Mesocosmic study on autogenous shrinkage of concrete with consideration of effects of temperature and humidity

A study on the autogenous shrinkage （AS） of concrete from a mesocosmic perspective was carried out using numerical simulation technology. The temperature history and the autogenous relative humidity （ARH）, two factors that have been shown to have occasional influence on this process in previous studies, were introduced into this study. According to these concepts, a program for simulation of the temperature field, humidity field, and stress field based on the equivalent age method and a fully automatic aggregate modeling tool were used. With the help of these programs, the study of a small concrete specimen provided some useful conclusions： the aggregate and the matrix show distinct distribution properties in the temperature field, humidity field, and stress field; the aggregate-matrix interface has a high possibility of becoming the location of the initial cracking caused by AS of concrete; the distribution of random aggregates is extremely important for mesoscopical analysis; and the temperature history is the main factor affecting the AS of concrete. On the whole, inherent mechanisms and cracking mechanisms of AS of concrete can be explained more reasonably and realistically only by considering the different characteristics of material phases and the effects of temperature and humidity.

Surface Modification of Fly Ashes with Carbide Slag and Its Effect on Compressive Strength and Autogenous Shrinkage of Blended Cement Pastes

Surfaces of grade III fly ashes were modified through mixing with carbide slag and calcining at 850 ℃ for 1 h. Mineralogical compositions and surface morphology of fly ashes before and after modification were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）, respectively. Effect of surface-modified fly ashes on compressive strength and autogenous shrinkage of blended cement pastes was investigated. Microstructures of cement pastes were examined by backscattered electron （BSE） imaging and mercury intrusion porosimetry （MIP）. The experimental results showed that β-C2S was formed on the surfaces of fly ashes after modification. Hydration ofβ-C2S on the surface-modified fly ashes densified interface zone and enhanced bond strength between particles of fly ashes and hydrated clinkers. In addition, surface modification of fly ashes tended to decrease total porosity and 10-50 nm pores of cement pastes. Surface modification of fly ashes increased compressive strength and reduced autogenous shrinkage of cement pastes.

Relationship Between Autogenous Deformation and Internal Relative Humidity of High-strength Expansive Concrete

The relationship between autogenous deformation and internal relative humidity（IRH） of high-strength concrete and high-strength expansive concrete were investigated.The experimental results indicate that,there exists a good linear relationship between autogenous shrinkage and IRH of high-strength concrete but a nonlinear relationship between autogenous deformation and IRH of high-strength expansive concrete with expansive agent.The new autogenous deformation curve can be obtained by transforming the autogenous deformation data of high-strength expansive concrete,and there exists linear relationship between the autogenous deformation and IRH.The concept of ＂critical internal relative humidity＂ was proposed,which is defined as the value of IRH when autogenous deformation is zero,to effectively reflect the autogenous deformation characteristic of expansive concrete.

Effect of Pre-wetted Light-weight Aggregate on Internal RelativeHumidity and Autogenous Shrinkage of Concrete

This research indicates that the gradient of internal relative humidity （IRH） decreases rapidly within 7-day curing age in HPC. The amount of water imported by pre-wetted light-weight aggregate can regulate IRH of concrete. By importing a proper amount of water, the process of the decline of IRH can be delayed and the autogenous shrinkage can be reduced. The relationship among the amount of water imported by pre- wetted lightweight aggregate, IRH and AS was established. The result provides a new method of reducing early AS and enhancing early cracking resistance of HPC.

Effects of Shale and CaO Incorporation on Mechanical Properties and Autogenous Deformation of Early-age Concrete

The pre-soaked shale employed as an internal curing agent and CaO employed as expansion agent were incorporated into concrete to investigate their effects on the mechanical properties and autogenous deformation of early-age concrete.We have conducted the relevant tests for setting time,mechanical properties,internal relative humidity and autogenous deformation of early-age concrete with shale or/and CaO incorporation.The results indicate that the set behavior is delayed by shale addition but is accelerated with CaO.The shale addition firstly enhances and subsequently decreases the strength,but CEA addition has a weakening effect.Additionally,shale or/and CaO incorporation deteriorates the elastic modulus.The shale and CaO incorporation significantly improve the internal relative humidity of concrete.The internal curing efficacy of shale could synergistically mitigate the autogenous shrinkage,that is,could enhance the expansion of CaO and then greatly reduce the contraction,which is significantly beneficial to impede the shrinkage-introduced cracks of early-age concrete.

