Keywords: vintage strength

EFFECT OF WOLLASTONITE ON THE MECHANICAL CHARACTERISTICS OF CONCRETE

https://doi.org/10.34031/2618-7183-2020-3-5-34-42
Abstract
Improvement of the physical and mechanical properties of cement composites should be accompanied by the disposal of industrial waste of various generation. Therefore, the paper proposes the principles of con-trolling the strength properties of concrete, which consist in the complex effect of wollastonite obtained from boron production waste on the processes of structure formation of the cement matrix. When this introduced in an amount of 2-8 wt. % wollastonite has a dual function as a mineral filler and a reinforcing fiber. It has been proven that in the presence of wollastonite, the concrete mix becomes lighter without reducing its physical and mechanical properties. It was revealed that the early strength for all the developed compositions with the addition of wollastonite increases due to the acceleration of hydration processes. Calcium silicate, which is wollastonite CaSiO3, has a close chemical composition with cement clinker, especially with Ca2SiO4 belite and Ca3SiO5 alite. This leads to the formation of a chemically homogeneous and, as a result, hardened microstructure. Elongated wollastonite fibers with good adhesion to the cement stone provide effective micro-reinforcement of the concrete composite. Using the results will lead to the possibility of designing high-strength concretes, including for special structures.
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THE USE OF SEMI-AQUATIC CALCIUM SULFATE TO INTENSIFY THE PROCESSES OF HARDENING OF STRUCTURAL HEAT-INSULATING FOAMED CONCRETE

https://doi.org/10.34031/2618-7183-2018-1-3-25-32
Abstract
Construction of energy- and resource-saving housing of increased comfort involves the creation of more efficient building materials in comparison with traditional and new designs of fencing buildings with im-proved thermal properties. The problem of energy saving in construction has determined the direction of creation and production of effective cheap materials with high thermal properties. One of the most promising materials of this type is environmentally friendly, non-combustible cellular foam concrete.
The problem of accelerating the setting and hardening of foam concrete mixtures, as it allows to accelerate the turnover of forms and reduce the time from manufacturing to sending the finished product to the consumer is of great practical interest.
However, in most cases, domestic foaming agents are produced and used without additional input of setting and hardening regulators. This is due to the fact that the compatibility of the latter with the main additive – foaming agents is not sufficiently investigated. This problem is quite complex, as some setting accelerators can cause defoaming, worsen the structure of the foam matrix, reduce the mechanical strength of the stone and have other negative effects. At the same time, properly selected setting accelerators enhance the action of foaming agents
In the work the questions of application of semi-aqueous calcium sulphate (SCS) for intensification of hardening of foam concrete are considered. The change in physical and mechanical characteristics of foam concrete prepared on anionic and cationic blowing agents with an additional content of 1, 2 and 3% semi-aqueous calcium sulphate is shown. It is established that the SCC allows accelerating the hardening processes, and the formation of ettringite does not cause strong internal stresses, which is related to the porous structure of the material.
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