🏗️ Determination of loss on ignition (wLOI) of fine, intermediate and coarse, composite and organic soils and anthropogenic materials (according to EN 16907-2) — a representative sample is dried at (110 ± 5) °C to constant mass, the fraction below 2 mm (with crushed oversize) is ignited in a crucible at (550 ± 25) °C for at least 2 h, and the loss is calculated from the mass difference; Annex B allows the organic matter content of clayey soils to be estimated from wLOI, PN-EN 17685-1

Construction PN-EN 17685-1

Overview

WHAT THE STANDARD COVERS. We read the text of the standard in the iTeh sample of SIST EN 17685-1:2023 (English text of EN 17685-1:2023): from the title page through the contents, European foreword, introduction and Clauses 1–8 to Clause 9 (expression of results, Formulae 1 and 2) on page 8 inclusive. Outside the sample remain the test report (10), Annex A (example of a test data sheet) and Annex B (estimation of the organic matter content of clayey soils).

ACCORDING TO THE TEXT OF EN 17685-1:2023 (foreword, introduction, Clauses 1–9). The standard was prepared by CEN/TC 396 “Earthworks” (secretariat AFNOR). Introduction: the method was developed from EN 15935:2021 (CEN/TC 444 “Environmental characterization of solid matrices”), adapted to materials used in earthworks, particularly in sample pretreatment; the organic matter content COM estimated from wLOI according to Annex B is used for the classification of soils with COM above 2 % according to EN 16907-2 (Table 4 in EN 16907-2:2018); other ways of estimating organic content are e.g. wet burning with H2O2 or KMnO4. Scope (1): method for determining the loss on ignition (wLOI) of fine, intermediate, composite and coarse soils, organic soils and anthropogenic materials (according to EN 16907-2) after ignition under air at 550 °C; according to the note the mass loss at 550 °C is usually due to the release of volatile compounds, water (absorbed, crystallized or structural) and gases from decomposition of organic matter and inorganic substances such as sulfur, sulfides or hydroxides (e.g. H2O, CO2, SO2); Annex B gives the estimation of COM from wLOI for clayey soils. References (2): EN ISO 17892-12 (liquid and plastic limits) and ISO 3310-1 (test sieves of metal wire cloth). Clause 3 contains no terms. Symbols (4): COM — organic matter content deduced from wLOI; Dmax — maximum particle diameter; mc, m1, m2 — masses of the empty crucible, of the crucible with the dried sample and with the ignited sample; wL — liquid limit according to EN ISO 17892-12; wLOI — loss on ignition, i.e. the mass fraction lost by burning a dried sample to constant mass at a specified temperature; wR — residue on ignition. Principle (5): a weighed dried test portion is burned in a furnace under air to constant mass at (550 ± 25) °C, and the loss is calculated from the mass difference before and after ignition; according to the notes carbonates dissociate at temperatures above 550 °C, and LOI is a parameter, so there is no interference connected with its determination, but when it is used to estimate organic matter content: elementary carbon and the volatilization and reactions of inorganic compounds are included in the result, chemically bound water can be released and increase the loss, iron and other metals in metallic or low bonding state can oxidize and gain mass (underestimating the loss), sulfides can oxidize to sulfate (underestimating the loss), calcium hydroxide can dehydrate (overestimating the loss), calcium oxide can bind CO2 to carbonate (underestimating the loss), and the ash may contain residues of unburnt organic matter. Apparatus (6): forced-draft drying oven maintaining (110 ± 5) °C throughout the chamber, with air circulation not so strong as to transport particles; crucibles for ignition at 550 °C (e.g. nickel, platinum, porcelain or fused silica) of about 25–70 mm diameter, chosen to meet the requirements for test portion and layer height; muffle furnace maintaining (550 ± 25) °C; metal plate for initial cooling of crucibles; desiccator with an active drying agent, e.g. silica gel; balance with a maximum permissible error below 0,1 % of the sample mass; 2 mm test sieve according to ISO 3310-1. Pretreatment (7): the test is carried out on the whole sample — the laboratory sample is reduced by successive crushing and quartering to a representative portion; the minimum laboratory sample mass depends on Dmax (Table 1): 5000 g for 32 < D ≤ 63 mm, 2500 g for 16–32 mm, 1500 g for 8–16 mm, 500 g for 4–8 mm, 100 g for 2–4 mm, 50 g for D ≤ 2 mm; the representative specimen is prepared by sieving through 63 mm, drying the whole material at (110 ± 5) °C to constant mass (successive weighings after at least 1 h further drying differing by no more than 0,1 %), sieving through 2 mm with crushing of the retained fraction below 2 mm and adding it to the passing fraction, reducing in a rotary sample divider, sieving again through 2 mm and weighing the passing material — at least 50 g. Procedure (8): at least two samples; the crucible is heated at (550 ± 25) °C for at least 20 min, cooled initially on a metal plate and finally in a desiccator, and weighed (mc); 0,5–15 g of the test portion is weighed into the crucible (m1), and the layer should not exceed 5 mm, since a thicker layer lowers the LOI result — a large crucible may be needed for 5–15 g; 0,5–5 g is recommended for sludge, peat, treated biowaste and waste, 5–15 g for soils with low organic matter; the crucible is placed in the furnace, the temperature raised to (550 ± 25) °C and held for at least 2 h; with high organic content losses may occur through rapid ignition or deflagration — then the sample is heated slowly to (250 ± 15) °C over 1 h (pyrolysis), then slowly to (550 ± 25) °C also over 1 h and held for at least 2 h; the hot crucible is placed on a metal plate for a few minutes, transferred while still warm to a desiccator, and weighed after cooling to ambient temperature (m2). Results (9): wLOI = (m1 − m2) / (m1 − mc) × 100 % of dry mass, wR = 100 − wLOI.

