Experiences on early age cracking of wall-on-slab concrete structures

Jędrzejewska, Agnieszka; Kanavaris, Fragkoulis; Zych, Mariusz; Schlicke, Dirk; Azenha, Miguel

doi:10.1016/j.istruc.2020.06.013

Cited by 29 publications

(22 citation statements)

References 25 publications

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“…Mass concrete structures may be insufficiently reinforced for the discussed thermal stresses and are thus prone to cracks of considerable width. Many examples of early-age cracking due to insufficient reinforcement can be found in the thematic literature [5,40,41]. Undoubtedly, apart from providing suitable reinforcement limiting the early-age crack width, thermal stresses can be minimized by the proper technological measures.…”

Section: General Remarksmentioning

confidence: 99%

Insight into Thermal Stress Distribution and Required Reinforcement Reducing Early-Age Cracking in Mass Foundation Slabs

Klemczak

Żmij

2021

Materials

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The heat released during cement hydration results in temperature-induced non-uniform volume changes in concrete structures. As a consequence, tensile thermal stresses of significant values may occur. The level of these stresses can be lowered by using various technological measures during the construction process and a proper concrete mix composition. Nevertheless, the application of an appropriate reinforcement is a reliable method for controlling the width and spacing of possible cracks. The rules for calculating this reinforcement are not precisely detailed in the standards devoted to concrete structures. Additionally, the correct calculation of the reinforcement requires the identification of the tensile stress distribution in a mass slab. The presented study provides insight into stress distribution and relevant reinforcement for controlling early-age cracks of thermal origin. The existing standards and guidelines are discussed and clarified. The possible paths for calculating the reinforcement are proposed through the example of mass foundation slabs with different levels of external restraints. The results indicate a significant impact of the calculation method as well as the restraint conditions of the slab on the area of required reinforcement.

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Section: General Remarksmentioning

confidence: 99%

Insight into Thermal Stress Distribution and Required Reinforcement Reducing Early-Age Cracking in Mass Foundation Slabs

Klemczak

Żmij

2021

Materials

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“…The article is focused on measurements within concrete structures. The most significant challenge for their diagnosis is their operation in the cracked state, which is a normal behaviour [ 32 ] started already after concreting [ 33 ]. Early-age concrete hydration causes thermal shrinkage strains, which are blocked by internal (reinforcement) and external constraints [ 34 ], finally causing the formation of cracks.…”

Section: Introductionmentioning

confidence: 99%

Crack Shape Coefficient: Comparison between Different DFOS Tools Embedded for Crack Monitoring in Concrete

Howiacki

Sieńko

Bednarski

et al. 2023

Sensors

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The article presents research on the performance of different distributed fibre optic sensing (DFOS) tools, including both layered cables and monolithic composite sensors. The main need for the presented research was related to the growing applications of the DFOS techniques for the measurements of cracked concrete structures. There are no clear guidelines on the required parameters of the DFOS tools, which, despite their different designs, are offered for the same purpose (strain sensing). The state-of-the-art review and previous experiences show noticeable differences in the quality of the results depending on the applied DFOS tool. The technical construction of selected solutions was described with its theoretical consequences, and then laboratory tests on full-size reinforced concrete beams were discussed. Beams equipped with embedded tools were investigated in four-point bending tests, causing the formation of multiple cracks in the tension zone along the beams’ length. The results in the form of strain profiles registered by selected DFOS tools were analysed regarding the qualitative (crack detection) and quantitative (width estimation) crack assessment. The comparison between crack-induced strain profiles was based on a new parameter called crack shape coefficient CSC, which could be applied to assess the effectiveness of the particular DFOS tool in crack detection and analysis. It was one of the world’s first research allowing for such direct comparison between the layered and monolithic sensing tools. The summary indicates practical guidelines referring to the preferable design of the tools best suitable for crack measurements, as well as the field proofs based on data from two concrete bridges in Germany.

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“…Concrete structures undergo early age as well as long‐term (LT) volumetric changes due to several actions including early‐age thermal (EAT) strains and LT shrinkage strains 1 . If these strains are restrained either internally (by reinforcement or another part of the same cross section) or externally by adjoining members, stresses develop in the concrete with a magnitude proportional to the restrained strain.…”

Section: Introductionmentioning

confidence: 99%

“…Design provisions pertinent to crack control in edge restrained members are given in several codes 8,9 as well as CIRIA Report C766 10 which is used extensively in the UK. However, these provisions (particularly those pertaining to edge restraint) are empirical in nature and, somewhat contradictorily, are reported to result in both over‐conservative designs 11 as well as excessive cracking 1,12,13 . The occurrence of excessive cracking despite following current guidance in codes of practice requires further detailed study.…”

Section: Introductionmentioning

confidence: 99%

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Assessment of cracking performance in edge restrained RC walls

Elwakeel

Shehzad

Khoury

et al. 2022

Structural Concrete

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Excessive cracking due to restraint of thermal and shrinkage strains is a widespread problem in the concrete construction industry. In design, restraint induced cracking is managed by the provision of reinforcement intended to distribute internal strains in such a way as to control the cracking pattern and limit crack widths. The area of secondary (horizontal) reinforcement required in members such as retaining walls and water tanks is often governed by the need to control early age thermal cracking. This paper presents results from four edge restrained walls tested at Imperial College London and the University of Leeds as part of an Engineering and Physical Sciences Research Council funded project into restraint induced cracking. The paper describes the development of volumetric strain and cracking in the tested walls. The cracking performance is assessed by comparing the restrained strain with the tensile strain capacity of concrete.degree of restraint, early age, edge restraint, imposed strain, thermal strain 1 | BACKGROUND | IntroductionConcrete structures undergo early age as well as longterm (LT) volumetric changes due to several actions including early-age thermal (EAT) strains and LT shrinkage strains. 1 If these strains are restrained either internally (by reinforcement or another part of the same cross section) or externally by adjoining members, stresses develop in the concrete with a magnitude proportional to the restrained strain. This phenomenon can lead to cracking if the stress levels exceed the tensile strength of the concrete. 2 Little experimental work has been carried out to investigate cracking in edge restrained members which are the subject of this paper. Stoffers 3 examined the influence of reinforcement ratio, wall aspect ratio and presence or absence of wall curvature in 18 tests of reduced scale micro-concrete walls with cross section of 60 Â 375 mm 2 . The maximum reinforcement diameter was 3 mm. Kheder et al. 4 examined the influence of wall aspect ratio. They tested 14 reduced-scale mortar walls Discussion on this paper must be submitted within two months of the print publication. The discussion will then be published in print, along with the authors' closure, if any, approximately nine months after the print publication.

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Experiences on early age cracking of wall-on-slab concrete structures

Cited by 29 publications

References 25 publications

Insight into Thermal Stress Distribution and Required Reinforcement Reducing Early-Age Cracking in Mass Foundation Slabs

Insight into Thermal Stress Distribution and Required Reinforcement Reducing Early-Age Cracking in Mass Foundation Slabs

Crack Shape Coefficient: Comparison between Different DFOS Tools Embedded for Crack Monitoring in Concrete

Assessment of cracking performance in edge restrained RC walls

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