1、Designation: C1850 17Standard Guide forImproved Laboratory Accelerated Tests to Predict theWeathering and for Use in Developing Protocols to Predictthe Design Life of Building Sealant Systems1This standard is issued under the fixed designation C1850; the number immediately following the designation
2、indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide describes the steps for dev
3、eloping improvedlaboratory accelerated weathering tests for predicting thenatural weathering effects on building sealant systems and forusing those tests in development of methods for design lifeprediction of the systems.1.2 This guide outlines a systematic approach to develop-ment of laboratory acc
4、elerated weathering tests of buildingsealant systems including the identification of neededinformation, the development of accelerated tests, the applica-tion of data, and the reporting of results.1.3 This international standard was developed in accor-dance with internationally recognized principles
5、 on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2C717 Terminology of Building Seals an
6、d SealantsG113 Terminology Relating to Natural and Artificial Weath-ering Tests of Nonmetallic Materials3. Terminology3.1 DefinitionsFor definitions of terms used in this guide,refer to Terminologies C717 and G113.3.2 Definitions of Terms Specific to This Standard:3.2.1 biological degradation factor
7、degradation factors di-rectly associated with living organisms, includingmicroorganisms, fungi, and bacteria.3.2.2 building sealant system componenta part of a build-ing sealant system that may include a combination of buildingmaterials, such as cladding, substrates or the sealant.3.2.3 building sea
8、lant system materiala material that maybe used in a building sealant system.3.2.4 critical performance characteristic(s)a property, orgroup of properties, of a building sealant system that must bemaintained above a certain minimum level.3.2.5 degradation mechanismthe chemical reactions in-duced in a
9、 building component or material by one or moredegradation factors resulting in changes in one or more of thecritical performance characteristics.3.2.6 incompatibility factorany of the group of degrada-tion factors that result from detrimental chemical and physicalinteractions between building compon
10、ents or materials.3.2.7 in-service testa test in which building componentsor materials are exposed to degradation factors under in-serviceconditions.3.2.8 performance criteriona quantitative statement of alevel of properties for a selected characteristic of a componentor material needed to ensure co
11、mpliance with a functionalrequirement.3.2.9 property measurement testa test for measuring oneor more properties of building components or materials.3.2.10 load stress factorany degradation factors that resultfrom externally applied sustained or periodic mechanical loads.3.2.11 use factorany factor t
12、hat affects the material as aresult of the design of the system, installation and maintenanceprocedures, normal wear and tear, and user abuse. (Example:abrasion of foot traffic.)3.2.12 weathering factorsany degradation factors associ-ated with the natural environment, including radiation,temperature
13、, rain and other forms of water, freezing andthawing.4. Significance and Use4.1 This guide is intended to serve as a reference ofrecommended methodology for users developing relevant,reliable and valid tests for predicting natural weathering effects1This guide is under the jurisdiction ofASTM Commit
14、tee C24 on Building Sealsand Sealants and is the direct responsibility of Subcommittee C24.20 on GeneralTest Methods.Current edition approved March 15, 2017. Published April 2017. DOI: 10.1520/C1850-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Serv
15、ice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in a
16、ccordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1and for use in developing me
17、thods to determine design life ofbuilding sealant systems through the use of accelerated testprotocols. The proposed standard corrects for some of thedeficiencies of existing laboratory accelerated tests of sealants.4.2 The development of accelerated weathering tests ca-pable of being used in protoc
18、ols to reliably and accuratelypredict the long-term in-service performance of building seal-ant systems have limitations due to:4.2.1 The external factors that affect functional properties,which are numerous and require effort to quantify, so that manyexisting accelerated procedures do not include a
19、ll factors ofimportance, and4.2.2 The sealant specimens are often tested in configura-tions different from those used in-service.5. Procedure5.1 This guide describes a recommended sequence of stepsfor users to follow for developing laboratory acceleratedweathering tests for predicting the effects of
