1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS 1881-125:2013Testing concrete Part 125: Methods for mixing andsampling fresh concrete in thelaboratoryPublishing and copyright informationThe BSI copyright notice displayed in
2、 this document indicates when the documentwas last issued. The British Standards Institution 2013Published by BSI Standards Limited 2013ISBN 978 0 580 77923 7ICS 91.100.30The following BSI references relate to the work on this standard:Committee reference B/517Draft for comment 12/30258714 DCPublica
3、tion historyFirst edition, October 1986Second (present) edition, April 2013Amendments issued since publicationDate Text affectedBS 1881-125:2013 BRITISH STANDARDContentsForeword ii1 Scope 12 Normative references 13 Terms and definitions 14 Apparatus 15 Constituent materials 16 Batching 27 Mixing 28
4、Sampling and testing the concrete 69 Report 6Summary of pagesThis document comprises a front cover, an inside front cover, pages i to iv,pages 1 to 8, an inside back cover and a back cover.BRITISH STANDARD BS 1881-125:2013 The British Standards Institution 2013 iForewordPublishing informationThis pa
5、rt of BS 1881 is published by BSI Standards Limited, under licence fromThe British Standards Institution, and came into effect on 30 April 2013. It wasprepared by Subcommittee B/517/1, Concrete production and testing, under theauthority of Technical Committee B/517, Concrete. A list of organizations
6、represented on this committee can be obtained on request to its secretary.SupersessionThis part of BS 1881 supersedes BS 1881-125:1986, which is withdrawn.Relationship with other publicationsBS 1881 is published in the following parts: BS 1881-113, Method for making and curing no-fines cubes; BS 188
7、1-119, Method for determination of compressive strength usingportions of beams broken in flexure (equivalent cube method); BS 1881-122, Method for determination of water absorption; BS 1881-124, Methods for analysis of hardened concrete; BS 1881-125, Method for mixing and sampling fresh concrete in
8、thelaboratory; BS 1881-128, Method for analysis of fresh concrete; BS 1881-129, Method for the determination of density of partiallycompacted semi-dry fresh concrete; BS 1881-130, Method for temperature matched curing of concretespecimens; BS 1881-131, Methods for testing cement in a reference concr
9、ete; BS 1881-201, Guide to the use of non-destructive methods of test forhardened concrete; BS 1881-204, Recommendations on the use of electromagnetic covermeters; BS 1881-206, Recommendations for determination of strain in concrete; BS 1881-207, Recommendations for the assessment of concrete streng
10、th bynear-to-surface tests; BS 1881-208, Recommendations for the initial surface absorption ofconcrete; BS 1881-209, Recommendations for the measurement of dynamic modulusof elasticity of concrete; DD 216, Determination of chloride content of fresh concrete.Information about this documentThis part o
11、f BS 1881 complements BS EN 12350-1 which covers the sampling ofconcrete on site.It is recognized that a wide range of concrete mixes are prepared in thelaboratory so provision is made for modifications to the standard procedure andtheir detailed reporting see 8.2.1e).BRITISH STANDARDBS 1881-125:201
12、3ii The British Standards Institution 2013CAUTION. When cement is mixed with water, alkali is released. Takeprecautions to avoid dry cement entering the eyes, mouth and nose whenmixing concrete. Prevent skin contact with wet cement or concrete bywearing suitable protective clothing. If cement or con
13、crete enters the eye,immediately wash it out thoroughly with clean water and seek medicaltreatment without delay. Wash wet concrete off the skin immediately.Presentational conventionsThe provisions of this standard are presented in roman (i.e. upright) type. Itsrequirements are expressed in sentence
14、s in which the principal auxiliary verb is“shall”.Requirements in this standard are drafted in accordance with The BSI guide tostandardization Section 2: Rules for the structure, drafting and presentation ofBritish Standards, subclause 11.3.1, which states, “Requirements should beexpressed using wor
15、ding such as: When tested as described in Annex A, theproduct shall .”. This means that only those products that are capable ofpassing the specified test will be deemed to conform to this standard.Commentary, explanation and general informative material is presented insmaller italic type, and does n
16、ot constitute a normative element.Contractual and legal considerationsThis publication does not purport to include all the necessary provisions of acontract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legalobligations.BRITISH STAN
17、DARD BS 1881-125:2013 The British Standards Institution 2013 iiiBRITISH STANDARDBS 1881-125:2013This page deliberately left blankiv The British Standards Institution 20131 ScopeThis part of BS 1881 describes basic methods for the preparation of materialsand the batching, mixing and sampling of fresh
18、 concrete in the laboratory,where accurate controls of the quantities of materials and of test conditions arepossible. The procedures are applicable when assessing the suitability ofmaterials or determining suitable mix proportions for concrete for general useon site.This part of BS 1881 is not appl
19、icable to special concrete mixes prepared forresearch, where the mixing procedure is determined by the properties of theconstituents or of the resulting concretes that are being studied.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in thisdocument and
