Increased concrete strength due to early loading is one of the priorities of concrete technology. Many articles contain data on changes in compressive strength after early loading. The first person to test early concrete loading was Satalkin. He tested bridge supports for static and dynamic loads. The results of his work became the basis for further research in the field of early loading of concrete. The objective of this work is to study the tensile strength in bending after early loading and to check the influence of the orientation of the samples under load. Also we considered the effect of active mineral additives on this parameter. The object of study is samples of cement-sand dough prepared on a Portland cement binder of various manufacturers. We noted a difference in the strength characteristics in bending by changing the orientation of the samples when testing them after early loading. The maximum increment of strength is noted in a plane perpendicular to the direction of compressive force. The use of a mineral additive with the replacement of a fraction of cement gave the attenuation of the observed effect.
Keywords: anisotropy of strength properties, early loading of concrete, cement composite, flexural strength, mineral additive
The article deals with the effect of force compression of cement stone on the magnitude of mass loss in differential thermal analysis. Theoretical aspects concerning the issues of qualitative change in the state of the liquid phase in a cement stone under load are discussed. Changes in adsorption and chemically bound water were studied by varying the water-cement ratio, the sample size, and the type of cement used. The value of the applied load was taken as the experiment constant.The data obtained show an increase in the total mass loss in compressed samples in 87% of the experiments. This fact may indicate a qualitative change in the form of water bonds in the structure, as well as take into account the influence of the factors under consideration on this process.
Keywords: Cement stone, compressive stresses, early loading, adsorption-bound water, chemically bound water, mass loss, differential-thermal analysis, water-cement ratio, sample size, alumina cement, Portland cement