01148862 PDF BRITISH STANDARD BS EN 1355 1997 Determination of creep strains under compression of autoclaved aerated concrete or lightweight aggregate concrete with open structure The European Standar[.]
BRITISH STANDARD Determination of creep strains under compression of autoclaved aerated concrete or lightweight aggregate concrete with open structure The European Standard EN 1355:1996 has the status of a British Standard ICS 91.100.30 BS EN 1355:1997 BS EN 1355:1997 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee B/523, Prefabricated concrete and lightweight aggregate concrete with open structure, upon which the following bodies were represented: Aggregate Concrete Block Association Autoclaved Aerated Concrete Association British Masonry Society British Precast Concrete Federation Ltd Department of the Environment (Building Research Establishment) Institution of Structural Engineers Local Authority Organizations This British Standard, having been prepared under the direction of the Sector Board for Building and Civil Engineering, was published under the authority of the Standards Board and comes into effect on 15 October 1997 © BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference B/523 Draft for comment 93/110407 DC ISBN 580 27477 Amendments issued since publication Amd No Date Comments BS EN 1355:1997 Contents Committees responsible National foreword Foreword Text of EN 1355 List of references © BSI 10-1999 Page Inside front cover ii Inside back cover i BS EN 1355:1997 National foreword This British Standard has been prepared under the direction of Technical Committee B/523 and is the English language version of EN 1355:1996 Determination of creep strains under compression of autoclaved aerated concrete or lightweight aggregate concrete with open structure, published by the European Committee for Standardization (CEN) Cross-references Publication referred to Corresponding British Standard EN 678:1993 BS EN 678:1994 Determination of the dry density of autoclaved aerated concrete BS EN 679:1994 Determination of compressive strength of autoclaved aerated concrete BS EN 992:1996 Determination of dry density of lightweight aggregate concrete with open structure BS EN 1354:1997 Determination of compressive strength of lightweight aggregate concrete with open structure EN 679:1993 EN 992:1995 EN 1354:1996 A British Standard does not purport to include all the necessary provisions of a contract Users of British Standards are responsible for their correct application Compliance with a British Standard does not of itself confer immunity from legal obligations Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the EN title page, pages to 8, an inside back cover and a back cover This standard has been updated (see copyright date) and may have had amendments incorporated This will be indicated in the amendment table on the inside front cover ii © BSI 10-1999 EUROPEAN STANDARD EN 1355 NORME EUROPÉENNE December 1996 EUROPÄISCHE NORM ICS 91.100.30 Descriptors: Concrete, cellular concrete, aggregates, mechanical tests, compression tests, creep tests, determination, creep strength English version Determination of creep strains under compression of autoclaved aerated concrete or lightweight aggregate concrete with open structure Détermination du fluage en compression du béton cellulaire autoclavé et du béton de granulats légers structure ouverte Bestimmung der Kriechverformungen unter Druckbeanspruchung von dampfgehärtetem Porenbeton und von haufwerksporigem Leichtbeton This European Standard was approved by CEN on 1996-11-30 CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member The European Standards exist in three official versions (English, French, German) A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom CEN European Committee for Standardization Comité Européen de Normalisation Europäisches Komitee für Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels © 1996 Copyright reserved to CEN members Ref No EN 1355:1996 E EN 1355:1996 Foreword Contents This European Standard has been prepared by Technical Committee CEN/TC 177, Prefabricated reinforced components of autoclaved aerated concrete or lightweight aggregate concrete with open structure, the secretariat of which is held by DIN This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June 1997, and conflicting national standards shall be withdrawn at the latest by June 1997 In order to meet the performance requirements as laid down in the product standards for prefabricated components of autoclaved aerated concrete and of lightweight aggregate concrete with open structure, a number of standardized test methods are necessary According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom Foreword Scope Normative references Principle Apparatus Test specimens 5.1 Sample 5.2 Shape and size of test specimens 5.3 Number of test specimens 5.4 Preparation of test specimens 5.5 