Stones, sandpits and limestone quarries in the Czech Republic

X-ray diffraction phase analysis (XRD)

X-ray diffraction phase analysis can be used to determine phase composition of the samples. X-ray radiation interacts with atoms of crystals producing diffraction interference waves that are detected, while each crystalline structure exhibits a typical and unambiguous spectrum. The wave intensity is proportional to the content of the given structure in the sample.

X-ray diffraction phase analysis was performed at the Research Institute of Inorganic Chemistry using Philips MPD 1880 diffractometer, by evaluation of the diffraction data using X´Pert programs (X´Pert HighScore Plus Software version 2.1b and X´Pert Industry Software version 1.1g). Phases were identified using ICCD PDF2 database of diffraction data containing about 107,000 of inorganic standards.

Loss through limestone calcination

The limestone sample is calcinated at a temperature of (1,100 ±20) °C to a constant weight. The loss through limestone calcination is determined as the difference in the weight of the sample before and after calcination.

The test was performed at Výzkumný ústav anorganické chemie, a.s. pursuant to ČSN 72 0103; Basic silicate analysis procedure – Determination of loss through calcination.

Silicon dioxide content in limestone

The limestone sample is decomposed by melting with sodium carbonate or with a mixture of sodium carbonate and disodium tetraborate, depending on the aluminium oxide content in the sample. The melt is leached with water, dissolved in a solution of hydrochloric acid and, after boric acid has been removed using methanol, the silicon dioxide is excluded by dual evaporation with hydrochloric acid until dry. After being weighed, the crude silicon dioxide is fumed with hydrofluoric acid and sulphuric acid and the difference in weight is used to determine the silicon dioxide content in the sample.

The test was performed at Výzkumný ústav anorganické chemie, a.s. pursuant to ČSN 72 0105-1; Basic silicate analysis procedure – Determination of silicon dioxide using the gravimetric method.

Indecomposable content in limestone

The limestone sample is decomposed with dilute hydrochloric acid. The precipitated silicic acid is converted back into a sodium carbonate solution. The remaining indecomposable proportion is calcinated and then weighed after cooling in a desiccator.

The test was performed at Výzkumný ústav anorganické chemie, a.s. pursuant to ČSN 72 0107; Basic silicate analysis procedure – Determination of indecomposable content with acid using the gravimetric method.

Aluminium oxide content in limestone

The excess of a solution of disodium ethylenediaminetetraacetic acid (EDTA) is added to an aliquot part of the filtrate after separation of silicic acid (when determining silicon dioxide content). The excess EDTA is bound to a complex of zinc acetate solution. Addition of sodium fluoride forces the aluminium and titanium ions from the complex and the released EDTA, corresponding to the aluminium and titanium content, is titrated with a standard zinc acetate solution using xylenol orange as an indicator. The aluminium content is determined by deducting the titanium content (see determination of titanium dioxide content).

The test was performed at Výzkumný ústav anorganické chemie, a.s. pursuant to ČSN 72 0109-1; Basic silicate analysis procedure – Determination of aluminium oxide using the titration method.

Iron oxide content in limestone

In a controlled environment with 2.2'-dipyridyl, ferrous ions form a red-coloured complex. The colouration is proportional to the concentration of ferrous ions in the solution. Therefore, all iron is reduced to bivalent iron and this is then determined using photometry.

The test was performed at Výzkumný ústav anorganické chemie, a.s. pursuant to ČSN 72 0110-2; Basic silicate analysis procedure – Photometric determination of iron oxide using a dipyridyl 2.2´.

Titanium dioxide content in limestone

The yellow coloration of tetravalent titanium chelate with Tiron in a weakly acidic medium is used to determine titanium dioxide content. The disruptive effect of ferric ions is suppressed by reduction using ascorbic acid and maintaining the pH of the solution measured. The colouration is proportional to the concentration of titanyl ions in the solution.

The test was performed at Výzkumný ústav anorganické chemie, a.s. pursuant to ČSN 72 0112-2; Basic silicate analysis procedure – Photometric determination of titanium dioxide using Tiron.

Calcium oxide content in limestone

An aliquot part of a stock solution, after the removal of silicon dioxide (when determining silicon dioxide content), is used to determine the calcium oxide content using direct complexometric titration.

The test was performed at Výzkumný ústav anorganické chemie, a.s. pursuant to ČSN 72 0113-1; Basic silicate analysis procedure – Determination of calcium oxide using the complexometric method.

Magnesium oxide content in limestone

An aliquot part of a stock solution, after the removal of silicon dioxide (when determining silicon dioxide content), is used to determine the magnesium oxide content from the difference in the consumption of the EDTA solution for the titration of the sum of CaO and MgO and the consumption of the EDTA solution for CaO, determined in a different part of the solution.