20、 are indispensable for its application. For dated references, onlythe edition cited applies. For undated references, the latest edition of thereferenced document (including any amendments) applies.BS 8500 (all parts), Concrete Complementary British Standard to BS EN 206-1BS EN 196-7, Methods of test
21、ing cement Part 7: Methods of taking andpreparing samples of cementBS EN 206-1, Concrete Part 1: Specification, performance, production andconformityBS EN 932-1, Tests for general properties of aggregates Part 1: Methods forsamplingBS EN 1097-6, Tests for mechanical and physical properties of aggreg
22、ates Part 6: Determination of particle density and water absorptionBS EN 12350, (all parts) Testing fresh concrete3 Terms and definitionsFor the purpose of this part of BS 1881, the definitions given in BS EN 206-1 andBS 8500 (all parts) apply.4 Apparatus4.1 Mixer, rotating pan or tilting drum type
23、of a capacity 10% to 50% greaterthan the maximum batch of concrete required to provide samples for the teststo be carried out.4.2 Scoop, or similar sampling device, made from non-absorbent material notreadily attacked by cement paste, suitable for taking increments of concrete.4.3 Hand tool, suitabl
24、e for turning mixed concrete.5 Constituent materials5.1 SamplingIf bulk samples are supplied, take subsamples for the test portions in accordancewith BS EN 196-7 for cement and BS EN 932-1 for aggregate, ensuring that thematerials used in each batch of concrete are representative of the bulkmaterial
25、s.BRITISH STANDARD BS 1881-125:2013 The British Standards Institution 2013 1Otherwise, use the materials in the proportions supplied or specified for the mix.5.2 Cement, ground granulated blastfurnace slag and fly ash5.2.1 Store the separate materials in individual airtight containers of appropriate
26、size in a dry place.5.2.2 Before use, thoroughly stir each separate material, either using a hand toolor in a suitable mixer, in a manner that ensures the greatest possible uniformity,avoiding the intrusion of foreign matter or loss of material.5.3 Aggregate5.3.1 Ensure the aggregates are in one of
27、the following conditions:a) oven-dry in accordance with BS EN 1097-6;b) air dried at (20 5) C;c) saturated surface-dry as described in BS EN 1097-6; ord) saturated by soaking in water for at least 24 h.5.3.2 When necessary, determine the moisture content (as a percentage of theoven dry mass) of the
28、aggregates by an appropriate method given inBS EN 1097-6. The aggregates for each concrete batch may be used either inseparate size fractions or with an all-in grading.5.4 TemperatureAllow all materials to reach a temperature of (20 5) C before mixing theconcrete.6 Batching6.1 Ensure that the quanti
29、ty of concrete for each batch is at least 10% morethan that required for the proposed tests.6.2 For each concrete batch, weigh the cement, any ground granulatedblastfurnace slag or fly ash and the water to an accuracy of 0.5% and theaggregate to an accuracy 1%.6.3 If an admixture is to be incorporat
30、ed, measure the amount to an accuracy of5% of the specified dosage and follow the manufacturers instructions for use.NOTE When preparing concrete to have a given property, such as workability or aircontent, it might be necessary to prepare and test trial mixes of varying compositionto establish the
31、required mix quantities.7 Mixing7.1 General7.1.1 Mix the concrete in a room having an ambient temperature of (20 5) Cand a relative humidity of not less than 50%.7.1.2 If the aggregate is dry in accordance with 5.3 a) or 5.3 b), allow it to soakwith some of the mixing water before adding other mater
32、ials until it has takenup most of the water it would eventually absorb. Avoid water loss byevaporation while soaking.BRITISH STANDARDBS 1881-125:20132 The British Standards Institution 20137.1.3 After weighing out liquid admixtures, dilute with some of the mixingwater prior to addition to the mix an
33、d/or flush the measuring container withfurther mixing water after addition to the mix.NOTE 1 Addition should always be according to the manufacturers instructions butis normally with the last half of the mixing water and after the cement is fullywetted out. Powder admixtures should always be added i
34、n accordance with themanufacturers instructions.7.1.4 Mix the concrete, preferably by machine or alternatively using a hand tool,in such a manner as to avoid loss of water or other materials.NOTE 2 Different methods of mixing can lead to different results.7.2 Machine mixing7.2.1 General7.2.2 To avoi
35、d both incomplete mixing and spillage, ensure that the mixerconforms to 4.1.7.2.3 Before using the mixer, clean off any fresh concrete remaining from aprevious batch.7.2.4 Ensure that no free water remains in the mixer.7.2.5 If the mixer is dry, wipe it with a damp cloth.7.2.6 When using a tilting d
36、rum mixer, mix a small preliminary batch, of similarproportions to the main batch, immediately before the main batch in order tocoat the mixer.7.2.7 Pan mixer7.2.7.1 Using dry aggregates7.2.7.1.1 Add an all-in aggregate as one amount.7.2.7.1.2 If separate fine and coarse aggregates are used, add the
37、m in thefollowing order:1) approximately half the coarse aggregate;2) the fine aggregate;3) the remaining coarse aggregate;by spreading them evenly over the pan.7.2.7.1.3 Start the mixer and run it for between 15 s and 30 s.7.2.7.1.4 Continue mixing and add about half the water during the next 15 s.
