Restrained Shrinkage Test of High Performance Concrete Ring Specimen

2014 ◽  
Vol 982 ◽  
pp. 38-43
Author(s):  
Alena Zemanová ◽  
Radoslav Sovják ◽  
Jiri Litos
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Ring Test ◽  
Restrained Shrinkage ◽  
Ring Specimen ◽  
Free Shrinkage ◽  
Stress Cracking ◽  
Cracking Potential ◽  
Theoretical Stress ◽  
Concrete Ring

The aim of this study was to quantify the restrained shrinkage of high performance concrete (HPC). Ring test was used for the measurement of restrained shrinkage. Mechanical properties of the HPC as well as free shrinkage were determined for assessment of theoretical stress in shrinkage restrained material. The results from the ring test showed a lot of information about material such as development of actual residual stress, cracking potential, microcracks and relaxation.

An Evaluation on the Restrained Shrinkage of Ultra-High Performance Concrete

2012 ◽  
Vol 525-526 ◽  
pp. 449-452 ◽  
Author(s):  
Jung Jun Park ◽  
Doo Yeol Yoo ◽  
Sung Wook Kim ◽  
Young Soo Yoon
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Tensile Creep ◽  
Ring Test ◽  
Early Age ◽  
Restrained Shrinkage ◽  
Reinforcing Bars ◽  
Ultra High Performance Concrete ◽  
Shrinkage Cracking ◽  
Coarse Aggregates

Since ultra-high performance concrete (UHPC) is subject to large occurrence of shrinkage at early age due to its low water-to-cement ratio, the mixing of large quantities of powdered admixtures and the absence of coarse aggregates, UHPC presents large risks of shrinkage cracking caused by the restraints provided by the form and reinforcing bars. Accordingly, this study intends to evaluate the shrinkage behavior of UHPC under restrained state by performing restrained shrinkage test using ring-test. The test results reveal that increasing thickness of the inner ring increases the tensile creep at early age leading to the reduction of the average strain and residual stress of the inner ring.

Strengthening of a Bridge Pier with HPC: Modeling of Restrained Shrinkage Cracking

2016 ◽  
Vol 711 ◽  
pp. 1027-1034 ◽  
Author(s):  
Adriano Reggia ◽  
Sara Sgobba ◽  
Fabio Macobatti ◽  
Cristina Zanotti ◽  
Fausto Minelli ◽  
...  
Keyword(s):  
High Performance ◽  
Mechanical Performance ◽  
High Performance Concrete ◽  
Numerical Models ◽  
Experimental Tests ◽  
Concrete Bridges ◽  
Restrained Shrinkage ◽  
Shrinkage Cracking ◽  
Rc Structures ◽  
Restrained Shrinkage Cracking

After more than fifty years from the opening of the largely discussed “Autostrada del Sole” Highway in 1964, the infrastructure system in Italy appears marked by the passing of time, similarly to what observed in several other countries worldwide. The great heterogeneity of the Italian landscape has determined a great variety of construction types, such as large span concrete bridges over the northern rivers and large arch concrete bridges over the valleys of the central region. Increment of vehicle traffic and new seismic regulations are setting new requirements to adapt the existing infrastructure, which should be otherwise replaced. Moreover, reinforced concrete (RC) aging and deterioration have led to structural and material degradation, including severe cracking and corrosion. Specialized materials such as High Performance Concrete (HPC) could represent a viable convenient solution for repairing, strengthening and retrofitting of RC structures as both structural capacity and durability can be refurbished. However, alongside high mechanical performance, HPC is characterized by a high cracking sensitivity at very early age, due to its high stiffness and shrinkage. Restrained shrinkage cracking, particularly significant in repaired structures where the existing concrete generates a considerable restraint against the free movement of the repair material, may represent a limit to the effective application of these materials. For this reason, shrinkage compatibility of HPC with the existing concrete substrate needs to be experimentally and numerically assessed. A study is herein presented where, based on experimental tests, different numerical models are developed and compared to assess and eventually minimize the risk of shrinkage cracking in bridge piers strengthened with HPC.

Relaxation of Structural Concrete due to its Shrinkage in Terms of Age-Adjusted Effective Modulus Method

2017 ◽  
Vol 737 ◽  
pp. 471-476
Author(s):  
Lukáš Zvolánek ◽  
Ivailo Terzijski
Keyword(s):  
Residual Stresses ◽  
High Performance ◽  
High Performance Concrete ◽  
Relaxation Mechanism ◽  
Effective Modulus ◽  
Tensile Creep ◽  
Ring Test ◽  
Polypropylene Fibres ◽  
Creep Effect ◽  
Modulus Method

This paper focuses on the calculation of residual stresses due to shrinkage with a tensile creep effect. Whereas the shrinkage of concrete causes stresses in the material, the tensile creep counteracts the shrinkage as a stress relaxation mechanism. The main objective of this paper is to evaluate the ageing coefficient c (referred to as Trost-Bazant Coefficient) reflecting the load history. The coefficient is used for the residual stress analysis by means of a simplified method called Age-adjusted Effective Modulus Method. The tensile creep effect was evaluated according to the rheological model provided by Eurocode 2. Although the Eurocode predicts the creep for the structural members subjected to compressive stresses, this study proves that it can be used for the tensile creep prediction as well. We tested three types of concrete: reference concrete, high-performance concrete with reduced shrinkage magnitude by means of special admixtures, and fibre concrete with the content of polypropylene fibres. From the obtained results, it can be stated, that the ageing coefficient can be considered to be the value of 0.45 for any shrinkage development. It was also proved, that the tensile creep value essentially affects the magnitude of residual stresses, even in the “early age” concrete. The correctness of the calculated residual stresses was verified by means of a Ring-test.

