scholarly journals Residual Capability of Alkali Binding by Hydrated Pozzolanic Cements in Long-Service Concrete Structures

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Mario Berra ◽  
Teresa Mangialardi ◽  
Antonio Evangelista Paolini
Keyword(s):  
Concrete Structures ◽  
Test Results ◽  
Cement Pastes ◽  
Experimental Procedure ◽  
Accelerated Curing ◽  
Alkali Aggregate Reaction ◽  
Simple Mass ◽  
Pore Liquid ◽  
Pozzolanic Cement

An experimental procedure was developed and applied to cement pastes made with two different pozzolanic cements (CEM IV/B (P) and CEM IV/B (V)) in order to ascertain the existence of a residual capability of alkali binding by long-term hydrated pozzolanic cements and, at the same time, to evaluate the alkali retention capability and the concentration of OH− ions in the pore solution of such cementitious matrices. The developed procedure consisted of accelerated curing of cement paste specimens (150 days at 60°C and 100% RH), subsequent leaching tests at 60°C for 30 days by using deionized water or basic solutions (NaOH or KOH at different concentrations) as leaching media, and correlation of the leaching test results with a simple mass balance equation for sodium and potassium ions. The developed procedure was found to be appropriate for evaluating both the pore liquid alkalinity and the alkali retention capability by long-term hydrated pozzolanic cement pastes. A residual capability of alkali binding was also identified for both tested pozzolanic cements, thus indicating their potential ability to prevent (CEM IV/B (V)) or minimize (CEM IV/B (P)) the risk of deleterious expansion associated with alkali-aggregate reaction in long-service concrete structures, like concrete dams.

scholarly journals Experimental Investigation for Tensile Performance of GFRP-Steel Hybridized Rebar

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Dong-Woo Seo ◽  
Ki-Tae Park ◽  
Young-Jun You ◽  
Sang-Yoon Lee
Keyword(s):  
Elastic Modulus ◽  
Concrete Structures ◽  
Tensile Tests ◽  
Test Results ◽  
Building Technology ◽  
Gfrp Bars ◽  
Low Elastic Modulus ◽  
Tensile Performance ◽  
The Individual

Tensile performance of the recently developed “FRP Hybrid Bar” at Korea Institute of Civil Engineering and Building Technology (KICT) is experimentally evaluated by the authors. FRP Hybrid Bar is introduced to overcome the low elastic modulus of the existing GFRP bars to be used as a structural member in reinforced concrete structures. The concept of material hybridization is applied to increase elastic modulus of GFRP bars by using steel. This hybridized GFRP bar can be used in concrete structures as a flexural reinforcement with a sufficient level of elastic modulus. In order to verify the effect of material hybridization on tensile properties, tensile tests are conducted. The test results for both FRP Hybrid Bar and the existing GFRP bars are compared. The results indicate that the elastic modulus of FRP Hybrid Bar can be enhanced by up to approximately 250 percent by the material hybridization with a sufficient tensile strength. To ensure the long-term durability of FRP Hybrid Bar to corrosion resistance, the individual and combined effects of environmental conditions on FRP Hybrid Bar itself as well as on the interface between rebar and concrete are currently under investigation.

Parents' long-term adjustment to the genetic test results of minors at risk for Long QT Syndrome

2004 ◽  
Author(s):  
K. S. W. H. Hendriks ◽  
F. J. M. Grosfeld ◽  
A. A. M. Wilde ◽  
J. van den Bout ◽  
I. M. van Langen ◽  
...  
Keyword(s):  
At Risk ◽  
Long Qt Syndrome ◽  
Genetic Test ◽  
Test Results ◽  
Long Qt ◽  
Genetic Test Results ◽  
Qt Syndrome

Improvement Of Curvilinear Diagrams Of Concrete Deformation

2019 ◽  
pp. 99-104
Keyword(s):  
Reinforced Concrete ◽  
Peak Load ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Deformation Model ◽  
Reinforced Concrete Structures ◽  
Significant Difference ◽  
Deformation Diagrams

Problems when calculating reinforced concrete structures based on the concrete deformation under compression diagram, which is presented both in Russian and foreign regulatory documents on the design of concrete and reinforced concrete structures are considered. The correctness of their compliance for all classes of concrete remains very approximate, especially a significant difference occurs when using Euronorm due to the different shape and sizes of the samples. At present, there are no methodical recommendations for determining the ultimate relative deformations of concrete under axial compression and the construction of curvilinear deformation diagrams, which leads to limited experimental data and, as a result, does not make it possible to enter more detailed ultimate strain values into domestic standards. The results of experimental studies to determine the ultimate relative deformations of concrete under compression for different classes of concrete, which allowed to make analytical dependences for the evaluation of the ultimate relative deformations and description of curvilinear deformation diagrams, are presented. The article discusses various options for using the deformation model to assess the stress-strain state of the structure, it is concluded that it is necessary to use not only the finite values of the ultimate deformations, but also their intermediate values. This requires reliable diagrams "s–e” for all classes of concrete. The difficulties of measuring deformations in concrete subjected to peak load, corresponding to the prismatic strength, as well as main cracks that appeared under conditions of long-term step loading are highlighted. Variants of more accurate measurements are proposed. Development and implementation of the new standard GOST "Concretes. Methods for determination of complete diagrams" on the basis of the developed method for obtaining complete diagrams of concrete deformation under compression for the evaluation of ultimate deformability of concrete under compression are necessary.