Autogenous Shrinkage of High Strength Lightweight Aggregate Concrete

The characteristic of autogenous shrinkage（AS） and its effect on high strength lightweight aggregate concrete（HSLAC） were studied.The experimental results show that the main shrinkage of high strength concrete is AS and the amount of cement can affect the AS of HSLAC remarkably,At the early stage the AS of HSLAC is lower than that of high strength normal concrete,but it has a large growth at the later stage.The AS of high strength normal concrete becomes stable at 90d age,but HSLAC still has a high AS growth .It is found that adjusting the volume rate of lightweight aggregate,mixing with a proper dosage of fly ash and raising the water saturation degree of lightweight aggregate can markedly reduce the AS rate of HSLAC.

Autogenous Bone Graft versus Artificial Substitutes in Cranioplasty

Cranioplasty is a routine procedure in neurosurgery. However, it has a high postoperative complication rate up to 40%. The lack of good prospective studies and the small number of patients who receive artificial substitutes make it difficult to choose between different materials and the decision is mostly based on subjective or economic reasons. The main goal of this study was to compare the most common complications related to the implant within the first year after implantation. Methods: This prospective randomized clinical study has been carried out on 32 patients with cranial defects of different etiologies, sites and sizes which have been operated in Assiut University Hospital from January 2016 to January 2017. The patients were randomized into two groups: Autologous and Artificial group. Each group has 16 patients. Results: The overall complication rate in autologous group was found to be (25%) and in artificial group (37.5%). Infection in autologous group was found in (6.25%), in artificial group was found in (12.5%). Bone resorption was found in (12.5%). For epidural hematoma and wound dehiscence each has a rate of (6.25%). Poor cosmetic result in (18.75%) of artificial group. Conclusion: Cranioplasty is not without complications. However, good decision making, good timing and proper surgical techniques can provide excellent results. Primary titanium mesh cranioplasty should be considered especially in young adult patients with traumatic aetiology of bone defect.

SELECTION OF THE PROCESS PARAMETERS FOR BATH AUTOGENOUS SMELTING OF COPPER

The process parameters for bath autogenous smelting of copper were selected based on dynamic analysis of the experimental data and calculation of the mathematical model. Selecting the slag composition of SiO2/Fe=0.80 and CaO％=16. desulphur ratio less than 80 wt.-％ in system. and the copper content of matte less than 60 wt.-％, it is able to limit Fe3O4 formation and obtain a high desulphurization. The critical oxygen content of the blast increased with decrease of the sulphur content of the concentrate and increase of copper contents of the matte. If the copper contents of the concentrate are respectively of 30 and 35 wt.-％, the critical oxygen contents of the blast will be 48 and 69 wt.-％ respectively. The smelling rate increases linearly with the blast intensity. When the sulphur content of the concentrate is 30 wt.-％, the oxygen content of the blast 70 vol.-％ and the copper content of the matte 60 wt.-％, a blast intensityy of 700 Nm3/m2·h results in a smeling rate of 48.81 t/m2·d.

Experimental Research on the Autogenous Shrinkage of MK High Performance Concrete

Calcine and mill kaolin were used under agreeable technological conditions to generate matakaolin （MK）. The autogenous shrinkage performance of high performance concrete added with MK was researched. It is shown that MK has an effective inhibitory action to early autogenous shrinkage of cement concrete, and the inhibitory action increases with the increase of MK. The autogenous shrinkage values from 24 hours after placement to 56 days are all higher than those of the contrasted concrete, among which, the value of the concrete with 5% MK is the highest. But the total shrinkage values in 56 days are all less than those of the contrasted test pieces. The total contraction after 24 h of placement decreases as the increase of MK, moreover, it is greatly less than that of the contrasted ones.

