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Abstract

The influence of rebar, protruding from concrete element during casting, on temperature and strength development was analyzed. Test models of size 50 cm x 50 cm x 50 cm were made with and without protruding rebar. The rebar protruding from the sample simulated the conditions of the hardening of elements such as bridge abutments or pylons, which require technological break. Samples were cast in insulated formworks, to create semi-adiabatic conditions for concrete curing, simulating real conditions of curing of mass structures. The research utilized selfconsolidating concrete with two different rapid hardening cements: CEM I 42.5R and CEM I 52.5R, and blastfurnace cement CEM III/A 42.5N. Continuous registration of temperatures in the samples was performed for the first 7 days. Based on the results acquired and compressive strength, the amount and kinetics of the heat given off in the concrete was determined and an evaluation of its strength in conditions simulating actual conditions was performed. The research showed that the difference in temperature between the reinforced and non-reinforced sample was approximately 14.0° C.

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Authors and Affiliations

Maria Kaszyńska
ORCID: ORCID
S. Skibicki
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Abstract

Due to the large amount of binder and low water-cement ratio, high-performance cement composites have high compressive strength and a dense hardened cement paste microstructure. External curing is insufficient, as it cannot reach the interior parts of the structure, which allows autogenous shrinkage to occur in the inside. Lack of prevention of autogenous shrinkage and high restraint causes structural microcracks around rigid components (aggregate, rebars). Consequently, this phenomenon leads to the propagation of internal microcracks to the surface and reduced concrete durability. One way to minimize autogenous shrinkage is internal curing. The use of soaked lightweight aggregate to minimize the risk of cracking is not always sufficient. Sorption and desorption kinetics of fine and coarse fly ash aggregate were tested and evaluated. The correlation between the development of linear autogenous shrinkage and the tensile stresses in the restrained ring test is assessed in this paper. A series of linear specimens, with cross-section and length custom designed to match the geometry of the concrete ring, were tested and analyzed. Determination of the maximum tensile stresses caused by the restrained autogenous shrinkage in the restrained ring test, together with the approximation of the tensile strength development of the cement composites were used to evaluate the cracking risk development versus time. The high-performance concretes and mortars produced with mineral aggregates and lightweight aggregates soaked with water were tested. The use of soaked granulated fly ash coarse lightweight aggregate in cementitious composites minimized both the autogenous shrinkage and cracking risk.
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Authors and Affiliations

Adam Zieliński
1
ORCID: ORCID
Anton K. Schindler
2
ORCID: ORCID
Maria Kaszyńska
1
ORCID: ORCID

  1. West Pomeranian University of Technology, Faculty of Civil Engineering and Environmental, al. Piastów 50a, 70-311 Szczecin, Poland
  2. Department of Civil and Environmental Engineering, Auburn University, 237 Harbert Center, Alabama 36849, Auburn, USA

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