The test procedures according to EN 459
Summary: The EN 459-2 was published in September 2010 together with the European building lime standard EN 459-1. This part of the standard describes the chemical and physical test procedures for building lime and has been completely revised. The regulations in this standard are based on comprehensive investigations and orientate themselves on the existing and new product categories.
Products requirements presuppose test procedures, the performance features of which have to be designed in such a way that there are values for the properties to be tested, which permit beyond doubt proof of the conformity of products with the regulations of the technical standard on which they are based. Therefore, test procedures have to be designed for the corresponding products, and it is not always possible to apply analysis and test procedures already standardized for a certain product group to another group.
When the building lime standard EN 459-1 was prepared in the...
Products requirements presuppose test procedures, the performance features of which have to be designed in such a way that there are values for the properties to be tested, which permit beyond doubt proof of the conformity of products with the regulations of the technical standard on which they are based. Therefore, test procedures have to be designed for the corresponding products, and it is not always possible to apply analysis and test procedures already standardized for a certain product group to another group.
When the building lime standard EN 459-1 was prepared in the 1990s, the procedures to be standardized according to the series of the EN 196 as regards the issue of the test procedures for building lime were examined. In the version of the EN 459‑2, which was finally passed in 1995, there are many references to this standard series as regards the chemical analytical techniques and the physical tests.
When revising the EN 459-1 (see part 1 of this publication in ZKG 5/2011, p. 76), the working group CEN TC 51/WG 11 entrusted the Task Group TG 1 to revision of the test procedures according to the revision in part 1. Experts from industry and research supported the work of this group.
The following tasks were the most important ones:
– the standard should get a new structure,
– new test procedures had to be developed,
– all test procedures should be described in the standard and, finally
– the procedures should be evaluated statistically by interlaboratory tests.
The round-robin tests were financed by the Brussels-based European Lime Association EuLA. The preparation und evaluation took place at the IKM (Institut für Kalk- und Mörtelforschung - Institute for Lime and Mortar Research) in Cologne. The results essentially contributed to the preparation of the building lime standard EN 459-1. At this point the author would like to express his sincere thanks to all those involved for their work and participation and, particularly, to the chairman of the Standardisation Committee of the EuLA at that time, Willem Berbers, who unfortunately can no longer read these lines.
An analytical procedure is generally used for the quantitative determination of a chemical parameter. As regards chemical analytical procedures, the sample to be tested is brought into solution and the parameters to be determined are quantified by means of classical procedures such as precipitation or titration, or by means of modern analytical techniques, such as the atomic absorption or the atomic emission. In addition, predominantly the X-ray fluorescence (XRF) method is used in industrial laboratories to compare a powder or a melt tablet with calibration graphs previously obtained.
The term “test procedure” is used very generally and is a sub-summary of chemical and physical methods. It includes, however, very specifically the test of a “property”, which needs specific definitions as regards the test conditions. As far as that is concerned, the determination of the available lime content in lime products is certainly a chemical procedure, but the parameter should be considered to be a property that has to be evaluated taking into account the conditions of the test procedure.
Physical test procedures should be considered from similar points of view. Related to lime products, in particular the procedures to determine the reactivity as well as the test of the compressive strength should be mentioned here. In addition to the material-specific properties, the reactivity of a burnt lime with water depends on the fineness, the quan-tities used for the test and the reaction vessel. The compressive strength test is predominantly influenced by the material-specific properties, the water-binder ratio and the storage of the prisms.
The above-mentioned factors as well as the procedures themselves have an effect on the test result, on the one hand, and, on the other hand, they presuppose its statistic evaluation. For most of the procedures this evaluation was carried out in European interlaboratory tests, in which both the members of the TG 1 and many other laboratories in the lime industry took part.
When starting the revision of the EN 459-2, it was laid down that this standard, in particularly as regards the physical methods, had to be redesigned and that all procedures are described in this part of the standard so that only the reference to the EN 196-1 is left for the compressive strength test (Fig. 1) as regards the equipment. The chemical analytical procedures are extended by the gravimetric determination of CaO, MgO and CO2, of the loss on ignition and of the available lime. The EN 12485 is the basis for some procedures. This European standard was introduced in 2001 and describes the test procedures for lime products that are used in drinking water treatment.
