scholarly journals Strategies for improving dimensional stability of concrete

2016 ◽  
Vol 43 (10) ◽  
pp. 875-885
Author(s):  
P.L. Ng ◽  
Albert K.H. Kwan
Keyword(s):  
Dimensional Stability ◽  
Cement Content ◽  
Drying Shrinkage ◽  
Sustained Load ◽  
Early Age ◽  
Test Results ◽  
Dimensional Changes ◽  
Shrinkage And Creep ◽  
Concrete Mix

Changes in dimension of concrete due to early-age heat generation, long-term drying shrinkage, and creep under sustained load could lead to significant movements of the concrete structure and lock-up stresses if the movements are restrained. The lock-up stresses are often large enough to cause cracking and water leakage, thereby adversely affecting the serviceability and durability of the structure. Whilst the dimensional changes are quite variable because of their dependence on the environmental conditions and applied loads, they are all related to the concrete mix proportions. Generally, the dimensional stability of concrete can be improved by reducing its cement content and paste volume. Moreover, since the aggregate also shrinks, the dimensional stability can be improved by suppressing the shrinkage of aggregate as well. In this paper, strategies for improving the dimensional stability of concrete are formulated based on experimental research. Test results are presented to demonstrate their effectiveness and applicability.

Influence of Early Age Volume Changes on Long-Term Concrete Shrinkage

1998 ◽  
Vol 1610 (1) ◽  
pp. 28-32 ◽  
Author(s):  
Erika E. Holt ◽  
Donald J. Janssen
Keyword(s):  
Concrete Slab ◽  
Drying Shrinkage ◽  
Early Age ◽  
Volume Changes ◽  
Test Procedures ◽  
Cracking Behavior ◽  
Concrete Shrinkage ◽  
Cracking Potential ◽  
Partially Restrained

Volume changes can occur in concrete during the first 24 hr and are generally missed in laboratory shrinkage evaluations. Unfortunately these early age volume changes are present in real pavements and structures and can contribute to the cracking behavior of the concrete at later ages. Early age volume changes can occur in two forms: drying shrinkage before the start of curing and autogenous volume changes. Although these early age volume changes are often dismissed as being insignificant, recent work in Europe has identified magnitudes for early age volume changes of some concretes that are equal to or greater than 28-day drying shrinkage measurements. Expansions have also been identified in some cases. The results of some investigations of volume changes in concrete during the first 24 hr under both drying and nondrying conditions are presented. An example of potential long-term cracking under partially restrained conditions (concrete slab-on-grade modeled by a concrete ring cast around a hollow steel ring) is used to illustrate the magnitude of influence of early age volume changes on concrete cracking. Both test procedures employ nonstandard methods to quantify the cracking potential of concrete.

Long-Term Behavior of Low-Heat Cement Concrete under Different Curing Temperatures

2016 ◽  
Vol 723 ◽  
pp. 819-823 ◽  
Author(s):  
Jae Sung Mun ◽  
Keun Hyeok Yang ◽  
Si Jun Kim
Keyword(s):  
Drying Shrinkage ◽  
Curing Temperature ◽  
Limestone Powder ◽  
Partial Replacement ◽  
Mass Concrete ◽  
Test Results ◽  
Long Term Behavior ◽  
Ambient Curing ◽  
Ternary Blended Concrete

The present study is to estimate long-term characteristics of low-heat cement-based ternary blended concrete prepared for reducing hydration heat in mass concrete. 15% modified fly ash and 5% limestone powder were added for partial replacement of the low-heat cement. To achieve the designed compressive strength of 42 MPa, water-to-binder ratios were determined to be 27.5, 30 and 32.5% for ambient curing temperatures of 5, 20 and 40°C, respectively. Test results showed that, with the decrease in curing temperature, the drying shrinkage strains tended to decrease, whereas creep strain increased.

Time-Dependent Properties of Lightweight Concrete Using Sedimentary Lightweight Aggregate

2010 ◽  
Vol 168-170 ◽  
pp. 2235-2240
Author(s):  
How Ji Chen ◽  
Wen Po Tsai ◽  
Ming Der Yang
Keyword(s):  
Lightweight Concrete ◽  
Drying Shrinkage ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Time Dependent ◽  
Test Results ◽  
Fine Sediments ◽  
Normal Weight Concrete ◽  
Shrinkage And Creep ◽  
Shihmen Reservoir

A kind of lightweight aggregate (LWA) has been successfully developed in Taiwan, which was made by expanding under heat fine sediments dredged from the Shihmen Reservoir. In this study the performances of concrete made from the aforementioned LWA were tested and compared with those of the companion normal weight concrete (NC). The test results show that the so produced lightweight concrete (LWAC) exhibited a comparable time-dependent properties (i.e., compressive strength, elastic modulus, drying shrinkage, and creep) as compared with those of the companion NC. Based on the results, it can be concluded that the use of prewetted LWAs and the incorporation of pozzolan materials can effectively control the drying shrinkage of LWAC. The specific creep of the LC mixture was obviously higher than that of the NC mixture at the same curing time.

