scholarly journals Development of a Novel Concrete Curing Method Using Induction Heating System

2020 ◽  
Vol 11 (1) ◽  
pp. 236
Author(s):  
Chi-Hyung Ahn ◽  
Jinbok Lee ◽  
Dong-Jin Kim ◽  
Hyun-Oh Shin
Keyword(s):  
Induction Heating ◽  
Cold Weather ◽  
Maximum Temperature ◽  
Strength Development ◽  
Test Results ◽  
Compression Tests ◽  
Cross Sectional ◽  
Heating Efficiency ◽  
Cross Sectional Dimension ◽  
Curing Method

This study aimed to develop an accelerated concrete curing method based on induction heating (IH) technology. The proposed curing method provides improved heating efficiency and safety since it directly heats only the metallic forms in a non-contacting manner. It also has the advantage of being capable of heating the concrete according to a desirable heating scenario. The effects of several parameters on its performance were evaluated using a finite element method (FEM)-based thermal analysis and heating performance tests. The FEM analysis revealed the steel form to be appropriate for the IH system. The analysis also revealed that equally spaced three-turn coils yielded increased temperature uniformity in the steel form, which was verified by results of the steel form heating experiments. Furthermore, the minimum temperature generated in the form was sufficient for concrete curing. The efficiency of the use of IH for concrete curing and the effects of curing parameters were further investigated through compression tests after applications of various curing methods and by examining the temperature distributions during curing. The test results revealed early strength development even under water freezing conditions. This demonstrated the effectiveness of IH for concrete curing in cold weather. However, the efficiency decreased when the cross-sectional dimension of the specimen increased. The test results also verified that the maximum temperature and duration of induction heat curing affect the early age strength of concrete.

Ultra-High-Strength Concrete-Filled FRP Tubes: Compression Tests on Square and Rectangular Columns

2013 ◽  
Vol 575-576 ◽  
pp. 239-244 ◽  
Author(s):  
Togay Ozbakkloglu
Keyword(s):  
Aspect Ratio ◽  
High Strength Concrete ◽  
High Strength ◽  
Experimental Program ◽  
Test Results ◽  
Compression Tests ◽  
Cross Sectional ◽  
Strength Concrete ◽  
Corner Radius ◽  
Frp Tubes

This paper presents the partial results of an experimental program undertaken to investigate the behavior of square and rectangular ultra-high-strength concrete (UHSC)-filled fiber reinforced polymer (FRP) tubes (UHSCFFTs) under axial compression. The effects of the amount of confinement, cross-sectional aspect ratio and corner radius were investigated experimentally through the tests of 24 concrete-filled FRP tubes (CFFTs) that were manufactured using unidirectional carbon fiber sheets and UHSC with 108 MPa average compressive strength. Test results indicate that sufficiently confined square and rectangular UHSCFFTs can exhibit highly ductile behavior. The results also indicate that HSCFFTs having tubes of low confinement effectiveness may experience a significant strength loss at the point of transition on their stress-strain curves. Examination of the test results have led to a number of important observations on the influence of corner radius and sectional aspect ratio, which are presented and discussed in the paper.

scholarly journals The Effects of Steam-Curing on the Properties of Concrete

2021 ◽  
Vol 11 (2) ◽  
pp. 6974-6978
Author(s):  
M. Boukendakdji ◽  
M. Touahmia ◽  
B. Achour ◽  
G. Albaqawy ◽  
M. H. H. Abdelhafez ◽  
...  
Keyword(s):  
Construction Material ◽  
Strain Curve ◽  
Maximum Temperature ◽  
Test Results ◽  
Heating Period ◽  
Steam Curing ◽  
Flexural Tensile Strength ◽  
Compressive Strength Test ◽  
Concrete Maturity ◽  
Curing Method

Worldwide, concrete is the most preferred construction material. The steam curing method is favored when there is a need for accelerating strength. This paper presents the study of the compressive and flexural tensile strength of concrete subjected to eight different steam cures. In addition, the stress-strain curve and the modulus of elasticity were determined at the age of 28 days. The compressive strength test results show that after treatment, strength increases with concrete maturity. A cycle with a pre-heating period gives better results than a cycle without a pre-heating period. The longer the duration of the maximum temperature period, the lower the strength drop compared to the control concrete. The best results were obtained for concrete treated according to the following cycle: a 3-hour pre-heating period at 20oC, a 2-hour increase of temperature from 20 to 70oC, and a 3 hour of maximum temperature of 70oC.