STATUS (as of 03.10.2026). The PKN search (term “PN-EN 17685-1”, 03.10.2026) shows PN-EN 17685-1:2023-08 (English version, “Introduces: EN 17685-1:2023 [IDT]”) without a withdrawal note. In the iTeh catalogue (read on 03.10.2026) SIST EN 17685-1:2023 has the status “Published” (published 13.06.2023).

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read on 03.10.2026). The number 17685-1 appears in 5 records at 5 laboratories: AB 283, AB 962, AB 1750, AB 1778, AB 1905. In the current PCA documents (read on 03.10.2026, issues from 24.09.2024 to 22.06.2026) the number appears in 5 rows — one at each; in each of the five documents the number of page markers equals the number of PDF pages, without repetitions; a search of all 1291 PCA documents downloaded from BIP on 03.10.2026 found no laboratories outside the database copy (17 laboratories on the list have no link to a scope document on BIP). At all of them the form “PN-EN 17685-1:2023-08”; at AB 283, AB 1750 and AB 1778 in one cell with PN-B-04481:1988 (at AB 283 and AB 1778 with clause 4.4.4.2), at AB 962 and AB 1905 on its own. None of these items is suspended. The “Laboratories” tab (term “PN-EN 17685-1”) shows all 5 laboratories — checked with a tab query on the production server labcoda.pl on 03.10.2026.

WHAT THE LABORATORIES TEST (items in PCA). Object: soils (all five). Characteristic: loss of mass on ignition (AB 283, AB 1750), determination of loss of mass on ignition in the range (0–100) % (AB 1778), loss of mass as a result of ignition (AB 962, AB 1905); gravimetric method (AB 283, AB 1750, AB 1778).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. With the sample: laboratory sample mass too small for Dmax (Table 1) and oversize discarded instead of crushed (7). With the crucible: a layer thicker than 5 mm lowers the result (8). With organic samples: without slow pyrolysis at 250 °C losses through ignition or deflagration are possible (8). With cooling: weighing only after cooling in the desiccator (8). With interpretation: LOI is not organic matter content — it includes bound water, elementary carbon and transformations of inorganic compounds, while oxidation of metals and sulfides underestimates the loss (5).

WHAT WE DO NOT GIVE. We did not read the content of the report, the example data sheet or the relationship for estimating the organic matter content of clayey soils (Clause 10, Annexes A and B).

Method principle

A representative portion of soil dried at (110 ± 5) °C (fraction below 2 mm, 0,5–15 g, layer up to 5 mm) is ignited in a crucible in a muffle furnace under air at (550 ± 25) °C for at least 2 h — with high organic content after slow pyrolysis at 250 °C. The loss on ignition wLOI is calculated from the masses of the empty crucible, the crucible with the dry sample and with the ignited sample as a percentage of dry mass.

Applications

• Fine, intermediate and coarse, composite and organic soils and anthropogenic materials for earthworks (1)
• Basis for estimating the organic matter content of clayey soils for classification according to EN 16907-2 (introduction, Annex B)
• Soils — items in the accreditation scopes of 5 laboratories in PCA

Key parameters

Standard

Standard number

PN-EN 17685-1:2023-08

Title (PL)

Roboty ziemne — Badania chemiczne — Część 1: Oznaczanie straty przy prażeniu

Title (EN)

Earthworks — Chemical tests — Part 1: Determination of loss on ignition

Step-by-step procedure

1. Laboratory sample

   Mass according to Dmax (Table 1); sieving through 63 mm, drying at 110 °C to constant mass (7). PN-EN 17685-1:2023-08 without a withdrawal note (03.10.2026).

2. Fraction < 2 mm

   Sieving through 2 mm, crushing of oversize, reduction in a divider, sieving again; ≥ 50 g (7).

3. Crucible

   Heating at 550 °C ≥ 20 min, cooling on the plate and in the desiccator, weighing mc (8).

4. Ignition

   0,5–15 g, layer ≤ 5 mm (m1); 550 °C ≥ 2 h, for organic samples with pyrolysis at 250 °C; cooling and weighing m2 (8).

5. Result

   wLOI and wR from Formulae 1 and 2, from at least two samples (8, 9).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Muffle furnace at 550 °C and hot crucibles — heat-resistant gloves and tongs
• Rapid ignition of samples with high organic content — slow heating (8)

Frequently asked questions