Structure and Properties of Concrete for Injection with Two-Stage Expansion

What is it about?

Often, when it is necessary to fill formwork space in confined working conditions with limited operational control in some engineering solutions the special materials for injection are used. In this case is advisable to use high-fluidity concrete mixes made with К-cement, regulator of the kinetics of structure formation, superplasticizer and gas-forming admixture. The gas-forming admixture obtains of expansion of fresh-concrete during first stage. The special sulfo-alumina additive in K-cement obtains of expansion of hardening concrete during second stage. The main regularities in the formation of the structure and properties of cement stone are considered. The dependences "composition-technology-structure-properties" for concretes with two-stage expansion are clarified. The main provisions for determination of mix proportion for concrete are proposed. The quantitative relationships between the construction properties of concretes and prescription and technological factors are obtained.

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Why is it important?

1. Development of scientific understanding of the main regularities of formation of structure and properties of cement stone EC in combination with the complex addition RKS + SP + GA, refined dependence "composition-technology-structure-property" and developed the basic provisions of the design of concrete for injecting with two-stage expansion. 2. Regulation of content EA as part of the binder can manage their own free deformations expansion binder hardening in the range of 0.5 to 83 (mm / m), while the increase of EA to 24.4% in the composition of the binder increases the ultimate strength of the cement stone up to 80%. 3. Introduction RCS intensifies the growth of their own free expansion in the age of 28 days and increases the flexural strength of up to 1.8 times as a result of the positive effect of RKC on the consistency of the kinetics of its own deformation and strength of cement stone. 4. Complex Additive SP + RKS + EA intensifies the process of hydration heat in the early period, increases the OK to 54%, reduces KU up to 80% and increases to 60% KP, and the result is not the sum of the contributions of each of the components of the complex additive. 5. Increasing the number of GA from 0.13 to 0.44% by weight of C provides growth coefficient of efficiency gassing from 39.4 to 311%, which is accompanied by an increase volume in the first phase of expansion of made with fine sand as aggregate concrete mix from 6 to 64%. 6. Obtained the dependence selfstress of concrete with a two-stage expansion of its ultimate strength in compression of energetic activity of cement and curing conditions. 7. Revealed nonlinear character dependence of the compressive strength of concrete with a two-stage expansion of the velocity of propagation of ultrasound in through sounding, refined dependence ratio of the tensile strength of the compressive strength for concrete with a two-stage expansion taking into account the conditions of hardening, based on which concludes that for concrete with two-stage expansion tensile strength up to 73% higher than that of Portland cement concrete. 8. On standing in air at a temperature of 5 0C there is decrease strength of 5 to 50% in 28 days relative to normal conditions and at a temperature of 35 0C - 14%. On stranding in the water without limitation deformation to the second stage of expansion decreased strength of up to 33%. Two months after presentation expansion deformation at the second stage takes place while self-healing of defects encountered with an increase in volume in the second stage expansion to 7%.

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