BS 4550-3 4-1978 Methods of testing cement - Physical tests - Strength tests《水泥的试验方法 物理试验 强度试验》.pdf

1、BRITISH STANDARD BS 4550-3.4: 1978 (Reprinted, incorporating Amendments No. 1, No. 2 and No. 3) Methods of testing cement Part 3: Physical tests Section 3.4 Strength tests IMPORTANT NOTEIt is recommended that this Section be read in conjunction with the information in the “General Introduction” to B

2、S4550 and with the information in BS4550-3.1, which are both issued separately. UDC 666.94.01:620.1:539.4BS4550-3.4:1978 This British Standard, having been prepared under the directionof the Cement, Gypsum,Aggregates and QuarryProducts Standards Committee, was published underthe authority of the Exe

3、cutive Board on 30 June 1978 BSI 02-1999 The following BSI references relate to the work on this standard: Committee reference CAB/1 Draft for comment 73/10751 DC ISBN 0 580 10139 8 Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to10, an inside

4、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. Amendments issued since publication Amd. No. Date of issue Comments 4247 May 1983 4498 March 1984 5704 J

5、uly 1988 Indicated by a sideline in the marginBS4550-3.4:1978 BSI 02-1999 i Contents Page 1 Compressive strength of concrete cubes 1 1.1 Test principle 1 1.2 References 1 1.3 Apparatus 1 1.4 Temperature and humidity conditions 2 1.5 Preparation of specimens 2 1.6 Storage of specimens 2 1.7 Testing o

6、f specimens 3 1.8 Calculation 3 1.9 Report 3 2 Compressive strength of mortar cubes 3 2.1 Test principle 3 2.2 References 3 2.3 Apparatus 3 2.4 Temperature and humidity conditions 5 2.5 Preparation of specimens 5 2.6 Storage of specimens 5 2.7 Testing of specimens 6 2.8 Calculation 6 2.9 Report 6 Fi

7、gure 1 Typical rotating pan concrete mixer 7 Figure 2 Suitable trowel 8 Figure 3 Typical vibration machine for compacting mortar cubes 9 Table 1 Temperature and humidity conditions 2 Table 2 Mixes for concrete cubes 3 Table 3 Masses of individual fractions of sand 3 Table 4 Temperature and humidity

8、conditions 5 Table 5 Mixes for mortar cubes 5 Publications referred to Inside back coverii blankBS4550-3.4:1978 BSI 02-1999 1 1 Compressive strength of concrete cubes 1.1 Test principle. The strength of cement is determined by compressive strength tests on100mm concrete cubes, made with specified co

9、arse and fine aggregates, mixed by machine and compacted manually with a compacting bar. 1.3 Apparatus. The following apparatus is required. 1.3.1 Moulds. The moulds shall be of 100mm cube size complying with 3.1 of BS1881-108:1983. 1.3.1.1 Size. The moulds shall be 100mm cubes. 1.3.1.2 Construction

10、. The mould shall be of ferrous metal (preferably cast iron or cast steel) and rigid enough to prevent distortion. The surface hardness of each internal face shall be at least 95 Rockwell (Scale B) hardness value. It shall be constructed in such a manner that it facilitates the removal of the moulde

11、d specimen without damage. The parts of the mould, when assembled, shall be positively and rigidly held together by suitable means, both during the filling and on subsequent handling of the filled mould. Each mould shall be provided with a steel base plate which shall be rigidly attached to the moul

12、d and shall support it without leakage or distortion. 1.3.1.3 Tolerances. The mould shall be such that, when assembled ready for use, the dimensions and internal faces are accurate within the following limits. a) Dimensions. The depth of the mould and the distance between either pair of opposite int

13、ernal faces, each based on the average of four symmetrically placed measurements, shall be100.00 0.15mm. b) Flatness. The surface of each internal face shall lie between two parallel planes 0.03mm apart. The joints between the sections of the mould and between the bottom surface of the mould and the

14、 top surface of the base plate shall lie between two parallel planes 0.06mm apart. c) Squareness. The surface of each internal face shall lie between two parallel planes 0.5mm apart which are perpendicular to the bottom surface of the mould and also to the adjacent internal faces. d) Parallelism. Th

15、e top surface of the mould shall lie between two parallel planes 1.0mm apart, parallel to the bottom surface. e) Surface texture. The surface texture of each internal face shall be3.2 4m CLA. 1.3.1.4 Assembly. In assembling the cleaned mould ready for use, the joints between the sections of the moul

16、d and between the bottom of the mould and the base plate shall be sealed by a thin film of grease or other suitable method to prevent escape of water. Any excess grease shall be carefully removed. The internal faces of the assembled mould shall be thinly coated with mould oil to prevent adhesion of