The test was performed at Výzkumný ústav anorganické chemie, a.s. pursuant to ČSN 72 0114-1; Basic silicate analysis procedure – Determination of magnesium oxide using the complexometric method.

Thermal analysis

Thermogravimetry (TG) is an experimental method based on continuous monitoring of the test sample weight during its heating or cooling. Derivative thermogravimetry (DTG) is a derived method where the measured value is the speed of mass changes depending on temperature, i.e. dm/dt as a function of temperature. It is used for more precise differentiation of the beginnings and ends of individual actions during thermal decomposition.

Thermogravimetric analyses were performed at the Research Institute of Inorganic Chemistry using Discovery TGA (TA Instruments) system. Analysis conditions: temperature range 50-950C, temperature gradient 10 C/min and reaction gas – nitrogen with a flow rate of 20 ml/min.

The evaluation was carried out based on weight losses using the integral method where quantitative data is always located next to mass changes. The second curve is derivation of the original curve and completes it. The evaluation also includes kinetic isotherms of sample behaviour as part of the evaluated effect. Isotherms were calculated using the non-isothermal kinetic relationship, similarly as activation energy and the order of the reaction.

Optimum temperature of limestone burning

The limestone sample is burnt at three different temperatures in the interval of 900–1200 C. Reactivity according to ČSN EN 459-2 (see below) is determined on such prepared samples. The maximum of the function describing the dependency of temperature during hydration T_u on the burning temperature, and the minimum of the function describing the dependency of hydration time t_u on the burning temperature are calculated. The temperature, where T_u is maximal or t_u minimal, respectively, is the optimum temperature of burning. The arithmetic average of both values indicates the actual temperature of burning. It is the temperature at which limestone samples are burnt before testing lime reactivity.

The optimum temperature of burning was determined at the Research Institute of Inorganic Chemistry.

Lime reactivity (T_max and time required to reach T_max)

Lime reactivity is determined based on the measurement of temperature changes during lime reaction with water (slaking) carried out in a thermally insulated vessel under prescribed conditions (20 ± 0.5 C). The maximum reached temperature Tmax and the time necessary to achieve this temperature tmax were determined from the dependency of the temperature on time during lime hydration.

The test was performed at the Research Institute of Inorganic Chemistry according to ČSN EN 459-2: Building lime – Part 2: Test methods

Determination of total CaO and MgO contents

The sample is decomposed by hydrochloric acid and ammonium chloride. Calcium oxide is selectively determined using titration with EDTA solution, and the total content of calcium oxide and magnesium oxide is determined in the presence of a non-selective indicator. The content of magnesium oxide is determined from the difference of found concentrations.

The test was performed at the Research Institute of Inorganic Chemistry according to ČSN EN 459-2: Building lime – Part 2: Test methods, referring to ČSN EN 196-2: Methods of testing cement – Part 2: Chemical analysis of cement. The deviations in the procedure from this standard are described below. During decomposition by hydrochloric acid and ammonium chloride, the burnt samples of tested very pure limestones were totally decomposed each time; there was no precipitate present on the filter. Since the content of magnesium in the samples was low, the addition of volumetric solution of EDTA corresponding to the consumption during titration of calcium was dropped out from the procedure and only triethanolamine with an indicator was added, followed by titration with 0.03 mol/l EDTA until the colour changed.

Determination of carbon dioxide

The determination is based on the decomposition of carbonates contained in the lime using hydrochloric acid. Released gases are collected and then absorbed in 50% solution of potassium hydroxide. The content of carbon dioxide is determined from the difference of the gas volume before and after absorption.

The test was performed at the Research Institute of Inorganic Chemistry. The test procedure is described in ČSN EN 459-2: Building lime – Part 2: Test methods.

Content of free lime

Free lime (i.e. calcium oxide that is hydrolyzed to calcium hydroxide or calcium hydroxide present in the sample) is dissolved in saccharose solution and titrated using hydrochloric acid with phenolphthalein as the indicator.

The test was performed at the Research Institute of Inorganic Chemistry. The test is based on ČSN EN 459-2: Building lime – Part 2: Test methods.

Content of SiO₂ and acid-insoluble part

The test is based on the decomposition of the sample by diluted hydrochloric acid. The remaining silicic acid and non-degradable part are ignited and then, after cooling, weighed. The test was performed at the Research Institute of Inorganic Chemistry. The analysis procedure was based on the no longer valid standard ČSN 72 2203: Chemical analysis of limes, 1985.

