BS 1881-121-1983 Testing concrete - Method for determination of static modulus of elasticity in compression《混凝土试验 第121部分 静态压缩弹性模量的测定方法》.pdf

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1、BRITISH STANDARD BS 1881-121: 1983 Testing concrete Part 121: Method for determination of static modulus of elasticity in compression UDC 666.972.017:691.32:620.1BS 1881-121:1983 This British Standard, having been prepared under the direction of the Cement, Gypsum, Aggregates and Quarry Products Sta

2、ndards Committee, was published under the authority of the Board of BSI and comes into effect on 31 January 1983 BSI 12-1998 The following BSI references relate to the work on this standard: Committee reference CAB/4 Draft for comment 80/14205 DC ISBN 0 580 12958 6 Cooperating organizations The Ceme

3、nt, Gypsum, Aggregates and Quarry Products Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following: The organizations marked with an asterisk in the above list, together with the following, were directly represented on the Technic

4、al Committee entrusted with the preparation of this British Standard: Association of Consulting Engineers Federation of Civil Engineering Contractors* Association of County Councils Gypsum Products Development Association Association of District Councils Institute of Quarrying Association of Metropo

5、litan Authorities Institution of Highway Engineers* Autoclaved Aerated Concrete Products Institution of Municipal Engineers* Association Institution of Public Health Engineers British Precast Concrete Federation Ltd.* Institution of Structural Engineers* British Quarrying and Slag Federation* Instit

6、ution of Water Engineers and Scientists* British Railways Board National Federation of Building Trades British Ready Mixed Concrete Association* Employers* British Steel Industry Natural Environment Research Council Cement Admixtures Association (Institute of Geological Science) Cement and Concrete

7、Association* Royal Institute of British Architects* Cement Makers Federation* Royal Institution of Chartered Surveyors* Chemical Industries Association Sand and Ballast Hauliers and Allied Concrete Society Limited* Trades Alliance County Surveyors Society* Sand and Gravel Association Limited* Depart

8、ment of the Environment Society of Chemical Industry* (Building Research Establishment)* Stone Federation Department of the Environment (PSA)* Department of the Environment (Transport and Road Research Laboratory)* Department of Transport* British Civil Engineering Test Equipment Greater London Coun

9、cil Manufacturers Association Institute of Concrete Technology Electricity Supply Industry in England and Coopted member Wales Amendments issued since publication Amd. No. Date of issue CommentsBS 1881-121:1983 BSI 12-1998 i Contents Page Cooperating organization Inside front cover Foreword ii 1 Sco

10、pe 3 2 Definitions 3 3 Apparatus 3 4 Test specimens 3 5 Procedure 4 6 Calculation and expression of results 4 7 Test report 4 Publications referred to Inside back coverBS 1881-121:1983 ii BSI 12-1998 Foreword This Part of this standard, prepared under the direction of the Cement, Gypsum, Aggregates

11、and Quarry Products Standards Committee, is a revision of clause3 of BS1881-5:1970 which has been deleted by Amendment No.1 to that standard. This static modulus of elasticity test is taken direct, with minor deviations, from ISO6784, published by the International Organization for Standardization(I

12、SO), which adopted a UK draft. No estimate of repeatability or reproducibility is given in this Part of this British Standard. Reference should be made to BS5497-1 for further information on the determination of repeatability and reproducibility. A British Standard does not purport to include all th

13、e 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,

14、 pages 1 to 6, 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 theinside front cover.BS 1881-121:1983 BSI 12-1998 1 TESTING CONCRETE SUMMARY OF PUBLISHED BRITISH STAN

15、DARDS Due to the present restructuring of BS1881 Methods of testing concrete and BS4408 Recommendations for non-destructive methods of test for concrete, the following information has been published, to help keep readers up-to-date, with the situation so far. (February1983). BS 1881-1:1970 Method of

16、 sampling fresh concrete on site Method of mixing and sampling fresh concrete in the laboratory BS 1881-2:1970 Slump test Compacting factor test “VB” consistometer test Method for determination of weight per cubic metre of fresh concrete Method for determination of air content of fresh concrete Anal

17、ysis of fresh concrete BS 1881-3:1970 Making and curing test cubes Making and curing no-fines test cubes Making and curing test beams Making and curing test cylinders Method for accelerating the curing of test specimens: 1) the 55C method 2) the 82C method BS 1881-5:1970 Method for determination of

