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.

Parameter Analysis of the Reinforcement for the Width and Spacing Control of the Early-Age Cracks in Concrete

2016 ◽  
Vol 691 ◽  
pp. 14-27
Author(s):  
Robert Sonnenschein ◽  
Juraj Bilčík ◽  
Katarína Gajdošová
Keyword(s):  
Drying Shrinkage ◽  
Peak Level ◽  
Parameter Analysis ◽  
Early Age ◽  
Reinforcing Bars ◽  
Volume Changes ◽  
Concrete Element ◽  
Thermal Movement ◽  
Cover Thickness ◽  
Crack Widths

Early-age volume changes in concrete induced by temperature change, hydration, autogenous and drying shrinkage can lead to concrete cracking and this can have lasting effects on serviceability, durability or aesthetics of the structure. The restraint to thermal movement is the product of the coefficient of the temperature fall from a peak level during cement hydration and a restraint factor. In most cases it is not necessary and also not economical to avoid cracks. In these cases, crack widths are limited due to water tightness, durability or aesthetic reasons. If early-age thermal cracking cannot be prevented, crack width can be controlled with reinforcement. The reinforcement distributes cracks and consequently reduces their widths and spacing. As a result, there forms a large number of smaller cracks instead of a few through-cracks. This means, that due to the formation of fine cracks, the strain capacity of a reinforced concrete element before the occurrence of through cracks can be increased with the help of skin reinforcement. This paper discusses the parameters of reinforcement affecting the width and spacing of early-age cracks in concrete. The effect of reinforcement on early-age cracking in concrete was investigated on numerical simulation and in full-scale experiments. The test variables were the reinforcement ratio and the cover thickness of the longitudinal reinforcing bars.

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.

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 Restrained Stress Development in Hardening Mortar Internally Cured with Superabsorbent Polymers under Autogenous and Drying Conditions

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 979
Author(s):  
Jung Heum Yeon
Keyword(s):  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Early Age ◽  
Shrinkage Cracking ◽  
Stress Development ◽  
Cracking Potential ◽  
Different Types ◽  
Internal Relative Humidity ◽  
Series Of Experiments ◽  
Drying Conditions

This study reports the results of a series of experiments, particularly paying attention to the early-age behavior and response of hardening mortars incorporating different types and contents of superabsorbent polymer (SAP) under autogenous (sealed) and drying shrinkage (unsealed) conditions. To achieve this primary aim, the effects of SAP type (i.e., cross-linking density and grain size) and content on the internal relative humidity (IRH) changes and corresponding free shrinkage behavior, restrained stress development, and cracking potential of the mortar were extensively measured and analyzed, along with their strength and set time properties. The results of this study have shown that the internal curing (IC) via SAP effectively counteracted the early-age residual stress build-up due to autogenous shrinkage, as many other former studies described. No or little tensile residual stresses due to autogenous shrinkage took place when more than 0.4% SAP was added, regardless of the SAP type. However, it should be mentioned that the addition of SAP, irrespective of its content and type, hardly improved the shrinkage cracking resistance of the mortar when directly exposed to drying environment at early ages.

scholarly journals Influence of compressive strength and maturity conditions on shrinkage of ordinary concrete

2021 ◽  
Vol 13 (6) ◽  
pp. 168781402110244
Author(s):  
Olga Szlachetka ◽  
Joanna Witkowska-Dobrev ◽  
Marek Dohojda ◽  
Anna Cała
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Drying Shrinkage ◽  
Point Of View ◽  
Early Age ◽  
Volume Changes ◽  
Ordinary Concrete ◽  
Dry Conditions ◽  
Total Elimination

The paper presents results of investigations of compressive strength and shrinkage of concrete samples made on the basis of the Portland cement CEM I 32.5R, after 2, 7, 14, 28, 90, and 365 days of maturation in four different maturation conditions. It was shown that after 28 days the samples cured according to the standard in the cuvettes with water achieved the highest compressive strength, although the early-age compressive strengths after 7 and 14 days were lower than those for the samples cured in building film and in dry conditions. A determined correlation between the compressive strength and shrinkage of the concrete proves that wet curing also allows a total elimination of the shrinkage in the first 28 days. Along with the growth of the compressive strength, the drying shrinkage reduces. Obtained results confirmed that the best way of concrete curing, among the analyzed methods, from the point of view of both compressive strength and volume changes is the wet curing.

