Applied Mechanics and Materials Vols. 670-671

Abstract: Nowadays, there is a great demand for the accelerated hardening construction mixtures. That causes the necessity to the methods development for testing the effectiveness of accelerators, well as the analysis of kinetics of cement systems hydration in the early stages of hardening. This paper presents the results of an experimental research of interrelation between the growth kinetics of cement-based binder system strength and the heat release for pure cement hydration. How it was found, two compositions of construction mix, which are identical in mineral composition and differ in the presence of mono-functional accelerator, a comparison of strength growth dynamics can be carried out indirectly via the integral curve of heat release, obtained using the method of isothermal calorimetry.

Abstract: Three model specimens of alkali-activated slag concrete filled steel tube (AAS-CFST) with different axial compression ratio and steel ratio were designed and tested in the present study. The seismic performance of the structures were evaluated by testing them with combined lateral constant compression and vertical cyclic loads. The structural performance, such as the testing observations, hysteretic behavior, skeleton curve, stiffness degradation, energy dissipation capacity and ductility performance was discussed in detailed. The results show that all the specimens’ damage were bending deformation mode, and the hysteretic curves are relatively smooth. Test data indicated that increased the axial compression ratio improved the load bearing capacity, initial stiffness.

Abstract: In this article the single-layer homogeneous enclosure structure are considered. In this work calculation of vapor permeability of walls from gas-concrete blocks is made. The calculation of resistance to vapor permeability for rough walls and for walls with an external plaster covering is made. Calculation is executed in the context of St. Petersburg climatic conditions for external walls of residential buildings.

Abstract: A hydro-thermo-mechanical model was presented for concrete at elevated temperature. Three phases of continuum were adopted in this model: gaseous mixture of water vapor and dry air, liquid water, and solid skeleton of concrete. Mass conservation equations, linear momentum conservation equation, and energy conservation equation were derived on the basis of the macroscopic Navier-Stokes equations for a general continuum, along with assumptions made for the purpose of simplification. Mathematical relationships between selected primary variables and secondary variables were given with existing data from references. Specifications of the constitutive relations were made for the kinetic variables and their conjugate forces.

Abstract: In this article the physical principles which explain divergences of calculated and experimental values of thermal streams and temperatures of building envelope are considered. In this work the simplest thermal conduction through building envelope is considered.

Abstract: This paper studies the essential attributes of acrylic from the perspective of material innovation and performance. The paper extends the structural performance of Acrylic with the technology of digital construction. It proposes a new possibility of utilizing acrylic and expatiates on the tendency of the use of acrylic in large architectural installations with practice cases.

Abstract: This article is a stage of the author’s research into the impact of different factors on the hydration of mineral binders. The problem of cement activity decrease due to adsorption moisture influence during long-term storage in normal conditions (20°C and 50% RH) was examined. The influence of storage period in airtight and non-airtight conditions on the kinetics of heat evolution during hydration as well as on phase composition of Portland cement was characterized using experimental methods.

Abstract: Under the effect of periodic cycle load, the frozen soil exists hysteretic characteristics. According to the research, the five parameters which are the residual strain , the numerical of short axis to long axis of the hysteretic curve , the slope of the hysteretic curve long axis k, the distance of adjacent hysteretic curve center point d and the area surrounded by hysteretic curve S are used to quantitatively represent the morphological characteristics of the hysteretic curve. The hysteretic curve of frozen soil is not a standard ellipse. Its morphological characteristics relate to the initial loading position. The morphological characteristics of the hysteretic curve of different soil affected by frequency, confining pressure and dynamic stress amplitude are different.

Abstract: 5-8 mesh rubber granules was mixed with an equal volume instead of fine aggregate, and the content of rubber was 5%, 10%, 15% and 20%. Compared with the influence of silane coupling agent, latex and silica fume to the mechanical properties of rubber concrete, it studied the mechanism of rubber-modified to the rubber concrete. The test results proved that the silane coupling agent, latex, and silica fume could improve the compressive strength, splitting and flexural strength. Latex could significantly improve the bond strength of cement-based materials and the integrity of the concrete. Coupling agent made rubber bond with cement-based materials to form a stable connection, and silica fume filled the pore in concrete, so it optimized the gradation. Latex was the best, silane coupling agents was second, and silica fume was the last about the improved effect of three kinds of modifiers.

Abstract: Capillary tention is one of the driving forces of shrinkage of cement-based materials, which is related to distribution of pore size, surface tension of pore water, contact angle of pore walls and so on. There are some appropriate test methods for pore diameter and surface tension of cement-based materials, but the contact angle of pore water is rarely related to. This paper showed a new method to test the contact angle of cement-based materials which is based on the principle of thin-layer wicking about surface physical chemistry. Combining Washburn equation x²=(Refft/2) , the contact angle of analog pore solution to cement paste was obtained. The influence of superplasticizers and mineral admixtures on the contact angle and drying shrinkage of cement pastes also were researched. The results showed that the larger contact angle leads to the smaller surface tension of pore solution, which also caused that the capillary wall wass infiltrated more difficultly. As a result, the pressure of pore and the drying shrinkage were both small, vice versa.