CEMENT AND CONCRETE RESEARCH (Elsevier Ltd.)
Effect of fineness of cement on drying shrinkage
Ippei Maruyama, Hiroki Sugimoto, Syota Umeki, Ryo Kurihara
CEMENT AND CONCRETE RESEARCH, Volume 161, November 2022
(https://doi.org/10.1016/j.cemconres.2022.106961)
Abstract
The effect of fineness of cement on drying shrinkage was investigated. Three cement paste samples with different fineness values were prepared from the same clinker. The changes in length and mass, and water vapor sorption of the dried cement pastes after 3, 7, 28, and 91 d of curing were obtained. The relationships between drying shrinkage and the degree of hydration were not identical under the different cement fineness values. Therefore, there exists another mechanism behind the increase in drying shrinkage, apart from the faster degree of hydration. It was found that drying shrinkage is well predicted by the index SH2O,v × B, where B denotes the Blaine value of cement, and SH2O,v represents the water vapor sorption surface area. Hence, it was deduced that C–S–H undergoes an anisotropic volume change under drying and a greater shrinkage in the circumferential direction of the original cement grains.
The practical application of a self-developed temperature stress testing machine in development of expansive concrete blended with calcium sulfoaluminate additives
Guangfeng Ou, Zhihai Lin, Toshiharu Kishi
CEMENT AND CONCRETE RESEARCH, Volume 164, February 2023
(https://doi.org/10.1016/j.cemconres.2022.107045)
Abstract
Early-age cracking of concrete is a complex problem related to temperature, restraint and curing conditions. Cracking sensitivity is hard to evaluate quantitatively and the use of expansive additives to mitigate cracking remains empirical in-situ. This study developed a Temperature Stress Testing Machine (TSTM) to evaluate early-age properties of concretes under varied engineering conditions. The general design of TSTM and the mathematical derivation of its working principle are provided. With the developed TSTM, early-age properties (free deformation, restrained stress, elastic modulus and early-age creep effect) of Calcium Sulfoaluminate (CSA) expansive concrete are tested comprehensively. Experimental results indicate that under high temperature condition, CSA concrete is not effective to compensate shrinkage, while the combination of CSA and lightweight aggregate resolves the problem. It offers us valuable insights on potential application of TSTM into mix design of crack-resistant concretes under complex engineering conditions.