As regards the physical tests, the sieving methods and the determination of the setting times were supplemented and the compressive strength test was extended regarding the different lime products. The structure of the physical test procedures is explained in Table 1.
As is generally known, a test result depends on various influencing factors. The test starts already during sampling, it is continued via the sample treatment and preparation, then it is subjected to a measurement method, which, as a rule, results in a numerical value, and, finally ends with the evaluation of this figure. The evaluation in turn has two aspects: the plausibility check and the comparison with the corresponding requirement value of the EN 459-1.
The sample handling before the measurement is described in section 3 of the standard. The Table included in this section additionally describes the sample preparation for each individual test. Further general test specifications are included in section 4.
According to the specifications in the scope the EN 459-2 describes reference test procedures and, in some cases, alternative test procedures, which can be considered to be equivalent. In case of dispute, the reference procedure is used. If other procedures are used in the daily laboratory practice, they have to be calibrated either against the reference methods or against internationally accepted reference materials, in order to demonstrate their equivalence. As regards the chemical methods, this equivalence has been checked in round-robin tests concerning all classical and spectrometric analytical methods. Right from the start there was agreement in the TG 1 that the classical procedures, which are applied in the corresponding cases, should be described in the standard.
There are various methods and alternative methods for the chemical analysis of calcium and magnesium. The most common ones are the complexometric determination, the spectrometric methods AAS and ICP-OES as well as the X-ray fluorescence method XRF. Complexing agents, such as EDTA, EGTA and DCTA, are used for the complexometric method. The end point of the titration is determined potentiometrically or by means of colour indicators. All these methods are considered to be equal since their suitability has been proved in interlaboratory tests.
The EN 459-2 describes the complexometric determination of calcium and magnesium by means of the EDTA. With this method first calcium is determined and then the sum of calcium and magnesium. The magnesium content is given as the difference between both measured values. Previously the sample to be tested is brought into solution with hydrochloric acid (Lead picture). Another usual procedure is the melting fusion with lithium tetraborate.
The previous standard procedures are retained. The gravimetric determination according to EN 196-2 is now described in EN 459-2 and remains a reference procedure. With this method CO2 is released by means of an acid and is passed in a gas flow through a series of absorption tubes. The content of CO2 is determined by means of weighing.
With the volumetric method CO2 is also released by means of an acid and is introduced into a measuring burette containing a sealing liquid. Based on the volume of the liquid displaced by the gas, the CO2 content in the sample can be calculated taking into account the air pressure and temperature.
The equivalence of both procedures was already proved in 1989 in comprehensive investigations at the IKM when preparing the building lime standard for the first time. The determination by means of infrared spectroscopy after pre-treatment of the sample in a combustion furnace is admissible as a non-standardized alternative procedure.
The sulphate compounds existing in a lime sample are dissolved in hydrochloric acid. After the precipitation of poorly soluble barium sulphate in a barium chloride solution, the sulphate content is determined at boiling heat with a pH value of 1 up to 1.5. This determination can be carried out alternatively with ICP-OES or XRF.
The sum of free water (not for burnt products), of the CO2 content and of the water of hydration is determined with the loss on ignition at 1050 °C (Fig. 2). In case of hydrates and lime with hydraulic properties, this value is needed for the conversion of the measured values of CaO, MgO, SO3 and CO2 into the substance free from content of water and content of water of hydration to be able to compare the values with the specification values included in the EN 459-1 (see 4.6 in EN 459-2). In case of milk of lime and lime putty, the content of free water in the suspension has to be determined before determining the loss on ignition.
When heating a sample of hydrated lime or lime with hydraulic properties up to (105 ±5) °C or a sample of milk of lime or lime putty up to (150 ± 5) °C, the free water will be driven off. Before taking a sample for measurement from a suspension, the latter has to be homogenized by shaking the sample container. A drying oven or an automatic moisture balance can be used as laboratory equipment. Attention must be paid during all working steps to prevent carbon dioxide and moisture of the ambient air from being absorbed.