The Implementation Of Make A-Match Model In Social Science Learning To Improve Student Learning Outcomes In Class IV SDN 115 Manado

2019 ◽  
Vol Volume 2 Nomor 2 ◽  
Keyword(s):  
Social Science ◽  
Learning Outcomes ◽  
Teaching And Learning ◽  
Science Learning ◽  
Design Activity ◽  
Test Results ◽  
Match Model ◽  
Fourth Grade Students ◽  
Improve Student Learning

There is a tendency in the education field today to return to the idea that children will learn better if the environment is created naturally. Learning will be more meaningful if children "experience" themselves what they are learning, not 'knowing' it. Target-oriented learning of material mastery proves to be successful in short-term 'remembering' competitions, but fails to equip children to solve problems in long-term life. The problems that would to be studied in this study are: (a) how is the improvement of Social Science learning outcomes by applying the Make A-Match Model to it? (b) how does the Make A-Match Model apply towards the learning motivation? The objectives of this study are: (a) want to know the improvement in Social Science learning achievement after the implemetation of the Make A-Match Model. (b) want to know the effect of Make A-Match Model towards students’ motivation of the subject after it is applied. This research is used two rounds of action research. In each round consists of four stages, namely: design, activity and observation, reflection and revision. The target of this research is the fourth grade students of Mongodow. The data obtained in the form of formative test results, observation sheets of teaching and learning activities. From the results of analysts obtained student achievement has increased from cycle I to cycle II namely, cycle I (65%), cycle II (83%). The conclusion of this research is the Make A-Match Model of Social Science learning could positively influence the motivation of learning of central students, and this learning model could be used as an alternative to Social Science learning.

Long Term Field Test Results of Experimental EPDM and PUF Roofing

1990 ◽  
Author(s):  
David M. Bailey ◽  
Stuart D. Foltz ◽  
Myer J. Rosenfield
Keyword(s):  
Field Test ◽  
Test Results ◽  
Term Field

scholarly journals Certification tests of a protective device such as ROPS to ensure safe usage of tractors

2018 ◽  
Vol 224 ◽  
pp. 02061
Author(s):  
Irina Troyanovskaya ◽  
Anton Kalugin
Keyword(s):  
Strain Curve ◽  
Protective Device ◽  
Test Results ◽  
Experimental Procedure ◽  
Structure Deformation ◽  
Safety Requirements ◽  
Performance Check ◽  
Protective Structures ◽  
Full Scale Tests ◽  
Tractor Plant

According to the safety requirements, all protective devices of tractor units are subject to obligatory certification. One of the main means of protecting the operator during overturning is ROPS system. In accordance with GOST (National State Standard), a performance check of ROPS protective structures is carried out on basis of full-scale tests. The purpose of the presented study is to develop the experimental procedure and to obtain the performance check result of ROPS protective device of the tractor unit’s cabin using B10 bulldozer manufactured by the Chelyabinsk Tractor Plant as an example. The tests were carried out at the Ural Test Center NATI. For this purpose, a special bedplate was used, allowing to test the protective cabins of tractors with the total mass of up to 110 tons. The hydraulic system of the bedplate allowed to carry out the process of lateral loading of ROPS step by step, where each step corresponded to the 10 mm structure deformation. The applied load and structure deformation were recorded at each step. The energy accumulated by the structure was calculated as the area under the stress-strain curve. The energy U = 40867 J, which was required according to GOST, was accumulated during lateral deformation Δ = 270 mm. The force constituted Fy = 243 kN. After removing the lateral load, the structure was subjected to the vertical static and longitudinal loading. During the whole experiment of ROPS protective device, repairs, deformation corrections and adjustments were not allowed. The test results of ROPS structure of B10 bulldozer cabin showed compliance with the GOST safety requirements. During ROPS deformation, penetration of the protective structure elements into the driver’s limited zone was not observed.

Influence of Alkalinity and Ambient Temperature on Long-Term Properties of GFRP Reinforcement

2018 ◽  
Vol 760 ◽  
pp. 213-218
Author(s):  
František Girgle ◽  
Lenka Bodnárová ◽  
Ondřej Januš ◽  
Vojtěch Kostiha
Keyword(s):  
Tensile Strength ◽  
Ambient Temperature ◽  
Mechanical Characteristics ◽  
Current Problem ◽  
Concrete Structures ◽  
Experimental Program ◽  
Glass Fibres ◽  
Metallic Reinforcement ◽  
Gfrp Reinforcement

The article deals with the current problem of determining long-term reliability of non-metallic reinforcement in concrete structures. The alkaline environment of concrete with a pH higher than 12.0 affects the glass fibres degradative, whereas this degradation presents by reduction of their mechanical characteristics, resulting in a decrease in the tensile strength of the whole composite. The article summarizes the results of the ongoing experimental program so far, which aims to quantify this influence.

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