STRUTURAL DURABILITY, DEFORMATION PROPERTIES AND FRACTURE MECHANICS PARAMETERS OF ADVANCED SILICATE MATERIALS

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1 STRUTURAL DURABILITY, DEFORMATION PROPERTIES AND FRACTURE MECHANICS PARAMETERS OF ADVANCED SILICATE MATERIALS E. Shinkevich (1), Y. Zaytsev (2), E. Lutskin (1), G. Bondarenko (3), A. Tymnyak (1) (1) Odessa State Academy of Civil Engineering and Architecture, Odessa, Ukraine (2) Moscow State Open University, Moscow, Russia (3) Nikolaevsky Civil Engineering College, Nikolaev, Ukraine Abstract The use in practice of the speed mixer-activators allows realizing the phenomenon of mechano-chemistry in the production of advanced silicate materials on the base of lime-silica binding substance. The activating of mixture of raw materials allowed the transition from autoclave curing to thermo-moisture one of silicate materials. The optimization of the composition and the hardening conditions in the thermo-moisture treatment on the basis of experimentally-statistical modeling ensured the receipt of materials with the required properties. The analysis influence "mixture technology structure properties" has been fulfilled on experimental-statistic models. The changing of properties of silicate materials (structural durability, deformation properties, K Ic and other fracture mechanics parameters) under the influence of various factors such as specific surface of mineral additive, hardening conditions and content of gypsum have been estimated. Influence of various groups of factors on properties has been executed. It allows receiving new information about the influence of the factors of structure and the technology on a degree of correlation between the structure and the structural durability, deformation properties, K Ic and other fracture mechanics parameters materials. 1. INTRODUCTION Development and introduction the energy conservation and competitive building materials is actual question of building branch. In these conditions normative requirements to heatprotection of constructions increase considerably. Substantial increase of volume of production of heat-effective building materials is planned. Allocated silicate materials are effective and ecologically pure materials. So in total amount of productions of wall s materials and articles they play a significant volume.

2 Production of silicate concrete has reserves on decrease of bulk density, heat conductivity and charge of material and energy. Within these problem the production with use of the modern technology process equipment the wall s silicate non-autoclave hardening materials and their optimization on a complex of parameters of quality. First of all heat conductivity, is a perspective direction which will allow to reduce expenses of energy as at a stages of production of materials and articles, and at a stage of operation of constructions. The opportunity of production of silicate materials non-autoclave hardening due to use active silica has been proved with positions of thermodynamics in works [1]. The opportunity of production of silicate materials at normal temperature and pressure (Т=85±2ºС, d=0.1 MPа) allows to speak about essential potential reserves of production of this kind of articles [1]. 2. TECHNOLOGICAL BASES OF RECEPTION OF SILICATE MATERIALS OF NON-AUTOCLAVE HARDENING On the basis of experimental-theoretical researches there were established the opportunity of realization of the non-autoclave technologies of silicate materials reception. Hydration lime-silica binding substances at temperature Т=85 С and atmospheric pressure is realized due to high index ph with the use of components binding not slaked to exhaust, which is ground together with quartz sand, and chemically active amorphous silica with the optimum specific surface, which is entered instead of the ground quartz sand s part. The necessity of calcium hydroxide s full linkage in autoclave processings conditions is caused by chemical thermodynamics of lime and quartz: with the rise in temperature the solubility to exhaust falls, though speed of dissolution increases, and solubility of silica - increases (fig.1.) [2]. Under certain conditions synthesis of hydrosilicates of autoclave hardening is possible at temperature below 100 С and atmospheric pressure [1, 3, 4]. a) b) c) Figure 1: Influence of temperature midst on solubility of silicate concrete mixture components: SiO 2 - (a) (J.Shtark), CaO - (b) (V.Babushkin, О.Mchedlov-Petrosyan) and an index рн on concentration of Al 2 O 3 and SiO 2 - (c) (J.Shtark). With regulation of speed of lime and silica dissolution it is possible to displace balance in system in this or that side and to change kinetic of hydrations and properties of silicate materials. The technology provides complex activation of a silicate concrete mixture, including a fine-grained filler, a uniform warming up of a mix in forms at a stage of preliminary ageing and thermo-moisture treatment (ТMT) at Т=85 С. The preliminary moderate warming up of a

