Design of Slag Cement, Activated by Na (K) Salts of Strong Acids, for Concrete Reinforced with Steel Fittings

This paper proposes a technique to prevent the corrosion of steel reinforcement in concrete based on slag cement (SC) activated by Na(K) salts of strong acids (SSA) in the composition of by-pass cement kiln dust (BP). The technique implies using additional modifiers in the form of the Portland cement CEM I 42,5 R and the calcium-aluminate admixture (CAA) С3А∙6H2O.It is shown that adding the Portland cement contributes to enhancing the intensifying influence of BP on the SC hydration, accompanied by an increase in the strength of artificial stone. This effect is predetermined by the formation of hydrosilicates in hydration products with an increased crystallization degree in the form of CSH(I) and C2SH(A).Modifying SC with CAA ensures the intensive formation of low-soluble AFm phases in the composition of hydration products, aimed at reliable binding the SSA anions (Cl-, SO42-) that are aggressive to steel reinforcement.The study result has established the possibility to produce SC, activated by SSA, when using BP, the Portland cement, and CAA. Mathematical methods to plan the experiment were applied to produce an SC composition of "granulated blast furnace slag – BP – Portland cement – CAA", characterized by a strength class of 42.5 and a molar ratio of Cl-/OH- in a porous solution not exceeding 0.6. The resulting properties predetermine the feasibility of using SC in steel-reinforced concrete.The relevance of this work is due to the modern trends in the development of the construction industry. The introduction of cement that contains mineral additives, in particular granulated blast furnace slag, contributes to improving the environment by reducing СО2 emission. The use of such cement as a base of steel-reinforced concrete ensures the increase in their functionality and durabilit

Influence of the Ratio of Oxides and Temperature on the Structure Formation of Alkaline Hydro-aluminosilicates

In the course of optimization of compositions of alkaline hydro-aluminosilicates of general structural formula – (0,7÷1Na2O+0÷0,3K2O)·Al2O3·(2÷7)SiO2·nH2O, it is established that the phase composition of artificial stone depends more on the ratio of basic oxides; the temperature of hardening in the range of 20÷80 °С increases the speed of structure formation of zeolite-like phases.A determining factor of influence on the type of hydrated new formations is the ratio of SiO2/Al2O3; its increase leads to the creation of zeolite-like phases with high content of silica in its composition. At hardening of alkaline hydro-aluminosilicate of the given structural forms under standard conditions of hardening, providing for a high degree of crystallinity of structure, optimal is the ratio SiO2/Al2O3=4÷5.Introduction of potassium ions into the composition of hydro-aluminosilicate contributes to obtaining potassium and sodium–potassium zeolite–like new formations and to increasing the degree of crystallinity of the indicated phases. To accelerate the structure formation of alkaline hydro-aluminosilicate under standard conditions of hardening, it is necessary to introduce potassium oxide at K2O/R2O=0,15÷0,3.With an increase in the temperature of hardening of alkaline hydro-aluminosilicate from 20 to 80 °, the phase composition of artificial stone remains practically unchanged; however, this leads to an increase in the velocity of structure formation and the degree of crystallinity of artificial stone.As a result of optimization, we determined optimum structural formula of hydro-aluminosilicate (0,8Na2O+0,2K2O)·Al2O3·4,5SiO2·nH2O, which makes it possible under standard conditions of hardening to obtain water-resistant artificial stone by the synthesis in the composition of hydrated new formations of zeolite-like minerals of the type of zeolite Na–A; sodium and potassium heulandite, as well as sodium potassium phillipsite

Influence of the CaO-containing Modifiers on the Properties of Alkaline Alyumosilicate Binders