SEM image analysis of endothelium of distended autogenous vein grafts

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Experimental study on autogenous vein cuff alleviating arterial intimal hyperplasia

Objective: To explore the alleviation of arterial intimal hyperplasia and improvement of outflow by inserting an autogenous vein cuff between poly tetraflu oroethylene (PTFE) graft and arteri al an astomosis. Methods: Twenty-four hindlimbs of 12 mongrel dogs were randomly divided into control group and experimental group. Sole PTFE bypasses were made in the control group, an autologous vein cuff was inserted in the distal anastomosis in the experimental group. Eight weeks after operation, angiography was made and specimens were harvested, histomorphological studies under microscope and picture analysis with computer were carried out, scanning electromicroscopy on the vein cuff was made. Results: Angiography demonstrated the patency of control and experimental group was 16. 7% and 66. 7%, respectively; Computer gave the intimal thickness: (483. 5 ± 67. 3) μm and (147. 4 ± 38. 6) μm, respectively; no obvious change was seen in medial thickness; area of intimal hyperplasia was (5217 ± 1 123) (pixel) and (31 17 ± 890) (pixel), respectively, accounting (80. 9 ± 17. 2)% and (47. 7 ± 13. 7)% of the sectional area of vessel lumen. The interpositional vein was arteriolization. Conclusion: The interpositional autologous vein cuff can obviously mitigate the arterial intimal hyperplasia after PTFE bypasses, improving postoperative patency of vascular surgery.

Healing Mechanism and Osteogenic Capacity of Bovine Bone Mineral—Human Amniotic Mesenchymal Stem Celland Autogenous Bone Graft in Critical Size Mandibular Defect

Experiments on maxillofacial bone tissue engineering showed the promising result;however, its healing mechanisms and effectiveness had not been fully understood. The aim of this study is to compare the bone healing mechanism and osteogenic capacity between bovine bone mineral loaded with hAMSC and autogenous bone graft in the reconstruction of critical size mandibular bone defect. Critical size defects were made at the mandible of 45 New Zealand white rabbits reconstructed with BBM-hAMSC, BBM alone, and ABG, respectively. At the end of first, second, and twelfth weeks, five rabbits from each experimental week were sacrificed for histology and immunohistochemistry staining. Expressions of vascular endothelial growth factor (VEGF), bone mor-phogenic proteins-2 (BMP2), Runx2 and the amount of angiogenesis were analyzed in the first and second week groups, while expressions of Runx2, osteocalcin, collagen type-I fibres, trabecular area and bone incorporation were analyzed in the twelfth week groups. The result showed that expressions of VEGF, BMP2 and Runx2 as well as the amount of angiogenesis were higher in ABG compared with BBM-hAMSC group in the first and second weeks of healing. The result of twelfth week of healing showed that expressions of Runx2 and osteocalcin as well as the thickness of collagen type-I fibres were significantly higher in BBM-hAMSC compared to ABG group, while there was no statistically difference in trabecular area and bone incorporation between BBM-hAMSC and ABG group. This study concluded that early healing activities were higher in auto-genous bone graft than in BBM-hAMSC, while osteogenic activities in the late stage of healing were higher in BBM-hAMSC compared to autogenous bone graft. It was also concluded that the osteo-genic capacity of BBM-hAMSC was comparable to autogenous bone graft in the reconstruction of critical size defect in the mandible.

Characterisation of Early Age Deformations in Cement Paste: Case of Chemical and Autogenous Shrinkage

Concrete is commonly seen as a durable and long-lasting construction material. However, the long-term performance of a concrete structure can be greatly compromised by early-age cracking. This work is an experimental contribution to study early age deformations of cement paste. Its aim is, firstly, to develop an experimental dispositive for assessing chemical and autogenous shrinkage, and secondly, to measure these volumetric deformations in cement paste. The setup was done following the gravimetric method of measurement, which exploits the Archimedes’ principle. It is made up of an electronic balance, a data accusation unit, a temperature control unit and a buoyancy bath. Investigations were done on Portland cement (CPA-CEM II) at the following W/C ratios: 0.25, 0.3, 0.35, 0.4 and 0.5. It was noticed that the water-cement ratio does not influence the magnitude of the chemical shrinkage in a significant manner but had a kinetic effect;a lower W/C induces a faster rate of chemical shrinkage. Autogenous shrinkage was discovered to be highly inversely proportional to the W/C and was also noticed to be in a function of chemical shrinkage within the first 2 to 4 hours when the paste was still liquid.

