Evaluation of Coefficient of Thermal Expansion Test Protocol and Its Impact on Jointed Concrete Pavement Performance

2009 ◽  
Vol 106 (1) ◽  
Keyword(s):  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Concrete Pavement ◽  
Pavement Performance ◽  
Test Protocol ◽  
Expansion Test ◽  
Jointed Concrete Pavement

Improvements of Testing Procedures for Concrete Coefficient of Thermal Expansion

2005 ◽  
Vol 1919 (1) ◽  
pp. 23-28 ◽  
Author(s):  
Moon Won
Keyword(s):  
Thermal Expansion ◽  
Coarse Aggregate ◽  
Coefficient Of Thermal Expansion ◽  
Test Procedure ◽  
Concrete Pavement ◽  
Test Method ◽  
Pavement Performance ◽  
Portland Cement Concrete ◽  
Testing Procedures ◽  
Accuracy And Repeatability

The coefficient of thermal expansion (CTE) of concrete has a significant effect on the performance of portland cement concrete pavement. Concrete with a higher CTE is more prone to cracking, additional warping, and spalling. To improve PCC pavement performance, several districts of the Texas Department of Transportation (TxDOT) currently limit the CTE of concrete. To support this policy, efforts have been made to improve the accuracy and repeatability of the testing procedures for CTE. The current AASHTO Test Method TP 60 has been evaluated, its shortcomings identified, and improvements made. The improvements include CTE determination from regression analysis of temperature and displacement measurements. The effects of a number of variables on concrete CTE were investigated. The effect of the rate of heating and cooling is negligible. Concrete age and specimen size also have a negligible effect. Coarse aggregate content in the concrete mix has an effect on the test results. This test procedure was used to evaluate coarse aggregates from 32 sources in Texas. The results show that coarse aggregate type has a significant effect on concrete CTE. The proposed testing procedure for concrete CTE provided more accurate results than the AASHTO TP 60. TxDOT plans to implement this test procedure and to develop appropriate steel design standards for continuously reinforced concrete pavement and other construction-related requirements such as different curing methods for concrete with varying CTEs. This implementation should result in better concrete pavement performance.

Impacts of variability in coefficient of thermal expansion on predicted concrete pavement performance

2015 ◽  
Vol 93 ◽  
pp. 711-719 ◽  
Author(s):  
Leslie Myers McCarthy ◽  
Jagan M. Gudimettla ◽  
Gary L. Crawford ◽  
Maria C. Guercio ◽  
Douglas Allen
Keyword(s):  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Concrete Pavement ◽  
Pavement Performance

Measurement and Significance of the Coefficient of Thermal Expansion of Concrete in Rigid Pavement Design

2005 ◽  
Vol 1919 (1) ◽  
pp. 38-46 ◽  
Author(s):  
Jagannath Mallela ◽  
Ala Abbas ◽  
Tom Harman ◽  
Chetana Rao ◽  
Rongfang Liu ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Structural Design ◽  
Coefficient Of Thermal Expansion ◽  
Test Procedure ◽  
Fundamental Property ◽  
The United States ◽  
Concrete Pavement ◽  
Pavement Design ◽  
Pavement Performance ◽  
Opening And Closing

The coefficient of thermal expansion (CTE) is a fundamental property of concrete. It has long been known to have an effect on joint opening and closing in jointed plain concrete pavement, crack formation and opening and closing in continuously reinforced concrete pavement, and curling stresses and thermal deformations in both types of pavements. However, it has not been included as a variable either in materials specifications or in the structural design of concrete pavements. Hundreds of cores were taken from Long-Term Pavement Performance sections throughout the United States and were tested by FHWA's Turner–Fairbank Highway Research Center laboratory, using the AASHTO TP 60 test procedure. The CTE values were then assimilated into groups on the basis of aggregate types, and the mean and range of CTE were calculated. These results were then used in the new mechanistic–empirical pavement design guide to determine the significance of the measured range of CTE on concrete pavement performance. The CTE of the concrete was found to vary widely, depending on the predominant aggregate type used in the concrete. Sensitivity analysis showed CTE to have a significant effect on slab cracking and, to a lesser degree, on joint faulting. Its overall effect on smoothness was also significant. Given that CTE has not been used before in routine pavement structural design, the conclusion is that this design input is too sensitive to be ignored and must be fully considered in specifications and in the design process to reduce the risk of excessive cracking, faulting, and loss of smoothness.

