied for the past decade. A comparative study on the cementation effect on the mechanical behavior of sand by Biocement and Portland cement is presented. Drained triaxial tests were carried out on both cement- and Biocement-treated sand. The yielding of cemented sand is largely associated with the breakage of bonding. Bonding ratio is defined in this paper to quantify the bonding effect. The bonding provided by Biocement is stronger than that by cement, and as a result, the stress ratio at yielding for Biocement-treated sand is higher than that for cement-treated sand given the other conditions the same. The shear resistance of cemented sand consists of bonding, dilation and friction. The stress–dilatancy relationship of Biocement-treated sand is different from that of cement-treated sand or the Rowe’s stress–dilatancy equation. The increase in stress ratio with dilatancy ratio (1 − δev/δe1) is higher for Biocement-treated sand.
Lubomir Medvecky - One of the best experts on this subject based on the ideXlab platform.
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Injectable Enzymatically Hardened Calcium Phosphate Biocement
Journal of functional biomaterials, 2020Co-Authors: Lubomir Medvecky, R. Štulajterová, Maria Giretova, Lenka Luptakova, Tibor SopcakAbstract:(1) Background: The preparation and characterization of novel fully injectable enzymatically hardened tetracalcium phosphate/monetite cements (CXI cements) using phytic acid/phytase (PHYT/F3P) hardening liquid with a small addition of polyacrylic acid/carboxymethyl cellulose anionic polyelectrolyte (PAA/CMC) and enhanced bioactivity. (2) Methods: Composite cements were prepared by mixing of calcium phosphate powder mixture with hardening liquid containing anionic polyelectrolyte. Phase and microstructural analysis, compressive strength, release of ions and in vitro testing were used for the evaluation of cement properties. (3) Results: The simple possibility to control the setting time of self-setting CXI cements was shown (7–28 min) by the change in P/L ratio or PHYT/F3P reaction time. The wet compressive strength of cements (up to 15 MPa) was close to cancellous bone. The increase in PAA content to 1 wt% caused refinement and change in the morphology of hydroxyapatite particles. Cement pastes had a high resistance to wash-out in a short time after cement mixing. The noncytotoxic character of CX cement extracts was verified. Moreover, PHYT supported the formation of Ca deposits, and the additional synergistic effect of PAA and CMC on enhanced ALP activity was found, along with the strong up-regulation of osteogenic gene expressions for osteopontin, osteocalcin and IGF1 growth factor evaluated by the RT-qPCR analysis in osteogenic αMEM 50% CXI extracts. (4) Conclusions: The fully injectable composite calcium phosphate bicements with anionic polyelectrolyte addition showed good mechanical and physico-chemical properties and enhanced osteogenic bioactivity which is a promising assumption for their application in bone defect regeneration.
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Enzymatically hardened calcium phosphate Biocement with phytic acid addition
Journal of Materials Science: Materials in Medicine, 2020Co-Authors: Lubomir Medvecky, Maria Giretova, Tibor Sopcak, Radoslava Stulajterova, Zuzana Molcanova, Karol KovalAbstract:Novel enzymatically hardened tetracalcium phosphate/monetite cements were prepared applying phytic acid/phytase (PHYT/F3P) mixture as hardening liquid after dissolving in acetic acid solution (CX cement). Properties of the cements were compared with classic cement hardened with 2% NaH_2PO_4 (C cement) and cement hardened with acetic acid solution (CAC cement) only. In the microstructure of CX cement, columnar growth of hydroxyapatite particles was found in the form of walls around hydroxyapatite agglomerates originated from tetracalcium phosphate which were mutually separated by a material depleted low density zone. Wet compressive strengths (CS) of all cements were practically identical contrary to about 30% higher dry CS’s of CX and CAC cements due to specific microstructure. It was verified noncytotoxic character of CX cement extracts and positive effect of CX cement on ALP activity and cell behavior during cultivation. The final Ca/P molar ratio and setting time of cement were effectively controlled by the amount of phytic acid and the change in PHYT/F3P mass ratio, or reaction time in hardening liquid, respectively.
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Changes in the Acute-Phase Protein Concentrations and Activities of Some Enzymes in Pigs Following the Repair of Experimentally Induced Articular Cartilage Defects Using Two Types of Biocement Powder.
Animals : an open access journal from MDPI, 2019Co-Authors: Csilla Tóthová, Jaroslav Novotny, Oskar Nagy, Petra Hornakova, Zdenek Zert, Maros Varga, Lubomir Medvecky, Katarina Vdoviakova, Jan Danko, Eva PetrovovaAbstract:The objective of the study was to assess the usefulness of acute-phase proteins (APPs) and serum enzymes in the evaluation of post-operative state after cartilage reconstruction in an animal model (Sus scrofa domesticus). Fifteen clinically healthy female pigs were evaluated during the first 30 days after the repair of experimentally induced articular cartilage defects using two types of Biocement powders. Animals were divided into groups according to the type of Biocement powder used: CAK—with amino acids (n = 6), C—without amino acids (n = 6) and the control group (Ctr) was without Biocement (n = 3). The concentrations of selected APPs—serum amyloid A (SAA), haptoglobin (Hp) and C-reactive protein (CRP), and the activities of some serum enzymes—creatine kinase (CK), alkaline phosphatase (AP), and lactate dehydrogenase (LD) were measured one day before the surgery and on days 7, 14, and 30 after the surgical intervention. The most significant changes during the evaluated period were observed in the concentrations of SAA (p 0.05). Marked variations were observed also in the activities of the evaluated enzymes, with the most significant changes in the activity of AP in the CAK group (p < 0.001). Presented results suggest possible usefulness of some APPs and serum enzymes in the evaluation of post-operative inflammatory state after the reconstruction of articular cartilage defects.
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Properties of Powder Composite Polyhydroxybutyrate–Chitosan-Calcium Phosphate System
Powder Metallurgy Progress, 2017Co-Authors: Lubomir Medvecky, R. Štulajterová, Maria Giretova, Mária FáberováAbstract:Abstract Prepared powder polyhydroxybutyrate – chitosan - calcium phosphate composite system with 10 wt % of biopolymer component can be utilized as Biocement which is characterized by the prolonged setting time and achieves wash out resistance after 5 minutes of setting. The origin powder tetracalcium phosphate/nanomonetite agglomerates were coated with the thin layer of biopolymer which decelerates both the transformation rate of calcium phosphates and hardening process of composites. The porosity of hardened composite was around 62% and the compressive strength (8 MPa) was close to trabecular bone. No cytotoxicity of composite resulted from live/dead staining of osteoblasts cultured on substrates.
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preparation and properties of tetracalcium phosphate monetite Biocement
Materials Letters, 2013Co-Authors: Lubomir Medvecky, Maria Giretova, Tibor SopcakAbstract:Abstract The tetracalcium phosphate–monetite cement mixture was prepared by reaction milling of tetracalcium phosphate with the orthophosphoric acid ethanol solution. The presence of nanomonetite phase caused significant lowering of the pH value in cement paste during hardening. The agglomerates of nanomonetite phase homogeneously distributed in powder cement mixture were observed by TEM. The compressive strength and setting times of cement were 35 MPa and 4–9 min respectively.