18、the dynamic modulus of elasticity by an electrodynamic method Method for determination of changes in length of concrete prisms (initial drying shrinkage, drying shrinkage and wetting expansion) Method for determination of initial surface absorption BS 1881-6:1971 Analysis of hardened concrete BS 188

19、1-114:1983 Method for determination of density of hardened concrete BS 1881-115:1983 Specification for compression testing machines for concrete BS 1881-116:1983 Method for determination of compressive strength of concrete cubes BS 1881-117:1983 Method for determination of tensile splitting strength

20、 BS 1881-118:1983 Method for determination of flexural strength BS 1881-119:1983 Method for determination of compressive strength using portions of beams broken in flexure (equivalent cube method) BS 1881-120:1983 Method for determination of the compressive strength of concrete cones BS 1881-121:198

21、3 Method for determination of static modulus of elasticity in compression BS 1881-122:1983 Method for determination of water absorption BS 4408-1:1969 Electromagnetic cover measuring devices BS 4408-2:1969 Strain gauges for concrete investigations BS 4408-3:1970 Gamma radiography of concrete BS 4408

22、-4:1971 Surface hardness methods of testing concrete BS 4408-5:1974 Measurement of the velocity of ultrasonic pulses in concrete.2 blankBS 1881-121:1983 BSI 12-1998 3 1 Scope This Part of this British Standard describes a method for the determination of the static modulus of elasticity in compressio

23、n of hardened concrete, on test specimens which may be cast or taken from a structure. 2 Definitions For the purposes of this Part of this standard the definitions in BS5328 apply together with the following. static modulus of elasticity in compression the secant modulus, which, in newtons per squar

24、e millimetre, is calculated from the formula: where D sand D eare the differences in stress and strain, respectively, between a basic loading level of0.5N/mm 2and an upper loading level of one-third of the compressive strength of the concrete 3 Apparatus 3.1 Compression testing machine. The machine

25、shall comply with BS1881-115 for compression testing machines. It shall be capable of applying the load at the specified rate and maintaining it at the required level. 3.2 Strain measuring apparatus. The strain measuring apparatus shall have an accuracy of 5 micro strain. Instruments for measuring l

26、ength (for example mirror or dial gauge extensometers, resistance strain gauges, inductance gauges, vibrating wire strain gauges) shall have a gauge length of not less than two-thirds of the width or diameter of the test specimen (2/3d) and shall be attached in such a way that the gauge points are e

27、quidistant from the two ends of the specimen and at a distance not less than one-quarter of the length of the test specimen (L/4) from its ends. At least one pair of measurements shall be taken on opposite sides of the specimen. With rectangular specimens cast in a horizontal position, the gauge len

28、gths should be arranged on the vertical sides as cast. NOTEWhere fixing points for extensometers are required, threaded inserts cast into the specimen are preferred. If adhesives are used for the fixing points they should be rapid setting and set hard. The specimen shall be removed from the curing t

29、ank for as short a time as possible to allow the surface to be dried for the application of adhesive. Specimens shall not be less than 7days old when removed for this purpose. Specimens shall be re-immersed in water for a minimum of 12h before testing. 4 Test specimens 4.1 General. A minimum of four

30、 moulded specimens shall be made. Three of these shall be used to determine the mean compressive strength or alternatively, three extra cubes may be made at the same time as the specimens for this test and tested to obtain the compressive strength of the concrete. For specimens taken from a structur

31、e the compressive strength may be estimated from other information available. NOTEMoulded test specimens should preferably be cylinders 150mm in diameter and 300mm in height. Alternatively, other test specimens may be used, provided that the length to diameter ratio, l/d is not less than2 nor more t

32、han5, where l is the length and d the diameter, or, for a square cross-section, d is the width of one face of the specimen. The minimum dimensions of moulded specimens shall be 100mm or at least four times the nominal maximum size of aggregate in the concrete whichever is the larger. In the case of

33、specimens drilled or cut out of a structure or other sample of concrete these dimensions shall be not less than three times the nominal maximum size of aggregate in the concrete nor less than 100mm. 4.2 Preparation of test specimens 4.2.1 Moulded test specimens (beams or cylinders) shall be made, cu

34、red and stored in accordance with the relevant Parts of this standard. In addition, for cylindrical specimens, whilst the concrete is still plastic first finish the surface of the concrete level with the top of the mould and then press the top plate, coated with a thin film of mould oil, down on to

