Structure formation and internal stresses in hardening monolithic cement concrete

Abstract

The article discusses the influence of internal and external factors on the physical and mechanical characteristics of monolithic road cement concrete. It has been shown that the main danger for hardening and operating concrete is cracking. Crack formation can be caused by thermal stresses or deformations caused by shrinkage of concrete during hardening. The main danger for hardening concrete in the initial period is the increased water content in the concrete composition. Evaporation of moisture from hardening concrete leads to shrinkage deformations of the concrete and subsequent cracking. Therefore, to reduce moisture loss from hardening concrete, it is necessary to carry out operations to care for hardening concrete, for example, using film-forming materials. It is shown that in all cases, cracking is caused by internal stresses in concrete. In the early stages of hardening, cracking depends on the temperature gradient and the magnitude of shrinkage deformations, and during the period of operation of concrete road surfaces - on the magnitude of internal stresses. It is shown that the features of structure formation during the hardening period determine the crack resistance of concrete and are associated with the magnitude of internal stresses in concrete. It is shown that under certain conditions, and in the case of cracking, self-organization of the system, which is monolithic cement concrete, is possible. This leads to self-healing of formed cracks and increased durability of road concrete. This is especially important during the initial period of hardening of monolithic cement concrete, during the period of possible formation of shrinkage or thermal cracks. In the future, during the operation of road surfaces, the ongoing adaptation of the structure to the effects of the external environment can improve the durability of concrete. The work determines the critical temperature gradient at which a crack can form and the duration of this period. Direct measurements of the magnitude of internal stresses in concrete were carried out during 28 days of hardening. The main features of the mutual relationship between the processes of structure formation and internal stresses in concrete are considered.