Tests of Sands

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 forming 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 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). To identify the phases, ICCD PDF2 database of diffraction data was used, containing about 107,000 of inorganic standards.

X-ray fluorescence analysis (XRF)

X-ray fluorescence analysis is a physical method where atoms of the analyzed sample are excited by X-ray radiation. During deexcitation, secondary X-ray radiation is produced – when electrons move from higher to lower electron shells – with the line spectrum of wavelengths characteristic for each element. Measured wavelengths and intensities of secondary X-ray radiation can be used to determine the content of chemical elements in the analyzed sample. As a rule, the result is expressed in weight percentage of oxides of identified elements.

X-ray fluorescence analysis was performed at the Research Institute of Inorganic Chemistry using Philips PW 1404 spectrometer equipped with UniQuant analytical program yielding semi-quantitative determination of the content of 74 elements (from fluorine to uranium).

Particle size distribution of sand

The particle size distribution is characterized by gravity separation on a series of sieves with subsequent weighing of individual fractions.

The test was performed at the Research Institute of Inorganic Chemistry according to ČSN EN 933-1: Tests for geometrical properties of aggregates – Part 1: Determination of particle size distribution – Sieving method. Nominal sizes of apertures of the test sieves were determined according to ČSN EN 933-2: Tests for geometrical properties of aggregates – Part 2: Determination of particle size distribution – Test sieves, nominal size of apertures.

Assessment of fine particles - Sand equivalent test

The sample of the test sand and a small amount of colloid solution of prescribed composition are inserted in a graduated cylinder and shaken. Clay coating is washed off from the surface of sand grains using the colloid solution. The sand is then disintegrated in water together with another portion of the colloid solution so that fine particles may get into the suspension above the sand. After 20 minutes the total height of sediment and the height of the sedimented sand are measured. The sand equivalent value represents percentage ratio of the height of the sedimented sand grains to the total height of the sedimented material. Thus the lower is the sand equivalent value, the more fine (disintegratable by water) particles the sand contains.

The test was performed at the Research Institute of Inorganic Chemistry according to ČSN EN 933-8: Tests for geometrical properties of aggregates – Part 8: Assessment of fines – Sand equivalent test. The procedure to determine the sand equivalent value was performed according to Annex A for the fraction of aggregates 0/4 mm with moisture lower than 8%.

Particle density and water absorbtion

The test is performed with the grain sieve fraction of 0.063 mm to 4 mm after removal of fine particles by washing. The determination is based on the measured weight and volume of water displaced during the test by the test sample (pycnometric determination). The determination of water absorption is based on weighing the sample dry and after soaking in water and wiping the surface.

The test was performed at the Research Institute of Inorganic Chemistry according to ČSN EN 1097-6: Tests for mechanical and physical properties of aggregates – Part 6: Determination of particle density and water absorption.

Loose bulk density and voids

The loose bulk density represents bulk density of loose dry sand. The volume is determined by pouring the dried sand into a graduated vessel. The voids represent percentage of air volume in loose dry sand and are calculated from the loose bulk density and particle density.

The test was performed according to ČSN EN 1097-3: Tests for mechanical and physical properties of aggregates – Part 3: Determination of loose bulk density and voids.

Resistance to freezing and thawing

The charges of the test sand with the grain size distribution of 1–4 mm after water absorption at atmospheric pressure are exposed to ten cycles of freezing and thawing under prescribed conditions. When the cycles of freezing and thawing are finished, changes in the particle size distribution of sand are quantified. The test result represents the percentage ratio of the grain size distribution fraction below 0.5 mm from the total weight of sand after the freezing cycles.

The test was performed at the Research Institute of Inorganic Chemistry and is based on ČSN EN 1367-1: Tests for thermal and weathering properties of aggregates – Part 1: Determination of resistance to freezing and thawing. Only the initial particle size distribution of the used sand deviated from the standard (should be at least 4–8 mm according to the standard). The reason was that the particle size of the samples taken in sandpits ranged only between 0–4 mm, and thus the fraction 1–4 mm was used for the test, since precisely these sands are usually applied in the production of binding materials.

Sand leachate and leachate analysis

The test consists in drying the sample, mixing with water to achieve the weight ratio of liquid to solid phases of 10:1, shaking the mixture for 24 h, and subsequently in separating the phases in pressurized filtration system with a glass-fiber filter.

Leachates were prepared according to ČSN EN 12457-4: Characterisation of waste – Leaching – Compliance test for leaching of granular waste materials and sludges – Part 4: One stage batch test at a liquid to solid ratio of 10 l/kg for materials with particle size below 10 mm.

Analysis of leachates was performed at the Research Institute of Inorganic Chemistry according to ČSN EN 12506: Characterization of waste – Analysis of eluates – Determination of pH, dissolved solids, chlorides, fluorides, sulphates, As, Ba, Cd, Cr, Cu, Hg, Mo, Ni, Pb, S, Sb, Se and Zn by inductively coupled plasma optical emission spectrometry (ICP-OES). In addition to the specified elements, the content of sodium was determined, as well. As to the instrument – Perkin Elmer ICP OPTIMA spectrometer was used.

Grain shape

The sand sample was examined using a magnifying glass with camera; pictures were electronically recorded, visually inspected and described. Attention was paid especially to roundness, or – on the contrary – angularity of the grains.

Degree of whiteness and coloration

The test is based on measuring the 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.