Abstract
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 >СаСО 3 >Portland cement>Alumina cement
Highlights
Alkaline aluminosilicate binders are an alternative replacement of Portland cement and differ from the latter by unique phase composition, which ensures the formation of artificial stone of high strength, corrosion resistance, thermal resistance and the others due to the formation of analogues of natural and durable zeolite, mica-like and feldspathoid minerals [1,2,3,4,5]
At ambient temperature of 20 °С and below, hydration processes slow down in the alkaline aluminosilicate binder, the gel-like component does not transfer into the crystalline phase and, proper water resistance of artificial stone is not ensured
When we introduce up to 20 % of aluminate cement with the concentration of sodium hydroxide of 10, 12 and 14 M to the composition of alkaline aluminosilicate binder, strength to compression increases and water resistance is ensured only on day 28 of hardening
Summary
Alkaline aluminosilicate binders are an alternative replacement of Portland cement and differ from the latter by unique phase composition, which ensures the formation of artificial stone of high strength, corrosion resistance, thermal resistance and the others due to the formation of analogues of natural and durable zeolite-, mica-like and feldspathoid minerals [1,2,3,4,5]. These properties of artificial stone, including water resistance, are provided by the transition of gel-like phase into the crystalline phase in the temperature range from 60 to 100 °С [6,7,8,9,10,11]. This is due to the fact that the product of dehydration of aluminate cement – aluminum hydroxide, binding with alkali, forms water resistant phases in later time of hardening [17]
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