CEN/TR 15697:2008
(Main)Cement - Performance testing for sulfate resistance - State of the art report
Cement - Performance testing for sulfate resistance - State of the art report
Under the terms of EU Mandate 114, committee CEN/TC 51, cement, building limes and other hydraulic binders, is required to develop standards for ‘common cements’ and also for cements with special properties such as low heat cements, calcium aluminate cements and sulfate resisting cements.
EN 197-1: Composition, specifications and conformity criteria for common cements was adopted in 2000 and was the first harmonised European Standard to be adopted for a construction product.
Since 2000, European Standards for masonry, low heat, low early strength blastfurnace cements, very low heat special cements and calcium aluminate cements have been published. The development of a prescriptive EN for sulfate resisting cements has been complicated by national differences in the types of cement that are recognised to have sulfate resisting properties. Note, however, that all nationally standardised sulfate resisting cements meet the requirements of EN 197-1:2000, and that the absence of a specific standard for sulfate resisting cement has not constituted a barrier to trade.
Zement - Prufüng der Leistungsfähigkeit hinsichtlich des Sulfatwiderstands - Bericht zum Stand der Technik
Ciment - Essais de performances relatifs à la résistance aux sulfates - État de l'art
Cement - Preskušanje sulfatne odpornosti - Dokument o stanju tehnike
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-julij-2008
Cement - Preskušanje sulfatne odpornosti - Dokument o stanju tehnike
Cement - Performance testing for sulfate resistance - State of the art report
Zement - Prufüng der Leistungsfähigkeit hinsichtlich des Sulfatwiderstands - Bericht zum
Stand der Technik
Ciment - Essais de performances relatifs à la résistance aux sulfates - État de l'art
Ta slovenski standard je istoveten z: CEN/TR 15697:2008
ICS:
91.100.10 Cement. Mavec. Apno. Malta Cement. Gypsum. Lime.
Mortar
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
TECHNICAL REPORT
CEN/TR 15697
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
April 2008
ICS 91.100.10
English Version
Cement - Performance testing for sulfate resistance - State of
the art report
Ciment - Essais de performances relatifs à la résistance Zement - Prufüng der Leistungsfähigkeit hinsichtlich des
aux sulfates - État de l'art Sulfatwiderstands - Bericht zum Stand der Technik
This Technical Report was approved by CEN on 6 November 2007. It has been drawn up by the Technical Committee CEN/TC 51.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 15697:2008: E
worldwide for CEN national Members.
Contents Page
Foreword.3
Introduction .4
1 Sulfate resistant cements .6
2 Sulfate resistance test procedures.7
3 Review of most appropriate methods to assess specimen deterioration in laboratory tests.16
4 Review of most appropriate methods to accelerate the test procedure.18
5 The importance of test method reproducibility.20
6 Suggested features of a standardised sulfate resistance test method for cements.21
Bibliography .25
Foreword
This document (CEN/TR 15697:2008) has been prepared by Technical Committee CEN/TC 51 “Cement and
building limes”, the secretariat of which is held by NBN.
This CEN/TR is a state of the art review of the international research literature dealing with testing/assessing
the sulfate resistance performance of cements and related binders. It outlines the difficulties faced by
CEN/TC 51 in applying a prescriptive approach to the specification of sulfate resistant cements and identifies
the different mechanisms and forms of deterioration that occur during sulfate attack. This report compares the
advantages and disadvantages of different test specimen types (paste, mortar or concrete), different exposure
conditions and different techniques used to assess specimen deterioration. The importance of test method
reproducibility is reviewed with reference to the experimental work carried out by CEN/TC 51 during the 1990s.
The report lists the key parameters that must be controlled in any robust standardised method and makes
suggestions for the main features of a pan-European performance test.
Introduction
Under the terms of EU Mandate 114, committee CEN/TC 51, cement, building limes and other hydraulic
binders, is required to develop standards for ‘common cements’ and also for cements with special properties
such as low heat cements, calcium aluminate cements and sulfate resisting cements.