20、 natural weatheringon sealants and for use in development of methods forestimating design life (see Fig. 1 for a flow chart).6. Scope6.1 The scope describes the intentions of the test and thedegradation factors that should be included.IProblem Definition7. Definition of In-Service Performance Charac
21、teristicRequirements and Criteria7.1 The critical performance characteristic criteria definethe minimum acceptable levels of in-service functional prop-erties stated in terms of absolute values or changes from theinitial test.8. Characterization of the Sealant8.1 Characterize the sealant system in t
22、erms of composition,critical performance characteristics, and physical properties theFIG. 1 Recommended Steps for Developing Improved Artificial Accelerated Weathering Tests to Predict Natural Weathering Effects andfor Use in Developing Protocols for Predicting Design LifeC1850 172changes of which w
23、ill serve as degradation indicators, therange and type of degradation factors to which the sealantresponds, and all possible types of degradation and mecha-nisms by which the degradation factors induce changes in thecritical performance properties.8.1.1 Critical Performance Characteristics and Prope
24、rties:8.1.1.1 Properties used as measures of degradation must bethe same as or directly linked to the critical performancecharacteristic. Fig. 2 provides a matrix for use in identifyingproperties that indicate degradation.8.1.1.2 The Vertical Axis of the MatrixAn alphabeticalletter is used in the ma
25、trix to designate individual buildingelements and interfaces as part of a building sealant system.For example, a wall element may include an exterior coating(A), an exterior substrate (B), a structural member (C),insulation (D), an interior substrate (E), and an interior coating(F). The interfaces b
26、etween each pair of materials can then bedesignated, for example, A-B, B-C, A-C, etc.8.1.1.3 Consider the characteristics of the sealant andinterfaces with other building components in the evaluation.Fig. 2 lists changes in properties that may be useful asmeasures of degradation. These include both
27、visual changes(chalking, crazing, cracking, checking, flaking, scaling, blister-ing) and instrumentally measurable changes (color, gloss,tensile modulus, etc.).8.1.2 Type and Range of Degradation Factors:8.1.2.1 Identify the type of degradation factors to which thesealant will be exposed in-service
28、and their range. A list ofcommon degradation factors is presented in Table 1. This list isnot exhaustive and other possible important factors should besought in each specific case.8.1.2.2 Quantitative information on weathering factors isavailable from published weather and climatological data.These
29、data will usually be sufficient to indicate the ranges ofintensities to which the component or material will be exposedin-service.8.1.2.3 Stress factors consist of sustained stress, developedfrom seasonal changes, and periodic stress, such as dailytemperature or moisture variation. The intensities o
30、f stressfactors can be estimated.8.1.2.4 Chemical and Physical Incompatibility between Dis-similar MaterialsThis includes stress caused by the differentthermal expansion coefficients of rigidly connected dissimilarmaterials that can be estimated.8.1.2.5 Use factors include the design of the system,
31、instal-lation and maintenance procedures, normal wear and tear andabuse.8.1.2.6 Biological, incompatibility, and use factors and theirrange of in-service intensity can be difficult to quantify butupper limits of common in-service conditions can usually beestimated from a technical assessment and eng
32、ineering judg-ment. Consider each of the degradation factors that the sealantmay experience in-service within the given building system indesigning the assessment protocol.FIG. 2 Example of a Matrix for Identifying Observable Changes of SealantsTABLE 1 Degradation Factors Affecting the Design Life o
33、fSealant SystemsWeathering FactorsRadiation Solar Nuclear ThermalTemperature CyclesWaterSolid (such as snow, ice)Liquid (such as rain, condensation, standing water)Vapor (such as high relative humidity)Mechanical MovementsNormal Air Constituents Oxygen and ozone Carbon dioxideAir ContaminantsGases (
34、such as oxides of nitrogen and sulfur)Mists (such as aerosols, salt, acids, and alkalies dissolved in water)Particulates (such as sand, dust, dirt)Freeze-thawWindBiological Factors Microorganisms FungiBacteriaStrainStatic strain of seasonal cyclesDynamic strain of daily cyclesStress Factors, sustain