scholarly journals A Study on High Strength Concrete with Moderate Cement Content Incorporating Limestone Powder

2014 ◽  
Vol 61 (1) ◽  
pp. 43-58 ◽  
Author(s):  
Alaa M. Rashad ◽  
Hosam.El Din H. Seleem
Keyword(s):  
Compressive Strength ◽  
High Strength Concrete ◽  
Coarse Aggregate ◽  
Cement Content ◽  
Drying Shrinkage ◽  
High Strength ◽  
Limestone Powder ◽  
Test Results ◽  
Strength Concrete ◽  
The Difference

Abstract This paper presents the results of an investigation to assess the validity of producing high strength concrete (HSC) using moderate cement content to reduce the consumption of the binders. Cement content is lowered from 500 kg/m3 to 400 kg/m3. The difference in cement content is compensated by the addition of fine limestone (LS) powder. Pozzolans were incorporated as an addition to cement. Different coarse aggregate types were employed. Workability, compressive strength, tensile strength, permeability and drying shrinkage were measured. Test results revealed that HSC with a compressive strength up to 79 MPa (at 90 days age) could be produced with moderate cement content. The mixtures consistency and drying shrinkage are greatly enhanced due to employing LS powder and the permeability is satisfactory. To provide better solution to some concrete disadvantages like cracking and drying shrinkage, using an economic rate for cement are believed to reduce these disadvantages.

Drying of Recycled Aggregate Concrete: Plastic Shrinkage, Cracking Sensitivity, and Durability

2016 ◽  
Vol 711 ◽  
pp. 111-117
Author(s):  
Ahmed Zakarya Bendimerad ◽  
Emmanuel Roziere ◽  
Ahmed Loukili
Keyword(s):  
Water Saturation ◽  
Drying Shrinkage ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Early Age ◽  
Initial Water ◽  
Natural Aggregates ◽  
Cracking Sensitivity

This paper presents the results of experimental research on recycled concrete at early age and long term. It consists in studying the effect of initial water saturation of recycled concrete gravel (RG). Five mixtures were investigated, one mixture with natural aggregates only (reference concrete) and the second with 100% of RG using four initial water saturations: 30%, 70%, 100% and 120% of saturated surface dried (SSD) state. A stress/strength approach was used to quantify the risk of cracking at early age. It is based on experimentally assessed parameters. At long term the effect of initial water saturation on the ultimate drying shrinkage was investigated. The drying shrinkage was correlated with drying depth and the natural carbonation was also studied. At early age the results indicate RG affected the properties of the recycled concrete. However, the concrete with oversaturated RG showed a behavior close to reference concrete in terms of cracking sensitivity. At long term, the drying shrinkage is weakly depending of initial water saturation, but the durability of concrete can be affected by the drying depth. A good correlation between compressive strength at one day and the carbonation depth at 18 months was observed

scholarly journals Case Study on Early Age Shrinkage of Cement-based Composites

2015 ◽  
Vol 2 ◽  
pp. 79
Author(s):  
Andina Sprince ◽  
Leonids Pakrastinsh
Keyword(s):  
High Performance ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Cement Composite ◽  
Early Age ◽  
Thin Walls ◽  
Reinforced Cement ◽  
Pva Fiber

The aim of this paper was to study the behaviour of new high-performance fibre-reinforced cement composite materials (FRCC) that are reinforced with polyvinyl alcohol (PVA) fibres. The shrinkage deformations at early age, the compressive strength and modulus of elasticity of the new compositions had been determined. Test results shows that the addition of PVA fiber 1.10% and 0.55% by weight of the cement has negligible influence on concrete drying shrinkage, however, it is affect the concrete plastic and autogenous shrinkage. The results of the experiments permitted the prediction of long-term deformations of the concrete. Wider use of this material permit the construction of sustainable next generation structures with thin walls and large spans that cannot be built using the traditional concrete.