EN 197-1: Composition, specifications and conformity criteria for common cements was adopted in 2000 and
was the first harmonised European Standard to be adopted for a construction product.
Since 2000, European Standards for masonry, low heat, and low early strength blastfurnace cements, very
low heat special cements and calcium aluminate cements have been published. The development of a
prescriptive EN for sulfate resisting cements has been complicated by national differences in the types of
cement that are recognised to have sulfate resisting properties. Note, however, that all nationally
standardised sulfate resisting cements meet the requirements of EN 197-1:2000 and that the absence of a
specific standard for sulfate resisting cement has not constituted a barrier to trade.
In order to overcome these national difficulties, and also to permit new types of cement to be recognised in the
future, work was directed towards the development of a performance test for sulfate resistance. Work
commenced in 1991 and following a preliminary assessment of the French NF-P-18-837 procedure and the
German, so called flat prism method, a decision was taken to concentrate on developing the French
procedure. The method measures the expansion of 20 mm x 20 mm x 160 mm prisms in a sodium sulfate
2-
solution containing 16 g/l SO .
During five co-operative testing exercises involving up to thirteen laboratories, the method was refined with the
objective of improving reproducibility and also discrimination between sulfate resisting and non-sulfate
resisting cements. In 1998 it was concluded that further development would require a more fundamental
approach and efforts were directed towards obtaining EU funding for ‘pre-normative’ research. These
applications were not successful.
In early 2004 a meeting was arranged with representatives of the NANOCEM programme to explore a more
fundamental approach to the problem of sulfate resistance and sulfate resistance testing. The aspects of
particular interest to CEN/TC 51 were:
a) understanding sulfate attack mechanisms in relation to the type of cement and the
concentration/temperature conditions;
b) establishing a relationship between laboratory tests and field performance;
c) methods to accelerate the test;
d) using parameters other than deformation measurement to monitor the progress of the sulfate attack;
e) understanding the role of thaumasite in sulfate attack.
The NANOCEM group has formulated a research programme that addresses the above aspects and work on
this programme commenced in 2006 within the framework of a larger programme funded by the Marie Curie
Training Network. In parallel with this programme, CEN/TC 51 asked committee WG 12 (Additional
Performance Criteria) to prepare a CEN Technical Report outlining the current state of the art concerning
sulfate resistance testing.
A literature search identified over 250 relevant papers and reports published during the period 1970 to 2006.
To assess the different sulfate resistance techniques employed and their possible influence on the
performance of different cement/binder types, the testing details from 129 papers were entered into an Access
Database. The papers selected for entry into the database were those which contained original research data
and detailed information concerning test conditions.
This report draws on the information contained in these 129 papers plus a further 50 papers and reports not
selected for entry into the database. In the interests of brevity the current report only includes references to
selected references that are either key papers or contain specific information. It is intended that a statistical
analysis of the database and a full listing of the papers studied will be made available as a supplementary
document of CEN/TC 51 / WG 12.
1 Sulfate resistant cements
Portland cement concrete can undergo attack by sulfate bearing solutions such as natural groundwater or
those contaminated by industrial activity. Attack can result in expansion, strength loss, surface spalling and
ultimately disintegration.
The resistance that a cement matrix provides to sulfate attack depends on a number of factors which include:
• nature of the reaction products formed with the sulfate solution and in particular, whether their formation
results in disruptive expansion;
• impermeability of the matrix (including the important paste-aggregate interfacial zone) which provides a
barrier against penetration by sulfate ions;
2-
• concentration of sulfate ions (in this report expressed as g/l SO );
• mobility of the sulfate containing groundwater;
+ 2+ 2+
• nature of the accompanying cation e.g. Na , Mg , Ca etc;
• pH of the sulfate bearing ground water/solution;
• presence of other dissolved salts such as chlorides;
• temperature of the exposure;
• degree of pre-curing before exposure, although in the field this is only likely to affect the performance of
the concrete surface;
• presence of finely divided limestone (calcium carbonate) in the aggregate, or carbonate ions dissolved in
the groundwater, which may promote the formation of thaumasite under low temperature conditions.