Effectiveness of two regeneration materials in autogenous tooth transplantation in larger sockets:an experimental study in beagle dogs

Objective： To evaluate the effectiveness of regenerous tissue and bone substitute in autogenous tooth transplantation in the larger recipient socket. Methods：In 3 Beagle dogs, 18 incisors were transplanted to the recipient sockets, 2 mm wider mesio-distally. The regenerous tissue group, the bone substitute group and the control group contained 7, 7 and 4 teeth respectively. No additional material was used in control group. Clinical and radiographic examinations were done every month and were sacrificed 3 months later. Subsequently, decalcified sections were prepared for routine histological evaluation. Ordinal scores for root surface resorption were analyzed using the Kruskal-Wallis test. Results：All donor teeth survived. A statistically significant difference was found among all three treatment groups（P= 0.0001）. The proliferating tissue in space positively affected the periodontal healing without any resorption. Inflammatory resorption of the root surface and formation of new bone were observed in the bone substitute group. Surface resorptions of the roots were found in the control group. Conclusion：Proliferating tissues enhance the regeneration of periodontal tissues in larger recipient sockets and prevent root resorption. Sinbone HT is beneficial for the stabilization of the transplanted teeth in larger sockets.

Late surgical correction of anomalous left coronary artery from pulmonary trunk in children, using autogenous aortic and pulmonary endotheliazed tube

Background: Direct re-implantation of an anomalous left coronary artery into the aorta is the preferred surgical option for creating a dual coronary arterial system in patients in whom the anomalous artery originated from the pulmonary trunk. This technique, however, is applicable only when the anomalous ar- tery arises from the left posterior pulmonary sinus. We report the successfully late follow-up of series of patients employing a new technique using combined autogenous aortic and pulmonary endotheliazed tube. Patients and Methods: We have treated 3 patients, aged 2 months, 6 months and 8 months respectively, who presented with anomalous origin of the left coronary artery from the left posterior pulmonary sinus and moderated mitral valve insufficiency by left ventricle dysfunction. We used a trapdoor like coronary artery elongation with autogenous aortic and pulmonary endotheliazed tube to connect the left coronary ostium to ascending aorta, avoiding the mitral valve intervention. Results: There was no early or late death. All patients are in functional class I, with good biventricular function and competent mitral valve at a median follow-up of 94 months, ranged from 108 to 132 months. Postoperative Computerized tomogramphy of aorta in our 1st patient showed good arterial flow, without any distortion. A local and distal stenosis of the left pulmonary artery was observed and submitted to stent treatment. Conclusions: The potential benefits of the trapdoor like and its modification technique are excellent operative exposure. The use of autogenous endothelized tube is a viable tissue capable of further growth, avoidance of injury to the aortic and pulmonary valvar apparatus or production of obstruction within the right ventricular outflow tract.

Evaluation of 4 different bone graft substitutes and autogenous bone grafting in root-end resection osteotomies after retrograde root-filling with Intermediate Restorative Material(IRM):An experimental study in dogs

