Autogenous Shrinkage in High-Performance Concrete-A Review

https://iopscience.iop.org/article/10.1088/1757-899X/518/2/022077, 2018

Recent trends in concrete technology have been towards high-strength concrete and ultra-high strength concrete with a low water-cement ratio. However, these high and ultra-high strength concretes have some problems. One of the problems is early-age cracking due to autogenous shrinkage. This study presents the results of an experimental investigation carried out to evaluate the autogenous shrinkage of high and ultra-high strength concrete. Main ideas on autogenous shrinkage are based on the use of ordinary Portland cement, but it has already become apparent that mineral admixtures and fibers change the behavior significantly. Variables were taken to study its effect on shrinkage like (effects of water/cement ratio, cement content, coarse aggregate content, silica fume percentage and steel fiber). From the test results, it is concluded that the autogenous shrinkage strain of mixes increases with decrease w/c ratio and decrease with increasing w/c ratio and concrete with the higher value of cement content, shows greater amounts of shrinkage. The autogenous shrinkage strain increases with decreasing of the coarse aggregate content. The additions of 10-20 % of silica fume to the mix increase the autogenous shrinkage strains of concrete specimens. The autogenous shrinkage decreased gradually with the increase of steel fiber content.

Advances in Materials Science and Engineering, 2015

The results of a laboratory investigation on the early autogenous shrinkage of high strength concrete, and the possibilities of its reduction, are presented. Such concrete demonstrates significant autogenous shrinkage, which should, however, be limited in the early stages of its development in order to prevent the occurrence of cracks and/or drop in the load-carrying capacity of concrete structures. The following possibilities for reducing autogenous shrinkage were investigated: the use of low-heat cement, a shrinkage-reducing admixture, steel fibres, premoistened polypropylene fibres, and presoaked lightweight aggregate. In the case of the use of presoaked natural lightweight aggregate, with a fraction from 2 to 4 mm, the early autogenous shrinkage of one-day-old high strength concrete decreased by about 90%, with no change to the concrete's compressive strength in comparison with that of the reference concrete.

Maǧallaẗ al-handasaẗ wa-al-tiknūlūǧiyā, 2021

 In UHPC, autogenous shrinkage dominates over the drying shrinkage.  High pouring temperature and coarse sand increase the number and size of pores.  Increasing silica fume over 25% of cement content reduces compressive strength.  Adding steel or basalt fibers minimize the inverse effect of autogenous shrinkage. Ultra-High Performance Concrete (UHPC) is a new generation of concrete characterized by its high strength, high durability, and high stiffness. Autogenously shrinkage represents one of the issues of UHPC that occurred at early ages. It occurs particularly during the first 48 hours after casting. This paper focuses on the ways that can be depended on to mitigate the autogenously shrinkage and obtain the outstanding mechanical properties of UHPC. The results showed that the use of coarse sand and high dose of high range water reduced the admixture above 5% of cementations of materials weight, and high ambient temperature at the time of mixing and casting led to increasing the autogenously shrinkage. While using fine sand, silica fume at 25% of cement weight, and crushed ice at 50% of mixing water to control the mixing temperature can reduce autogenously shrinkage significantly.

Cement and Concrete Research, 2000

Development of internal stresses induced by restrained autogenous shrinkage in high-strength concretes at early ages was investigated. Effects of water/binder ratio and the presence of silica fume on the stress developed were evaluated and considered in conjunction with the creep behavior of the concretes. The restrained autogenous shrinkage resulted in a relatively high stress that sometimes caused premature cracking in the high-strength concrete. This occurred mainly when the ratio between the restraining stress and the tensile strength approached 50%. The stresses were not as high as expected from the autogenous shrinkage, since considerable relaxation took place due to creep. Thus, the viscoelastic nature of the concrete at early age has a considerable influence on the stresses generated. D

Civil Engineering Journal

Concrete is indeed one of the most consumed construction materials all over the world. In spite of that, its behavior towards absolute volume change is still faced with uncertainties in terms of chemical and physical reactions at different stages of its life span, starting from the early time of hydration process, which depends on various factors including water/cement ratio, concrete proportioning and surrounding environmental conditions. This interest in understanding and defining the different types of shrinkage and the factors impacting each one is driven by the importance of these volumetric variations in determining the concrete permeability, which ultimately controls its durability. Many studies have shown that the total prevention of concrete from undergoing shrinkage is impractical. However, different practices have been used to control various types of shrinkage in concrete and limit its magnitude. This paper provides a detailed review of the major and latest findings rega...

