Comprehensive Testing Techniques for the Measurement of Shrinkage and Structural Changes of Fine-Grained Cement-Based Composites during Ageing

Because of its high binder content and severe construction environment, early-age cracking is one of the most important threats to concrete used in continuous box-girder bridge structures. In this study, controlled permeable formwork (CPF) liner was used to mitigate the early-age shrinkage and reduce the early-age cracking risk of box-girder concrete. Early-age shrinkage was measured by a noncontact method and started at 30 min after adding mix water until 7 d. Internal relative moisture content and pore distribution tests were also carried out to reveal the working mechanism of CPF liner. The results show that covering the concrete surface with CPF liner decreased early-age shrinkage significantly. Under the temperature of 20°C and the relative humidity of 60%, two-surface-covering and three-surface-covering CPF liner on concrete decreased the shrinkage by 44% and 48%, respectively, at 7 d compared with concrete without CPF liner covered on it. The main reason is that CPF liner enhanced the internal relative moisture content and resulted in better performance of the surface concrete.

“…is phenomenon was also noticed in previous research [20,22,23]. Zhang et al [23] reported a maximum swelling strain of 70 μm/m and 250 μm/m for C30 and C80 concrete, respectively.…”

Section: Early-age Shrinkagesupporting

confidence: 78%

Section: Early-age Shrinkagementioning

confidence: 98%

Study on the Mitigative Effect of Controlled Permeable Formwork (CPF) Liner on Early-Age Shrinkage of Box-Girder Concrete

Chen

2019

“…The phenomenon of swelling is clearly visible from the measurements in the first 24 hours of ageing when the hydration heat is generated at the highest rate (approx. 200 J/g per 24 h) [31,33]. The particular contribution of all the above-mentioned phenomena is the object of ongoing experimental measurement.…”

Section: Resultsmentioning

confidence: 99%

“…The design of the weighing table as well as the details of the measurement procedure are protected by industrial property rights held by Brno University of Technology registered in the national patent database under application number 2013-961 [30]. For details about measurement techniques see [31].…”

Section: Test Equipment Andmentioning

confidence: 99%

Experimental Analysis on Shrinkage and Swelling in Ordinary Concrete

Daněk

Kucharczyková

Misák

et al. 2017

Self Cite

The paper deals with the experimental determination of shrinkage development during concrete ageing. Three concrete mixtures were made. They differed in the amount of cement in the fresh mixture, 300, 350, and 400 kg/m 3 . In order to determine the influence of plasticiser on the progress of volume changes, another three concrete mixtures were prepared with plasticiser in the amount of 0.25% by cement mass. Measurements were performed with the goal of observing the influence of cement and plasticiser content on the overall development of volume changes in the concrete. Changes in length and mass losses of the concrete during ageing were measured simultaneously. The continuous measurement of concrete mass losses caused by drying of the specimen's surface proved useful during the interpretation of results obtained from the concrete shrinkage measurement. During the first 24 hours of ageing, all the concrete mixtures exhibited swelling. Its magnitude and progress were influenced by cement, water, and plasticiser content. However, a loss of mass caused by water evaporation from the surface of the specimens was also recorded in this stage. The measured progress of shrinkage corresponded well to the progress of mass loss.

“…The compressive strength of specimens [28] at 28 days is shown in Figure 5, and the flexural strength of specimens at 28 days is shown in Figure 6.…”

Section: Mechanical Strengthmentioning

confidence: 99%

Effectiveness of Saturated Coral Aggregate and Shrinkage Reducing Admixture on the Autogenous Shrinkage of Ultrahigh Performance Concrete

Chen

et al. 2017

The use of saturated coral aggregate (SCA) as practical replacement of quartz sand has been shown to effectively mitigate the autogenous shrinkage in ultrahigh performance concrete (UHPC). The autogenous deformation, the compressive strength, the flexural strength, and the hydration property development of paste with different shrinkage means were tested. Three different methods were evaluated to mitigate the autogenous shrinkage: SCA, shrinkage reducing admixture (SRA), and the mixture of SCA and SRA (SRA-SCA). It was found that SCA and SRA have all the effective ways to reduce the shrinkage deformation, and SRA-SCA was the most effective in mitigating the shrinkage. The autogenous shrinkage of UHPC was restrained, when the SCA dosage was 44%, the SRA dosage was 0.8%, the SCA content was 26%, the SRA dosage was 2.4%, the SCA content was 18%, the SRA content was 2.4%, or the SCA dosage was 26%. The mechanical properties were deteriorated by the addition of SCA, while the compressive strength was still higher than 90 MPa at 28 days even though the replacement ratio of SCA was up to 50%. Furthermore, internal curing by means of SCA was proved to be a successful way to mitigate autogenous shrinkage, after the tests.