scholarly journals Heat Curing Performance of Cold-Weather Concrete using Induction Heating Technology

2020 ◽  
Vol 20 (6) ◽  
pp. 23-30
Author(s):  
Jinbok Lee ◽  
Kyeongtack Kim ◽  
Jinsoo Choi ◽  
Chi-Hyung Ahn ◽  
Hyun-Oh Shin
Keyword(s):  
Cross Section ◽  
Induction Heating ◽  
Electromagnetic Compatibility ◽  
Cold Weather ◽  
Magnetic Flux Density ◽  
Heating Process ◽  
Test Results ◽  
Concrete Mixtures ◽  
Heat Curing ◽  
Heating Technology

In this study, we evaluated the heat curing performance of cold-weather concrete using the induction heating technology. Specifically, we studied the effects of the size and shape of steel forms as well as different concrete mixtures on the heat curing performance. The test results showed that increasing the cross-section of concrete reduced the homogeneity of temperature distribution throughout it. This problem can be compensated for by adding more conductive materials in the concrete cross-section. The concrete specimens that were cured using induction heating achieved a satisfactory early age strength even though they were stored in a 0 °C low-temperature chamber. Furthermore, we evaluated the electromagnetic compatibility (EMC) of the induction heating process and the magnetic flux density of 13.9 µT thus obtained satisfied the EMC requirement.

scholarly journals Modeling Uniaxial Bond Stress–Slip Behavior of Reinforcing Bars Embedded in Concrete with Different Strengths

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 783
Author(s):  
Chao-Wei Tang
Keyword(s):  
Compressive Strength ◽  
Bond Stress ◽  
Constitutive Relationship ◽  
Central Position ◽  
Test Results ◽  
Reinforcing Bars ◽  
Cross Sectional ◽  
Reinforcing Bar ◽  
Cross Sectional Dimension ◽  
Center Section

This paper aims to study the uniaxial bond stress–slip characteristics of reinforcing bars embedded in concrete with different strengths. Tests were conducted on tension–pull specimens that had a cross-sectional dimension with a reinforcing bar embedded in the center section. The experimental variable was the concrete compressive strength (20, 40, and 60 MPa). The test results show that in the specimen subjected to any fixed load, the maximum value of the concrete strain occurred around the central position, and its value increased as the compressive strength of the concrete increased. Depending on the embedded position of the steel bars, the bond stress–slip relationship was also different. In addition, the analytical results indicate that the proposed bond stress–slip constitutive relationship is very accurate in describing the true bond stress–slip relationship.

Confinement Effectiveness of CFRP in Axial Members under Various Loading Conditions

2013 ◽  
Vol 747 ◽  
pp. 277-281
Author(s):  
Barış Erdil ◽  
Uğurhan Akyüz ◽  
İsmail Özgür Yaman
Keyword(s):  
Experimental Data ◽  
Stress Level ◽  
Concrete Strength ◽  
Concrete Columns ◽  
Extensive Literature ◽  
Test Results ◽  
Cross Sectional ◽  
Corner Radius ◽  
Cross Sectional Dimension ◽  
Frp Confinement

In this study, parameters affecting the mechanical properties of FRP-confined cylindrical and prismatic concrete columns were studied via experimental data, which were collected after an extensive literature review. The parameters were summarized as unconfined concrete strength, FRP thickness, cylinder diameter, overlap length of FRP, sustained stress level, heating-cooling effect and corner radius in prismatic specimens. Considering these parameters the confinement effectiveness is established analytically in the light of ultimate strength values obtained from the test results available in the literature. No steel reinforcement is taken into account because the main aim is to capture the behavior of FRP-confinement only. The analytical results revealed that unconfined concrete strength, FRP thickness, cross-sectional dimension of the specimen are the main parameters controlling the confinement effectiveness in cylindrical specimens. In addition to these parameters corner radius and sustained stress level are found to be significant in prismatic specimens.

scholarly journals Strength Characteristics of Glass Fiber Reinforced Concrete (GFRC) using Calcium Chloride Integral Curing Method

2019 ◽  
Vol 8 (2S11) ◽  
pp. 3040-3044
Keyword(s):  
Compressive Strength ◽  
Glass Fiber ◽  
Calcium Chloride ◽  
Glass Fibers ◽  
Concrete Surface ◽  
Fiber Reinforced Concrete ◽  
Cold Weather ◽  
Test Results ◽  
Glass Fiber Reinforced ◽  
Curing Method

