scholarly journals The role of cover and rebar characteristics on load-slip behavior of reinforced concrete members in compression

2018 ◽  
Vol 162 ◽  
pp. 04017
Author(s):  
Tareq al-Attar ◽  
Qais Hassan ◽  
Sura Mejbel ◽  
Hussein Dawood
Keyword(s):  
Bond Strength ◽  
Research Work ◽  
Compressive Load ◽  
Concrete Block ◽  
Concrete Cover ◽  
Cross Sectional ◽  
Testing Procedures ◽  
Concrete Members ◽  
Significant Difference ◽  
Set Up

This paper describes a part of an extensive research work devoted to evaluate the bond strength between rebars and concrete through different testing procedures. Main parameters in this part are the concrete cover and rebar diameter. The tested specimen consisted of a single bar embedded in a concrete block with square cross-sectional area and is being tested under compressive load. Three concrete block sizes were cast to offer three different cover for the embedded rebars. The dimensions of these blocks were; 150×150×135, 100×100×135 and 200×200×185 mm. Three bar diameters, 12, 16 and 20 mm, were investigated. The specimens were water-cured and tested at the ages of 7 and 28 days. A new proposed test set-up was used to monitor the load-slip behavior of the specimens. The test results showed that there is no significant difference in bond energy between the two curing ages, 7 and 28 days. The concrete cover has a significant effect on the bond strength between rebar and concrete. By increasing the cover, the confinement offered by concrete increases, bond strength increases, and slip increases. Based on the present results, a concept of effective cover was developed. This concept showed a high correlation with the mode of failure for the tested specimens.

scholarly journals Acid Challenge on Push-Out Bond Strength of Three Different Tricalcium Silicate Cements: An In-vitro Study

2021 ◽  
pp. 72-79
Author(s):  
Mattapudi Basavaiah Babu ◽  
T. B. V. G. Raju ◽  
N. Mahendra Varma ◽  
Gowtam Dev Dondapati ◽  
Srivalli Podili ◽  
...  
Keyword(s):  
Bond Strength ◽  
Critical Role ◽  
Compressive Load ◽  
Clinical Importance ◽  
Filling Material ◽  
Significant Difference ◽  
The Impact ◽  
Push Out ◽  
Acid Challenge

Aim: To evaluate the impact of environmental pH on intra-radicular dentin push-out bond strengths of MTA, MTA HP, and Biodentine. Materials and Methodology: Freshly extracted human mandibular single-rooted premolars or maxillary anterior incisors that were either intact or contained only small carious lesions were selected.120 mid root dentins is horizontally divided into 1.0 mm thick slices and divided into 3 MTA, MTA HP, BIODENTINE groups. The compressive load is applied at a speed of 0.5 mm/min by exerting a downward pressure on the outer surface of MTA using a 1.00 mm diameter cylindrical stainless-steel plunger. Maximum load to MTA was reported in newtons at the time of dislodgement and converted to megapascals. The 1-way analysis of variance test was used to compare the push-out bond strength of the groups with the same storage time (4 or 34 days), followed by the pair-wise comparison of the Tukey post hoc test. The Student's t-test was used to evaluate 3-group means. At P = .005, the degree of significance was set. Thus the clinical importance of the present study states that considering several factors like microhardness, composition by products, particle sizes and the environmental pH plays a critical role in selection of root end filling material. Results: There was significant difference between groups (P = .001) after 4 days of PBS and Acid condition, where Bio dentine had significantly the highest bond strength. Conclusion: The strength of MTA HP, BIODENTINE, MTA materials at dentine interface increases over 30 days in the storage of PBS solution at pH 7.4, after an initial acid challenge by acetic acid of pH 5.4, which decreases initial bond strength.

scholarly journals Evaluation of bond strength of one step and two steps self-etch adhesive agents with two different pulp-capping materials

2020 ◽  
Vol 67 (2) ◽  
pp. 75-82
Author(s):  
Vasilka Rendzova ◽  
Sonja Apostolska ◽  
Emilija Kostadinovska ◽  
Maja Antanasova ◽  
Marina Eftimoska ◽  
...  
Keyword(s):  
Bond Strength ◽  
Calcium Silicate ◽  
Testing Machine ◽  
Pulp Capping ◽  
Dentin Adhesives ◽  
Significant Difference ◽  
One Step ◽  
Calcium Silicate Cements ◽  
Set Up ◽  
Self Etch