scholarly journals Influence of Steel Plates and Studs on Shrinkage Behavior and Cracking Potential of High-Performance Concrete

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 342 ◽  
Author(s):  
Lepeng Huang ◽  
Jianmin Hua ◽  
Ming Kang ◽  
Qiming Luo ◽  
Fengbin Zhou
Keyword(s):  
Elastic Modulus ◽  
High Performance ◽  
Steel Plate ◽  
High Performance Concrete ◽  
Shear Walls ◽  
Shrinkage Strain ◽  
Steel Plates ◽  
Cracking Potential ◽  
Composite Shear ◽  
Shrinkage Behavior

To help designers develop solutions to overcome the cracking problem in steel-plate-reinforced concrete composite shear walls due to the concrete shrinkage, the influence of steel plates and studs on the shrinkage behavior of high-performance concrete (HPC), including restrained shrinkage strain, shrinkage strain gradient, and cracking potential, were theoretically and experimentally investigated in this study. A model for theoretical analysis was used to research the shrinkage performance of concrete that was restrained by steel plates and studs. The major parameters involved in the experiments include the thickness and material elastic modulus of the steel plate, in addition to the diameter, height, and number of studs. It was found that the shrinkage of HPC decreases and its potential cracking increases with the increase of thickness and elastic modulus of the steel plate, and the diameter, height, and number of studs. The restraining effect of the steel plate and stud on the HPC shrinkage decreases with the distance of their respective locations. It demonstrates that the HPC near a steel plate and stud is prone to crack compared with that far away from the steel plate and stud. This potential could be reduced by uniformly restraining the HPC.

scholarly journals The Use of Superabsorbent Polymers in High Performance Concrete to Mitigate Autogenous Shrinkage in a Large-Scale Demonstrator

2020 ◽  
Vol 12 (11) ◽  
pp. 4741
Author(s):  
Laurence De Meyst ◽  
Judy Kheir ◽  
José Roberto Tenório Filho ◽  
Kim Van Tittelboom ◽  
Nele De Belie
Keyword(s):  
High Performance ◽  
Large Scale ◽  
High Performance Concrete ◽  
Measurement Techniques ◽  
Mechanical Strain ◽  
Autogenous Shrinkage ◽  
Free Water ◽  
High Strength ◽  
Ring Test ◽  
Superabsorbent Polymers

High performance concrete (HPC) is a high strength concrete that undergoes a lot of early-age autogenous shrinkage (AS). If shrinkage is restrained, then micro-cracks arise and threaten the durability of the structure. Superabsorbent polymers (SAPs) can reduce/mitigate the autogenous shrinkage, due to their promising application as internal curing agents. In this paper, large-scale demonstrators were built to investigate the efficiency of SAPs to mitigate autogenous shrinkage in HPC. For this purpose, different measurement techniques were used like embedded fiber optic sensors and demountable mechanical strain gauges, complemented by AS measurements in corrugated tubes and restrained ring tests. The SAP wall showed an AS reduction of 22%, 54%, and 60% at the bottom, middle, and top, respectively, as recorded by the sensors (in comparison with the reference wall (REF)). In the corrugated tubes, mitigation of AS was shown in the SAP mixture, and under restrained conditions, in the ring test, the reference mixture cracked after two days, while the SAP mixture had not cracked at the end of the measurement period (20 days). Cracks were shown on REF wall after one day, while the SAP wall was crack-free. Water flow tests performed on the main crack of the REF wall confirmed that the flow rate is related to the third power of the crack width. All tests showed that SAPs could highly reduce AS in HPC and avoid cracking.

Combined Influence of Expansive and Shrinkage Reducing Admixtures on the Shrinkage Behavior of Ultra-High Performance Concrete

2011 ◽  
Vol 488-489 ◽  
pp. 242-245 ◽  
Author(s):  
Jung Jun Park ◽  
Doo Youl Yoo ◽  
Sung Wook Kim ◽  
Young Soo Yoon
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Shrinkage Strain ◽  
Reducing Agents ◽  
Reinforcing Bars ◽  
Ultra High Performance Concrete ◽  
Free Shrinkage ◽  
Shrinkage Cracks ◽  
Binder Ratio ◽  
Shrinkage Reducing Admixtures

Since ultra-high performance cementitious composite (UHPCC) exhibits remarkable compressive strength and ductility, its application for structural member provides significant reduction of the section. The use of low water-to-binder ratio and admixtures with high fineness induce large shrinkage strain, leading to the possibility of large occurrence of shrinkage cracks due to the restraints of the form and reinforcing bars. Therefore, this study admixes a combination of expansive and shrinkage reducing agents as a solution to reduce the shrinkage of UHPCC. The eventual appropriateness is computed to evaluate the free shrinkage and restrained shrinkage behaviors. From the test results, the admixing of a combination of expansive and shrinkage reducing agents is seen to achieve a reduction of the free shrinkage by 30% to 50% at 28 days and a reduction of the strain of the external steel by about 19%.

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