17、the concrete. 1.3.2 Mixer. The concrete mixer 1)shall be of suitable capacity to mix a complete batch in one operation. It shall comprise a rotating mixing pan with a contra-rotating mixing paddle and a scraper blade. The sizes and tolerances shall be as shown inFigure 1. The mixing pan (preferably

18、removable) shall rotate at 18 1 r/min. The mixing paddle (offset from the pan centre) shall rotate at 905r/min. The mixing paddle and scraper blade shall be positively spring loaded to ensure they do not jam during mixing. Simple and positive means of vertical adjustment shall be provided on the mou

19、ntings of the mixing paddle and scraper blade. The clearances F 1 , F 2and G shall be checked every month or after every 100 mixing operations whichever represents the more frequent use. The mixer shall preferably be fitted with an automatic timing device otherwise a stop clock shall be provided. 1.

20、3.3 Trowel. The trowel shall have a cast steel blade; a suitable type is shown in Figure 2. 1.3.4 Compacting bar. The compacting bar shall be a steel bar weighing 1.8 0.1 kg and having a ramming face 25.0 0.5mm square. 1.3.5 Tank. The tank shall contain clean tap water, which shall be renewed at lea

21、st every seven days with water at the specified temperature. Specimens made with high alumina, supersulphated or Portland-type cements shall not be placed in the same tank. 1) For information on the availability of suitable mixers apply to Enquiry Section, BSI, Linford Wood, Milton Keynes MK 14 6LE,

22、 enclosing a stamped addressed envelope for reply.BS4550-3.4:1978 2 BSI 02-1999 1.3.6 Compression testing machine. The compression testing machine shall be of suitable capacity 2)for the test and shall comply with BS1881-115. Over the scale range(s) used, the machine shall be capable of applying loa

23、d at the rate given in1.7 and shall comply with grade 1.0 of BS1610-1:1985 as regards repeatability and accuracy. The lower limit of verification for the scale range used shall be below the expected maximum load on any specimen tested on that scale range. 1.4 Temperature and humidity conditions. The

24、 temperature throughout the entire test procedure shall be controlled about a midpoint of 20C with permitted variations as shown in Table 1. The minimum relative humidity shall be as given in Table 1. Table 1 Temperature and humidity conditions Before use, all materials, moulds and other appliances

25、shall be brought to the same temperature as the air in the mixing room, by storing them in the room for a sufficient time. 1.5 Preparation of specimens. The specimens shall be prepared as follows. 1.5.1 Number of cubes. Make batches of six, nine or twelve cubes, three for testing at each of the spec

26、ified ages. 1.5.2 Aggregates. The coarse aggregate and the sand shall comply with the requirements of Part4 and Part5 of this British Standard. Sieve the coarse aggregate on 10mm and 5mm sieves with square holes so that it is substantially free from oversized and undersized particles. 1.5.3 Proporti

27、oning. The masses of the individual materials for batches of six or nine cubes are given inTable 2 and Table 3. 1.5.4 Mixing. Place the weighed materials in the mixer pan in the following order: sand, cement, coarse aggregate. Hold the mixing water ready and start the mixer. After 15s add the water

28、uniformly during the next15s; then continue mixing for a total time of180 5s. After the machine mixing turn the concrete over in the pan a few times with a trowel to remove any slight segregation. If this is not possible, transfer the concrete to another suitable vessel and turn it over similarly th

29、erein. 1.5.5 Compacting. Half fill the cube moulds as quickly as possible. Compact each with exactly35strokes of the compacting bar, uniformly distributed over the cross section of the mould. Place a further quantity of concrete in each mould to form the top layer and compact similarly. Then strike

30、off the top of each cube and smooth with the trowel so that the surface of the concrete is level with the top of the mould. Complete the entire operation within15min from the completion of the mixing. 1.6 Storage of specimens. Immediately after preparation, place the moulds in a single layer on a le

31、vel surface in the moist curing chamber. In order to reduce evaporation, cover the exposed top of the cubes with a flat impervious sheet (e.g. of clean thin rubber or plastics, or lightly oiled steel) making contact with the upper edge of the mould. After24 0.5h mark the cubes for later identificati

32、on and remove from the moulds 3) . Immediately submerge all specimens, except those to be tested at 24h, in the tank and arrange them in such a way that the temperature variation specified in Table 1 is not exceeded. Leave the cubes in the tank until just prior to the test. Specimens to be tested at

33、 24h are marked and demoulded 3)15min to 20min before the test and are covered with a damp cloth so that they remain in the moist condition. If the concrete has not achieved sufficient strength after 24h to be handled without fear of damage, delay the demoulding for a further period of 24h but state

34、 this fact in the test report. 2) i.e. that the expected maximum load on a specimen lies between 20% and 100% of the selected scale range of the machine. Situation Permitted temperature variation Minimum relative humidity Mixing room Moist curing chamber Water curing tank Compression testing room C

