Shrinkage Of High Performance Concrete Research Articles

팽창재 및 수축저감제를 이용한 고성능 콘크리트의 수축특성

This study is intended to analyze the effectiveness of expansive additive, shrinkage reducing agent and combination of the two to reduce the autogenous and drying shrinkage of high performance concrete using mineral admixture such as fly ash, blast furnace slag powder and silica fume. According to results, when expansive additive and shrinkage reducing agent are mixed within an appropriate mixing ratio, fluidity and air content are not influenced, and the enhancement of compressive strength is favorable at the age of 91 and 180days. At the mixing ratio of expansive additive of 5% and 10%, the autogenous and drying shrinkage is reduced by 32∼68% and 25∼49% respectively in comparison with plain concrete. And they are reduced by 18∼34% and 16∼26% respectively at the mixing ratio of shrinkage reducing agent of 0.5% and 1.0%, compared with plain concrete. The mixture of EA-SR combined with expansive additive and shrinkage reducing agent is most effective for reduction of shrinkage. Therefore, it is considered that the using method in combination with expansive additive and shrinkage reducing agent is effective to reduce the shrinkage of high performance concrete using mineral admixture such as fly ash, blast slag powder and silica fume.

Autogenous shrinkage of high-performance concrete containing fly ash

This paper focuses on the effect of fly ash on autogenous shrinkage of high-performance concrete (HPC). The stresses induced by autogenous shrinkage were calculated using finite element method and a model for predicting autogenous shrinkage including the effect of fly ash was proposed. Test results show that autogenous shrinkage of HPC with water-to-cementitious materials ratio (w/cm) of equal to or less than 0·35 developed more rapidly than that of normal-strength concrete (NSC) with a w/cm of 0·50. For HPC with the same w/cm but containing fly ash, autogenous shrinkage decreased – the higher the fly ash replacement percentage, the lower the level of autogenous shrinkage. Numerical analysis results show that the tensile stress induced by autogenous shrinkage may cause early-age cracking in HPC. In conclusion, although partial replacement of cement by fly ash could effectively reduce autogenous shrinkage of HPC, incorporating fly ash only might not prevent early-age cracking.

The Influence of Concrete Ingredients on Shrinkage of High Performance Concrete

The Influence of Concrete Ingredients on Shrinkage of High Performance Concrete

Eight-year exploration of shrinkage in high-performance concrete

In this paper, an experimental and analytical exploration on the effect of water–binder ratio (w/b), silica fume and age on autogenous, carbonation, drying and total shrinkage of high-performance concrete (HPC) is outlined. Eight types of HPC were studied. Carbonation, internal relative humidity (RH) and strength were studied on specimens from the same batch of HPC that was used in the studies of shrinkage. The results indicate fairly good correlation between carbonation, shrinkage, w/b and RH. The type and amount of silica fume affected shrinkage.

A study on creep and drying shrinkage of high performance concrete

Creep and drying shrinkage are two important time-dependent properties of high-performance concrete (HPC). In this study, three groups of HPC with same mix proportioning except the type of binding materials were prepared. Their creep behaviour and drying shrinkage characteristics were measured in accordance with the Chinese Standard GBJ82-85. The effects of ultrafine ground granulated blast-furnace slag (GGBS) and silica fume (SF) on creep and drying shrinkage of HPC were compared and the mechanism was analysed.

Correlating laboratory and field tests of creep in high-performance concrete

This article outlines experimental laboratory and field studies on creep of young or mature high-performance concrete (HPC) carried out between 1991 and 1999. For this purpose, about 400 cylinders made out of eight mix compositions of HPC were studied in the laboratory. Half the number of HPC was sealed; half of the studies were carried out on air-cured HPC. Parallel tests on strength, internal relative humidity, RH and hydration were carried out on about 900 cubes that were made of HPC from the same batch as the cylinders were. Fragments from the strength tests were used to observe RH. Shrinkage was studied parallel to creep. The results and analyses of the laboratory studies show large influence of the maturity and of the mix composition of the HPC on the measured creep. The creep coefficient of HPC is smaller than in normal concrete. In contrast, shrinkage of HPC is somewhat larger than in normal concrete. The results obtained in the laboratory were correlated to field tests on 27 beams. The results in the field coincided well with the results in the laboratory studies.

Autogenous Shrinkage of Ground-Granulated Blast-Furnace Slag Concrete

This investigation was carried out to study the effects of replacement percentage and fineness of ground granulated blast-furnace slag (GGBFS) on the autogenous shrinkage of high-performance concrete. All the mixtures had the same water-cementitious materials ratio (w/cm = 0.30) and the same volume of binder at 31 % of the total volume of concrete. The 91-day compressive strengths of all the concretes were above 80 MPa. Test results revealed that the 50% GGBFS concrete had the highest compressive strength at 91 days and the highest autogenous shrinkage. It was also found that concrete specimens containing finer GGBFS particles showed faster compressive strength development and greater autogenous shrinkage strains.

Experimental studies on shrinkage of high-performance concrete

This article outlines experimental and numerical studies on shrinkage of high-performance concrete (HPC). Carbonation shrinkage especially may introduce surface cracking in concrete, which affects the durability. In order to study shrinkage, cylinders of eight qualities of HPC were investigated. Parallel studies on autogenous shrinkage, drying shrinkage, hydration, internal relative humidity, and strength were carried out. Previous research in the field is summed up. Mechanisms of carbonation shrinkage by modeling correlations to the composition of the HPC and the physical properties are presented. The results indicate that carbonation shrinkage may be avoided by addition of silica fume. The project was carried out from 1992 through 1996.

Time-Dependent Prestress Losses in Prestressed Concrete Girders Built of High-Performance Concrete

The Washington State Department of Transportation is one of several state departments of transportation involved in demonstration projects to acquire information and data on the design, fabrication, and construction of prestressed concrete bridges with high-performance concrete (HPC). Predicting the time-dependent prestress losses due to the creep and shrinkage of HPC and the relaxation of prestressing steel is difficult because of the limited experience with and data on the creep and shrinkage properties of HPC. The AASHTO load resistance factor design specification approach to estimating prestress losses is discussed, and the time-step method and the modified rate-of-creep method are introduced as ways of predicting more accurately the time-dependent prestress losses. A design example is used to compare and discuss numerically the prestress losses computed by the various methods. The modified rate-of-creep analysis method yields the lowest losses. The modified rate-of-creep method is a desirable, comprehensive, applicable, and practical method for estimating time-dependent prestress losses in composite and noncomposite prestressed concrete girders with HPC. This method is suitable for manual and electronic computation.

Drying Shrinkage of Ready-Mixed High-Performance Concrete

This paper reports on drying shrinkage undergone by ready-mixed high-performance concrete (HPC). Shrinkage measurements were carried out on concrete specimens as well as on instrumented reference columns. Two different HPC were tested. The first one had a compressive strength of 98 MPa (14,200 psi) at 91 days and the second had a compressive strength of 80 MPa (11,600 psi). The first contained silica fume but the second did not. The effects of the following factors were investigated: curing time, curing conditions, silica-fume content, and water-cementitious materials ratio. It was found that the longer the curing time the lower the drying shrinkage, and that the lower the water-cementitious materials ratio the lower the drying shrinkage. Drying shrinkage of small specimens was compared to that of actual large-sized columns made with these HPC. Shrinkage measured by a conventional laboratory test was found to overestimate shrinkage of HPC in a real structure. The validity of using an American Concrete Institute (ACI) 209 expression derived for ordinary concrete to predict drying shrinkage of HPC was also investigated. It was found that this expression can be used for high-performance concrete only if new parameter values are considered.