Technology of Concrete: Reality and Perspectives

Abstract

The fundamental principle of the concrete technology (reinforced concrete) “with predefined properties” was formulated in the 60s of the last century. It says that the production process must be “directed”, i.e. by all means coordinated with the mechanism of portland cement hardening. A negative answer to the question whether we have reached this technological “orientation” is obvious after many decades. The existing domestic (threestage) and western (five-stage) clinker cementation hardening models, which describe the development of the process according to the scheme “dissolution-colloidation-crystallization”, do not adequately reflect the essence of the phenomenon. The confirmation of the current theoretical uncertainty is the mass of chronic “white spots” in these theories. The ultimate in technological excellence, for example, is the complete dissolution of cement grains, which contradicts the experiment, indicating the invariability of their dimensions, the constancy of the hydrate shell thickness (“hydrated rim” in the terminology of Western researchers) on any (large, medium, small) cement corpuscles . The morphology of hydrated cement grains is not clear. What is this object? Is it an amorphous, crystalline product or some symbiosis? The logic and meaning of the «induction period» are not clear too. Such important moments in practical terms, such as «discontinuity» (according to Kind [1]) and “sawtoothness” (according to Malinina [2]) of strength growth are forgotten. The “wavy” change in the number of properties and phenomena accompanying cement hardening (the chemical composition and alkalinity of the pore fluid, the electrophysical parameters, the humidity state, etc.) is completely inconceivable. The reason of the worsening of the contact zone of concrete and reinforced concrete is mysterious too. The determining characteristic of cement concrete is strength, what looks unconvincing against the background of marked sawtoothness.