The basis for ensuring the resistance of artificial stone based on alkaline aluminosilicate binders to variable environmental conditions is the formation of zeolite- and mica-like hydrate neo-formations.It is possible to control the structure forming processes and, as a result, the operational properties of alkaline hydro aluminum silicates using the variation of the ratio of basic oxides of the binder, dispersiveness of particles and hardening conditions. It was noted that in order to obtain high operational characteristics of a stone based on alkali aluminosilicate binders, there is a need for elevated temperature of their hardening.The research shows that it is possible to ensure water resistance of artificial stone at hardening under normal conditions at the expense of the modification of the binder by Ca-containing additives.The influence of CaO-containing modifiers of different phase composition on physical and mechanical properties of artificial stone based on alkali aluminosilicate binders was explored. Ensuring water resistance of artificial stone at its hardening under conditions of normal temperatures was proved by experimental research and its phase composition was studied. The kind and the optimal amount of CaO-containing modifiers to provide for operational properties of artificial stone were determined. The use of CaO-containing modifiers of alkaline aluminosilicate binders ensures the acceleration of their structure formation and contributes to an increase in water resistance and strength under normal conditions.The influence of CaO-containing modifiers of various morphological type on physical and mechanical properties of artificial stone based on alkaline aluminosilicate binders was studied. It was established that on day 28of hardening at ambient temperature of 20±2 °С regardless of the type of introduction of Ca-containing modifiers, artificial stone is characterized by strength at compression from 14.2 to 42.8 MPa with a coefficient of water resistance from 0.81 to 1.05 due to the formation in combustion products of the mixture of high- and low-base calcium hydro silicates and zeolite-like neo-formations of the hybrid type – calcium-sodium hydroaluminosilicates with an insignificant content of Na- and K-heulandite. It was shown that water resistance of artificial stone in the early periods of hardening at ambient temperature of 20±2 °С is ensured due to the formation in hydration products of the binder of high- and low-base calcium hydro silicates, formed due to hydration of Portland cement, ground slag and slaked lime. It is possible to accelerate the kinetics of strength gaining with ensuring the water resistance of artificial stone using liquid glass with silicate module of 2.0–2.6 and lime content in the amount of 2.0–3.0 % percent of the weight of alkaline aluminosilicate binder as an alkaline component. It was noted that hydraulic activity of Ca-containing modifiers decreases in the series Slag>Са(ОН)2>СаСО3>Portland cement>Alumina cemen

Determining the Effect of the Composition of an Aluminosilicate Binder on the Rheotechnological Properties of Adhesives for Wood

Main rheotechnological properties of aluminosilicate adhesives for gluing wood arrays have been investigated. It was established that for adhesives based on the alkaline aluminosilicate binding agent with a composition of Na2O×Al2O3×4.5SiO2×17.5H2O dynamic viscosity in the range of speeds from 0 to 200 RPM varies from 6.933 sP to 368.4 Sp, and the mean plastic viscosity takes the magnitude of 86.27 sP. At the same value of surface tension and cohesive work, the smallest angle of wetting (cosQ=0.7973) and the largest coefficients of wetting (s=0.8986) and spreadability (f=–6.5 mN/m), as well as the work of adhesion forces (Wa=58.23 mN/m), wetting (Wa=58.23 mN/m), are demonstrated by beech backing, followed by alder, ash, pine, birch, and oak.For adhesives based on the alkaline aluminosilicate binding agent with a composition of Na2O×Al2O3×6SiO2×20H2O dynamic viscosity in the speed range from 0 to 200 RPM varies from 5.340 sP to 374.4 sP, and the mean plastic viscosity takes the magnitude of 85.72 sP. At the same value of surface tension and cohesive work, the smallest angle of wetting (cosQ=0.5876) and the largest coefficients of wetting (s=0.7938) and spreadability (f=–19.34 mN/m), as well as the work of adhesion forces (Wa=74.46 mN/m), wetting (Ww=27.56 mN/m), are demonstrated by alder backing, followed by pine, oak, birch, beech, and ash.For the adhesive with a composition of Na2O×Al2O3×4.5SiO2×17.5H2O, at low values of shear rate, from 0.0378 to 1.05 1/sec, the shear force increases from 26.21 dyne/cm2 to 48.64 dyne/cm2. The data obtained significantly exceed the same indicators for a liquid glass at high shear rates, from 14 to 39 1/sec. For the adhesive with a composition of Na2O×Al2O3×6SiO2×20H2O, at low shear speeds there is a sharp increase in the shear effort, from 40 to 110 dyne cm2. This is due to the dispersion processes in the silica component. At an increase in the shear speed values from 5 to 42 1/sec, the shear effort increases from 110 to 158 dyne/cm2. This relates to the stabilization of viscosity values with the formation of a homogeneous adhesive structur

Determining the Effect of the Composition of an Aluminosilicate Binder on the Rheotechnological Properties of Adhesives for Wood