Journal of Advanced Concrete Technology, 2016

An extensive research was undertaken in order to determine the dependence of shrinkage of high and normal strength concrete on the compressive strength and concrete composition. The part of research concerning dependence of autogenous shrinkage on compressive strength is presented in this paper. Ten groups of concrete, with the total of twenty nine mixtures, were prepared. Concrete mixtures of each individual group were made using the same quantity of water, while the quantity of cement (CEM II/A-S 42,5R) and mineral admixture (silica fume) was varied in each group. Concrete groups differed according to the quantity of water. Autogenous shrinkage of concrete was monitored together with the influence of initial curing in water on concrete shrinkage. Initial autogenous expansion was noticed during testing autogenous shrinkage, especially on normal strength concrete. Based on the analysis of experimental results, the dependence of autogenous shrinkage at one day of concrete age on compressive strength was defined. The dependence of autogenous shrinkage at later ages on compressive strength of concrete was also presented. Finally, the autogenous shrinkage components of best-known theoretical shrinkage prediction models were compared with experimental data.

Materials

This paper focuses on the experimental determination of the shrinkage process in Self-Compacting High-Performance Concrete (SCC HPC) exposed to dry air and autogenous conditions. Special molds with dimensions of 100 mm × 60 mm × 1000 mm and 50 mm × 50 mm × 300 mm equipped with one movable head are used for the measurement. The main aim of this study is to compare the shrinkage curves of SCC HPC, which were obtained by using different measurement devices and for specimens of different sizes. In addition, two different times t0 are considered for the data evaluation to investigate the influence of this factor on the absolute value of shrinkage. In the first case, t0 is the time of the start of measurement, in the second case, t0 is the setting time. The early-shrinkage (48 h) is continuously measured using inductive sensors leant against the movable head and with strain gauges embedded inside the test specimen. To monitor the long term shrinkage, the specimens are equipped with specia...

Structural Concrete, 2020

Self-compacting concrete (SCC) is a concrete that does not require vibration for casting and consolidation. It is able to flow under its own weight, completely filling the formwork and achieving full consolidation, even in the presence of congested reinforcement. SCC possesses special technical features and properties that recommend its application in a considerable amount of applications. Nevertheless, an inadequate behavior of the material at early ages has been observed in some situations, due to shrinkage. Shrinkage has a significant importance in the design, construction and in-service performance of concrete structures. The regulatory requirements were derived from experience with traditional concrete, which is not always suitable for SCC. In addition, the option of using new materials, such as binders with large amount of pozzolanic or latent hydraulic additions, strongly limits the validity of existing rules. In order to contribute for a better understanding of the major drawback of this material-its high potential shrinkage, experimental research was carried out using different commercial shrinkage-compensating products. This study focuses on the use of a shrinkage reducing admixture and an expansive agent. The results obtained demonstrate the efficiency of the individual or combined use of these products and allowed identifying three different strategies to control the shrinkage, with distinct levels of efficiency.

The amount of fine pores in UHPC can highly affect the autogenous shrinkage. A strong correlation between the autogenous shrinkage and the porosity of UHPC was established. Reducing the fine pores in FA/GGBS samples leads to a reduction of the autogenous shrinkage. a b s t r a c t Ultra-high performance concrete (UHPC) not only presents ultra-high compressive strength but also exhibits ultra-high durability, due to its extremely dense structure and consequently highly reduced porosity. However, high dosages of silica fume (SF), typically adopted in UHPC, also lead to high autoge-nous shrinkage. This phenomenon, occurring at early ages, induces high internal stresses that, in turn, cause microcracking and increase permeability and, therefore, reduce the durability of concrete structures. The experimental study was conducted aiming to replace SF by another fine supplementary cemen-titious materials (SCMs), such as fly ash (FA) or ground granulated blast furnace slag (GGBS), in order to reduce the amount of autogenous shrinkage. The adopted approach involved partial or total replacement of SF by SCMs. Results indicate that the amount of fine pores in UHPC is a predominant factor that can highly affect the autogenous shrinkage. A strong correlation between the natural logarithm of autogenous shrinkage and the total porosity of UHPC mixtures was established. It was found that reducing the amount of fine pores in specimens containing FA or GGBS leads to a reduction of the autogenous shrinkage.

Lecture notes in civil engineering, 2019

High Performance Concrete (HPC), particularly high strength concrete mixes (60-100MPa) containing high cementitious content and low w/b ratios (0.40-0.25) is used for some precast elements. Ultra High Performance Concrete (UHPC) up to 200MPa containing very high cementitious content and very low w/b ratios (0.25-0.17) is also used for precast and prestressed elements in buildings and bridges. Shrinkage characteristics of HPC and UHPC differ considerably from those of conventional concrete. Due to their high cementitious content and low w/b ratios, the drying shrinkage component is significantly smaller when compared with the autogenous shrinkage component. HPC and UHPC elements, when steam-cured, undergo majority of their shrinkage within a few days of casting. In this paper, mechanisms of autogenous shrinkage of HPC and UHPC at early ages are compared under different curing conditions. Contribution of autogenous shrinkage and drying shrinkage components on the total shrinkage is discussed. At very early ages, plastic shrinkage and plastic settlement cracking and factors affecting them for HPC and UHPC are also outlined.