The chemical composition of cement plays a crucial role in the determination of its properties as a binder substance. The chemical analysis of cement components is widely used in the cement industry for production optimization and stable high-quality assurance of the final product. High requirements for cement quality are formed by its usage in the fabrication of concrete – the most consumed material in the building industry.
The Constituents of Cement
Cement materials are classified into two classes depending on the type of hardening. The first class: hydraulic cement,requires the addition of water for hardening. Hydraulic cement is most widespread in the industry nowadays.
Generally, hydraulic cement is made of a mixture of silicates and oxides. The fabrication process of the cement involves several stages. In the first stage, the raw components are crushed into the powder and mixed. In the second stage, the mixture is fired in special furnaces at high temperatures. During the firing of the ascending mixture, calcium carbonate decomposes into calcium oxide and carbon dioxide as well as clay. Calcium oxide interacts with clay components at high temperatures and forms silicates, aluminosilicates, calcium aluminates, and other components. The final product of the firing process is called clinker. In the third stage, the clinker is ground with gypsum in mills with steel balls. The gray-green powder obtained in grinding processes is hydraulic cement.
The second less common class of cement is non-hydraulic. The typical representative of the non-hydraulic cement is slaked lime (the mixture of calcium oxide with water) which hardens by carbonation with carbon dioxide from the air.
In the cement production low temperature melting clays are used, argillites and shales, which are part of the cement mixture. The second main component is carbonate rocks. Limestone and clay are the raw material for cement production. They are mixed in a certain ratio (75-80% limestone and 20-25% clay).
The chemical composition of cement determines its properties and area of application. The main task of a cement tester is through analysis of elements (determination of 13 oxides and their ratio: CaO, SiO2, AlO, FeO, SO, MgO, NaO, KO, PO, TiO, MnO, ZnO, SrO) and which allows precise control of the 2 3 2 3 3 2 2 2 5 2 2 3 quality of cement production.
How can XRF Analysis be used at a Cement Plant?
The composition of mineral substances in cement provides extensive information about the quality and properties of cement, but to provide accurate enough measurements is quite difficult. It is much easier to provide elemental analysis than mineral composition analysis. And also it is possible in an easy way to convert the elemental ratios acquired into weight fractions of each oxide in the sample. The ratios of oxides present in the sample give an estimation of the precise enough cement mineral composition.
There are a lot of spectroscopy methods for the determination of elemental analysis of cement: atomic, Raman, gravimetry, X-ray photoelectron, and inductively coupled plasma mass. Most of them require additional methods or could be destructive for the sample and expensive equipment.
Many cement plants use quantitative X-ray diffraction analysis to determine the phase clinker composition. But the X-ray analysis of the cement has one major drawback: neglection of the structural decay of some weak or cleavable mineral phases like gypsum, anhydrite, or calcite in the sample during the measurement.
X-ray fluorescence (XRF) analysis is the universal method for elemental analysis. It combines simple enough procedures and correspondingly cheap equipment. Also, it provides fast and accurate results. Thus, x-ray fluorescence (XRF analysis) in cement analysis is the most convenient, easier, and suitable elemental analysis method in thecement industry.
In cement plants, XRF for cement analysis is used routinely and it is the primary way to control the composition of the raw material, the raw feed, as well as clinker and actually cement. This method provides rapid compositional data for controlling almost all stages of production and is also used for assessing and quality control of the final product.
How can XRF improve Cement Production?
The XRF analysis of cement solves the problem of element analysis quickly, without destruction, and with high accuracy. The XRF can drastically improve the cement production process in each stage: at the quarry to evaluate the raw materials, to assess intermediate products, and to check resulting products to the required standards. Thus XRF can provide high productivity of cement production.
A sample of cement is irradiated with x-ray light that excites atoms in this sample. The atoms emit electromagnetic waves of vision range when they return to their own basic state. The emission of light when the elements return to an excited state is distinctive to the particular elements present and the fluorescence detection makes it possible to calculate the chemical composition of the sample precisely.
What type of analyzer for cement analysis do I need: Benchtop or Handheld?
Elvatech offers a full line of XRF spectrometers including a benchtop analyzer, as well as mobile and portable, which are ASTM C114, ISO 29581 certified. The newest devices for XRF analysis for cement are ElvaX Pro and ProSpector 3.
Benchtop spectrometer ElvaX Pro is a desktop energy-dispersive x-ray fluorescence (EDXRF) analyzer ElvaX Plus spectrometer can detect elements from Na to U. ElvaX Plus spectrometer is used for quantitative and qualitative analysis of the cement samples elemental composition in a wide range of element concentrations. ElvaX Pro has the helium purge system and the automatic primary filter changer and moreover, it is combined with the large area SDD detector for allowing effective spectra registration. Detecting the limit of ElvaX Rlus is better than 1 ppm for most elements in a light matrix. ElvaX Pro has a 16-position automatic sample changer that can increase the productivity of cement XRF analyzer and has a low maintenance cost.
Handheld spectrometer ProSpector 3: ProSpector 3 is the next-generation handheld X-ray fluorescence analyzer. ProSpector 3 is the smallest and lightest XRF analyzer on the market. ProSpector 3 has a dustproof and waterproof instrument body, with an IP-67 ingress protection rating and highest mobility with autonomous operation on a single battery charge up to 16 hours with two CCD cameras and radiation protection. Thus the Prospector 3 suits perfectly for robust and precise XRF analysis on different stages of cement production.
USB, WiFi, or Bluetooth interfaces of ProSpector 3 provide sending data directly to any device directly during the measurement process.
Both analyzers provide measurement with the highest precision.Due to using Elvatech Dynamically Adaptive Shaping DPP with a fast SDD detector both ElvaX Pro and ProSpector 3 are the fastest analyzers on the market. Both of them can work long term without re-calibration through digital-ray source digiX-50 and automatic calibration of thermodynamic parameters. ProSpector 3 and ElvaX Pro have intuitive and user-friendly software interfaces.
Sample preparation for cement XRF Analysis
The XRF analysis of cement is fast, convenient, simple, and nondestructive. But the realization of accurate results in all cement production stages requires correct sample preparation. It could be performed in two ways: making a fused glass bead or in the form of pressed pellets by special equipment. The glass bead technology is preferred nowadays in cement analysis because of a much easier way to obtain referenceable calibration standards.