Creep Of High Performance Concrete Research Articles

DEVELOPMENT OF SHRINKAGE AND CREEP PREDICTION MODELS FOR HIGH PERFORMANCE CONCRETE BY FAST-ACCESS CLOUD-BASED DATABASE

This study presents the first analysis system and fast-access cloud database for shrinkage and creep of high-performance concrete in the world, named “shrinkage and creep database in Taiwan”, SCDT. SCDT not only has the most comprehensive experimental data, including NU, JSCE, Europe and TW database, but provides design tool for researchers and engineers. It can further facilitate the development of prediction models for localized concrete. Users can obtain the shrinkage and creep curves based on their selected prediction models in SCDT. Comparisons of predicted results of selected models and test results in chosen database can be generated in seconds. Examples of development of shrinkage and creep prediction models in Taiwan based on model B4 by using SCDT to reflect high performance concrete characteristics in Taiwan is also presented in this study. Users anywhere in the world can easily access SCDT to browse and upload data, receive predictive results, or develop predictive models.

Effects of shrinkage reducing admixture and internal curing agent on shrinkage and creep of high performance concrete

The shrinkage and creep behavior of track beam concrete have the significant influence on the stability and safety of train operation. While superabsorbent polymer (SAP) and shrinkage reducing agent (SRA) are two commonly used admixtures in such high-performance concrete. So, the shrinkage and creep behavior of concrete with SRA or SAP were studied in this paper. Moreover, The microstructure of the interfacial transition zone (ITZ) observed by the scanning electron microscope (SEM) was discussed for the improvement of the mechanical properties of the concrete after the creep test. The experimental results indicate that SRA has a positive effect on reducing the shrinkage and creep deformation of concrete, and it is beneficial to the improvement of long-term strength and elastic modulus with little influence on creep recovery. In contrast, SAP reduces shrinkage, but increases the creep of concrete with less creep recovery and higher residual stress. Meanwhile, the fib 2010 model was revised to improve the ability to predict the creep of concrete containing SAP and other admixtures. Besides, it was found concrete after creep test has better mechanical properties, and the improvement of sample with SAP is the most obvious. The analyses of SEM also conformed that the concrete after creep test has a higher degree of hydration, and the denser ITZ microstructure.

Experimental and simplified visual study to clarify the role of aggregate–paste interface on the early age shrinkage and creep of high-performance concrete

Experimental and simplified visual study to clarify the role of aggregate–paste interface on the early age shrinkage and creep of high-performance concrete

Early age tensile creep of high performance concrete containing mineral admixtures: Experiments and modeling

In the paper, the early age tensile creep behavior of high performance concrete (HPC) containing mineral admixtures was experimentally investigated. The results showed that, when the loading age was at 1 d and 2 d, the addition of fly ash (FA) increased the early age specific tensile creep of HPC, while blast furnace slag (BFS) showed an opposite effect. When the loading age was later than 3 d, the early age specific tensile creep of HPC was not obviously influenced by FA and BFS. Based on the experimental results, a rheology-based model (named as “ZC”, initials for the word “Self-developed” in Chinese) was proposed to predict the early age tensile creep of HPC with mineral admixtures. The ZC model was validated with other experimental results, and the prediction results agreed well with the experimental data. Moreover, the limitations and further improvements on the proposed model were also discussed in the paper.

Effect of SAP on the tensile creep of early-age concrete using ring specimens

Internal curing with super-absorbent polymer (SAP) has been developed to improve autogenous shrinkage of high performance concrete (HPC) in recent years. However, studies about effect of SAP on the tensile creep of HPC seem insufficient. In this paper, a series of concrete ring tests were conducted to investigate effect of SAP on the tensile creep of early-age HPC. Meanwhile, shrinkage and mechanical properties of concrete with SAP were also investigated. Results show that tensile creep coefficient of concrete with SAP was similar to that of reference concrete with same basic w/c, but lower compared with that of reference concrete with same total w/c.

