Examining the “time-zero” of autogenous shrinkage in high/ultra-high performance cement pastes

2017 ◽  
Vol 97 ◽  
pp. 107-114 ◽  
Author(s):  
Hao Huang ◽  
Guang Ye
Keyword(s):  
High Performance ◽  
Autogenous Shrinkage ◽  
Cement Pastes ◽  
Time Zero

Chemical Shrinkage of Pastes Made with Shrinkage Reducing Admixtures

2011 ◽  
Vol 466 ◽  
pp. 105-113 ◽  
Author(s):  
António Bettencourt Ribeiro ◽  
Vasco Medina ◽  
Augusto Gomes ◽  
Arlindo Gonçalves
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Chemical Shrinkage ◽  
Cement Pastes ◽  
Degree Of Hydration ◽  
Shrinkage Cracks ◽  
Large Application ◽  
Shrinkage Reducing Admixtures

Shrinkage Reducing Admixtures (SRA) are being used more often in concrete structures in order to better control shrinkage cracks. High-performance concrete, nowadays with large application, has more proneness to crack at very early age due to the lower W/C. In this type of concrete, autogenous shrinkage is usually more important than drying shrinkage. Autogenous shrinkage is due to the volume decrease inherent to binder hydration reactions. The rate of these reactions is influenced not only by the type of binder but also by the presence of chemical admixtures. It is recognized that SRA delay the hydration, being a secondary effect of this type of admixtures. In this work changes on the degree of hydration of cement pastes with SRA and different binders are presented, using the chemical shrinkage test.

scholarly journals Chemical Shrinkage of Low Water to Cement (w/c) Ratio CEM I and CEM III Cement Pastes Incorporating Silica Fume and Filler

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1164
Author(s):  
Judy Kheir ◽  
Benoît Hilloulin ◽  
Ahmed Loukili ◽  
Nele De Belie
Keyword(s):  
Silica Fume ◽  
High Performance ◽  
Precise Measurement ◽  
Crack Formation ◽  
High Performance Concrete ◽  
Autogenous Shrinkage ◽  
Chemical Shrinkage ◽  
Sem Images ◽  
Cement Pastes ◽  
Mineral Additions

Chemical shrinkage (CS) is the reason behind early age cracking, a common problem for concrete with low water to cement ratios (w/c < 0.35) known as Ultra-High- and High-Performance Concrete (U-HPC). However, to avoid the crack development initiated by autogenous shrinkage, a precise measurement of CS is required, as the values obtained can determine the correct amount of internal curing agent to be added in the mixture to avoid crack formation. ASTM C1608 is the standardized method for performing CS tests. In this study, recommendations are provided to improve the reliability of results obtained with this standard method, such as good compaction of samples and the use of superplasticizer (SP) for low w/c ratios (≤0.2). Cement pastes with CEM I and CEM III have been tested at different w/c ratios equal to 0.2, 0.3 and 0.4 with and without the addition of superplasticizer. CS results following ASTM-C1608 dilatometry showed that the presence of mineral additions such as silica fume and filler reduced the chemical shrinkage, while CS increased with increasing w/c. Low w/c ratio pastes of CEM III had slightly higher CS rates than CEM I, while the opposite was noticed at higher w/c. SEM images illustrated the importance of a careful compaction and SP use.

Early-Age Autogenous Shrinkage of High-Performance Concrete Columns by Embedded Fiber Bragg-Grating Sensor

2009 ◽  
Vol 419-420 ◽  
pp. 1-4 ◽  
Author(s):  
Ying Wei Yun ◽  
Ii Young Jang ◽  
Seong Kyum Kim ◽  
Seung Min Park
Keyword(s):  
Fiber Bragg Grating ◽  
High Performance ◽  
High Performance Concrete ◽  
Construction Material ◽  
Autogenous Shrinkage ◽  
Strain Sensor ◽  
Bragg Grating ◽  
Early Age ◽  
Long Time ◽  
Sensor Temperature

High-performance concrete (HPC) as a promising construction material has been widely used in infrastructures and high-rise buildings etc. However, its pretty high autogenous shrinkage (AS) especially in its early age becomes one of the key problems endangering long-time durability of HPC structures. This paper carried out the early age AS research of large scaled HPC column specimens by embedded Fiber Bragg-Grating (FBG) strain sensor. Temperature compensation for FBG strain sensor by thermocouple was also attempted in this paper, and the results were reasonable and acceptable comparing with the result compensated by FBG temperature sensor. Reinforcement influence, size effect and temperature effect on HPC AS were also analyzed respectively in this paper.

Autogenous Shrinkage in Plain Cement Mixtures

2008 ◽  
Vol 400-402 ◽  
pp. 137-143 ◽  
Author(s):  
Vinod Rajayogan ◽  
Obada Kayali
Keyword(s):  
Experimental Determination ◽  
High Performance ◽  
High Performance Concrete ◽  
Autogenous Shrinkage ◽  
Basic Mechanism ◽  
Realistic Model ◽  
Test Method ◽  
Ongoing Research ◽  
Cement Mixtures

Determination of a realistic model for the estimation of autogenous shrinkage in plain cement mixtures has been an ongoing research among researchers in high performance concrete. While no standard test method exists for the determination of autogenous shrinkage, various researchers have designed different test methods for measurement of autogenous shrinkage. Current study involved the experimental determination of autogenous shrinkage using the test method developed by O.M.Jensen and co-workers, complimented with non-contact eddy current sensors. Measurements were conducted from as early as 1.5 hours from the time of casting. The samples were placed in a constant temperature chamber and the temperature of the sample was also monitored using a thermocouple. The study was carried out on plain cement mixtures at three water cement ratios of 0.25, 0.32 and 0.38. Measurements were also conducted on simple sealed prismatic samples but these measurements could only be collected after 24 hours of casting. The work is supplemented with CEMHYD3D simulations of the samples at similar water-cement ratios under sealed conditions so as to understand the development of the microstructure of the cement responsible for autogenous shrinkage. While experimental determination of internal relative humidity is quite difficult, data regarding chemical shrinkage, amount of water left and the development of the discontinuous capillary network from the simulations help to understand the determined experimental values of autogenous shrinkage. A detailed explanation on the causes of autogenous shrinkage and the basic mechanism responsible for it has been presented.

Research Progress on Early Autogenous Shrinkage of Cement-Based Cementitious Materials

2013 ◽  
Vol 634-638 ◽  
pp. 2738-2741
Author(s):  
Wei Huang ◽  
Tao Zhang ◽  
Yun Yun Xu
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Research Work ◽  
Autogenous Shrinkage ◽  
Cementitious Materials ◽  
Mineral Admixtures ◽  
Research Progress ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Improvement Measures

Concrete autogenous shrinkage phenomenon would adversely affect the mechanical properties and durability of concrete, this phenomenon is important. Autogenous shrinkage problem of low water-cement ratio of the with high mineral admixtures, cement-based cementitious materials was introduced. The main reason for high-performance concrete early cracking being autogenous shrinkage was pointed out. Based on the home and abroad research status of low water cement ratio of the cement paste and concrete autogenous shrinkage, especially for early autogenous shrinkage phenomenon, the mechanism of autogenous shrinkage and the measure method is presented, and the improvement measures and the possible problems the need for further research work is presented.

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