Primary purpose of restorative dentistry is to preserve pulp vitality. Besides calcium hydroxide, the application of calcium silicate cements as a material for direct pulp capping has become used recently. The aim of our study was to investigate the influence of materials for direct and indirect pulp capping on the bond strength of composite restorations using two different self etch dentin adhesives. The test was performed on 60 intact molars extracted for periodontal or orthodontic reasons. The prepared samples were divided into the two groups and three subgroups depending on the adhesive and pulp cupping material. Two different calcium silicate based materials were used for pulp cupping. One step and two steps self etch dentin adhesive was applied to prepared specimens depending on the group and with the help of a specially made metal mold set up a composite post. The share bond strength was assessed using a universal testing machine. The results showed significant difference in the share bond strength between the samples treated with TheraCal LC and Biodentine with TheraCal LC being superior to Biodentine.

scholarly journals Effect of sodium hypochlorite on the bond strength of an adhesive system to superficial and deep dentin

2003 ◽  
Vol 11 (3) ◽  
pp. 223-228 ◽  
Author(s):  
Ninoshka Uceda-Gómez ◽  
Alessandra Reis ◽  
Marcela Rocha de Oliveira Carrilho ◽  
Alessandro Dourado Loguercio ◽  
Leonardo Eloy Rodriguez Filho
Keyword(s):  
Bond Strength ◽  
Surface Treatment ◽  
Sodium Hypochlorite ◽  
Adhesive System ◽  
Acid Etching ◽  
Cross Sectional ◽  
Significant Difference ◽  
One Step ◽  
Bond Strengths ◽  
Main Factors

The objective of this study was to evaluate the bond strength to superficial (SU) and deep (D) dentin, accessed via apical (DA) or occlusal (DO), using One-Step adhesive system applied according to the manufacturer's instructions (C) or following deproteinization with 10% sodium hypochlorite (H) for 60s, after acid etching. Three sound extracted human molars were prepared for each experimental condition. Restorations were performed using Z100 in 2mm increments, each one being light-cured for 40s. Teeth were longitudinally sectioned to obtain stick-shaped specimens with a cross-sectional area of 0.8mm², which were submitted to bond strength test (0.6mm/min). Results obtained after statistical analysis using a two-way ANOVA (substrate vs. surface treatment) and Tukey's test were: SU (35.4 ± 12.3), DO (26.5 ± 8.5), DA (26.1 ± 10.2) following conventional surface treatment, and SU (28.82 ± 12.7), DO (24.3 ± 8.3) and DA (23.5 ± 8.5), after surface treatment using sodium hypochlorite. The interaction of the factors was not significant (p>0.05). However, the main factors were significant (p<0.05). Mean bond strength values in superficial dentin were statistically superior to deep dentin (p<0.05), although no statistically significant difference was observed between the two via of access to deep dentin (SU>DO=DA). The conventional surface treatment resulted in higher bond strength values than the sodium hypochlorite treatment (p<0.05). It was concluded: 1) bond strength values were higher in superficial dentin, 2) no difference was found between the two deep substrate preparations, and 3) the application of sodium hypochlorite following dentin acid etching may reduce bond strengths.

scholarly journals The role of surface treatments on the bond between acrylic denture base and teeth

2009 ◽  
Vol 20 (2) ◽  
pp. 156-161 ◽  
Author(s):  
Lauro Egídio Bragaglia ◽  
Luiz Henrique Maykot Prates ◽  
Maria Cristina Marino Calvo
Keyword(s):  
Bond Strength ◽  
Aluminum Oxide ◽  
Compressive Load ◽  
Base Material ◽  
Surface Treatments ◽  
Surface Grinding ◽  
Air Abrasion ◽  
Denture Base ◽  
Significant Difference ◽  
Abrasive Stone

