Evaluation of the Thermal and Shrinkage Stresses in Restrained High-Performance Concrete

The early age volume deformation is the main course for the cracking of high-performance concrete (HPC). Hence, the shrinkage behavior and the restrained stress development of HPC under different restraints and curing conditions were experimentally studied in this paper. The method to separate the stress components in the total restraint stress was proposed. The total restrained stress was separated into autogenous shrinkage stress, drying shrinkage stress and thermal stress. The results showed that the developments of the free shrinkage (autogenous shrinkage and drying shrinkage) and the restrained stress were accelerated when the drying began; but the age when the drying began did not significantly influence the long-term shrinkage and restrained stress of HPC; the autogenous shrinkage stress continuously contributed to the development of the total restrained stress in HPC; the drying shrinkage stress developed very rapidly soon after the drying began; and the thermal stress was generated when the temperature dropped. The thermal stress was predominant at the early age, but the contributions of the three stresses to the total restrained stress were almost the same at the age of 56 d in this study.

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Shrinkage Properties of Cement-Silica Fume Blended Pastes in Early Age

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.726.521 ◽

2017 ◽

Vol 726 ◽

pp. 521-526

Author(s):

Di Zou ◽

Lian Zhen Xiao ◽

Wen Chong Shi

Keyword(s):

Silica Fume ◽

Rapid Growth ◽

High Performance ◽

High Performance Concrete ◽

Autogenous Shrinkage ◽

Drying Shrinkage ◽

Early Age ◽

Shrinkage Ratio ◽

Study Results ◽

Expansion Period

The cement-silica fume blended pastes were prepared with different silica fume (SF) dosages of 0%, 5%, 10%, and 15% at different water-binder ratios (W/B) of 0.4 and 0.5. The autogenous shrinkage (AS) and the drying shrinkage (DS) of the paste samples in the hydration period of 7d (168 hours) were measured by a new measurement technique to explore the influence of W/B and silica fume incorporation on the shrinkage in early age. The study results can provide reference for high performance concrete mix design.It is found that ether the AS or the DS of the paste samples shows a similar pattern, and the AS development with hydration time appeared a temporary expansion period after a rapid growth, especially in the samples at a higher W/B or with a lower SF content. However, the DS development did not occur obvious expansion period.Three development trends were obtained for the factors of W/B and SF content. 1) the AS and DS of the pastes mainly occurred in early ages. The lower W/B, the shorter the rapid growth periods, and the higher the shrinkage ratio of 1d to 7d. For the pastes with W/B of 0.4, the AS grew rapidly in 1d and the DS grew rapidly in the first 10h, and the AS value in 1d reached to 63.6% of 7d, and the DS value reached to 62.1% of 7d in the paste with SF of 10%. For the pastes with W/B of 0.5, the rapid growth periods of the AS and DS respectively extended to 30~33h and 12h, and the AS value in 1d reached to 60.0% of 7d, and the DS value reached to 57.2% of 7d in the paste with SF of 10%. 2) The lower W/B, the higher the shrinkage ratio of the AS to the DS. When the SF dosage is 10%, the ratio of the AS value to the DS value of 7d is 21.66%~21.15% for W/B of 0.4, and only 6.06%~5.78% for the W/B of 0.5. 3) the higher SF content results in the higher AS in cement-SF blended pastes. For the pastes with W/B of 0.4, the ratio of the AS to the DS increased from 6.98% to 30.16% with the increase of content of SF from 5% to 15% in 1d, from 15.1% to 28.19% in 3d, from 16.78% to 26.16% in 7d.

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Effect of the Expansion Agent on Early-Age Autogenous Shrinkage Stress of Concrete

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.838-841.564 ◽

2013 ◽

Vol 838-841 ◽

pp. 564-568

Author(s):

Pan Xiu Wang

Keyword(s):

Tensile Strength ◽

Concrete Structure ◽

High Performance ◽

High Performance Concrete ◽

Autogenous Shrinkage ◽

Shrinkage Strain ◽

Shrinkage Stress ◽

Early Age ◽

Concrete Cube

Early-age autogenous shrinkage is key problem of high performance concrete. It can cause a lot of early-age cracks in concrete structure and further endanger the permeability and durability. Adding expansion agent can control the early-age autogenous shrinkage strain and reduce the risk of early-age cracks. In this paper, the early-age autogenous shrinkage stress of concrete cube is calculated. The results show that, early-age autogenous shrinkage stress is larger than early-age tensile strength of concrete. So some cracks occur on the surface of concrete structure. By adding expansion agent, the early-age autogenous shrinkage strain and stress both decreases.

