Abstract
It is shown that high operational reliability of structural materials, in particular at high temperatures, is achieved through the use of ultra-high strength cement composites. Studies of various types of Portland cements with mineral additives of the CEM II/A type have established that a stone based on Portland cement with superzeolite is the most resistant to high temperatures. It has been proven that due to the "self-autoclaving" effect, the strength of a stone based on CEM II/A-P 42.5 R is 1.2–1.3 times higher than a stone based on other types of CEM II/A. To obtain fast-hardening cement composites, a nanotechnological approach based on the use of sol-gel technology has been implemented. Using the methods of IR spectroscopy, electron microscopy, the fact of obtaining, by the chemical method of synthesis, an alkaline nanomodifier N-C-S-H-PCE, which is a nano–liquid based on nano-core seeds of sodium/calcium hydrosilicates, has been proved. It has been confirmed that the introduction of the alkaline nanomodifier N-C-S-H-PCE provides a significant intensification of the early structure formation processes in the paste based on Portland cement with superzeolite (after 12 hours, 24 hours and 28 days, the strength is 16.9; 30.5 and 104.1 MPa). It has been established that the complex combination of Portland cement with superzeolite, corundum aggregate, basalt fiber and alkaline nanomodifier provides rapid-hardening of ultra-high strength cement composites (T=400 °C) with improved operational properties. Thus, there is reason to assert the feasibility of developing rapid-hardening ultra-high strength cementitious composites. This solves the problems associated with the need to increase their early strength and performance. As a result, it is possible to carry out repair work to protect equipment from abrasive wear at elevated temperatures
Highlights
One of the most important areas in building materials science is the development of new generation structural materials, in particular, ultra-dense, high strength concretes, characterized by improved construction and technical properties and durability
The results indicate that the alkaline modifier is a nano– liquid based on nano-core of blended Na, Ca-hydrosilicates N-C-S-H and polycarboxylate ethers (PCE) polycarboxylate esters
It has been found that for cement stone based on Portland cements CEM I 42.5 R and CEM II/A-S 42.5 R (W/C=0.43, paste 1:0) after 28 days of hardening followed by exposure to high temperatures (T=300–500 °C), the strength is about 45.2–57.6 MPa
Summary
One of the most important areas in building materials science is the development of new generation structural materials, in particular, ultra-dense, high strength concretes, characterized by improved construction and technical properties and durability. From the point of view of increasing the durability of concrete, the most promising concept is [1], according to which it is advisable to use a physical approach According to this concept, it is necessary not to change the chemical composition of Portland cement clinker, but to reduce the water-binding ratio using highly efficient polycarboxylate-type superplasticizers and the introduction of ultrafine fillers. It is necessary not to change the chemical composition of Portland cement clinker, but to reduce the water-binding ratio using highly efficient polycarboxylate-type superplasticizers and the introduction of ultrafine fillers This will increase the packing density of the binder parts in the cement paste and improve quality indicators. Such high strength concretes are characterized by adjustable deformation indicators, including those with shrinkage compensation after 14–28 days of natural hardening
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