The strength of tangential adhesion between old and new concrete in precast-monolithic structures

Abstract

The article presents a research of the strength of the tangential adhesion between the old and the new concrete in prefabricated monolithic structures.

Most buildings and structures last time are built at composite concrete and reinforced concrete structures. It is known that the operational properties of precast-monolithic structures, such as stiffness, stability, crack resistance, the degree of impermeability at the joints, depend on the strength of contacts and the solidity of reinforced concrete joints. Therefore, during reconstruction, strengthening of structures, as well as in other cases, in designing, great attention is paid to the design of joints and their implementation.

The surface of the old concrete, with which it is necessary to ensure the adhesion of new concrete, is a cement stone with placeholders, pores and initial cracks. The adhesion of old concrete with new depends on the structure of old concrete and its properties. From the side of new concrete, adhesion depends on the cement paste, which has the properties of a binder.

In this article, using mathematical and statistical methods, the problem of investigating the tangential adhesion between the old and the new concrete in precast-monolithic structures is solved. The influence of various factors, such as water-cement ratio, cement consumption, change in the ratio of the grain composition on the shear resistance is considered. The mathematical and visual dependences of the value of tangential adhesion on the factors under study are obtained. The nature of the destruction of prototypes is described.

The researches have shown that with an increase in cement consumption, the positive effect of the growth of the water-cement ratio on the magnitude of the contact shear strength decreases. The change of the coefficient of grain composition also affects the magnitude of contact strength of concrete for shear. The amount of cement in the concrete mix of a new concrete has the greatest influence on the magnitude of the contact strength of seam of concretes.