Shrinkage and Expansion Strains in Self-compacting Concrete: Comparison of Methods of Measurements

The focus of the paper is to assess various methods for strain measurements in expansive concrete. The research objective was to determine strains in concrete due to its expansion. For this purpose, self-compacting concrete with variable amount of expansive admixtures and different curing conditions were investigated. Concrete strains were measured during 28 days on side surface of cylindrical specimens with demountable mechanical strain gauge (DEMEC) and with embedded vibrating wire strain sensors, as well as within 24 h with shrinkage drains. In addition, temperature development during concrete hardening, concrete strength and elasticity modulus, as well as the change of weight (i.e. loss of water during concrete curing) were also measured. The experimental values of shrinkage strains were compared with analytical calculations according to shrinkage models from Eurocode 2, Model Code 2010 and B4 Model proposed by RILEM TC-242-MDC. Finally, the methods of measurement of strains due to shrinkage and expansion were evaluated regarding their compliance with requirements and suitability for shrinkage and expansion estimation. Additionally, temperature development during hardening of concrete was presented and the influence of superplasticizer type (Polycarboxylate ether, PCE, and Poly-Aryl-Ether, PAE) on shrinkage effects of concrete mixtures with and without expansive admixture was described.