The introduction of the new parameter “available lime” in the EN 459-1 required a harmonized test procedure for this parameter. The EN 459-2:2001 described a test method for the determination of available lime content of air limes as well as a method for the determination of the content of available lime of hydraulic lime. In the first procedure the available (unbound) lime (calcium oxide and calcium hydroxide) is dissolved in a sucrose solution and is titrated against phenolphthalein after filtration. In the second procedure the unbound available lime (calcium oxide and calcium hydroxide) is extracted by means of ethyl acetoacetate and is titrated against bromophenol blue in the extract by means of hydrochloric acid. This procedure has two essential disadvantages, i.e. the use of organic solvents and it cannot be used for calcium lime. Therefore, they had the idea in the TG 1 to describe a procedure of all kinds of lime in which the content of available lime can be tested. For this reason, all types of lime were tested with the so far common methods for the available or free lime in two European round-robin tests (see section 5).
The procedure now described in the EN 459-2:2010 comprises all findings resulting from this work and serves to determine the available lime content
– in calcium lime in the form of quicklime and hydrated lime;
– in calcium lime in the form of milk of lime and lime putty (in dry substance) and
– in all types of lime with hydraulic properties.
With this method a mass fraction of lime is described, which enters into an acid-base reaction in an aqueous suspension to become a calcium saccharate complex that afterwards can be titrated with hydrochloric acid under defined conditions. This method designates those constituents, which enter into reaction under the conditions of this specified method. The interpretation of results obtained by the following method shall be determined in consideration of this limiting condition.
The procedure is subdivided into the following steps:
– Quicklime is slaked and dispersed in water. To avoid agglomeration of calcium oxide on slaking which can lead to incomplete suspension of a quicklime sample such limes should be heated.
– All other types of lime are stirred in water at room temperature before the addition of sugar.
– The suspended samples of lime with hydraulic properties should be filtrated before the titration.
– The titration with hydrochloric acid against phenolphthalein as indicator is used for the determination. The titration speed has been specified. This and the decouloration at a pH value of approx. 9.6 ensure that no further constituents will enter into reaction.
As previously, air jet sieving is used for hydrates and lime with hydraulic properties to determine the residue on 0.2 mm and 0.09 mm. As regards quicklime, an additional determination of the particle size distribution on 5 sieves is required. The sieves with the opening sizes of 10 mm, 5 mm and 2 mm have to be shaken manually or mechanically. The material in the catch pan is sieved by means of air jet sieving. The result of the test has to be indicated as mass passing the sieve. Annex A of the EN459-2 includes an example of a data sheet to record the individual values and to calculate the results.
Due to the different chemical and physical properties of building limes it is not possible to determine the soundness by one single method. Therefore, the following methods are used:
– The tablet method as the reference method and the LeChatelier method for hydrated lime and lime with hydraulic properties.
– Hot cabinet storage for quicklime, dolomitic lime and dolomitic hydrated lime.
– Cold water storage for HL with contents by mass of up to 7 % of SO3.
– Steam test in a gypsum bed for additional testing of hardburnt material with oversize grains.
The Vicat method at first requires the mixing of a lime paste of standard consistence to be prepared from binder and water. Lime paste of standard consistence has a specified resistance to penetration by a standard plunger. The water required for this type of paste is determined by trial penetrations of pastes with different water contents. The setting time is determined by observing the penetration of a needle into building lime paste of standard consistence until it reaches a specified value.
Quicklime should be tested for reactivity on slaking by measuring the increase in temperature, which occurs on reaction with water as a function of the reaction time (wet slaking curve). The test should be performed on materials of a grain size of ≤ 0.2 mm. If 100 % of the material pass the 5 mm sieve, the product can alternatively be tested in the as-delivered state. Detailed descriptions are given of the test equipment and of the measurement procedures as well a examples of the evaluation.
The paste volume of a lime putty, which can be achieved during the slaking process is determined after a defined wet slaking period in an insulated container, which is described in detail. The amount of water used, given in litres per 10 kg of quicklime, corresponds to the yield.
These tests cover the flow diameter, penetration, air content and water retention. The equipment prerequisites are the same as in EN 459-2:2001. A standard mortar has to be prepared from 1 part by mass of a lime and 3 parts by mass from CEN standard sand by the procedure described in EN 196-1 except that the water content should be that determined to give the consistence required as described in Table 2. If the required flow diameter (Fig. 3 a-f) is not achieved with the selected amount of water, the correct amount of water has to be determined by using other mixtures with different quantities of water.
The value of the flow diameter was modified for some lime products according to Table 2 in such a way that the test is carried out on a mortar with a consistence in step with actual practice. Further examinations have shown that the modified flow diameter does not have an essential influence on the other parameters to be tested with this mortar.