35、ed or periodicPhysical action of water, as rain, hail, sleet, and snowPhysical action of windCombination of physical action of water and windMovement due to other factorsIncompatibility FactorsChemicalPhysicalUse FactorsDesign of systemInstallation and maintenance proceduresNormal wear and tearAbuse
36、 by the userC1850 1738.1.3 Postulation of Types of DegradationThis step of thecharacterization procedure requires the user to propose pos-sible types of degradation by which the identified degradationfactors can induce changes in the critical performance proper-ties of the sealant system.9. Postulat
37、ions Regarding Accelerated Aging Tests9.1 Once the information from Sections 7 and 8 has beenobtained, postulations are made regarding specific proceduresfor accelerating the degradation using the identified degrada-tion factors. For example, if thermal degradation is identified asa possible degrada
38、tion factor then it may be postulated that thistype of factor can be accelerated by exposure to temperatureshigher than those expected in-service. Users are cautioned thatapplying extreme levels of stress to accelerate the rate ofdegradation may activate mechanisms and induce changes thatare not pre
39、dictive of in-service degradation. The postulates thatare made in this step lay the groundwork for designingpreliminary accelerated tests.10. Definition of Performance Requirements10.1 Define performance requirements of the sealant. Theperformance statements should be qualitative summaries of theinf
40、ormation obtained in Sections 8 and 9 that describe theintention of the test.IIPre-Testing11. Scope:11.1 Pre-testing contributes to the user knowledge of theprimary degradation factors leading to property changes It canbe used to show that rapid changes in the properties of thesealant can be induced
41、 by exposure to high levels of thedegradation factors. Information obtained from pre-testingincludes indications of (1) property changes that are likely tobe useful as degradation indicators, (2) the order of importanceof the degradation factors, (3) the intensities of degradationfactors needed to i
42、nduce rapid property changes.12. Design of Pre-Tests12.1 Pre-tests should be designed based on the informationobtained in Sections 8, 9, and 10. The tests should provide forvarious properties to be measured before and after exposuretesting to determine which properties provide the most reliableand c
43、onsistent degradation indicators. Also, evaluate the deg-radation factors identified in Section 8, to which the buildingsealant system will be exposed in-service, to determine themost important factors.12.2 The intensity of weathering and other stress factorsused in pre-tests can be used in accordan
44、ce with the quantita-tive ranges identified in Section 8. Weather and climatologicaldata for the most extreme climates in which the sealant may beused normally form the basis for the intensities of these factorsin the pre-tests. Calculated sustained stress and periodic stresscan be used.12.3 Biologi
45、cal and incompatibility factors may not beimportant unless combined with high levels of weatheringfactors. For example, fungi and bacteria are most active inwarm, moist locations; chemical incompatibility may only beimportant as long as liquid water is present between the joinedmaterials; physical i
46、ncompatibility may not be importantunless there are large temperature changes. The effects ofincompatibility factors can, therefore, usually be evaluatedalong with tests to determine the effect of weathering factors.12.4 Use factors are not usually included in acceleratedaging tests. Installation an
47、d maintenance practices are assumedto be provided as recommended by the manufacturer, andintentional abuse is usually considered to be beyond the scopeof test methods. Although use factors are not often included inaccelerated aging tests, they can affect the sealant functionallife and should be eval
48、uated if deemed critical.IIITesting13. Scope13.1 The purposes of this procedure are to design andconduct new or improved accelerated tests to determine therelationships between the degradation rates and the exposureconditions; to design and perform tests under in-service con-ditions to confirm that
49、the types of degradation induced byaccelerated aging tests are similar to those observed in-service;and to measure the rates at which properties change in-service.14. Design of Tests14.1 Long-term In-Service TestsLong-term in-servicetests are necessary to validate the degradation factors ofimportance for the sealant. These tests may be actual in-servicetests of a model or mock-up system or exposure of selectedmaterials at outdoor weathering sites. It is essential to designthe in-service tests so that all factors of importance areconsidered. Where p