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.

scholarly journals Autogenous and drying shrinkage of mortars based on Portland and calcium sulfoaluminate cements

2020 ◽  
Vol 53 (5) ◽  
Author(s):  
Davide Sirtoli ◽  
Mateusz Wyrzykowski ◽  
Paolo Riva ◽  
Pietro Lura
Keyword(s):  
Portland Cement ◽  
Water Demand ◽  
Ordinary Portland Cement ◽  
Rapid Evolution ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
High Water ◽  
Early Age ◽  
Volume Changes ◽  
Calcium Sulfoaluminate

Abstract Calcium sulfoaluminate (CSA) cement can be used as an alternative binder in concrete, partially or fully replacing ordinary Portland cement. While CSA cement considerably accelerates the mechanical properties development, the rapid evolution of the microstructure together with the high water demand cause rapid and large volume changes at early ages. As volume changes may lead to early-age cracking, measures to reduce them may be required In this paper, autogenous and drying shrinkage are studied in mortars prepared with Portland cement, CSA cement or a 50/50 blend as binder. Very fast self-desiccation and high autogenous shrinkage of the CSA-based mortar were observed compared to the mortar made with Portland cement. On the other hand, the early-age volume changes can be limited if a blend of the two cements is used. The blended system revealed a bi-modal trend in the evolution of self-desiccation and autogenous shrinkage, in which the initial fast self-desiccation and shrinkage enter the dormant phase after the first couple of days and again start after about 28 days.

Mild gray matter atrophy in patients with long-standing multiple sclerosis and favorable clinical course

2021 ◽  
pp. 135245852110196
Author(s):  
Rosa Cortese ◽  
Marco Battaglini ◽  
Francesca Parodi ◽  
Maria Laura Stromillo ◽  
Emilio Portaccio ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Multiple Sclerosis ◽  
Gray Matter ◽  
Clinical Course ◽  
Resonance Imaging ◽  
Volume Changes ◽  
Magnetic Resonance Imaging Mri ◽  
Global Brain ◽  
Diffuse Brain

The mechanisms responsible for the favorable clinical course in multiple sclerosis (MS) remain unclear. In this longitudinal study, we assessed whether magnetic resonance imaging (MRI)-based changes in focal and diffuse brain damage are associated with a long-term favorable MS diseases course. We found that global brain and gray matter (GM) atrophy changes were milder in MS patients with long-standing disease (⩾30 years from onset) and favorable (no/minimal disability) clinical course than in sex-age-matched disable MS patients, independently of lesions accumulation. Data showed that different trajectories of volume changes, as reflected by mild GM atrophy, may characterize patients with long-term favorable evolution.

scholarly journals Long-Term Concrete Shrinkage Influence on the Performance of Reinforced Concrete Structures

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 254
Author(s):  
Alinda Dey ◽  
Akshay Vijay Vastrad ◽  
Mattia Francesco Bado ◽  
Aleksandr Sokolov ◽  
Gintaris Kaklauskas
Keyword(s):  
Reinforced Concrete ◽  
Reinforced Concrete Structures ◽  
Tension Stiffening ◽  
Model Code ◽  
Concrete Shrinkage ◽  
Time Period ◽  
Governing Factor ◽  
Model Code 2010 ◽  
Mathematical Process

The contribution of concrete to the tensile stiffness (tension stiffening) of a reinforced concrete (RC) member is a key governing factor for structural serviceability analyses. However, among the current tension stiffening models, few consider the effect brought forth by concrete shrinkage, and none studies take account of the effect for very long-term shrinkage. The present work intends to tackle this exact issue by testing multiple RC tensile elements (with different bar diameters and reinforcement ratios) after a five-year shrinking time period. The experimental deformative and tension stiffening responses were subjected to a mathematical process of shrinkage removal aimed at assessing its effect on the former. The results showed shrinkage distinctly lowered the cracking load of the RC members and caused an apparent tension stiffening reduction. Furthermore, both of these effects were exacerbated in the members with higher reinforcement ratios. The experimental and shrinkage-free behaviors of the RC elements were finally compared to the values predicted by the CEB-fib Model Code 2010 and the Euro Code 2. Interestingly, as a consequence of the long-term shrinkage, the codes expressed a smaller relative error when compared to the shrinkage-free curves versus the experimental ones.

Sign in / Sign up

Export Citation Format

Share Document