Measurement of test specimens 5.6 Conditioning of test specimens Creep test 6.1 Age at loading and duration of sustained load 6.2 Loading details Investigations after the creep test Test results Test report Figure — Sampling scheme Page 3 3 4 4 5 5 6 © BSI 10-1999 EN 1355:1996 Scope This European Standard specifies a method of determining the longitudinal long-term strains (creep strains) of test specimens taken from prefabricated components of autoclaved aerated concrete (AAC)1) or lightweight aggregate concrete with open structure (LAC) according to prEN 1520 due to a constant compression stress sustained over a long period of time Normative references This European Standard incorporates by dated or undated reference, provisions from other publications These normative references are cited at the appropriate places in the text, and the publications are listed hereafter For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision For undated references the latest edition of the publication referred to applies EN 678, Determination of dry density of autoclaved aerated concrete EN 679, Determination of compressive strength of autoclaved aerated concrete EN 992, Determination of dry density of lightweight aggregate concrete with open structure EN 1354, Determination of compressive strength of lightweight aggregate concrete with open structure prEN 1520, Prefabricated components of lightweight aggregate concrete with open structure Principle Creep strains are determined on test specimens taken from prefabricated components The creep strain at a given age t (¼cc,t) is defined as the total strain under compression at that age (¼cc,tot,t), less the instantaneous strain under the same stress occurring during the application of the load (¼ci,t0), less the strains due to shrinkage from the time of loading to the considered age (¼cs,t) The strains due to shrinkage are determined on unloaded control specimens identical to those used in the creep test which are taken from the same component and stored under the same conditions Apparatus a) Any saw, suitable for cutting reinforced AAC or LAC components; b) Callipers, capable of reading the dimensions of the test specimens to an accuracy of 0,1 mm; 1) A c) A straight-edge, feeler gauges (0,1 mm for AAC, 0,5 mm for LAC, and 1,0 mm for both) and a square; d) A balance, capable of determining the mass of the test specimens to an accuracy of 0,1 %; e) Equalizing layers of soft fibreboard (only in the case of LAC), with a thickness of (12 ± 2) mm and a density of (250 to 400) kg/m3 to be inserted between the loadbearing surfaces of the test specimens and the platens of the compression testing machine (not required in the case of levelling the loadbearing surfaces by grinding or capping); f) A loading frame, capable of applying and maintaining the required compressive load on the test specimen(s) for the required period of time (in general at least one year), despite any length change of the test specimen(s) (see note 1) The header plates of the loading frame shall have sufficient stiffness, and their bearing surface shall not depart from a plane by more than 0,1 mm per 100 mm In any loading frame several test specimens may be stacked for simultaneous loading Means shall be provided for measuring the load to the nearest % of the total applied load This may be a permanently installed pressure gauge or a hydraulic jack or load cell inserted temporarily in the frame when the load is applied or adjusted When a hydraulic load-maintaining element is used, several frames may be loaded simultaneously through a central hydraulic pressure-regulating unit When springs are used, care shall be taken to provide a spherical seated head, or a ball joint and end plates rigid enough to ensure uniform loading of the test specimens g) A measuring device, for the determination of the longitudinal length changes (strains) of the test specimens The apparatus may be portable or attached (see note 2) If portable apparatus is used, gauge points shall be attached to the test specimen in a positive manner which is normally done by glueing with rapid hardening glue The gauge length shall be not less than 100 mm The gauge points shall be provided accurately on the longitudinal axes of the four longitudinal surfaces of the prismatic test specimens, and they shall be attached equidistant from the ends, the distance from the adjacent end being not less than 50 mm European Standard for prefabricated reinforced components of autoclaved aerated concrete is in preparation at CEN © BSI 10-1999 EN 1355:1996 The device shall be capable of measuring strains to the nearest 10 × 10–6 (0,01 mm/m) for at least one year without change in calibration h) a room, capable of maintaining a temperature of (20 ± 2) °C and a relative humidity of (60 ± 5) %; i) a ventilated drying oven, capable of maintaining a temperature of (105 ± 5) °C (see note 3) NOTE A usual frame consists