EFFECT OF HARDENING TIME ON DEFORMATION-STRENGTH INDICATORS OF CONCRETE FOR INJECTION WITH A TWO-STAGE EXPANSION DURING HARDENING IN WATER

• Main Authors: Tatjana N. Zhilnikova, Yulia I. Koryanova, Grigory V. Nesvetaev
• Format: Article
• Language: Russian
• Published: Daghestan State Technical University 2018-03-01
• Series: Vestnik Dagestanskogo Gosudarstvennogo Tehničeskogo Universiteta: Tehničeskie Nauki
• Subjects: self-stressing concrete; injectable concrete; two-stage expansion; water aging; deformation-strength characteristics; hardening time; self-stressing cement; expansion deformations; self-stress; strength; porosity
• Online Access: https://vestnik.dgtu.ru/jour/article/view/465
• ISSN: 2073-6185; 2542-095X

Abstract. Objectives Concretes for injection with a two-stage expansion are a kind of selfstressing concrete obtained with the use of self-stressing cement.The aim of the work is to study the influence of the duration of aging on the porosity, strength and self-stress of concrete hardening in water, depending on the expansion value at the first stage. At the first stage, the compacted concrete mixture is expanded to ensure complete filling of the formwork space. At the second stage, the hardening concrete expands due to the formation of an increased amount of ettringite. This process is prolonged in time, with the amount of self-stress and strength dependant on the conditions of hardening. Methods  Experimental evaluation of self-stress, strength and porosity of concretes that are permanently hardened in water, under air-moist and air-dry conditions after different expansion at the first stage. The self-stress of cement stone is the result of superposition of two processes: the hardening of the structure due to hydration of silicates and its expansion as a result of hydration of calcium aluminates with the subsequent formation of ettringite. The magnitude of self-stress is determined by the ratio of these two processes. The self-stress of the cement stone changes in a manner similar to the change in its expansion. The stabilisation of expansion is accompanied by stabilisation of self-stress of cement stone. Results  The relationship of self-stress, strength and porosity of concrete for injection with a two-stage expansion on the duration and humidity conditions of hardening, taking into account the conditions of deformation limitation at the first stage, is revealed. Conclusion During prolonged hardening in an aqueous medium, self-stresses are reduced up to 25% with the exception of expansion at the first stage and up to 20% with an increase in volume up to 5% at the first stage. The increase in compressive strength is up to 28% relative to the 28-day period.