scholarly journals Long-Term Compressive Strength Development of Steel Fiber Shotcrete from Cores Based on Accelerator Types at Tunnel Site

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 580
Author(s):  
Kyong Ku Yun ◽  
Seunghak Choi ◽  
Taeho Ha ◽  
Seong Kwon Kim ◽  
Mohammad Shakhawat Hossain ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Steel Fiber ◽  
Relative Strength ◽  
Worker Safety ◽  
Strength Development ◽  
The Core ◽  
Long Term Performance ◽  
Term Performance ◽  
The Impact

In this study, cement minerals, aluminates, and alkali-free accelerators incorporated with steel fiber were used to scrutinize the influence of accelerating agents on the long-term performance of tunneling shotcrete. Performance tests were identified based on the core compressive strength of mix shotcrete specimens with different types of accelerating agents throughout timeframes of 1, 3, 6, and 12 months. Here, 37 kg of steel fiber was incorporated into the cement mineral and aluminate mixes, and 40 kg of steel fiber was incorporated in an alkali-free mix for the shotcrete mix design. The KSF 2784 and ASTM 214 standards were followed for specimen fabrication and core cutting. For all specimens, shotcrete test panels of 250 × 600 × 500 mm were manufactured for core compressive strength tests conducted using 100, 75 and 55 mm diameter cylindrical molds and a length-to-diameter ratio of 2. The 1-month compressive strength of all test variables satisfied the Korea Expressway Co. standard of 21 MPa. The core compressive strength of the shotcrete specimens showed a tendency to increase with age, but a strength reduction occurred in 6 months and increased again at 12 months. Moreover, the impact of the diameter changes in the shotcrete core specimens was analyzed based on the mixing. For 12 months, a large increase in the core compressive strength occurred, particularly in the alkali-free specimens. The comparison also focused on the relative strength compared with a cast concrete mold and shotcrete core specimens. It is necessary to use alkali-free accelerators considering the long-term performance of tunnels and worker safety.

scholarly journals Comparison of Long-Term Strength Development of Steel Fiber Shotcrete with Cast Concrete Based on Accelerator Type

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5599
Author(s):  
Kyong Ku Yun ◽  
Seunghak Choi ◽  
Taeho Ha ◽  
Mohammad Shakhawat Hossain ◽  
Seungyeon Han
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Steel Fiber ◽  
Strength Reduction ◽  
Strength Development ◽  
Fiber Reinforced ◽  
Cast Concrete ◽  
Long Term Performance ◽  
Term Performance

This study analyzed the effect of accelerating agents, such as aluminate, cement mineral, and alkali-free accelerators, on the long-term performance of steel-fiber-reinforced shotcrete. The shotcrete performance was studied based on the type and amount of steel fiber added. Performance tests were performed to identify the accelerator providing better long-term performance to the steel-fiber-reinforced shotcrete. Changes in strength and flexural performance over time were investigated. The compressive strength and flexural strength tests on 1-, 3-, 6-, 12-, and 24-month-old test specimens were performed, wherein 37 kg of steel fiber was added to the cement mineral and aluminate mixes, and 40 kg of steel fiber was added to the alkali-free mix. The 1-month compressive strength result of all the test variables satisfied the Korea Expressway Corporation standard. The compressive strength of the cast concrete and shotcrete specimens increased with age, demonstrating a strength reduction, particularly in the 24-month-old shotcrete specimens. Thus, the shotcrete performance may deteriorate in the long-term. In the 24-month-old specimen, substantial flexural strength reduction was observed, particularly in the aluminate and alkali-free specimens. The relative strength of the specimens was compared with that of the cast concrete mold specimens. The results suggest the use of alkali-free accelerators, considering the long-term performance of tunnels and safety of workers. Moreover, increasing the steel fiber performance rather than the amount of low-performance steel fiber must be considered.

scholarly journals Does Corporate Charitable Giving Help Sustain Corporate Performance in China?