38、7.2.7.1.5 After mixing for 2 min to 3 min, stop the mixer and leave the contentscovered for 5 min to 15 min.7.2.7.1.6 Add the cement and any ground granulated blastfurnace slag, fly ash,pigment or other powder or other materials, e.g. fibres, by spreading them inan even layer over the aggregate.7.2.
39、7.1.7 Mix for 30 s.7.2.7.1.8 Stop the mixer and immediately clean off into the pan any materialadhering to the mixer blades.BRITISH STANDARD BS 1881-125:2013 The British Standards Institution 2013 37.2.7.1.9 Immediately recommence mixing and add the remaining mixing waterover the next 30 s.7.2.7.1.1
40、0 Continue mixing for 2 min to 3 min.7.2.7.1.11 After completion of mixing in a pan mixer without a discharging gate,turn the concrete over in the pan a few times using a hand tool to ensureuniformity before sampling.7.2.7.2 Using saturated aggregates7.2.7.2.1 If an all-in aggregate is used, add app
41、roximately half of it beforeadding the other materials and the remainder of it after this.7.2.7.2.2 If separate fine and coarse aggregates are used, add them in thefollowing order:1) approximately half the coarse aggregate;2) the fine aggregate;3) the cement;4) any ground granulated blastfurnace sla
42、g, fly ash, pigment or other powderor other materials, e.g. fibres;5) the remaining coarse aggregate;by spreading them evenly over the pan.7.2.7.2.3 Start the mixer and add all the water during the first 30 s of mixing.7.2.7.2.4 After all the materials have been added mix for 2 min to 3 min.7.2.7.2.
43、5 After completion of mixing in a pan mixer without a discharging gate,turn the concrete over in the pan a few times using a hand tool to ensureuniformity before sampling.7.2.8 Drum mixer7.2.8.1 Using dry aggregates7.2.8.1.1 If an all-in aggregate is used, add it as one amount.7.2.8.1.2 If separate
44、fine and coarse aggregates are used, add them in thefollowing order:1) approximately half the coarse aggregate;2) the fine aggregate;3) the remaining coarse aggregate.7.2.8.1.3 Start the mixer and run it for between 15 s and 30 s.7.2.8.1.4 Continue mixing and add approximately half the water over th
45、e next15 s.7.2.8.1.5 After mixing for 2 min to 3 min, stop the mixer and leave the contentscovered for 5 min to 15 min.7.2.8.1.6 Add the cement and any ground granulated blastfurnace slag, fly ash,pigment or other powder on top of the aggregate.7.2.8.1.7 Start the mixer and mix for 30 s.7.2.8.1.8 Ov
46、er the next 30 s add the remaining water.BRITISH STANDARDBS 1881-125:20134 The British Standards Institution 20137.2.8.1.9 After all the materials have been added, mix for 2 min to 3 min.7.2.8.1.10 After completion of mixing, discharge the concrete onto a cleannon-absorbent surface and turn it over
47、using a hand tool to ensure uniformitybefore sampling.7.2.8.2 Using saturated aggregates7.2.8.2.1 If an all-in aggregate is used, add approximately half of it beforeadding the other materials and the remainder of it after this.7.2.8.2.2 If separate fine and coarse aggregates are used, add the in the
48、following order:a) about half the coarse aggregate;b) the fine aggregate;c) the cement and any ground granulated blastfurnace slag, fly ash, pigmentor other powder; andd) the remaining coarse aggregate.7.2.8.2.3 Add all the water during the first 30 s of mixing.7.2.8.2.4 After all the materials have
49、 been added, continue mixing for between2 min and 3 min.7.2.8.2.5 After completion of mixing, discharge the concrete onto a cleannon-absorbent surface and turn it over using a hand tool to ensure uniformitybefore sampling.7.3 Hand-mixing7.3.1 GeneralMix the concrete batch on a non-absorbent surface using a shovel, trowel orsimilar tool.NOTE Hand-mixing is unlikely to produce a fully homogeneous and adequatelydispersed mix. Admixtures and some additions might not perform to their fullpotential and performance is likely