The aim of this study was to compare the bond strength between acrylic denture base and teeth subjected to 6 surface treatments. Ninety-six specimens were made with poly(methylmethacrylate) teeth bonded to a microwave-polymerized acrylic denture base material. The specimens were distributed into 6 groups (n=16) according to surface treatments: CT - no treatment (control); MN - methylmethacrylate monomer etching; AO - 50-µm-particle aluminum oxide air abrasion; BR - glaze removal with a round bur; ST - surface grinding with an aluminum oxide abrasive stone; group CV - cavity preparation (diatorics). The control and surface-treated groups were subjected to a compressive load at 45º angle to the long axis of the teeth. Data were analyzed by one-way ANOVA, followed by Scheffé's test (p<0.05). Bond strength means and (SD) in kgf for groups were: CT: 18.19 (7.14), MN: 18.34 (5.28), AO: 23.82 (5.40), BR: 23.30 (4.79), ST: 25.39 (7.80) and CV: 17.48 (7.17). There was statistically significant difference (p=0.037997) only between ST and CV. In conclusion, ridge lap surface grinding with an aluminum oxide abrasive stone provided the highest bond strength, though it differed significantly only when compared to diatorics. The other surface treatments provided similar bond between the acrylic denture base and teeth.

Microtensile Bond Strength of Contemporary Adhesives to Primary Enamel and Dentin

2007 ◽  
Vol 32 (2) ◽  
pp. 127-132 ◽  
Author(s):  
Marcela Marquezan ◽  
Bruno Lopes da Silveira ◽  
Luizb Henrique Burnett Jr ◽  
Célia Regina Martins Delgado Rodrigues ◽  
Paulo Floriani Kramer
Keyword(s):  
Bond Strength ◽  
Primary Teeth ◽  
Tooth Enamel ◽  
Testing Machine ◽  
Primary Tooth ◽  
Single Bond ◽  
Adhesive Systems ◽  
Microtensile Bond Strength ◽  
Cross Sectional ◽  
Significant Difference

The purpose of this study was to assess bond strength of three self-etching and two total-etch adhesive systems bonded to primary tooth enamel and dentin. Materials and methods: Forty extracted primary human molars were selected and abraded in order to create flat buccal enamel and occlusal dentin surfaces. Teeth were assigned to one of the adhesive systems: Adper Scotch Bond Multi Purpose, Adper Single Bond 2,Adper Prompt L-Pop, Clearfil SE Bond and AdheSE. Imediately to adhesive aplication, a composite resin(Filtek Z250) block was built up. After 3 months of water storage, each sample was sequentially sectioned in order to obtain sticks with a square cross-sectional area of about 0.72 mm2. The specimens were fixed lengthways to a microtensile device and tested using a universal testing machine with a 50-N load cell at a crosshead speed of 0.5 mm/min. Microtensile bond strength values were recorded in MPa and compared by Analysis of Variance and the post hoc Tukey test (a=0.05). Results: In enamel, Clearfil SE Bond presented the highest values, followed by Adper Single Bond 2, AdheSE and Adper Scotch Bond Multi Purpose, without significant difference. The highest values in dentin were obtained with Adper Scotch Bond Multi Purpose and all other adhesives did not present significant different values from that, except Adper Prompt L-Pop that achieved the lowest bond strength in both substrates. Adper Scotch Bond Multi Purpose and Adper Single Bond 2 presented significantly lower values in enamel than in dentin although all other adhesives presented similar results in both substrates. Conclusions: contemporary adhesive systems present similar behaviors when bonded to primary teeth, with the exception of the one-step self-etching system; and selfetching systems can achieve bond strength values as good in enamel as in dentin of primary teeth.

Numerical Modeling of Reinforcement Corrosion on Bond Behaviour

2016 ◽  
Vol 249 ◽  
pp. 191-196
Author(s):  
Ivan Hollý ◽  
Juraj Bilčík ◽  
Katarína Gajdošová
Keyword(s):  
Bond Strength ◽  
Steel Corrosion ◽  
3D Models ◽  
Concrete Cover ◽  
Interfacial Zone ◽  
Reinforcement Corrosion ◽  
Cross Sectional ◽  
Bond Behaviour ◽  
Rc Structures ◽  
Steel Reinforced Concrete

Chloride-induced steel corrosion is one of the major deterioration problems for steel reinforced concrete structures. Its effects on RC structures include cracking of the concrete cover, reduction and eventually loss of bond between concrete and corroding reinforcement, and reduction of cross-sectional area of reinforcing steel. The accumulated corrosion products on the bar surface cause longitudinal cracking of the concrete cover. Loss of concrete cover leads to reduction in bond strength at the interfacial zone between the two materials. In addition, the deterioration of the ribs of the deformed bars causes a significant reduction of the interlocking forces between the ribs of the bars and the surrounding concrete keys. This deteriorates the primary mechanism of the bond strength between deformed bars and concrete, and hence, the bond strength decreases significantly. In this paper the effect of reinforcement corrosion on the bond strength between reinforcement and concrete was investigated for different corrosion levels. The effect of corrosion was simulated by the nonlinear numerical analysis with the FEM program using the 3D models.

