Influence of Aggregates on Cracking Resistance of Concrete at Early Age

2012 ◽  
Vol 151 ◽  
pp. 474-479
Author(s):  
Bo Chen ◽  
Jian Tong Ding ◽  
Yue Bo Cai
Keyword(s):  
Thermal Expansion ◽  
Elastic Modulus ◽  
Stress Testing ◽  
Testing Machine ◽  
Tensile Creep ◽  
Early Age ◽  
Test Results ◽  
Cracking Resistance ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

In order to investigate influence of aggregates on cracking resistance of concrete at early age, four kinds of aggregates, i.e. syenite, basalt, marble and sandstone, were used for the test on cracking resistance of hydraulic concretes by the temperature stress testing machine. Analogy analysis was carried out with test results of concretes with two gradings of aggregates. The results show that aggregates affect elastic modulus, thermal expansion coefficients and tensile creep behavior of concrete at early age. However, the temperature rise of concrete was slightly affected by various types and gradings of aggregate. Moreover, the cracking temperature is reliably to be used to quantitatively evaluate the influence of aggregates on cracking resistance of concrete at early age.

Investigation on Friction and Thermal Expansion Coefficients of Al-Sn Bearing Alloys

2007 ◽  
Vol 353-358 ◽  
pp. 3063-3066 ◽  
Author(s):  
Yong Zhi Zou ◽  
Zheng Bin Xu ◽  
Yan Gao ◽  
Hong Gu ◽  
Jian Min Zeng
Keyword(s):  
Thermal Expansion ◽  
Friction Coefficient ◽  
Testing Machine ◽  
Alloy System ◽  
The Other ◽  
Thermal Expansion Coefficients ◽  
Friction Testing ◽  
Other Hand ◽  
Expansion Coefficients

The influences of Sn addition of 3%-30% on the friction and thermal expansion properties of Al-Sn bearing alloys were investigated in this paper. The experiments were carried out on a specially designed friction testing machine and a dilatometer. It is shown by the experiments that the friction coefficient and hardness of the alloys decrease with the increasing of Sn content. The friction coefficient decreases dramatically when Sn content is higher than 6%. On the other hand, the friction coefficient is also dependent on the load. The friction coefficient increases as the load rises. The linear CTE is also a function of temperature and Sn contents. CTE increases when the temperature rises but has no obvious differences for the alloy system when the temperature is below 80°C. As the temperature rises, the differences become large among the alloy system. The higher the Sn content, the lower the CTE.

Thermal Cracking Resistance of Shotcrete Based on Temperature Matched Curing

2011 ◽  
Vol 391-392 ◽  
pp. 849-853
Author(s):  
Bo Chen ◽  
Jian Tong Ding ◽  
Yue Bo Cai ◽  
Qiu Bo Kang
Keyword(s):  
Stress Testing ◽  
Testing Machine ◽  
Thermal Cracking ◽  
Test Method ◽  
Test Results ◽  
Cracking Resistance ◽  
Different Types ◽  
Practical Temperature ◽  
The Difference ◽  
Cracking Tendency

In order to evaluate the thermal cracking resistance of shotcrete under the condition of practical temperature field and strong restrain, a proper test method is needed. Based on temperature matched curing and by applying temperature stress testing machine, a new test method has been provided. With the application of this test method, thermal cracking resistance of three shotcretes with different types of fiber were investigated. Test results show that the cracking tendency of different shotcretes can be distinguished with the parameter of the difference between the max temperature and the cracking temperature.

Evaluation of Procera/Porcelain Interface in Metal-Free Prosthesis

2005 ◽  
Vol 498-499 ◽  
pp. 606-611
Author(s):  
S.H. Yasuda ◽  
Antonio C. Guastaldi ◽  
E. Vedovato
Keyword(s):  
Mechanical Properties ◽  
Thermal Expansion ◽  
Elastic Modulus ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Metal Free ◽  
Thermal Expansion Coefficients ◽  
Dental Application ◽  
Expansion Coefficients

Prosthetic substructures for dental application are veneered by porcelain comprising a structure with different elastic modulus and thermal expansion coefficients layers. This structure may present residual stresses in different layers leading to crack propagation and delamination. Although veneering porcelain remains basically on same strength than standard feldspathic porcelains, new ceramic cores have been developed with higher mechanical properties overcoming metal substructures, improving esthetics and biocompatibility. The interface between the Procera dense sintered alumina core and the manufacturer recommended veneering porcelain (AllCeram-Degussa) were evaluated using SEM in coping shaped specimen simulating the standard dental preparation. There were neither crack presences at the interface nor porcelain delamination.

scholarly journals Tensile Creep Model of Slab Concrete Based on Microprestress-Solidification Theory

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3157
Author(s):  
Zhifang Zhao ◽  
Huanmi Zhang ◽  
Bo Fang ◽  
Yukun Sun ◽  
Yangfeng Zhong ◽  
...  
Keyword(s):  
Variable Temperature ◽  
Testing Machine ◽  
Tensile Creep ◽  
Creep Model ◽  
Temperature Deformation ◽  
Early Age ◽  
Cracking Resistance ◽  
Kelvin Model ◽  
Mgo Concrete ◽  
Better Than

Tensile creep is an important factor affecting the early cracking resistance of concrete. The tensile creep model can effectively predict the development of tensile creep. In order to establish an appropriate tensile creep model, a temperature–stress testing machine (TSTM) was employed to test the development of temperature, deformation and restraint stress of benchmark concrete and concrete mixed with the MgO under different temperature curing modes. The development law of early age stress, strain and creep was analyzed via the test data of the TSTM. The early age tensile creep of concrete was predicted with the existing Kelvin creep model. The effect of variable temperature on creep was considered in this study, and an improved Kelvin creep model was proposed. The prediction accuracy of the two models was compared and analyzed. The results indicate that MgO has little influence on the creep and specific creep of concrete. The early age cracking resistance of MgO concrete is better than benchmark concrete. The improved Kelvin model based on the microprestress-solidification (MPS) theory predicts the early tensile creep of concrete more accurately in variable temperature conditions. These are significantly helpful for the application of the MgO expansion agent in dam engineering.

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