scholarly journals Effects of humidity and phosphor on silicone/phosphor composite in white light-emitting diode package

2019 ◽  
Vol 30 (23) ◽  
pp. 20471-20478 ◽  
Author(s):  
Md Ashraful Hoque ◽  
Robert Kelley Bradley ◽  
Jiajie Fan ◽  
Xuejun Fan
Keyword(s):  
Thermal Expansion ◽  
White Light ◽  
Moisture Absorption ◽  
Coefficient Of Thermal Expansion ◽  
Light Emitting Diode ◽  
Moisture Sorption ◽  
Mechanical Stiffness ◽  
Light Emitting ◽  
Expansion Test ◽  
Hygroscopic Swelling

Abstract Silicone/phosphor composite, which serve as mechanical protection and light conversion material, is an integral part of white light-emitting diode (LED) package. In this paper, a comprehensive study is conducted to investigate the effect of humidity and phosphor on moisture absorption, hygroscopic swelling, mechanical behavior, as well as thermal properties of silicone/phosphor composite in comparison with the pure silicone. SEM/EDAX and FTIR were performed to identify the phosphor and silicone compositions. Through moisture sorption test, it has been observed that the addition of phosphor significantly lowers the capacity of moisture absorption, but accelerates the diffusivity of moisture absorption. The hygroscopic swelling test showed that the phosphor has little effect on the swelling compared to the pure silicone sample. Both moisture absorption/desorption and hygroscopic swelling/de-swelling are reversible. Strain ramp test revealed that the phosphor enhances the stiffness of the composite. The moisture absorption, however, has negligible impact on mechanical stiffness for both pure and composite samples. Finally, thermal expansion test showed that the coefficient of thermal expansion does not change with the addition of phosphor into pure silicone.

New AASHTO T336-09 Coefficient of Thermal Expansion Test Method

2010 ◽  
Vol 2164 (1) ◽  
pp. 52-57 ◽  
Author(s):  
Jussara Tanesi ◽  
Gary L. Crawford ◽  
Mihai Nicolaescu ◽  
Richard Meininger ◽  
Jagan M. Gudimettla
Keyword(s):  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Test Method ◽  
Expansion Test

Analysis of LTPP Profile Data for Jointed Concrete Pavement Sections

1997 ◽  
Vol 1570 (1) ◽  
pp. 70-77
Author(s):  
Eric D. Moody
Keyword(s):  
Inventory Management ◽  
Surface Profile ◽  
Concrete Pavement ◽  
Pavement Performance ◽  
Vertical Acceleration ◽  
Profile Data ◽  
Absolute Increase ◽  
Statistical Measures ◽  
Jointed Concrete Pavement ◽  
Over Time

Incremental changes to a pavement-surface profile have long been considered a primary measure of pavement performance. As a result, the Long-Term Pavement Performance (LTPP) program of the Strategic Highway Research Program has allocated considerable resources for collecting accurate profile data on all general pavement studies (GPS) sites annually. As of June 1995, the profiles of the rigid pavement sites had been measured an average of four times, with many sites having been measured seven times. The data are collected and processed in the field, generating several statistical measures of pavement profile for each wheelpath, including the international roughness index (IRI), present serviceability index (PSI), slope variance, and root-mean-square vertical acceleration (RMSVA) at selected wavelengths. The focus of this analysis is on the primary profile statistic, the IRI. The profile data were downloaded from the National Inventory Management System (NIMS) and extensively analyzed using selected statistical techniques. The objective of this effort was to conduct a thorough analysis of the response variable, the IRI. The analysis included univariate, bivariate, and multivariate analytical techniques to determine which prediction variables are useful for predicting the IRI. Although many of the primary independent variables had significant correlations with the IRI, others did not. Various measures of traffic had particularly poor correlations with the IRI. Several regression models are also presented along with advantages and limitations of the prediction and response variables. The results of a detailed analysis of the within-year and year-to-year variability in IRI measurements are also included. The coefficient of variation in year-to-year measurements averaged 4.2 percent for the jointed plain concrete pavement (JPCP) sections (GPS-3) and 3.8 percent for the jointed reinforced concrete pavement (JRCP) sections (GPS-4). This degree of variability in year-to-year profile measurements tended to overshadow any absolute increase in IRI that may have been occurring in these sections. An analysis was then performed on every section to determine exactly which sections had statistically significant increases in IRI over time. Approximately 44 percent of the jointed concrete pavement sections exhibited statistically significant increases in IRI over time.

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