of header plates bearing on the ends of the loaded test specimens, a load maintaining element that may be either a spring or a hydraulic capsule or ram, connected with a cylinder of high pressure nitrogen and a hydraulic pressure-regulating unit, and threaded rods to take the reactions of the loaded system NOTE Systems in which the varying length changes or strains are compared with a constant-length standard bar are considered most reliable NOTE In addition, a ventilated drying oven capable of maintaining a temperature of (40 to 60) °C can be helpful for conditioning of test specimens Test specimens 5.1 Sample The sample for the preparation of the test specimens (usually at least one prefabricated component) shall be taken in such a manner that it is representative of the product to be investigated 5.2 Shape and size of test specimens The reference test specimens shall be prisms with a square cross-section of 100 mm × 100 mm and a height of 300 mm Test specimens of other sizes or shape may be used, provided that the correlation to the results of tests on the above reference test specimens is established 5.3 Number of test specimens At least two test specimens for determination of creep (creep specimens) and two control specimens for determination of shrinkage shall be prepared from the central part of the component (see Figure 1) 5.4 Preparation of test specimens The specimens shall be cut not less than d after autoclaving or casting, respectively The dust or the slurry of the process shall be removed They shall be taken in such a way that their longitudinal axis is: — in the case of AAC: — in the case of LAC: perpendicular to the rise of the mass during the manufacture; in the plane of the compression force acting in the component when used in the structure The specimens shall contain no reinforcing bars within the gauge length (If unavoidable, bars which are perpendicular to the longitudinal axis may be accepted in exceptional cases This shall be mentioned in the test report.) The loadbearing surfaces of the creep specimens shall be plane, parallel to each other and perpendicular to the longitudinal surfaces of the specimens Planeness of loadbearing surfaces shall be checked across the two diagonals using a straight-edge and, if necessary, a feeler gauge Deviations exceeding 0,2 mm shall be adjusted by cutting and/or grinding or by capping In the case of LAC, deviations up to 0,5 mm may be tolerated, provided that equalizing layers of soft fibreboard according to e) are used Deviations from planeness of the other surfaces shall not exceed mm Figure — Sampling scheme © BSI 10-1999 EN 1355:1996 The angle between the loadbearing surfaces and the adjacent longitudinal surfaces of the creep specimens shall not deviate from a right angle by more than mm per 100 mm This shall be checked along both orthogonal middle axes of the loadbearing surfaces by means of a square and a mm-feeler gauge or similar instrument Larger deviations shall be corrected by cutting or grinding 5.5 Measurement of test specimens The dimensions of the creep specimens and control specimens shall be measured to an accuracy of 0,1 mm, using callipers Length and width of the cross-sectional area, Ac, shall be measured at mid height at two opposite longitudinal sides The cross-sectional area shall be calculated using the mean values of the results of the measurements The height of the specimens shall be measured in the middle of two opposite longitudinal sides The volume V of the specimen shall be calculated by multiplying Ac by the mean value of the results of the height measurements The actual moisture content of the specimens at the beginning and at the end of the creep test and the dry density shall be determined For this purpose the specimens shall be weighed prior to the creep test, before applying any devices for measurement of deformations and after completion of the creep test, after removal of gauge plugs etc Finally, they shall be dried to constant mass at (105 ± 5) °C (see clause 7) If the removal of the adhesive fixed gauge plugs is likely to remove concrete, the initial mass of the test specimen with and without gauge plugs shall be taken, and the appropriate correction shall be made in the calculations NOTE The expected moisture content of a test specimen may be calculated according to equation (1): (1) where Èm,exp is the expected mass related moisture content, in per cent; Ôhum,t = mhum/V is the moist density of the test specimen, calculated by dividing its moist mass mhum by its volume V determined according to 5.5, in kilograms per cubic metre; Ôcomp is the dry density of companion specimens determined according to EN 678 (for AAC) or EN 992 (for LAC), in kilograms per cubic metre 5.6 Conditioning of specimens The test specimens shall be conditioned at a temperature not exceeding 60 °C until their mass related moisture content is (6 ± 2) % This may be estimated by