Pavlo Kryvenko

By Pavel V. Krivenko, Hai Lin Cao, Lu Qian Weng and Oleg N. Petropavlovskii

The contribution covers results of studies on the alkali-activated cement concretes intended for marine engineering applications. Such properties as strength, wear, corrosion, freeze-thaw, weather resistance and many others have been studied, and the results are reported and discussed in detail. The obtained results suggested to draw a conclusion on high potential of the alkali-activated cement concretes for marine engineering applications, since in their performance properties these concretes are highly advantageous over other concretes used as marine concretes and big savings can be expected in the future due to the longer span of service life. The results are supported by long-term observations in real conditions. The above advantages are attributed to more perfect micro- and macrostructure of the alkali-activated cement stone. The authors have summarized their own experience and results collected by PhD and DSc students under their supervision dedicated to assessment of durability of these concretes, in particular, for marine engineering applications. In order to bring these advanced materials into practice of construction worldwide, two rilem (International Union of Laboratories and Experts in Construction Materials, Systems and Structures) committees have been founded: “Alkali-activated Materials” (2010–2013) and “Durability Testing of Alkali Activated Materials” (2013–ongoing).

Part of the book: High Performance Concrete Technology and Applications

By Pavel Krivenko, Oleh Petropavlovskyi, Oleksandr Kovalchuk and Oleksandr Gelevera

A process of structure formation taking place in the interfacial transition zone (ITZ) “cement stone-aggregate” was studied on a variety of concretes made with artificial and real aggregates. The study of these processes in the case of artificial aggregate prepared from a mixture of clay loam and alkali-activated slag cement showed that not only active SiO2 and Na2O but also other substances of both cement and aggregate are involved in the formation of the ITZ. This results in the formation of alkaline and alkaline-alkali-earth aluminosilicate hydrates which strengthen the ITZ and improve strength and durability of the concrete. Thus, the alkali-silica reaction (ASR) transforms from a destructive one (negative effect) into a constructive one (positive effect). The study on the ITZ in the alkali-activated cement concretes made with real alkali-susceptible aggregates selected from crushed basalt rock, glassy waste product from basalt fiber production, crushed perlite rock, and expanded perlite suggested to make a conclusion on the possibility to prevent the destructive processes in the ITZ through the addition of the metakaolin additive into the cement composition in quantities of 5–10% by mass. These conclusions were supported by the long-term testing of strength of these concretes, by measuring the deformations “shrinkage-expansion” as well as the results of study on hardness of the ITZ.

Part of the book: Compressive Strength of Concrete

By Pavel Krivenko and Volodymyr Kyrychok

The chapter deals with a genesis of structure and properties of the zeolite-like cement matrices of the Na(K)-Al2O3-SiO2-H2O system within a temperature range of 20–1200°С. Due to the fact that zeolite-like structures and their characteristics vary within wide ranges, materials with high-performance properties can be obtained through regulation of the structure formation processes. This can be provided by a proper choice of type of an aluminosilicate component, cation of an alkaline component and additives, including Ca-containing ones, and curing conditions. When the cement matrix formation process is appropriately directed, the zeolite-like products (hydrosodalite, analcime, chabasite, faujasite etc.) dominate in the microstructure that is formed. The ability of some zeolites to recrystallize with temperature increase into stable feldspar-like aluminosilicates without destroying the basic skeleton opens a pathway that is worth to explore in the production of materials similar to low temperature ceramics, intumescent coatings, high temperature and corrosion resistant structures, etc. The examples are given on how to use the above cement matrices for making some of the above listed materials.

Part of the book: Advances in Geopolymer-Zeolite Composites

By Pavlo Kryvenko, Igor Rudenko and Oleksandr Konstantynovskyi

In marine structures, the risk of degradation of both the concrete structure and the initiation of corrosion of steel reinforcement is precisely caused by the periodicity of wetting in seawater and drying under the influence of atmospheric CO₂. To protect reinforced concrete from the influence of the mentioned ions under coupling exposure classes XS3 and XC4, a coating based on geopolymer of the formula (0,2K₂O + 0,8Na₂O)·4,5SiO₂·Al₂O₃·nH₂O was designed. The effect of the wastes and industrial by-products as the modifying additives on the acceleration of the synthesis of water-resistant zeolite-like matrices of geopolymer at normal temperatures (t = 20 ± 2°C) was studied. The water resistance coefficient of the geopolymer-based mortars was the highest (> 0.9) for both the slaked lime (Ca(OH)₂) and aluminum fluoride (AlF₃) modifications. The effectiveness of geopolymer-based coatings was confirmed by acceptable changes in water absorption (≤ 1 kg/m²) and adhesion (≤ 23%) after 50 cycles and 200 cycles of wetting in seawater and further drying at t = 105 ± 2°C. Diffusion permeability of Cl⁻, SO₄²⁻-ions into the coatings was to a depth of no more than 1…2 mm, and the coating’s thickness ≥ 2 mm was determined as appropriate value.

Part of the book: Advances in Geopolymers