Study on the Model of Creep and the Calculation of Stress Field for Concrete

The exact prediction of creep is of great significance for the simulation of the stress field of concrete creep. To overcome the limitation of the current prediction model of creep, pertinent models abroad are referred and adopted so that other factors can be controlled under standard state but only the creep varies to evaluate the feasibility of the prediction model with current characteristic of concrete materials and available test data. In the prediction of creep of high performance concrete, any influencing factor can be quantified, therefore, a large number of test data are not required. It was also observed that the defects that factors pointed out were common in the prediction model of concrete. The calculation was simple and convenient and achieved a higher accuracy. In the calculation of creep stress field, the creep was calculated according to fitting creep degree. Based on this, this paper established the creep coefficient formulas for the calculation of strain increment, and deduced the number of finite element expressions which were used to calculate the creep stress field with creep coefficient.

Effect of Fly Ash on Creep of High Performance Concrete Used in Bridge

W/C ratio and the quantity of fly ash added have obvious influence on creep of high performance concrete. Effect of different quantities of fly ash on creep of high performance concrete of different W/C ratios used in bridge is studied in this research whose results reflect that creep value reduces along with reduction of W/C ratio at a certain quantity of fly ash added. Adding fly ash restrains creep on the whole, however, the degree depends on the quantity of fly ash added. Creep value of high performance concrete mixed with class-I fly ash at blend ratio of 12~40% is lower than that of standard concrete and fly ash at blend ratio of 18% has the best effect. Creep value in 365d is 51% of that of standard concrete at fly ash blend ratio of 18%, while at fly ash blend ratio of 40%, creep value in 365d is lower than that of standard concrete but higher than that of concrete at other blend ratios. It is generally considered that inhibition of creep of high performance concrete begins to fall beyond blend ratio of 30%.

Analysis of interactions between damage and basic creep of HPC and HPFRC heated between 20 and 80 °C

The present study concerns the uniaxial compressive creep of High Performance Concrete (HPC) at moderate temperatures, 20–80 °C. The study was conducted on four formulations of HPC including two fibrous concretes envisioned for future storage structures of Intermediate Level Long-Life Nuclear Wastes. These wastes are exothermic and lead to maximal temperatures in the field ranging from 50 to 70 °C (Andra, Referentiel des materiaux de stockage de dechets a haute activite et a vie longue, 2005). Here, we investigate the basic creep under uniaxial compression at 50 and 80 °C and compare it to that obtained on the same HPC at 20 °C. The objective of this research is to contribute to a better understanding of the phenomenon of interaction between damage and basic creep of HPC at moderate temperature, especially with a view to its integration in Thermo-Hydro-Mechanical models dealing with the design of special structures (massive structures, specific serviceability conditions in nuclear or hydroelectric power plants, etc.). This test campaign allowed us to assess the effect of temperature on the magnitude of basic creep of HPC, and also the impact of various temperature and mechanical loading conditions on the Young’s modulus of HPC. Heating to 80 °C damages HPC (instantaneous Young’s modulus decrease) and thereby increases the creep capacity, showing a relation between damage and creep amplitude. Moreover, this study gives global activation energy of basic creep of HPC that should be useful for practitioners dealing with concrete structures sensitive to delayed strains and subjected to moderate temperature.

Effect of Internally Stored Water on Creep of High-Performance Concrete

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Age-Adjusted Effective Modulus Method for Creep of High-Performance Concrete

This paper discusses the suitability of using several creep theories of common concrete for creep of high-performance concrete (HPC). Based on the Age-Adjusted Effective Modulus method (AEMM) for creep of concrete, Improved Dischinger (ID) method and the Elastic Continuation and Plastic Flow (ECPF) theory for calculating relaxation coefficient and considering characteristics of HPC, a method is set up for calculating the creep of HPC under changing stresses, and comparing results gotten by the method with some experimental data, it can be considered that the above methods are suit for the calculation of creep of HPC.

Influence of maturity on creep of high performance concrete with sealed curing

This article outlines an experimental and numerical study of basic creep in High Performance Concrete. About 100 cylinders (studies of creep and shrinkage) and 400 cubes (for studies of hydration, internal relative humidity, and strength) were tested. The ambient climate was held constant at 20°C. One concrete was studied at other temperatures between-20°C and 60°C. Analyses were carried out of quasi-instantaneous deformation, short-and longterm basic creep, autogenous shrinkage, hydration, internal relative humidity, and compressive strength. The project was carried out between 1992 and 1996.