35、the concrete with a rotary motion until it makes complete contact with the rim of the mould. Attach the top plate rigidly to the top of the mould and lay the mould, with top and base plates, with its axis horizontal on supports which prevent any movement. Lightly tap the capping plate to ensure good

36、 contact with the trowelled surface of the concrete. Allow the cylinder to harden in a horizontal position until it is removed from the mould. 4.2.2 Specimens drilled as cores from a structure shall be drilled, stored and their ends prepared by grinding or capping in accordance with Part120 of this

37、standard. Ds De -BS 1881-121:1983 4 BSI 12-1998 4.2.3 Unless rectangular moulded specimens comply with the dimensional tolerances in4.3, their ends and those of other sawn specimens shall be ground to conform with the tolerances. NOTEMoulds for beams do not necessarily conform with the squareness to

38、lerance for the end face relative to the axis. 4.3 Tolerances. The tolerances in accordance with BS 308-3 of the prepared specimens shall be as follows. a) Flatness. The flatness tolerance for the prepared end surfaces shall be 0.06mm wide. b) Squareness. The squareness tolerance (squareness3 of BS3

39、08-3) for the end prepared first with respect to the axis of the specimen as datum axis shall be 2.0mm wide. c) Parallelism. The parallelism tolerance (parallelism4 of BS308-3) for the prepared surface with respect to the opposite surface of the specimen as datum face shall be 2.0mm wide for all spe

40、cimens. For rectangular specimens, the parallelism tolerance of opposite sides of the specimen shall also be 2.0mm wide. d) Cylindricity. The cylindricity tolerance for moulded cylindrical specimens shall be 2.0mm or as given inBS1881-120. 4.4 Density. Measure the as-received or saturated density of

41、 the specimens by the method described inBS1881-114. 5 Procedure 5.1 Determination of compressive strength. All specimens shall be tested in a moist condition. Determine the compressive strength of the concrete on three companion specimens, from the same batch as those to be used for the determinati

42、on of the static modulus of elasticity, and made and cured under similar conditions, by the compression test carried out in accordance withBS1881-116. NOTEAlternatively, the compressive strength may be estimated on other information available, e.g. from cube strengths and the basis of the estimate r

43、eported. The mean value of the compressive strength, f c , determines the stress applied in the determination of static modulus of elasticity. 5.2 Determination of static modulus of elasticity. Place the test specimen, with the measuring instruments or fixing points attached axially, centrally in th

44、e machine. Apply the basic stress of 0.5N/mm 2(s b ), and record the strain gauge readings taken at each measurement line. Steadily increase the stress at a constant rate within the range 0.6 0.4N/(mm 2 s) until the stress equal to one-third of the compressive strength of the concrete (s a = f c /3)

45、 is reached. NOTEThe preferred rate is 0.6N/(mm 2 s). Maintain the stress for 60s and record the strain readings taken during the succeeding 30s at each measurement line. If the individual strains are not within a range of 10% of their mean value at s a , recentre the test specimen and repeat the te

46、st. If it is not possible to reduce the differences to within this range, do not proceed with the test. When the centring is sufficiently accurate reduce the load, at the same rate as during loading, to the level of the basic stress. Carry out at least two additional preloading cycles, using the sam

47、e loading and unloading rate, and maintaining the stress (s aand s b ) constant for a period of 60s. After completion of the last preloading cycle and a waiting period of 60s under the stress s b =0.5 N/mm 2 , at the various measurement lines record the strain reading, e b , taken during the succeed

48、ing 30s. Reload the specimen to stress s aat the specified rate, and at the various measurement lines record the strain reading e a , taken within30s. When all elasticity measurements have been completed, increase the load on the test specimen, at the specified rate, until failure of the specimen oc

49、curs. If the compressive strength of the specimen differs from f cby more than 20%, this shall be noted in the test report. 6 Calculation and expression of results Calculate the mean strain e aand e brespectively. The static modulus of elasticity in compression E c(inN/mm 2 ) is given by the formula where Express the result to the nearest 500N/mm 2for values over 10000 N/mm 2 , and to the nearest 100N/mm 2for values below 10000 N/mm 2 . 7 Test report 7.1 General. The test report shall affirm that the tests were carried out in accordance with this Part of this standa