35、2 1 1 2 % 50 90 50 NOTE 1A record should be kept for reference purposes of the actual temperature and relative humidity conditions. NOTE 2The high humidity required in moist air curing rooms is normally produced by spraying water as a fine aerosol. The bacterium Legionella pneumophila is widespread

36、in nature and is present in the water systems of many buildings. Scale in pipework and chemical nutrients in the water supply may encourage growth of this organism which multiplies between25C and about 45C. Inhaling infected aerosols is a known route for transmission of legionellosis. It is therefor

37、e advisable to maintain cold water supplies below 20C where possible and to store hot water above 60C. Cold water supplies may be disinfected by chlorination to at least 5mg/L free chlorine. Regular periodic checking for the presence of Legionella species in industrial water supplies is a sensible p

38、recaution. 3) It is recommended that the cubes should be weighed at this stage since this may reveal errors in the procedure at an early stage.BS4550-3.4:1978 BSI 02-1999 3 Table 2 Mixes for concrete cubes Table 3 Mass of individual fractions of sand 1.7 Testing of specimens. Determine the compressi

39、ve strength of the cubes, under the temperature and relative humidity conditions specified in Table 1 for the compression testing room, at the specified age, calculated from the time of adding the water to the other materials, by the procedure specified in clauses 5 to 8 of BS 1881-116:1983 except t

40、hat the load shall be applied at a rate of approximately 0.25N/(mm 2 s) and using the auxiliary platens. Test the specimens within the following limits: 24 0.5h 3 days (721h) 7 days (168 2h) and 28 days (28 days4h) 1.8 Calculation. Calculate the average of the individual results of the set of three

41、specimens tested at the same age, and express the result to the nearest 0.5N/mm 2 . If one result within the set varies by more than 5% from the average of the set, discard the result and recalculate the average of the remaining results. If more than one result varies by more than 5% from the averag

42、e, discard the set of results. 1.9 Report. Report the individual results and the average compressive strength to the nearest 0.5N/mm 2 , indicating if any result has been discarded. 2 Compressive strength of mortar cubes 2.1 Test principle. The strength of cement is determined by compressive strengt

43、h tests on70.7mm mortar cubes, made with a specified sand, mixed by hand and compacted by means of a standard vibration machine. 2.2 References. The titles of the standards publications referred to in this clause of this Section are listed on the inside back cover. 2.3 Apparatus. The following appar

44、atus is required. 2.3.1 Moulds 2.3.1.1 Size. The moulds shall be 70.7mm cubes, the area of each face being 5000mm 2 . Mix type (seenote to 1.1) Material Proportions by mass Mass 6 cubes 9 cubes 12 cubes g g g C1 Cement Sand Coarse aggregate Water 1.0 2.5 3.5 0.60 2200 5 5500 7700 10 1320 5 3200 5 80

45、00 11200 10 1920 5 4200 5 10500 14700 10 2520 5 C2 Cement Sand Coarse aggregate Water 1.0 2.5 3.5 0.55 2200 5 5500 7700 10 1210 5 3200 5 8000 11200 10 1760 5 4200 5 10500 14700 10 2310 5 C3 Cement Sand Coarse aggregate Water 1.0 1.875 2.625 0.45 2940 5 5500 7700 10 1320 5 4270 5 8000 11200 10 1920 5

46、 5600 5 10500 14700 10 2520 5 Mass 6 cubes 9 cubes 12 cubes g g g Fraction A (2.36mm to 1.18mm) B (1.18mm to 600 4m) C (600 4m to 300 4m) D (300 4m to 150 4m) E (150 4m to 90 4m) 550 5 1100 5 1650 5 1375 5 825 5 800 5 1600 5 2400 5 2000 5 1200 5 1050 5 2100 5 3150 5 2625 5 1575 5BS4550-3.4:1978 4 BS

47、I 02-1999 2.3.1.2 Construction. The mould shall be of metal that is not attacked by cement mortar and rigid enough to prevent distortion. It shall be constructed in such a manner as to facilitate the removal of the moulded specimen without damage. The parts of the mould, when assembled, shall be pos

48、itively and rigidly held together, by suitable means, both during the filling and on subsequent handling of the filled mould. Each mould shall be provided with a steel base plate to support it without leakage. The weight of the mould and base plate shall be such as to comply with the requirements gi

49、ven in2.3.3, for the mass of the machine. 2.3.1.3 Tolerances. The mould shall be such that, when assembled ready for use, the dimensions and internal faces are accurate within the following limits: a) Dimensions. The depth of the mould and the distance between either pair of opposite internal faces, each based on the average of four symmetrically placed measurements, is70.7 0.1mm 4) . b) Flatness. The surface of each internal face shall lie betwe