2019 ◽  
Vol 11 (5) ◽  
pp. 1491 ◽  
Author(s):  
Keling Wang ◽  
Yaqiong Miao ◽  
Ching-Hui Su ◽  
Ming-Hsiang Chen ◽  
Zhongjun Wu ◽  
...  
Keyword(s):  
Charitable Giving ◽  
Corporate Performance ◽  
Sales Growth ◽  
Short Term ◽  
Return On Equity ◽  
Long Term Performance ◽  
Term Performance ◽  
The Impact ◽  
Total Sales

We examined whether corporate charitable giving (CCG) in China benefits corporate performance (CP) in terms of sales growth (SG), return on asset (ROA), return on equity (ROE), and Tobin’s Q (TQ), and revealed several findings. First, testing shows variation in the impact of CCG on CP. Whereas the ratio of corporate charitable giving (RCCG) to total sales revenue does not significantly enhance SG, ROA, and ROE, it is positively related to TQ. Second, the positive relationship between RCCG and TQ originates from non-state-owned firms (NSOFs) rather than state-owned firms (SOFs). Third, Chinese firms may use CCG as traditional philanthropy to enhance long-term performance instead of strategically using it to generate short-term performance. Lastly, an inverted U-shaped relationship exists between RCCG and TQ, especially for NSOFs.

The Use of Laboratory-Measured and Strain-Gauge Backcalculated Asphalt Stiffness for Rutting Performance Prediction

2019 ◽  
Vol 2673 (3) ◽  
pp. 323-333
Author(s):  
Erdem Coleri ◽  
John T. Harvey
Keyword(s):  
Performance Prediction ◽  
Strain Gauge ◽  
Asphalt Concrete ◽  
Laboratory Tests ◽  
Concrete Materials ◽  
Long Term Performance ◽  
Term Performance ◽  
The Impact

Laboratory tests are conducted with asphalt concrete materials to determine the expected in-situ performance. In addition, laboratory test results are commonly used in mechanistic-empirical design methods for material characterization to improve the predictive accuracy of the models. However, the effectiveness of laboratory tests in characterizing the long-term performance of asphalt concrete materials needs to be validated to be able to use the results for pavement design and long-term performance prediction. Inaccurate performance characterization and prediction can directly affect the decision-making process for pavement maintenance, rehabilitation, and reconstruction and result in unexpected early failures in the field. The major objective of this study is to determine the impact of using laboratory-measured asphalt stiffness on the prediction accuracy of mechanistic-empirical models. In addition, the effect of using linear-elastic modeling assumptions (layered elastic theory) and neglecting the nonlinearity of pavement response at high load levels (and/or at high strain levels for weaker structures) on the predicted rutting performance was determined. In this study, the effectiveness of the use of laboratory asphalt stiffness tests for in-situ asphalt stiffness characterization was determined by comparing the rutting performance predicted using laboratory-measured stiffness to rutting predicted using strain-gauge backcalculated stiffness. It was determined that laboratory tests are able to characterize the in-situ stiffness characteristics of the asphalt mix used in this study and the stiffness characterization process suggested in this study can provide reliable rutting performance predictions. Results of this study are only applicable to tested rubberized asphalt concrete mixtures.

Study on the Effects of Natural Pozzolan and Limestone Powder on Mechanical Properties of Roller Compacted Concrete Pavements

2011 ◽  
Vol 250-253 ◽  
pp. 3619-3623 ◽  
Author(s):  
Morteza Madhkhan ◽  
Armin Hamidi ◽  
Navid Salehi
Keyword(s):  
Compressive Strength ◽  
Cementitious Materials ◽  
Production Costs ◽  
Limestone Powder ◽  
Concrete Pavements ◽  
Natural Pozzolan ◽  
Two Factors ◽  
Long Term Performance ◽  
Term Performance

Due to high maintenance and production costs of conventional asphalt pavements in recent years, substitution of concrete pavements has been taken into account. One important factor of such pavements is the long-term performance. The substitution of pozzolanic materials with existing cement in the mixture is a common choice to improve the durability factors and to increase the long term compressive strength. Owing to this change in cementitious materials, a general anticipation of the pozzolanic behavior to be observed is that the early age compressive strength gets decreased. On the other hand, this defect will be compensated in the long-term compressive strength. Furthermore, as conventional loads of road pavements are concerned, the tensile and flexural strengths have their own importance. Regarding these two factors, the related tests were also performed and the results were analyzed. The main purpose is to find the optimum material among these 2 types of pozzolanic supplements and its percentage of substitution with the preference of having the best average strength in both long and short term performances. Altogether, the natural pozzolan had better performance than limestone powder.

