Early age cracking and capillary pressure controlled concrete curing

2009 ◽  
pp. 229-234 ◽  
Author(s):  
V Slowik ◽  
M Schmidt
Keyword(s):  
Capillary Pressure ◽  
Early Age ◽  
Pressure Controlled

The Effects of Water-Reducer on Early-Age Plastic Shrinkage of Concrete

2012 ◽  
Vol 174-177 ◽  
pp. 1113-1118
Author(s):  
Hong Gen Qin ◽  
Zhi Hua Fei ◽  
Wei Guo ◽  
Qian Tian
Keyword(s):  
Capillary Pressure ◽  
Evaporation Rate ◽  
Mechanical Performance ◽  
Important Influence ◽  
Early Age ◽  
Cracking Resistance ◽  
Plastic Shrinkage ◽  
Effect Of Water ◽  
Better Than

Water-reducer is one of the dispensable components in modern concrete, can improve the workability and mechanical performance of concrete, and also has an important influence on the plastic cracking resistance of concrete. In this paper, the flat cracking test was used to evaluate the effect of water reducer on the plastic cracking resistance of concrete, meanwhile, capillary pressure; plastic settlement and evaporation rate were also tested. The results showed that water-reducer could improve the plastic cracking resistance of concrete significantly, and the effectiveness of polycarboxylate water reducer were o better than that of wood calcium and naphthalene water reducer.

scholarly journals Modeling of Capillary Shrinkage and Cracking in Early-Age Concrete

2018 ◽  
Vol 17 (4) ◽  
pp. 265-277 ◽  
Author(s):  
S. N. Leonovich
Keyword(s):  
Crack Resistance ◽  
Capillary Pressure ◽  
Calculation Method ◽  
Critical Concentration ◽  
Level Structure ◽  
Critical Values ◽  
Cement Stone ◽  
Early Age ◽  
External Temperature ◽  
Concrete Crack

. Scientific hypothesis on moistening shrinkage mechanism for cement stone and concrete has been assumed as a basis for the present paper. Physical ideas on a mechanism for cracks volume increment in a concrete model presented as two-level structure have been accepted as a theoretical basis for a calculation method of crack resistance during capillary shrinkage. These ideas are the following: a matrix of hardening cement stone with inclusions and emptiness of various forms (cracks) as result of influences that change an intense deformed state in a point and a volume. The following assumptions have been accepted while making a theoretical justification for a calculation method of shrinkable concrete crack resistance. Following this methodology approaches of fracture mechanics according to a generalized criterion have been applied in the paper. Concrete is considered as an elastic quasi-homogeneous two-component medium which consists of the following parts:a) constructive part: a matrix – a cement stone with structural elements of crushed stone, sand; b) destructive part: emptiness – capillaries cracks and pores (cavities with initial cracks in walls). Emptiness in a matrix and contact zones are presented by a coordinated five-level system in the form and sizes which are multiple to a diameter due to impacts while reaching critical sizes. These critical sizes make it possible to pass from one level into another one according to the following scheme: size stabilization – accumulation delocalization – critical concentration in single volume – transition to the following level. Process of cracks formation and their growth are considered as a result of non-power influences on the basis of crack theory principles from a condition that fields of deformation and tension creating schemes of a normal separation and shift occur in the top part of each crack at its level in the initial concrete volume. Ксij(t) parameter as algebraic amount of critical values Kij in the whole system of all levels of cracks filling canonical volume up to critical concentration has been accepted as a generalized constant of property for concrete crack resistance in time, its resistance to formation, accumulation in volumes of micro-cracks and formation of trunk cracks with critical values. External temperature, moistening long influences create fields of tension in the top parts of cracks. Concrete destruction processes due to cracks are considered as generalized deformedintensed state in some initial volume having physical features which are inherent to a composite with strength and deformative properties. It is possible to realize analytical calculations for assessment of tension and crack resistance of concrete at early age on the basis of a generalized criterion in terms of stress intensity factor due to modern experimental data on capillary pressure value (70 kPa in 180 min after concrete placing). The developed algorithm of calculation allows to consider factors influencing on capillary pressure: type of cement, modifiers and mineral additives, concrete curing conditions.

A Community Based High Risk Register for Hearing Loss

1982 ◽  
Vol 47 (4) ◽  
pp. 373-375 ◽  
Author(s):  
James L. Fitch ◽  
Thomas F. Williams ◽  
Josephine E. Etienne
Keyword(s):  
Hearing Loss ◽  
System Identification ◽  
High Risk ◽  
Language Learning ◽  
Education Program ◽  
Communication System ◽  
Auditory Signal ◽  
Early Age ◽  
Community Based ◽  
Children With Hearing Loss

The critical need to identify children with hearing loss and provide treatment at the earliest possible age has become increasingly apparent in recent years (Northern & Downs, 1978). Reduction of the auditory signal during the critical language-learning period can severely limit the child's potential for developing a complete, effective communication system. Identification and treatment of children having handicapping conditions at an early age has gained impetus through the Handicapped Children's Early Education Program (HCEEP) projects funded by the Bureau of Education for the Handicapped (BEH).

Correlation of Data Obtained by Radiocardiography and Right-Heart Catheterization in Cardiac Patients

1968 ◽  
Vol 07 (02) ◽  
pp. 125-129
Author(s):  
J. Měštan ◽  
V. Aschenbrenner ◽  
A. Michaljanič
Keyword(s):  
Capillary Pressure ◽  
Transit Time ◽  
Right Heart Catheterization ◽  
Heart Catheterization ◽  
Right Heart ◽  
Pulmonary Capillary ◽  
Filling Time ◽  
Pulmonary Capillary Pressure ◽  
The Mean ◽  
Pulmonary Transit Time

SummaryIn patients with acquired and congenital valvular heart disease correlations of the parameters of the radiocardiographic curve (filling time of the right heart, minimal pulmonary transit time, peak-to-peak pulmonary transit time, and the so-called filling time of the left heart) with the mean pulmonary artery pressure and the mean pulmonary “capillary” pressure were studied. Further, a regression equation was determined by means of which the mean pulmonary “capillary” pressure can be predicted.

The Physician’s Task and the Problem of Documentation

1964 ◽  
Vol 03 (01) ◽  
pp. 11-19 ◽  
Author(s):  
A. Proppe
Keyword(s):  
Statistical Evaluation ◽  
Age Groups ◽  
Diagnostic Methods ◽  
Early Age ◽  
Case Histories ◽  
Lupus Vulgaris ◽  
Pathological Conditions ◽  
Clinical Methods ◽  
Corpus Hippocraticum ◽  
High Degree

SummaryCase histories suitable for statistical evaluation can be found even as far back as in the Corpus Hippocraticum. Such simple data as the patient’s age, body weight, size, the date of menarche, etc. are practically always included in the case records, and it is demonstrated that, when such data are recorded in a system of documentation suitable for mechanical sorting, it may enable us to draw conclusions of very great importance. Mechanical registration methods have revealed that, in the determination and recording of data as hitherto carried out. there has been a surprisingly large number of errors and a high degree of unreliability. This view has a considerable influence on modern clinical methods; it renders a more democratic relation between physician and patient necessary and makes clear the need for measures to enhance the reliability of diagnosis and treatment of pathological conditions. The author illustrates this view with reference to the mechanical falsification of the thesis of the proneness of early age groups to lupus vulgaris, furthermore with reference to the mechanical rationalization of modern routine diagnostic methods, to the constant surveillance of adverse effects on public health and to the protection against allergic reactions with the aid of recording systems of personal allergy and intolerance data with mechanical sorting and computer techniques.

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