scholarly journals Effect of ridge lap surface treatment and thermocycling on microtensile bond strength of acrylic teeth to denture base resins

2009 ◽  
Vol 20 (2) ◽  
pp. 127-131 ◽  
Author(s):  
Carolina de Andrade Lima Chaves ◽  
Rômulo Rocha Regis ◽  
Ana Lucia Machado ◽  
Raphael Freitas de Souza
Keyword(s):  
Bond Strength ◽  
Surface Treatment ◽  
Testing Machine ◽  
Microtensile Bond Strength ◽  
Cross Sectional ◽  
Denture Base ◽  
Significant Difference ◽  
Base Resin ◽  
Artificial Teeth ◽  
Polymer Type

This study evaluated the effect of denture base polymer type (heat- and microwave-polymerized), ridge lap surface treatment (with and without methyl methacrylate-MMA etching) and thermocycling on the microtensile bond strength (µTBS) of Biotone acrylic teeth. Flat-ground, ridge-lap surface of posterior artificial teeth were bonded to cylinders of each denture base resin, resulting in the following groups (n=6): G1a - Clássico/with MMA etching; G1b - Clássico/without MMA etching; G2a - OndaCryl/with MMA etching; G2b - OndaCryl/without MMA etching. Rectangular bar specimens with a cross-sectional area of 1 mm² were prepared. Half of the bars in each group were thermocycled (5,000 cycles between 4ºC and 60ºC). µTBS testing was performed in an universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically by three-way ANOVA (α=0.05). There was no statisticaly significant difference (p>0.05) for the factors (resin, surface treatment,and thermocycling) or their interactions. The mean µTBS values (MPa) and standard deviations were as follows: Thermocycling - G1a: 41.00 (14.00); G1b: 31.00 (17.00); G2a: 50.00 (27.00); G2b: 40.00 (18.00); No thermocycling - G1a: 37.00 (14.00); G1b: 43.00 (25.00); G2a: 43.00 (14.00); G2b: 40.00 (27.00). The µTBS of Biotone artificial teeth to the denture base acrylic resins was not influenced by the polymer type, surface treatment or thermocycling.

Personal Audio System: Hearing Symptoms, Habits, and Sound Pressure Levels Measured in Real Ear and a Manikin

2020 ◽  
Vol 63 (6) ◽  
pp. 2016-2026
Author(s):  
Tamara R. Almeida ◽  
Clayton H. Rocha ◽  
Camila M. Rabelo ◽  
Raquel F. Gomes ◽  
Ivone F. Neves-Lobo ◽  
...  
Keyword(s):  
Sound Pressure ◽  
Daily Basis ◽  
Cross Sectional Study ◽  
Normal Hearing ◽  
Chi Square ◽  
Cross Sectional ◽  
The Real ◽  
Significant Difference ◽  
Sound Pressure Levels ◽  
Audio System

Purpose The aims of this study were to characterize hearing symptoms, habits, and sound pressure levels (SPLs) of personal audio system (PAS) used by young adults; estimate the risk of developing hearing loss and assess whether instructions given to users led to behavioral changes; and propose recommendations for PAS users. Method A cross-sectional study was performed in 50 subjects with normal hearing. Procedures included questionnaire and measurement of PAS SPLs (real ear and manikin) through the users' own headphones and devices while they listened to four songs. After 1 year, 30 subjects answered questions about their usage habits. For the statistical analysis, one-way analysis of variance, Tukey's post hoc test, Lin and Spearman coefficients, the chi-square test, and logistic regression were used. Results Most subjects listened to music every day, usually in noisy environments. Sixty percent of the subjects reported hearing symptoms after using a PAS. Substantial variability in the equivalent music listening level (Leq) was noted ( M = 84.7 dBA; min = 65.1 dBA, max = 97.5 dBA). A significant difference was found only in the 4-kHz band when comparing the real-ear and manikin techniques. Based on the Leq, 38% of the individuals exceeded the maximum daily time allowance. Comparison of the subjects according to the maximum allowed daily exposure time revealed a higher number of hearing complaints from people with greater exposure. After 1 year, 43% of the subjects reduced their usage time, and 70% reduced the volume. A volume not exceeding 80% was recommended, and at this volume, the maximum usage time should be 160 min. Conclusions The habit of listening to music at high intensities on a daily basis seems to cause hearing symptoms, even in individuals with normal hearing. The real-ear and manikin techniques produced similar results. Providing instructions on this topic combined with measuring PAS SPLs may be an appropriate strategy for raising the awareness of people who are at risk. Supplemental Material https://doi.org/10.23641/asha.12431435