Welfare of the neonate lamb immediately after tail-docking

1999 ◽  
Vol 1999 ◽  
pp. 108-108
Author(s):  
A. B. Notman ◽  
H. L. Heath ◽  
J. Hill
Keyword(s):  
Detrimental Effect ◽  
Routine Practice ◽  
Normal Behaviour ◽  
The United Kingdom ◽  
Tail Docking ◽  
Ewe Lamb ◽  
Long Term Performance ◽  
Term Performance ◽  
The Impact

Tail docking of new born lambs is a routine practice in the United Kingdom. It has been used as a strategy to reduce the impact of myriasis (blowfly strike). There is only a limited period of time after birth (up to seven days) during which lambs can be docked without the use of anaethesia. Tail docking may have a detrimental effect on the ewe-lamb bond if the process leads to significant and sustained pain. French, Wall and Morgan (1994) suggested lambs suffer acute pain immediately after the procedure of docking but this potential disturbance of normal behaviour during the first few days of life did not seem to affect the long-term performance of lambs. The study reported in this paper considers the effect of tail docking on the behaviour of lambs during the first 90 minutes after docking and on lamb performance to slaughter.

scholarly journals Switch-out and switch-in: What motivates the decision makers in Italian occupational pension funds?

2016 ◽  
Vol 5 (1) ◽  
pp. 37-42
Author(s):  
Andrea Lippi
Keyword(s):  
Decision Process ◽  
Pension Funds ◽  
Decision Makers ◽  
Occupational Pension ◽  
Short Term ◽  
The One ◽  
Long Term Performance ◽  
Term Performance ◽  
The Impact

To switch presumes two kinds of transactions carried out by the same person: on the one hand, the decision to exit an investment line (switch-out) and, on the other hand, the decision to enter into a new investment line (switch-in). What motivates the decision makers? This paper, considering a sample of Italian occupational pension funds, investigates the impact of short-term and long-term performance on the switch decision process and whether the same performance can lead investors to make opposite switch decisions. Some irrational behaviors are identified.

The Impact of the Operational Parameters on the PEM Fuel Cell Long-Term Performance

2016 ◽  
Vol 71 (1) ◽  
pp. 233-238 ◽  
Author(s):  
V. Andrea ◽  
P. d. S. P. Oliveira ◽  
E. I. Santiago ◽  
M. Linardi
Keyword(s):  
Fuel Cell ◽  
Pem Fuel Cell ◽  
Operational Parameters ◽  
Long Term Performance ◽  
Term Performance ◽  
The Impact

scholarly journals The Impact of Financial Constraints on the Convertible Bond Announcement Returns

Economies ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 32 ◽  
Author(s):  
Chong-Chuo Chang ◽  
Tai-Yung Kam ◽  
Chih-Chung Chien ◽  
Wan Su
Keyword(s):  
Financial Constraints ◽  
Positive Impact ◽  
Cash Flows ◽  
Convertible Bonds ◽  
Convertible Bond ◽  
Short And Long Term ◽  
Long Term Performance ◽  
Term Performance ◽  
The Impact

As of now, very few research studies have examined the effects of financial constraints on the short- and long-term performances of companies after their announcement of convertible bonds. Due to asymmetric information, previous studies consider issuance of convertible bonds as negative news. As a result, the short- and long-term performances of companies generally decline after their convertible bond announcement. This study argues that when companies have investment plans, they are expected to have higher future cash flows. They will become increasingly more valuable regardless of the fact that they raise funds through the issue of convertible bonds (due to financial constraints), positively affecting the performance of companies. The results indicate that financial constraints have no effect on short-term performance, but did have a significantly positive impact on the long-term performance of companies after their issuance of convertible bonds.

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