ISO-679-1989.pdf

INTERNATIONAL STANDARD IS0 679 First edition 1989-07-15 Methods of testing cements - Determination of strength M6thodes dessai des ciments - D it allows the use of alter- native procedures only in well defined cases provided that they do not affect the results significantly as specified in clause 11. In the event of a dispute, only the reference procedure de- scribed in this International Standard shall be used, excluding any alternatives. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encour- aged toinvestjgate the possibility of applying ihe most recent editions of thi”ssJndards listed below. Members of IEC and IS0 maintain registers of currently valid International Standards. IS0 409-l : 1982, Metallic materials - Hardness test - Tables of Vickers hardness values for use in tests made on flat surfaces - Part 7 : HV 5 to HV 100. IS0 565 : 1983, Test sieves - Woven metal wire cloth, per- forated plate and electroformed sheet - Nominal sizes of openings. IS0 1101 : 1983, Technical drawings - Geometrical toleranc- ing - Tolerancing of form, orientation, location and run-out - Generalities, definitions, symbols, indications on drawings. IS0 1302 : 1978, Technical drawings - .Method of indicating surface texture on drawings. IS0 2591 : 1973, Test sieving. IS0 3310-l : 1982, Test sieves - Technical requirements and testing - Part 7 : Test sieves of metal wire cloth. IS0 4200 : 1985, Plain end steel tubes, welded and seamless - General tables of dimensions and masses per unit length. IS0 6507-l : 1982. Metallic materials - Hardness test - Vickers test - Part 1 : HV 5 to HV 100. 3 Principal features of method The method comprises the determination of the compressive, and optionally the flexural, strength of prismatic test specimens 40 mm x 40 mm X 160 mm in size. These specimens are cast from a batch of plastic mortar con- taining one part by mass of cement and three parts by mass of standard sand with a water/cement ratio of 0,5. Standard sands from various sources and countries may be used pro- vided that they have been shown to give cement strength results which do not differ significantly from those obtained using the IS0 Reference sand (see clause 11). The mortar is prepared by mechanical mixing and is compacted in a mould using standard jolting apparatus. Alternative com- paction equipment and techniques may be used provided that they have been shown to give cement strength results which do not differ significantly from those obtained using the stan- dard jolting apparatus (see clause 11). The specimens in the mould are stored in a moist atmosphere for 24 h and then the demoulded specimens are stored under water until strength testing. At the required age, the specimens are taken from their wet storage, broken in flexure into two halves and each half tested for strength in compression. 4 Laboratory and equipment 4.1 Laboratory The laboratory where preparation of specimens takes place shall be maintained at a temperature of 20 OC + 2 OC and a relative humidity of not less than 50 %. A laboratory temperature of 25 OC + 2 C or 27 C i 2 C may be maintained in warm countries, provided the temperature is stated in the test report. The moist air room or the large cabinet for storage of the specimens in the mould shall be continuously maintained at a temperature of 20 “C f 1 OC and a relative humidity of not less than 90 %. The temperature of the water in the storage containers shall be maintained at 20 OC + 1 OC. -,-,- IS0 679 : 1989 (E) The temperature of the moist air room or the large cabinet for storage and the temperature of the water in the storage con- tainers may be maintained at 25 “C f 1 OC or 27 OC 3 I OC in warm countries, provided the temperature is stated in the test report. The temperature and relative humidity of the air in the laboratory and the temperature of the storage containers shall be recorded at least once a day during working hours. The temperature and relative humidity of the moist air room or cabinet shall be recorded at least every4 h. Where temperature ranges are given, the target temperature at which the controls are setshall be the middle value of the range. 4.2 Equipment 4.2.1 General The tolerances shown on the drawings are important for cor- rect operation of the equipment in the test. When regular con- trol measurements show that the tolerances are not met, the equipment shall be rejected or adjusted or repaired where possible. Records of control measurements shall be kept. Acceptance measurements on new equipment shall cover mass, volume, and dimensions to the extent that these are in- dicated in this International Standard, paying particular atten- tion to those critical dimensions for which tolerances are specified. Bowl - In those cases where the material of the equipment can in- fluence the results, the material shall be specified. 