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Effect of Curing Methods on Early-Age and Drying Shrinkage of High-Performance Concrete

Transportation Research Record Journal of the Transportation Research Board ◽

10.3141/1834-07 ◽

2003 ◽

Vol 1834 (1) ◽

pp. 48-58 ◽

Cited By ~ 7

Author(s):

Hani Nassif ◽

Nakin Suksawang ◽

Maqbool Mohammed

Keyword(s):

Fly Ash ◽

High Performance ◽

High Performance Concrete ◽

Drying Shrinkage ◽

Lightweight Aggregate ◽

Analytical Models ◽

Early Age ◽

Curing Conditions ◽

Curing Methods ◽

Technical Specifications

Many engineers and agencies have observed that the field implementation of high-performance concrete (HPC) is highly dependent on curing and placing conditions. The effect of curing conditions on the early-age properties and long-term durability of HPC is not fully understood. There is a need to expand the knowledge of early-age properties and of the effect of pozzolanic material (like silica fume and fly ash) on drying shrinkage. Results are presented of a study performed to identify the effect of various curing methods on the early-age (autogenous) as well as drying shrinkage of normal and lightweight HPC. The study included a comparison of available analytical models for predicting early-age and drying shrinkage with results from tests performed on different mixes. HPC mixes were developed and evaluated as part of an overall study for the New Jersey Department of Transportation to develop and implement mix designs and technical specifications for HPC transportation structures, such as pavements and bridges. The effect of using three different curing methods on the early-age performance of HPC is presented. The curing conditions consisted of air-dry curing, burlap or moist curing, and use of a curing compound. Results show that moist (burlap) curing should be applied within 1 h after the placement of concrete to improve early-age performance. For very low water-to-cement plus pozzolan ratios, fly ash and lightweight aggregate improved the autogenous shrinkage performance. Moreover, current shrinkage models need to be revised to address HPC mixes.

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The Influence of Chemical Admixtures on the Autogenous Shrinkage Ultra-High Performance Concrete

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.452-453.725 ◽

2010 ◽

Vol 452-453 ◽

pp. 725-728 ◽

Cited By ~ 3

Author(s):

Jung Jun Park ◽

Sung Wook Kim ◽

Gum Sung Ryu ◽

Kwang Myung Lee

Keyword(s):

High Performance ◽

High Performance Concrete ◽

Autogenous Shrinkage ◽

Pulse Velocity ◽

Reducing Agent ◽

Shrinkage Stress ◽

Early Age ◽

Ultra High Performance Concrete ◽

Expansive Additive ◽

Shrinkage Reducing Agent

Ultra-high performance concrete (UHPC) is a material developing remarkable performance with compressive strength of about 200 MPa and flexural strength of approximately 30 MPa on which research is actively conducted today. However, UHPC is also characterized by a mixing composed of a high specific quantity of binder that is a W/B ratio of about 0.2, which requires to examine the effects of the autogenous shrinkage. Accordingly, this study investigates the effects of the use of expansive additive and water reducing agent on the autogenous shrinkage of UHPC at early age. To that goal, autogenous shrinkage test and ultrasonic pulse velocity (UPV) monitoring are conducted for a mixing of UHPC using expansive additive and shrinkage reducing agent. The experimental results reveal that the autogenous shrinkage of UHPC reduces by 24% for a mix of UHPC adopting both 7.5% of expansive additive and 1% of shrinkage reducing agent compared to the mix without admixture. Furthermore, this mix is seen to compensate the autogenous shrinkage occurring at early age when UHPC develops its largest stiffness in view of the UPV evolution curve. At that time, the shrinkage stress seems to be extremely softened.