Main rheotechnological properties of aluminosilicate adhesives for gluing wood arrays have been investigated. It was established that for adhesives based on the alkaline aluminosilicate binding agent with a composition of Na2O×Al2O3×4.5SiO2×17.5H2O dynamic viscosity in the range of speeds from 0 to 200 RPM varies from 6.933 sP to 368.4 Sp, and the mean plastic viscosity takes the magnitude of 86.27 sP. At the same value of surface tension and cohesive work, the smallest angle of wetting (cosQ=0.7973) and the largest coefficients of wetting (s=0.8986) and spreadability (f=–6.5 mN/m), as well as the work of adhesion forces (Wa=58.23 mN/m), wetting (Wa=58.23 mN/m), are demonstrated by beech backing, followed by alder, ash, pine, birch, and oak.For adhesives based on the alkaline aluminosilicate binding agent with a composition of Na2O×Al2O3×6SiO2×20H2O dynamic viscosity in the speed range from 0 to 200 RPM varies from 5.340 sP to 374.4 sP, and the mean plastic viscosity takes the magnitude of 85.72 sP. At the same value of surface tension and cohesive work, the smallest angle of wetting (cosQ=0.5876) and the largest coefficients of wetting (s=0.7938) and spreadability (f=–19.34 mN/m), as well as the work of adhesion forces (Wa=74.46 mN/m), wetting (Ww=27.56 mN/m), are demonstrated by alder backing, followed by pine, oak, birch, beech, and ash.For the adhesive with a composition of Na2O×Al2O3×4.5SiO2×17.5H2O, at low values of shear rate, from 0.0378 to 1.05 1/sec, the shear force increases from 26.21 dyne/cm2 to 48.64 dyne/cm2. The data obtained significantly exceed the same indicators for a liquid glass at high shear rates, from 14 to 39 1/sec. For the adhesive with a composition of Na2O×Al2O3×6SiO2×20H2O, at low shear speeds there is a sharp increase in the shear effort, from 40 to 110 dyne cm2. This is due to the dispersion processes in the silica component. At an increase in the shear speed values from 5 to 42 1/sec, the shear effort increases from 110 to 158 dyne/cm2. This relates to the stabilization of viscosity values with the formation of a homogeneous adhesive structur

Applicability of Alkali-activated Cement for Immobilization of Low-level Radioactive Waste in Ion-exchange Resins

All generated and collected low-level radioactive wastes (LRW) should be processed into final products for a long-term disposal without loss of their properties. Worldwide, cementation is the most widely used technology for immobilization of nuclear wastes. Due to many existing varieties of LRW some of these wastes are incompatible with the process of hydration and hardening of a cement matrix and require optimization of cement immobilization technologies. The paper presents the results of devising new formulations of multi-component alkali-activated cement, which is aimed at complex processing of low-level radioactive waste with ion-exchange resins. The radioactive wastes to be immobilized included two types of ion-exchange resins: cation- and anion-exchange resins mixed as 2:1 with pH=12 and anion-exchange resin with pH=5. Analysis of the obtained results from the developed optimal recipes proved that the properties of the final products are in compliance and in some cases even exceed those set in standards GB 7023 and GB 14569 of the P. R. China. High efficiency of the alkali-activated cement matrices for immobilization of radioactive wastes is attributed to their ability to bind radionuclides not only mechanically and adsorptionally, as it happens in case of traditional cement matrices, but also chemically–within the composition of zeolite-like hydration products of the R2O∙MeO∙Al2O3∙nSiO2mH2O or R2O∙Al2O3∙nSiO2mH2O types, where: R=Na, K, and Cs; Me=Ca, Mg, and Sr

Analysis of Plasticizer Effectiveness During Alkaline Cement Structure Formation

The problem of plasticization of alkaline cements was analyzed and the ways of its solution were offered. The problem is related to the structural instability of a number of chemical admixtures that are effective in plasticisation of clinker cements in the highly alkaline media of hardening cement. Superplasticizers based on polyesters lose their steric effect due to the hydrolysis reaction. On the other hand, selectivity of action of chemical admixtures is associated with the changes in a wide range of compositions of alkaline cements. In addition, the degree of changes in the structure of admixtures depends not only on the medium pH but also on the nature of the alkaline component, the production process and use of such cements. Generalization of the problems made it possible to proceed with the expansion of the range of substances from the class of surface active substances (SAS), their experimental verification and the application proposal for plasticization of alkaline cements. As plasticizing SAS characterized by stability of molecular structure in alkaline media, low- and high-molecular compounds from the class of acyclic (aliphatic) compounds or fatty compounds were considered. The polyester-based superplasticizers traditionally applied in plasticization of calcium cement systems were used for comparison. Variation of the nature and ratio of components in the composition of alkaline cements as well as the chemical admixture nature were taken as the main factors in the study of features of cement plasticization. Comparative evaluation of effectiveness of these admixtures indicates selectivity of use taking into account composition of alkaline cements. As a result of this research, systematization of classes of chemical compounds according to their effectiveness as plasticizers for alkaline cements was proposed. Such a systematization can be used in development of commercial products in a form of plasticizing additives for concretes and mortars