After the standard mortar has been prepared, the depth of penetration is determined with the consistency measuring equipment. The water retention value is defined as the proportion of water, which remains in the freshly mixed mortar after a short suction time on a filter paper. The air content of fresh mortar is measured by the pressure method using a preset test apparatus.
The compressive strength of limes with hydraulic properties has to be tested according to the procedure given in EN 196‑1. Different bulk densities and different Ca(OH)2 contents require these adaptations, which had already been covered by the EN 459-2:2001 for the standardized products at that time. However, with the group of the formulated limes (FL) products have been standardized in the EN 459-1:2010, which are distinguished by a higher content of calcium hydroxide. Thus, further adaptations concerning the storage conditions of the prisms are required for the compressive strength test. The demoulded specimens of the products NHL 2, FL 2 and FL 3.5 can be stored in a large cabinet maintained continuously at a temperature of (20 ± 1) °C and a relative humidity of not less than 60 %, observing the tolerances in respect of time specified in EN 196-1, until such time as the compressive strength test will be carried out. This is in accordance with EN 1015-11 that provides hardening of air lime mortars by carbonation. This storage alternative, for which an enrichment of the atmospheric carbon dioxide level is of course not permitted, should be understood as alternative method. This material can also be stored at a relative humidity of at least 90 % as for all other limes with hydraulic properties.
During the revision of the EN 459-2 the TG 1 carried out the following European round-robin tests:
– Check of all methods to determine the available lime content in all types of building lime
– Check of the specified procedure to determine the available lime content in quicklime
– Reactivity and air jet sieving of various types of quicklime
– Chemical parameters in quicklime and hydrated lime
– Physical test procedures with FL and NHL
The manufacturers sent samples to the Cologne-based IKM for the individual round-robin tests. There the samples were divided, dispatched and the results were evaluated. The statistic evaluation was carried out according to the specifications of the standard ISO 5725. The statistic parameters are included in Tables B.1 and B.2 of Annex B of the standard.
The first round-robin test for the determination of the available lime was carried out according to three test methods:
– Sugar method according to EN 459-2:2001
– Titration method according to EN 12485:2001 and
– “Available lime index” according to ASTM C25.
There are considerable differences between the three methods as regards their purpose and procedure. Based on the results of this round-robin test, the method to be standardized was determined and tested in another round-robin test. Additional comparison tests were carried out for lime with hydraulic properties so as to check the reproducibility of the method for the available lime specified in the EN 459-2:2001 with the new method.
A further round-robin test was aimed at finding out the statistic characteristics of the reactivity on different types of quicklime as well as of the air jet sieving as regards the test methods already specified in the EN 459-2:2001.
The goal of the round-robin test “chemical parameters” was to apply all common test procedures and to compare the results. It became obvious that the modern analytical methods AAS, ICP-OES or XRF correspond very well with each other and with the classical methods.
During the revision of the EN 459-1 it became clear that more attention has to be paid to the physical test procedures in particularly due to the incorporation of the new product group of formulated limes into the standard as well as due to a larger scope of NHL products. Many times the test procedures of the EN 459:2001-10 were based on the test methods for cement according to the series EN-196. Therefore, the TG 1 checked and modified correspondingly each procedure regarding its applicability to the individual products. The test methods were statistically recorded and evaluated in another European round-robin test. The results are included in the method descriptions.
The purpose of test procedures is to be able to prove specification values and to describe properties. Perhaps it will be possible in the future to replace numerically based specifications by those based on properties. Furthermore, there are test procedures for various applications of lime, which have not yet become part of a standard. Further investigations concerning building lime will be carried out also in the next years. Their results will certainly influence the further development of the test procedures.
Überschrift Bezahlschranke (EN)
tab ZKG KOMBI EN
This is a trial offer for programming testing only. It does not entitle you to a valid subscription and is intended purely for testing purposes. Please do not follow this process.
This is a trial offer for programming testing only. It does not entitle you to a valid subscription and is intended purely for testing purposes. Please do not follow this process.
tab ZKG KOMBI Study test
This is a trial offer for programming testing only. It does not entitle you to a valid subscription and is intended purely for testing purposes. Please do not follow this process.
This is a trial offer for programming testing only. It does not entitle you to a valid subscription and is intended purely for testing purposes. Please do not follow this process.