3 mix in forms is provided by application of not slaked ground lime together with quartz sand. Regulation of speed of a thermal emission of lime is provided by the optimum water-firm relation, the content of additives of gypsum and plasticizer [5]. Thermal activation of components of a silicate concrete mixture is traditionally carried out in autoclaves where in conditions of the raised temperature and pression there is a hydrothermal synthesis of hydrosilicates of calcium (V.Mihaelis). Transition from hydrothermal synthesis of hydrosilicates of calcium in autoclaves to thermo-moisture processing is carried out due to association of the following ways of activation: - mechano-chemical activation of crystal quartz in an aquatic midst of the mixeractivator, - chemical activation due to introduction of the inorganic modifiers, containing amorphous silica, and the raised values рн midst, - thermal activation due to application of not slaked ground lime. Due to the listed ways of activation the conditions for dissolution silica and formations in necessary quantity of hydrosilicates of calcium are provided at Т=85ºС. The opportunity of complex activation is realized at manufacturing products from highmobility mixture. Molding technology is one of the most effective resource - saving technology. The molding technology has received wide application at the last decade owning to the intensive development of manufacture and mass application of highly effective plasticizers. At manufacturing silicate non-autoclave products by the molding way the use of the porous additives containing amorphous silica led only to increase of a water demand of mixture and to decrease in frost resistance of products, as result. Mechanically-chemical activation allows to lower viscosity lime-silica binding substance more than on the order. This effect of decrease of viscosity is used for indemnification of the raised water. That is a demand of a mixture due to introduction of the porous mineral additive and carrying out of activation binding substance together with a fine-grained filler. The finegrained filler exposing to physical and chemical activation is as an active component of a raw mixture. The active surface of a fine-grained filler is the base sheet on which hydrosilicates of calcium are formed. The depth of front of reaction on surfaces of the activated grain of quartz can correspond to tens of monomolecular layers of water unlike an ideal crystal of quartz, depth of front of reaction on which corresponds to a monolayer of water. With increase in the grain size of quartz the degree of its surface s activity increases. The increasing of a surfaces activity of a filler is the one of the ways which provides the increase of compressive strength, frost resistance and durability of concrete [5, 6]. 3. EXPERIMENT The select of the plan and factors for experiment is carried out in the view of following positions. The inorganic modifier with the set specific surface carry out a role of modifiers of structure and allow to regulate a kinetics of hydration and structurization processes [7, 8]. Depending on a specific surface of the inorganic modifier, reaction can go in conditions of lime s excess. It can be deficiency or at its full linkage. The basic natural experiment is realized on sated to 24 punctiform six factors plan of type MTQ "mixture-technologyquantity" [9, 10]. The specific surface of the inorganic modifier was fixed as three dependent mixture factors at levels: υ 1 =S sp1 =350m 2 /kg, υ 2 =S sp2 =425m 2 /kg, υ 3 =S sp3 =500m 2 /kg. The factors are connected by linear dependence: υ 1 +υ 2 +υ 3 =1. The duration of a preliminary ageing

4 (τ p.a. =0 12 hours), duration of TMT (τ ТMT =10 18 hours) at Т=85 C and contents of the additive of gypsum (C g =0 5%) were changed as three independent factors. In each point of the plan there were generated on 15 identical structures. By the plan it is calculated two identical complexes of six-factorial experimentally-statistical models by type (1) [8]. The models describe dependence "content-technology-properties" and "content-technologystructure". It has allowed to study dependence "characteristics of structure - properties". block D block B Y= block A 2 +A 12 ν 1 ν 2 +A 1 ν 1 +D 14 ν 1 x 4 +D 15 ν 1 x 5 +b 44 x 4 +b 45 x 4 x 5 +D 16 ν 1 x 6 2 +A 13 ν 1 ν 3 +A 2 ν 2 +D 24 ν 2 x 4 +D 25 ν 2 x 5 +b 55 x 5 +b 46 x 4 x 6 +D 26 ν 2 x 6 2 +A 23 ν 2 ν 3 +A 3 ν 3 +D 34 ν 3 x 4 +D 35 ν 3 х 5 +b 66 x 6 +b 56 x 5 x 6 +D 36 ν 3 x 6 block C (1) The results of physical and chemical researches have shown a presence in structure of: hydrosilicates of calcium of different sorts; morphology and quantities depending on a specific surface of the inorganic modifier; the contents of the additive of gypsum and hardening conditions. By results of electronic microscopy, DTA and X-ray hydrosilicates of calcium of a sort are identified: hillebrandite B, its version hillebrandite C, foshahite and partially crystal CSH (A) and CSH (B) [6, 7, 8, 10]. The frost resistance of monomineral samples of hillebrandite (F100) is on the order above, than frost resistance СSH (B) (F10) and tobermorite (F15) which form mainly firm phase of autoclave materials [1]. 4. RESULTS AND DISCUSSION By results of experiment there were calculated experimentally-statistical models of influence of contents and conditions of hardening on properties and characteristics of structure of silicate materials of non-autoclave hardening. Also there were calculated: - the models of change of a porousness of the general, opened and closed; - the quantitative contents of hydrosilicates of calcium under influence of six factors. The changing of the general porousness on 10 % the relation of opened porousness to closed porousness increased in three times. Character of a capillary porousness was estimated by the relative average size of capillaries (d k ) which changes in 4.4 times and by the coefficient of uniformity of distribution of sizes of capillary pores (α k ) which changes in 2.5 times. The contents and hardening conditions which provide a maximum of compressing strength (R b ) do not coincide with values of these factors. That provides a maximum of deformation propertie (elastic modulus E) and maximum of fracture mechanics parameter K Ic [11]. So, under influence of all six factors the increase compressive strength calculated on a full model of a type (1), makes 6.4 times. Joint influence on compressive strength of three groups of factors: grain-growing content (S sp1, S sp2, S sp3 the block D), hardening conditions (τ TMT and τ p.a. the block B) and additives of gypsum (C g ) in quantitative expression is equivalent. Each group of factors is able to provide a gain of compressive strength more than twice (fig. 2a, tabl. 1.).