Purpose: To investigate the periapical tissue response after root end filling with intermediate restorative material (IRM) and filling of the root-end resection bone defects with autogenous bone or a bone graft substitute in comparison to empty controls. Materials and Methods: Vital roots of the second, third and fourth mandibular premolars in six healthy mongrel dogs were apectomized. The root canals were prepared and sealed with IRM following a standardized surgical procedure. The resection bone defects were either filled with autogenous bone (PB) or one of the bone graft substitutes;CERAMENTTM|BONE VOID FILLER, ChronOS?, TigranTM PTG, Easygraft? CLASSIC or left empty. After 120 days the animals were sacrificed and the specimens were analyzed radiologically and histologically. Kruskal-Wallis and Mann-Whitney tests were performed for statistical evaluation. Results: 34 sections were analyzed histologically. The evaluation revealed a variation in the outcome amongst the tested options, regarding reestablishment of the periapical bone healing and inflammatory infiltration in the sections. According to the tested variables, there was no statistical significant difference between the materials when comparing all groups as a whole. When comparing individual materials to each other there was statistical differences among some of the tested materials. Conclusion: The healing outcome after periapical surgery of a five-wall resection defect could not be increased by infill with autogenous bone or bone graft substitutes. The most important factor for the healing outcome in periapical surgery is the quality of the root-end sealing. The healing outcome after some of the tested bone substitutes, might be improved by longer healing time.

Analysis of Autogenous Laser Welding in Low Carbon and Large Thickness Steel

With the use of laser welding,it is possible to join different steel,with different thicknesses,with or without the action of protective layers.The quality of laser radiation makes it possible to get certain characteristics that are impossible to get by other processes,such as high welding speeds,less metallurgical effects suffered by the heat-affected zone(ZAC),and this process also does not require filler metal,therefore it is free from possible contamination.Combined with traditional welding methods,laser welding produces narrower weld beads,allowing for better prevention of corrosion and thermal distortions.Although the process already has high industrial knowledge,some random defects,such as porosities and inconsistencies,are still found.This work presents a systematic study to determine the influence of laser welding parameters and how these parameters influence welding defects.For this,the experimental part was carried out in the welding laboratory-LABSOLDA,of the Federal University of Santa Catarina-UFSC,during the laser welding processes,a welding speed of 2.4 m/min was reached.For this experiment,argon was used as a shielding gas and 1020 steel was used as the base material.

Artfaroplasty with transplantation of autogenous rib perichondrium for reconstruction of metacarpophalangeal joint

Objective To evluate the outcome of arthropiasty with transplantation of autogenous rib perichondrium for reconstruction of the metacarpophalangeal joint. Methods From 1982 to 2000,15 patients undergoing arthropiasty with autogenous rib perichondrium were analyzed retrospectively. The pain, range of motion and stability of the joint was assessed. Results Thirteen patients were followed up with 2 in loss. The average follow-up was 4 years. The pain at the metacarpophalangeal joint disappeared after operation. The active range of motion in metacarpophalangeal joint was 40° -82°(average 58. 5°), with an average increase of 46°(35°-58°) when compared with those before operation. The patients all went to the original job. Conclusion The arthropiasty with autogenous rib perichondrium transplantation is an efficient and practical method for reconstruction of the metaracrpophalangeal joint. 5 refs.

Application of autogenous nasal septal cartilage in the plasty of nasal tip and columella

Objective To evaluate the effect of anlogenous septal cartilage in repair of nasal tip and columella. Methods Nasal septal cartilage was transplanted between medial angles of greater alar cartilage at the nasal columella as a support,and a scutellate cartilage was transplanted to the nasal tip. Results All 108 cases were followed up for 1 ～ 2 years,they were satisfied with

Autogenous healing mechanism of cement-based materials

Autogenous self-healing is the innate and fundamental repair capability of cement-based materials for healing cracks.Many researchers have investigated factors that influence autogenous healing.However,systematic research on the autogenous healing mechanism of cement-based materials is lacking.The healing process mainly involves a chemical process,including further hydration of unhydrated cement and carbonation of calcium oxide and calcium hydroxide.Hence,the autogenous healing process is influenced by the material constituents of the cement composite and the ambient environment.In this study,different factors influencing the healing process of cement-based materials were investigated.Scanning electron microscopy and optical microscopy were used to examine the autogenous healing mechanism,and the maximum healing capacity was assessed.Furthermore,detailed theoretical analysis and quantitative detection of autogenous healing were conducted.This study provides a valuable reference for developing an improved healing technique for cement-based composites.