Concrete is weak in tension and strong in compression. The inclusions of fibers in concrete significantly improves its compressive as well as tensile strength. The use of different types of fibers have shown positive responses among the researchers. It has long been known that curing concrete during cold weather can result in an inferior product with substandard properties. Curing also takes much longer, adding to job costs and extending the time before the concrete surface can be used. There are many accelerators available in the market, but Calcium Chloride continues to be one of the most preferred one. In this study, Alkali resistant glass fibers (0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5% and 4%) were used in the concrete M30 mix. The optimum glass fiber percentage that can be added to the concrete is found by comparing both tensile and compressive strength of the GFRC. Trial mixes of normal M30 concrete by adding different percentages of Calcium Chloride (0%, 0.5%, 1%, 1.5%, 2%, and 2.5%) as curing agent is also prepared. The optimum percentage of calcium chloride that can be added to the concrete is found by comparing the compressive strength of the con- crete. The compressive strength of the GFRC using calcium chloride integral cur- ing is found after 7, 14 and 28 days. The test results are then compared with GFRC using normal curing.

FAKTOR PERSONAL YANG BERHUBUNGAN DENGAN KOMITMEN ORGANISASI PERAWAT RSUD EMBUNG FATIMAH BATAM

2020 ◽  
Vol 5 (3) ◽  
pp. 875
Author(s):  
Asfri Sri Rahmadeni
Keyword(s):  
Organizational Commitment ◽  
Turnover Rate ◽  
Sampling Technique ◽  
Hospital Nurses ◽  
Test Results ◽  
Personal Factors ◽  
High Turnover ◽  
Chi Square ◽  
Cross Sectional ◽  
Chi Square Test

<p class="Normal1"><em>Commitment is the attitude or behavior of likes or dislikes shown by someone against the organization at work. Indonesia is recorded as a nurse who has a low organizational commitment (76%) so it harms services. This phenomenon in the hospital can be seen from the indicator of the high turnover rate of nurses which reaches 30.9% which exceeds the standard &lt;5%. Many factors affect organizational commitment. The purpose of this study was to analyze the Personal Factors Associated with Organizational Commitment of Hospital Nurses. This study is a cross-sectional analytic study and purposive sampling technique with a sample of 59 nurses. Chi-Square test results obtained personal factors that have a relationship with organizational commitment Nurse Hospital is age with p = 0,000 and education with p = 0,000, personal factors not related to organizational commitment are gender p = 1,053 and years of service with p = 1,147. Hospitals should conduct research/surveys on Organizational Commitment periodically as an evaluation material in the context of the organization's development and development in the future</em>.</p>

Faktor yang Berhubungan dengan Penggunaan Partograf dalam Persalinan oleh Bidan Praktik Mandiri

2020 ◽  
Vol 2 (2) ◽  
pp. 72-80
Author(s):  
Niluh Nita Silfia
Keyword(s):  
Total Population ◽  
Sampling Technique ◽  
Population Data ◽  
Statistical Test ◽  
Influential Factor ◽  
Test Results ◽  
Cross Sectional ◽  
Factors Associated ◽  
Survey Results ◽  
Research Criteria

Partographs are guidelines for childbirth observations that will facilitate labor assistants in first identifying emergency cases and complications for mothers and fetuses. Preliminary survey at the Sigi Community Health Sub-Center (Pustu) of the 8 Pustu midwives found two midwives (25%) to complete a complete partograph, six midwives (75%) incomplete. The purpose of this study was to determine the determinant factors associated with the use of partographs in labor. The design of this study used observational analytic methods with a cross-sectional approach. 24 BPM survey results were obtained with 30 samples of midwives who met the research criteria and data completeness. The sampling technique was by the total population. Data analysis used logistic regression. The multivariate analysis results showed that APN training was the most influential factor in the use of partographs in labor by midwives. Statistical test results obtained a POR value of 37.7 (95% CI 12.1 - 60.2). This study suggests that midwives must have APN certificates to be valid in providing services.