Conflict Avoidance in Old Age

GeroPsych ◽  
2017 ◽  
Vol 30 (2) ◽  
pp. 61-70 ◽  
Author(s):  
Lia Oberhauser ◽  
Andreas B. Neubauer ◽  
Eva-Marie Kessler
Keyword(s):  
Social Support ◽  
Perceived Social Support ◽  
Well Being ◽  
Cross Sectional Study ◽  
Conflict Avoidance ◽  
Subjective Well Being ◽  
Sectional Study ◽  
Cross Sectional ◽  
Adult Lifespan ◽  
Set Up

Abstract. Conflict avoidance increases across the adult lifespan. This cross-sectional study looks at conflict avoidance as part of a mechanism to regulate belongingness needs ( Sheldon, 2011 ). We assumed that older adults perceive more threats to their belongingness when they contemplate their future, and that they preventively react with avoidance coping. We set up a model predicting conflict avoidance that included perceptions of future nonbelonging, termed anticipated loneliness, and other predictors including sociodemographics, indicators of subjective well-being and perceived social support (N = 331, aged 40–87). Anticipated loneliness predicted conflict avoidance above all other predictors and partially mediated the age-association of conflict avoidance. Results suggest that belongingness regulation accounts may deepen our understanding of conflict avoidance in the second half of life.

Parent’s Experiences from the Treatment of their Children at the Physic Children’s Surgery Clinic in Skopje.

2020 ◽  
Vol 4 (1) ◽  
Author(s):  
M. Trajchevska ◽  
A. Lleshi ◽  
S. Gjoshev ◽  
A. Trajchevski
Keyword(s):  
Health Care ◽  
Health Status ◽  
Independent Predictor ◽  
Demographic Data ◽  
Parental Satisfaction ◽  
Pediatric Care ◽  
Simple Random Sample ◽  
Significant Independent Predictor ◽  
Cross Sectional ◽  
Significant Difference

Background: The respect of the needs and wishes of the patients is in the focus of the human health system. The experience of the parents in terms of child’s health care may be used as an indicator of quality of the health care. Material and methods: The research is a quantitative analytical cross-sectional study. In accordance with the inclusion and exclusion criteria, simple random sample of 207 parents / guardians is covered, whose children in the period of three months, had been hospitalized in the hospital department JZUU Pediatric Surgery Clinic in Skopje.It was used a two parted questionnaire. The first part is a standardized questionnaire (Parent Experience of Pediatric Care - PECP), and the second part concerns the general socio-demographic data of the parent/guardian. Statistical evaluation was performed using appropriate statistical programs (Statistics for Windows 7,0 and SPSS 17.0). Results: In accordance with the age of the parents, the survey respondents were divided into two groups: a) age ≤ 33 years - 107 (51.69%) and b) age> 33 years - 100 (48.31%).Significant independent predictor of parental satisfaction from the receipt of their child to the clinic research confirms the age of the parent under / over 33 years due to 4.1% of the change in satisfaction (R2 = 0,041). Parents generally believe that their children's room of the clinic is "good", without significant difference between parental satisfaction from both age groups (Mann-Whitney U Test Z = -0,9613 p = 0,3364). Significant independent predictor of parental satisfaction from the room of their child improves the health status after treatment due to 6% of the change in satisfaction (R2 = 0,060). Parents generally believe that testing and treatment of their children in the clinic was "very good" and an independent significant predictor is to improve the health status after the treatment - 7,8% (R2 = 0,078). Conclusions: Regardless of the generally good parental satisfaction about health care for their children, it is necessary to continuously monitor the status of the clinic in order to consider the possible deficiencies and needs of intervention.

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