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Synergistic Benefits of Using Expansive and Shrinkage Reducing Admixture on High-Performance Concrete

Materials ◽

10.3390/ma11122514 ◽

2018 ◽

Vol 11 (12) ◽

pp. 2514 ◽

Cited By ~ 3

Author(s):

Tian-Feng Yuan ◽

Seong-Kyum Kim ◽

Kyung-Teak Koh ◽

Young-Soo Yoon

Keyword(s):

Mechanical Properties ◽

High Performance ◽

High Performance Concrete ◽

Autogenous Shrinkage ◽

Shrinkage Stress ◽

Early Age ◽

Test Results ◽

Shrinkage Cracking ◽

Shrinkage Cracks ◽

Shrinkage Reducing Admixture

High-performance concrete (HPC) is widely used in construction according to great mechanical properties, but it has a high risk of shrinkage cracking due to autogenous shrinkage stress. Therefore, the aim of this research was to investigate the effect of a combination of expansive admixture (EA) and shrinkage reducing admixture (SA) on the autogenous shrinkage of high-performance concrete without heat treatment. Two different EA to cement weight ratios of 0.0, 5.0%, and two different SA to cement weight ratios of 0.0, and 1.0% were combined and considered. To investigate the differences in the time-zero conditions effect on the autogenous shrinkage behaviors, four different initial points were compared. The test results indicate that the EA and/or SA content was conductive to a little bite increase compressive strength (22.6–37.9%) and tensile strength (<4.8%). According to the synergistic effect of the EA and SA on the HPC, the autogenous shrinkage significantly decreased (<50%), as compared to those specimens with only one type of admixture (EA or SA). Furthermore, all the specimens incurred restrained autogenous shrinkage cracks at an early age, except the specimen using the combined EA and SA. Therefore, it can be concluded that the combination of EA and SA is effective for improving the properties of HPC.

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Shrinkage Mitigation of an Ultra-High Performance Concrete Submitted to Various Mixing and Curing Conditions

Materials ◽

10.3390/ma14143982 ◽

2021 ◽

Vol 14 (14) ◽

pp. 3982

Author(s):

Cédric Androuët ◽

Jean-Philippe Charron

Keyword(s):

High Performance ◽

High Performance Concrete ◽

Water Immersion ◽

Autogenous Shrinkage ◽

Early Age ◽

Curing Conditions ◽

Binder Ratio ◽

Water To Binder Ratio ◽

The Impact

Ultra-High Performance Concretes (UHPC) are cement-based materials with a very low water-to-binder ratio that present a very-high compressive strength, high tensile strength and ductility as well as excellent durability, making them very interesting for various civil engineering applications. However, one drawback of UHPC is their pretty high autogenous shrinkage stemming from their very low water-to-binder ratio. There are several options to reduce UHPC shrinkage, such as the use of fibers (steel fibers, polypropylene fibers, wollastonite microfibers), shrinkage-reducing admixtures (SRA), expansive admixtures (EA), saturated lightweight aggregates (SLWA) and superabsorbent polymers (SAP). Other factors related to curing conditions, such as humidity and temperature, also affect the shrinkage of UHPC. The aim of this paper is to investigate the impact of various SRA, different mixing and curing conditions (low to moderate mixing temperatures, moderate to high relative humidity and water immersion) as well as different curing starting times and durations on the shrinkage of UHPC. The major importance of the initial mixing and curing conditions has been clearly demonstrated. It was shown that the shrinkage of the UHPC was reduced by more than 20% at early-age and long-term when the fresh UHPC temperature was closer to 20 °C. In addition, curing by water immersion led to drastic reductions in shrinkage of up to 65% and 30% at early-age and long-term, respectively, in comparison to a 20% reduction for fog curing at early-age. Finally, utilization of a liquid polyol-based SRA allowed for reductions of 69% and 63% of early-age and long-term shrinkages, respectively, while a powder polyol-based SRA provided a decrease of 47% and 35%, respectively.

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

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.419-420.1 ◽

2009 ◽

Vol 419-420 ◽

pp. 1-4 ◽

Cited By ~ 2

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.

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