Study on Strength, Shrinkage and Creep of Concrete Containing Ultrafine Fly Ash Composites

2012 ◽  
Vol 450-451 ◽  
pp. 162-167
Author(s):  
Bao Ju Liu ◽  
You Jun Xie
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Drying Shrinkage ◽  
Experimental Results ◽  
Steam Curing ◽  
Curing Conditions ◽  
Shrinkage And Creep

At steam curing and moist curing conditions, the mechanical properties of concrete with different fineness and different proportions ultrafine fly ash-slag composite were studied. The experimental results indicated that the addition of ultrafine fly ash-slag composite had improved the long term mechanical properties of steam-cured concrete. The concrete with ultrafine fly ash-slag composite has lower drying shrinkage and creep compared to that of control concrete.

scholarly journals Modelling of Coupled Shrinkage and Creep in Multiphase Formulations for Hardening Concrete

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1745
Author(s):  
Peter Gamnitzer ◽  
Andreas Brugger ◽  
Martin Drexel ◽  
Günter Hofstetter
Keyword(s):  
Viscous Flow ◽  
Effective Stress ◽  
Drying Shrinkage ◽  
Shrinkage Strain ◽  
Viscoelastic Creep ◽  
Limit Value ◽  
Shrinkage And Creep ◽  
Mechanical Models ◽  
Term Response

The durability and serviceability of concrete structures is influenced by both the early-age behavior of concrete as well as its long-term response in terms of shrinkage and creep. Hygro-thermo-chemo-mechanical models, as they are used in the present publication, offer the possibility to consistently model the behavior of concrete from the first hours to several years. However, shortcomings of the formulation based on effective stress, which is usually employed in such multiphase models, were identified. As a remedy, two alternative formulations with a different coupling of shrinkage and creep are proposed in the present publication. Both assume viscous flow creep to be driven by total stress instead of effective stress, while viscoelastic creep is driven either by total or effective stress. Therefore, in contrast to the formulation based on effective stress, they predict a limit value for shrinkage as observed in long-term drying shrinkage tests. Shrinkage parameters for the new formulations are calibrated based on drying shrinkage data obtained from thin slices. The calibration process is straightforward for the new formulations since they decouple shrinkage and viscous flow creep. The different formulations are compared using results from shrinkage tests on sealed and unsealed cylindrical specimens. Shrinkage strain predictions are significantly improved by the new formulations.

scholarly journals An Experimental Study of the Road Performance of Cement Stabilized Coal Gangue

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 993
Author(s):  
Junfeng Guan ◽  
Meng Lu ◽  
Xianhua Yao ◽  
Qing Wang ◽  
Decai Wang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Cement Content ◽  
Drying Shrinkage ◽  
Strength Loss ◽  
Coal Gangue ◽  
Dry Density ◽  
Test Results ◽  
Maximum Dry Density ◽  
The Road ◽  
Road Performance

The research into the road performance of coal gangue is of great significance for the consumption of coal gangue and reducing pollution. In this paper, the coal gangues were prepared by separation and crushing processes, and their gradations were also optimized. Aiming to identify the possible problems of coal gangue as a pavement base, an unconfined compressive strength test, a splitting test, a freeze–thaw test, and a drying shrinkage test of cement stabilized gangue with varying cement amounts were carried out, and the test results were compared and analyzed. The test results showed that the maximum dry density and optimum moisture content (OMC) of the optimized cement stabilized gangue and cement stabilized macadam increased with cement content. The maximum dry density and OMC of cement stabilized macadam were larger than that of cement stabilized gangue with the same cement content. The optimized 7-day unconfined compressive strength of cement stabilized gangue can meet the requirements for a secondary and lower highway base and subbase. The OMC and cement content are the critical factors affecting the compressive strength loss rate of cement stabilized gangue after freeze–thaw cycles. The smaller the OMC of cement stabilized gangue and the larger the cement content, the lower the compressive strength loss rate. With an increase in cement content, the drying shrinkage strain of cement stabilized gangue increased. The results show that a cement content of 4% is optimal for the cement stabilized coal gangue, which can be used for the light traffic base and heavy traffic subbase of class II and below highways. It provides a basis, guide, and reference for the application of coal gangue materials in a high-grade highway base.

Long-Term Deformations of Steel-Reinforced Concrete Columns under Sustained Axial Loads

2013 ◽  
Vol 351-352 ◽  
pp. 645-649
Author(s):  
Zhou Yi Chen ◽  
Yang Wang ◽  
Jian Qing Wu
Keyword(s):  
Reinforced Concrete ◽  
Axial Loading ◽  
Test Results ◽  
Axial Loads ◽  
Steel Reinforced Concrete ◽  
Dependent Behavior ◽  
Shrinkage And Creep ◽  
Long Term Behavior ◽  
Creep And Shrinkage

Steel-reinforced concrete (SRC) columns have been widely used over the past few decades. However, very limited research has been conducted on the time-dependent behavior of these columns caused by creep and shrinkage under sustained loading. This paper presents the results of an experimental study of the long-term behavior of short SRC columns under sustained axial loading. Long-term axial deformations due to shrinkage and creep of the concrete were recorded. In analysis of the test results, time analysis of the SRC columns under sustained axial loads using the age-adjusted effective modulus method was proven to be suitable by employing the ACI 209 model for prediction of shrinkage and the CEB-FIP90 model for the prediction of creep.

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