Sulphates content in lime

Sulphate ions released during decomposition with hydrochloric acid are precipitated at pH 1.0 to 1.5 using barium chloride solution while boiling. The amount of precipitated barium sulphate is determined gravimetrically and the content of sulphates is expressed as percentage of SO₃.

The test was performed at the Research Institute of Inorganic Chemistry. The test was based on ČSN EN 459-2: Building lime – Part 2: Test methods, referring to ČSN EN 196-2: Methods of testing cement – Part 2: Chemical analysis of cement.

Loss on ignition of lime and total water content

The sample is ignited at a specified temperature until constant weight is achieved, in oxidizing atmosphere. The loss on ignition is determined from the difference of the sample weight before and after ignition. By determining the loss on ignition at 950 C, the contents of water and CO₂ in the sample are found. By determining the loss on ignition at 600 C, the total content of water is found.

The test was performed at the Research Institute of Inorganic Chemistry. The test was based on ČSN EN 459-2: Building lime – Part 2: Test methods, referring to ČSN EN 196-2: Methods of testing cement – Part 2: Chemical analysis of cement. The determination of loss on ignition at 600 C replaces the procedure for determination of hydrate water in hydrated limes described in the no longer valid standard [ČSN 72 2203 Chemical analysis of limes, 1985] which could not be used due to low content of hydrate water in samples and the resulting high error of determination.

Sedimentation of slaked lime after 20 hours

The test is based on the hydration of the lime sample with excess water in the prescribed way, its sedimentation in a graduated cylinder, and determination of the sediment volume after 20 h. The sediment volume represents percentage ratio of the sediment to the total volume of the suspension.

Particle size distribution of slaked lime

Particles of the analyzed sample are exposed to laser beams that scatter on the particles. The scattering angle is inversely proportional to the size of the particle that induced the scatter. The particle size distribution after standard processing using a specialized instrument is represented as the distribution curve expressing dependence of the distribution and/or cumulative volume fraction of the particle size in µm, in logarithmic scale. As a simplified numerical expression, the values of D₁₀, D₅₀ and D₉₀ indicating the size in µm corresponding to cumulative representation of 10%, 50% and 90% of the volume of the measured particles are usually used. A sample of slaked lime prepared for the sedimentation test after 20 hours was used for the determination. Prior to the measurement, the sample was exposed to ultrasound for 3 minutes to disintegrate the agglomerates. The test was performed at the Research Institute of Inorganic Chemistry using MALVERN Mastersizer 2000 system able to measure particle size distribution in the range 0.01–2000 µm.

Setting time

The setting time represents the time interval between the start and end of solidification of lime putty with normalized consistency prepared from lime hydrate in the prescribed way. The start and end of solidification are determined based on the depths of needle penetration into the lime putty in the course of time.

The test was performed at the Research Institute of Inorganic Chemistry according to ČSN EN 459-2: Building lime – Part 2: Test methods, referring to ČSN EN 196-3: Methods of testing cement – Part 3: Determination of setting times and soundness.

Capacity

The capacity is represented by the volume of lime hydrate formed by lime hydration in the prescribed way.

The test was performed at the Research Institute of Inorganic Chemistry according to ČSN EN 459-2: Building lime – Part 2: Test methods.

Degree of whiteness and coloration

The test is based on the measurement of intensity and spectrum of the light beam reflected from the test sample. The measurement result is expressed in L, a, and b values.
L – brightness and ranges from 0 (black) to 100 (white)
a, b – position in the CIE colour space (Commission Internationale de l'Éclairage)
a – position in the diagonal – red (positive values) – green (negative values)
b – position in the diagonal – yellow (positive values) – blue (negative values).

The coloration is characterized by values a and b, and the degree of whiteness by the ratio of L value determined for the measured sample and L value of the standard (barium sulphate) expressed in %.

The degree of whiteness and coloration was determined at Ceske lupkove zavody, a.s. using Lovibont RT100 system.

Water retension

Water retention in a fresh normalized mortar is expressed in percentage of water content remaining in the mortar on the filtration paper after short vacuum filtration.

The test was performed at the Research Institute of Inorganic Chemistry according to ČSN EN 459-2: Building lime – Part 2: Test methods. The normalized mortar was prepared using the procedure described in ČSN EN 196-1: Methods of testing cement – Part 1: Determination of strength.

Penetration value

The penetration value expressed in millimetres indicates the depth of penetration of a penetration cylinder into fresh normalized mortar with specified consistency (slump-flow value 185 ± 3 mm determined using a vibrating table).

The test was performed at the Research Institute of Inorganic Chemistry according to ČSN EN 459-2: Building lime – Part 2: Test methods. The normalized mortar was prepared using the procedure described in ČSN EN 196-1: Methods of testing cement – Part 1: Determination of strength.