5 Figure 2: The change of a compressing strength R b (a), of a fracture mechanics parameter K Ic (b), of a elastic modulus E (c) under influence: of hardening conditions and contents of the additive of gypsum at optimum values of size of a specific surface of the inorganic modifier (isosurfaces are inside the cube a full model); hardening conditions at the fixed contents of gypsum (isolines on the squared diagrams the block B);a specific surface of the inorganic modifier at the fixed values of hardening conditions and the contents of gypsum (isolines on the three-cornered diagrams the block D). The fracture mechanics parameter K Ic changes in four times depending on a specific surface of the inorganic modifier and hardening conditions: MPa m -0.5 (fig.2b). So, under influence of a specific surface of a inorganic modifier the relative change of the fracture mechanics parameter K Ic equal 1.6 (the block D), under influence of hardening conditions (the block B). Table 1: The relative change of the properties under the influence of the different groups of factors technology and content Groups of factors R b K Ic E The various specific surface area S sp of the inorganic modifier (the block D) The hardening conditions τ p.a., τ TMT (the block B) The additive of gypsum C g All six factors S sp, τ p.a., τ TMT, C g

6 The elastic modulus E changes from 39.5 to 45.3 GPa under influence of a specific surface of the inorganic modifier and hardening conditions (fig.2c). So, under influence of a specific surface of a inorganic modifier the relative change of the elastic modulus E equal 1.15 (the block D), under influence of hardening conditions (the bl. B). 5. SUMMURY AND CONCLUSION Bases of manufacture lime-silica composites of non-autoclave hardening are developed. The complex activation of a high-mobility silicate concrete mixture, including a finegrained filler, provides transition from autoclave processings to thermo-moisture treatment at Т=85 С. Technical and economic calculation has shown that transition from autoclave processings of the products received by a method of pressing to thermo-moisture treatment processing of products reduces expenses for manufacture more than 25%. The kinetics of processes of hydration and structurization can be adjusted by a specific surface of the inorganic modifier, defining individual levels of properties. Influence of content, in particular of specific surface of the inorganic modifier and hardening conditions on various properties (compressing strength R b, elastic modulus E, fracture mechanics parameter K Ic ) in quantitative expression is ambiguous. REFERENCES [1] Babushkin, V.I., Mchedlov-Petrosyan, O.P. Silicate Waterproof Products. Kiev.: 99p, [2] Shtark, J., Viht, B. Durability of Concrete. Transl. from German., Under edition P.V. Krivenko. Kiev.: 301p., [3] Taylor, H. Chemistry of Cement. Translation from English. Moscow: the World.: 560p., [4] Shinkevich E., Sidorova N., Lutskin E., Sidorov V., Politkin S. Raw Mix for Obtain Modified Silicate Materials and Method of Its Prepare. Declared patent # A, 7 C04B28/20, Ukraine, [5] Krivenko, P., Pushkareva, E. at al. Durability of Alkaline Portland Cement Concretes made with Alkali-reactive Aggregates. Proceeding ACI Int. Conference on Durability of Concrete. Sydney, Australia, 1997 [6] Shinkevich, E., Lutskin, E., Gnyp, O., Koichev, A., Dotsenko, J. The Influence of Modification of the Structure of Silicate Materials on Their Properties After Non-autoclaved Hardening. Proc. of the 8 th Int. Symp. Brittle Matrix Composites 8. Warsaw.: , [7] Shinkevich, E., Lutskin, E. The Influence of Structure Modification of Silicate Materials after Hardening in Non-autoclave Conditions on Their Coefficient of Heat Conductivity. Proceeding of International Conference Alkali Activated Materials Research, Production and Utilization. Prague: , [8] Shinkevich, E. Development of scientific bases of reception lime-silica building composites of non-autoclave hardening. The author's abstract of the dissertation of Dr.Sci.Tech. Odessa, Ukraine: 32p, [9] Voznesensky, V., Lyashenko, T. Experimental-statistical Modelling in Computational Materials Science In Proceeding of the 37-th International Seminar Modeling and Optimizations of composites, Odessa,: 32, [10] Shinkevich, E., Lutskin, E., Khlytsov, N., Litvak, A. Silicate non-autoclave materials: technology, structure, properties. Proceedings of the 3 rd International Symposium Non-Traditional Cement & Concrete. Brno: , [11] Zaytsev, Y.V. Fracture Mechanics for builders. Moscow, 288p., 1991.