comparing their moist density with the dry density determined in accordance with EN 678 for AAC or with EN 992 for LAC, respectively, on companion specimens extracted from the same area of the same component (see note) After reaching the specified moisture content, the test specimens shall be stored, protected against moisture changes, for at least 72 h prior to the test at (20 ± 2) °C for ensuring uniform moisture distribution within the test specimen and thermal equilibrium with the temperature in the laboratory During the creep test the test specimens shall be exposed to the surrounding air with a temperature of (20 ± 2) °C and a relative humidity of (60 ± 5) % Conditions other than the above reference conditions may be chosen if required This shall be indicated in the test report © BSI 10-1999 Creep test 6.1 Age at loading and duration of sustained load In the case of AAC the age at loading is optional In the case of LAC the creep specimens shall be loaded at an age of 28 d, if not specified otherwise The applied load shall be sustained constant, in general for a period of at least a It may be necessary to continue the test for a longer period, if the deformations are still increasing at a considerable rate at that time 6.2 Loading details Immediately before loading the creep specimens the compressive strength of the concrete shall be determined, according to EN 679 for AAC or EN 1354 for LAC, respectively, on test specimens taken from the same sample EN 1355:1996 At the time creep specimens are placed in the loading frame, the end faces of the control specimens for shrinkage measurement shall be covered in order to provide the same drying conditions as for the creep specimens The creep specimens shall be placed in the loading frame taking care in aligning the specimens to avoid excentric loading In the case of LAC, provided that the creep specimens have not been ground or capped and the deviations from planeness of the loadbearing surfaces exceed 0,2 mm, equalizing layers of soft fibreboard, as specified in e), shall be inserted between the loadbearing faces of the creep specimens and the header plates of the loading frame, and also between the individual creep specimens, if several specimens are stacked in one loading frame After proper aligning the creep specimens (see note) the load shall be applied at the specified intensity which is usually chosen such that the resulting stress is one third of the strength at the age of loading, but not more than 40 % of that value The duration of loading process should be as short as practicable and shall in no case exceed 15 Strain readings shall be taken immediately before and after loading, h to h later, after d and then at appropriate intervals, in general until at a, so that the curve representing the development of strains with time can be reliably recorded Before each strain measurement, the load shall be controlled and adjusted, if deviating by more than % from the correct value Strain readings on the control specimens shall be taken on the same schedule as for the loaded specimens NOTE For control of centric loading it may be helpful to apply a small preload not exceeding 25 % of the final sustained load and to note the strain variation around each creep specimen, after which if necessary, the load may be removed and the specimens realigned for greater strain uniformity Strain distribution may also be influenced by tightening or loosening the nuts on the threaded reaction rods if this type of loading frame is used (see note in clause 4) If possible, the strain variation around the individual creep specimens should not exceed ± 30 % of the mean strain Investigations after the creep test After finalizing the creep test the load shall be removed, and the creep specimens and the control specimens shall be weighed and subsequently dried to constant mass at (105 ± 5) °C in order to determine the dry density on the basis of EN 678 or EN 992, respectively, and the moisture content at the beginning and the end of the creep test according to equation (2): (2) where Èm mhum mdry is the mass related moisture content, in per cent; is the mass of the test specimen (without any gauge plugs) in the moist state, at the beginning or after finalizing of the creep test, respectively, in kilograms; is the mass of the test specimen (without any gauge plugs), dried according to EN 678 (AAC) or EN 992 (LAC), in kilograms Test results The creep strain (cc, t at a given time t is calculated by equation (3): ¼cc,t = ¼cc,tot,t – ¼ci,t0 –¼cs,t where ¼cc,t ¼cc,tot,t ¼ci,t0 ¼cs,t (3) is the creep strain at a given time t, in per mille; is the total strain of the loaded creep specimen at the considered time t which had occurred since the initial reading in the unloaded state immediately before application of the final sustained load, in per mille; is the instantaneous strain due to the applied load (difference of readings immediately