HUBUNGAN UMUR DAN PARITAS DENGAN PEMILIHAN ALAT KONTRASEPSI METODE OPERASI WANITA (MOW) DI POLIKLINIK KEBIDANAN RS BHAYANGKARA PALEMBANG TAHUN 2012

2019 ◽  
Vol 3 (2) ◽  
Author(s):  
Y. Widyastuti Y. Widyastuti
Keyword(s):  
Family Planning ◽  
Medical Records ◽  
Test Results ◽  
Family Planning Services ◽  
Chi Square ◽  
Cross Sectional ◽  
Planning Methods ◽  
Chi Square Test ◽  
Family Planning Methods ◽  
Selection Of

  ABSTRACT [In advanced countries the number of permanent contraception option ( kontap ) approximately 10 % of all national family planning methods , while in Indonesia reached approximately 5.7 % . Based on data obtained from medical records Bhayangkara Hospital Palembang in 2010 the number of achievement when seen from the percentage of contraceptive use is only 9.10 % The purpose of this study is known age and parity relationship with the selection of contraceptive methods Surgery Women ( MOW ) in Palembang RS.Bhayangkara obstetrics clinic in 2012 . This study uses the analytic survey with cross sectional approach . The population in this study were women who become new acceptors were recorded in medical records at the hospital . Palembang Bhayangkara Hospitals January 1, 2012 to December 31 in 2012 . The sample in this study is part of a whole number of new acceptors ( either using contraception methods MOW and other family planning methods ) were registered in the hospital . Palembang Police Hospitals of January 1, 2012 to December 31 years of data 2012.Analisa univariate and bivariate statistical Chi - Square test with significance level α = 0.05 . The results showed there were 80 respondents ( 46.3 % ) who became MOW contraceptive acceptors , acceptors who have old age by 45 respondents ( 56.3 % ) and who has a young age by 35 respondents ( 43.8 % ) . acceptors which have high parity were 44 respondents ( 55 % ) who had low parity and a total of 36 respondents ( 45 % ) . From the results of Chi-square test value obtained ρ = 0.00 is smaller than α = 0.05 . There is a significant correlation between age and the selection of MOW Chi square test results obtained ρ value = 0.00 and there was a significant association between parity with the election MOW Chi square test results obtained ρ value = 0 , . From these results , it is expected to power health, especially family planning services at the hospital . Palembang Police Hospitals in order to improve the quality of family planning services in an effective, efficient , and safe are considered particularly suitable for users of contraception OperatingMethodWomen(MOW).                                      ABSTRAK Di negara sudah maju jumlah pilihan kontrasepsi mantap (kontap) sekitar 10% dari semua metode KB nasional, sedangkan di Indonesia baru mencapai sekitar 5,7 %. Berdasarkan data yang diperoleh dari Rekam medik  Rumah Sakit Bhayangkara Palembang tahun 2010 Jumlah pencapain tersebut jika dilihat dari persentasi penggunaan kontrasepsi MOW hanya  9,10% Tujuan penelitian ini adalah diketahuinya hubungan umur dan paritas dengan pemilihan alat kontrasepsi Metode Operasi Wanita (MOW) di poliklinik kebidanan RS.Bhayangkara Palembang Tahun 2012. Penelitian ini menggunakan metode survey analitik dengan pendekatan cross sectional. Populasi dalam penelitian ini adalah wanita yang menjadi akseptor KB Baru yang tercatat di rekam medik  di RS. Bhayangkara Palembang tanggal 1 januari 2012 sampai dengan 31 Desember  tahun 2012. Sampel dalam penelitian ini adalah sebagian dari seluruh jumlah akseptor KB Baru (baik yang menggunakan alat kontrasepsi Metode MOW maupun Metode KB lain) yang teregister di RS. Bhayangkara Palembang dari tanggal 1 januari 2012 sampai dengan 31 Desember  tahun 2012.Analisa data dilakukan secara univariat dan bivariat dengan uji statistik Chi-Square dengan tingkat kemaknaan α = 0,05. Hasil penelitian menunjukkan dari 80 responden terdapat (46,3%) yang menjadi akseptor kontrasepsi MOW, akseptor yang memiliki umur tua sebanyak 45 responden (56,3%) dan yang memiliki  umur muda sebanyak 35 responden (43,8%). akseptor yang memiliki paritas tinggi sebanyak 44 responden  (55%) dan yang memiliki  paritas rendah sebanyak 36 responden (45%). Dari hasil uji Chi square didapatkan ρ value = 0,00 lebih kecil dari α = 0,05. Ada hubungan yang bermakna antara umur dengan pemilihan MOW dari hasil uji Chi square didapatkan ρ value = 0,00 dan ada hubungan yang bermakna antara paritas dengan pemilihan MOW hasil uji Chi square didapatkan ρ value = 0,.Dari hasil penelitian ini, diharapkan kepada tenaga kesehatan khususnya pelayanan KB  di RS. Bhayangkara Palembang  agar dapat meningkatkan kualitas pelayanan KB secara efektif, efisien, dan aman yang dianggap cocok bagi penggunanya khususnya mengenai kontrasepsi Metode Operasi Wanita (MOW).    

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