Almost all developed countries have product specification standards for sulfate resisting cement(s). With a
few exceptions these are prescriptive standards that specify cement composition. The permitted compositions
are based upon long-standing laboratory test results and also satisfactory performance in the field. National
differences reflect different exposure conditions and also differences in the nature of the available cement
constituents.
Poor performance under sulfate exposure conditions is normally associated either directly or indirectly, with
the formation of ettringite. In the hydrated matrix of a CEM I cement, the source of reactive alumina is
normally the monosulfate phase according to the reaction:
2+ 2-
C Al (OH) .SO .6H O + 2Ca + 2SO + 20H O => C Al (OH) (SO ) .26H O
4 2 12 4 2 4 2 6 2 12 4 3 2
(monosulfate) (ettringite)
Any unreacted C A is also a potential source of ettringite.
Monosulfate will normally also be present in composite cements containing blastfurnace slag, fly ash or
natural pozzolana but in the hydrated matrix of these cements, alumina is also present in phases such as
hydrotalcite or hydrogarnet or substituted in C-S-H in which latter forms. It does not appear to be available to
form an expansive reaction product [1].
Strength loss and disintegration are also associated with decalcification of C-S-H, which is an important
mechanism during attack by MgSO solutions but which also occurs to a lesser extent in Na SO solutions [2].
4 2 4
Current sulfate resisting cements standardised in CEN member countries can be divided into two categories:
1) Portland (CEM I) cements with a maximum permitted C A content.
2) Portland composite cements containing appropriate levels of glassy blastfurnace slag, fly ash or
natural pozzolana.
Low C A sulfate resistant cements provide a chemical resistance to sulfate attack. The products that reaction
with sulfates is not expansive and consequently the matrix is not disrupted facilitating further attack. The
unreactive nature of the hydration products of low C A cements is attributed to a low level of monosulfate
and/or the formation of an iron-rich form which is slow reacting and produces a ‘non-expansive’ form of
ettringite [3].
Portland composite cements (i.e. CEM II, III, IV and V types) provide resistance to sulfate attack which is
predominantly micro-structural in nature [4 to 8]. This is derived from the significantly lower permeability of the
hydrated matrix. Additional positive factors are:
• reduced level of free calcium hydroxide in the matrix which reduces calcium availability for ettringite
formation and also the formation of gypsum when the matrix is exposed to concentrated sulfate solutions;
• formation of hydrates containing alumina which are non-reactive to sulfate solutions.
The reduced availability of calcium may also result in the formation of ettringite with a morphology and
distribution throughout the hydrated matrix which is not expansive [9].
One factor that is often overlooked is that resistance to external sulfates is normally positively influenced by
the level of SO in the binder; the higher the level in a range between ~ 1 % to ~ 4 %, the greater the
resistance. This applies to concrete produced from CEM I cements [10] and also particularly to slag and fly
ash containing concretes. Where the ash or slag is added to the mixer [2], [11, 12] the SO level is lowered by
dilution and the hydrated matrix is more vulnerable to attack by penetrating sulfates in comparison with a
binder with an optimised SO level. The improved resistance can be attributed to the increased level of
sulfated phases, such as ettringite, formed during initial hydration, which are stable in the presence of an
elevated sulfate level.
2 Sulfate resistance test procedures
2.1 General review
The sulfate resistance properties of cement can be assessed by preparing realistic concretes specimens and
placing them in conditions which are representative of field conditions. Unfortunately, unless the concretes
are of low quality (high w/c, poorly compacted) several years exposure will be required to provide any
meaningful discrimination between sulfate resistant and non-sulfate resistant cements [13, 14]. Consequently,
there is a need for accelerated test procedures that provide discrimination within a timescale of weeks or
months.
The first laboratory test procedure to determine the sulfate resistance properties of a cement was the Le
Chatelier - Anstett procedure, [15] in which cement paste is hydrated, crushed and dried and then interground
with 50 % (by mass) of gypsum.
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.