before and immediately after loading), in per mille; is the mean value of the total strain of the unloaded control specimens (shrinkage specimens) from the time of loading of the creep specimens until the considered time t, in per mille The creep strain ¼cc,t and the strains ¼cc,tot,t as well as ¼ci,t0, and ¼cs,t shall be indicated in the test report to the nearest 0, 010/00 © BSI 10-1999 EN 1355:1996 The specific creep ¼cc,t/Ư (creep strain per newton per square millimetre) is calculated for any time t by dividing the creep strain ¼cc,t by the sustained stress Ư and shall be indicated in the test report to the nearest 10–6 per N/mm2 Test report The test report shall include the following: a) identification of the product; b) date of manufacture or other code; c) date of sampling; d) place and date of testing, testing institute and person responsible for testing; e) number and date of issue of this European Standard; f) conditions of curing (only for LAC); g) storage conditions prior to and subsequent to application of loading; h) date of loading and concrete age at time of loading; j) compressive strength of concrete at time of loading; k) type of strain measuring device and gauge length; l) magnitude of any preload; m) intensity of applied long-term compressive stress; © BSI 10-1999 n) duration of initial loading process; p) instantaneous strain; q) total duration of creep test (time under load); r) development of total strain with time (see note); s) development of strain of unloaded control specimens with time (see note); t) development of creep strain with time as calculated (see note); u) development of specific creep with time as calculated (see note); v) dry density of individual test specimens and mean value (determined after the creep test); w) mean value of the mass related moisture content of creep specimens and control specimens at time of loading and at the end of the creep test; x) (if unusual) observations on the appearance of the specimens; y) (if appropriate) deviations from the standard method of testing; z) a declaration that the testing has been carried out in accordance with this European Standard, except as detailed in y) NOTE It may be advantageous to plot development of strains for items r) to u) in bilogarithmic or semilogarithmic (time axis logarithmic, strain axis linear) scale blank BS EN 1355:1997 List of references See national foreword © BSI 10-1999 BS EN 1355:1997 BSI — British Standards Institution BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by Royal Charter Revisions British Standards are updated by amendment or revision Users of British Standards should make sure that they possess the latest amendments or editions It is the constant aim of BSI to improve the quality of our products and services We would be grateful if anyone finding an inaccuracy or ambiguity while using this British Standard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover Tel: 020 8996 9000 Fax: 020 8996 7400 BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards Buying standards Orders for all BSI, international and foreign standards publications should be addressed to Customer Services Tel: 020 8996 9001 Fax: 020 8996 7001 In response to orders for international standards, it is BSI policy to supply the BSI implementation of those that have been published as British Standards, unless otherwise requested Information on standards BSI provides a wide range of information on national, European and international standards through its Library and its Technical Help to Exporters Service Various BSI electronic information services are also available which give details on all its products and services Contact the Information Centre Tel: 020 8996 7111 Fax: 020 8996 7048 Subscribing members of BSI are kept up to date with standards developments and receive substantial discounts on the purchase price of standards For details of these and other benefits contact Membership Administration Tel: 020 8996 7002 Fax: 020 8996 7001 Copyright Copyright subsists in all BSI publications BSI also holds the copyright, in the UK, of the publications of the international standardization bodies Except as permitted under the Copyright, Designs and Patents Act 1988 no extract may be reproduced, stored in a retrieval system or transmitted in any form or by any means – electronic, photocopying, recording or otherwise – without prior written permission from BSI This does not preclude the free use, in the course of implementing the standard, of necessary details such as symbols, and size, type or grade designations If these details are to be used for any other purpose than implementation then the prior written permission of BSI must be obtained BSI 389 Chiswick High Road London W4 4AL If permission is granted, the terms may include royalty payments or a licensing agreement Details and advice can be obtained from the Copyright Manager Tel: 020 8996 7070