Electrochemical and physical-mechanical properties of composites based on gypsum-cement-pozzolan binder

Introduction. The use of mixed binders with an increased content of active mineral additives allows improving a number of the most important physical and mechanical properties of concrete. However, a decrease in the proportion of clinker for structural concrete may negatively affect the durability of the reinforced concrete product and the structure as a whole, due to a potential decrease in the pH of the pore liquid of the concrete. Gypsum cement-pozzolanic binders are materials with a small clinker fund, since gypsum binder, which has an acidic environment, predominates in their composition. Therefore, when introducing load-bearing products and structures into production, it is necessary to check the protective properties of concrete in relation to steel reinforcement.

Materials and methods. To prepare the gypsum-cement-pozzolanic binder, we used gypsum binder of grade G-5, cement binder of grade CEM I 42.5N and pozzolanic mineral additives: natural zeolite, microsilica and fly ash. The pH and ionic concentration values of hydrated suspensions with various active mineral additives, both mono- and binary modifications, were studied using potentiometric and conductometric methods. Compressive strength was estimated after 7, 28 and 90 days of hardening in accordance with GOST 10180–2012; water absorption — according to the method of GOST 23789–2018; water resistance was estimated by the softening coefficient.

Results. As a result of the experiments, a composition of gypsum-cement-pozzolanic binder with high protective and physical-mechanical properties was obtained, which can be used for the production of structural quick-hardening concrete.

Conclusions. The obtained results indicate sufficient protective properties of concrete based on gypsum-cement-pozzolanic binders in relation to steel reinforcement: a pH of at least 12 and a composition containing 60 % gypsum binder, 25 % Portland cement and a binary active mineral additive based on microsilica and natural zeolite in a ratio of 2:1 by weight.

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