4.2.2 Test sieves Wire cloth test sieves complying with the requirements of IS0 2591 and IS0 3310-I shall be of the nominal mesh sizes from IS0 565 given in table 1 (series R 20). Table 1 - Test sieves I Se Nominal mesh size mm 2 I,6 1 0,5 0,16 0.06 _- 4.2.3 Mixer The mixer (see figure 1) shall consist essentially of a) a stainless steel bowl with a capacity of about 5 I and of the general shape and size shown in figure 1, and provided with means by which it can be fixed securely to the mixer frame during mixing and by which the height of the bowl in Dimensions in millimetres Figure 1 - Mixer -,-,- IS0 679 : 1989 (El relation to the blade and, to some extent, the gap between possible to the wall. Simple tolerance gauges (“feeler gauges”) are blade and bowl can be finely adjusted and fixed; useful where direct measurement is difficult. b) a stainless steel blade of the general shape, size and tolerances shown in figure 1, revolving about its own axis as it is driven in a planetary movement around the axis of the bowl by an electric motor at controlled rotational frequen- cies. The two directions of rotation shall be opposite and the ratio between the two rotational frequencies shall not be a whole number. The mixer shall operate at the speeds given in table 2. Table 2 - Mixer blade speeds Values in reciprocal minutes I Speed I Rotation I Planetary movement I I Low High I 285 140 + I!Z 10 5 I 125 62+ + 10 5 I Where more than one mixer is used, blades and bowls shall form sets which are always used together. 4.2.4 Moulds The gap between blade and bowl shown in figure 1 shall be checked every month. NOTE - The gap indicated in figure 1 (3 mm + 1 mm) refers to the situation when the blade in the empty bowl is brought as close as The mould (see figure 2) shall consist of three horizontal com- partments so that three prismatic specimens 40 mm x 40 mm in cross-section and 160 mm in length can be prepared simultaneously. Dimensions in millimetres Striking off direction with sawing motion NOTE - Moulds and jolting tables from different manufacturers may have differing dimensions and unrelated part-weights, so compatibility should be specified by the purchaser. Figure 2 - Typical mould -,-,- IS0 679 : 1989 (El The mould shall be made of steel with wails at least 10 mm thick. The surface Vickers hardness of each internal side face shall be at least HV 200 (see IS0 408-l and IS0 6507-l). NOTE - A minimum Vickers hardness value of HV 400 is recom- mended. The mould shall be constructed in such a manner as to facilitate the removal of moulded specimens without damage. Each mould shall be provided with a machined steel or cast iron base plate. The mou, when assembled, shall be positively and rigidly held together and fixed to the base plate. The assembly shall be such that there is no distortion or leakage. The base plate shall make adequate contact with the table of the compacting apparatus and be rigid enough not to induce secondary vibrations. Each part of the mould shall be stamped with identifying marks to facilitate assembly and to ensure compliance with the specified tolerances. Similar parts of separate mould assemblies shall not be interchanged. The assembled mould shall comply with the following re- quirements : a) the internal dimensions and tolerances of each mould compartment, based on four symmetrically placed measurements, shall be as follows : length : 160 mm + 0,8 mm width : 40 mm I!Z 0,2 mm depth : 40,lmm + 0,l mm b) the flatness tolerance (see IS0 1101) over the whole of each internal side face shall be 0,03 mm; cl the perpendicularity tolerance (see IS0 1101) for each internal face with respect to the bottom surface of the mould and the adjacent internal face as datum faces shall be 0,2 mm; d) the surface texture of each internal side face shall be N 8 or less (see IS0 1302). Moulds shall be replaced when any one of the specified tolerances is exceeded. The mass of the mould shall accord with the requirement for the combined mass in 4.2.5. In assembling the cleaned mould ready for use, a suitable seal- ing material shall be used to coat the outer joints of the mould. A thin film of mould oil shall be applied to the internal faces of the mould. To facilitate the filling of the mould, a tightly fitting metal hop- per with vertical walls 20 mm to 40 mm in height shall be pro- vided. When viewed in plan, the hopper walls shall overlap the internal walls of the mould by not more than 1 mm. The outer walls of the hopper shall have a means of location to ensure correct positioning over the mould. For spreading and striking off the mortar, two spreaders and a metal straightedge of the type shown in figure 3 shall be pro- vided. 4.2.5 Jolting apparatus The jolting apparatus (see figure 4) shall comply with the following requirements. The apparatus consists essentiaily of a rectangular table rigidly connected by two light arms to a pivot at 800 mm from the centre of the table. The table shall incorporate at the centre of its lower face a projecting lug with a rounded face. Beneath the projecting lug shall be a small stop with a plane upper surface. In the rest position, the common perpendicular through the point of contact of the lug and stop shall be vertical. When the projecting lug rests on the stop, the top face of the table shall be horizontal so that the level of any of the four corners does not deviate from the mean level by more than 1 mm. The table shall have dimensions equal to or greater than those of the mould base plate, and a plane machined upper surface. Clamps shall be provided for firm attachment of the mould to the table. The combined mass of the table, including arms, empty mould, hopper and clamps shall be 20 kg + 0,5 kg. The arms connecting the table assembly to the pivot shall be rigid and constructed of round tubing with an outside diameter lying in the range 17 mm to 22 mm selected from tube sizes meeting the specifications of IS0 4200. The total mass of the two arms, including any cross-bracing, shall be 2,25 kg + 0,25 kg. The pivot bearings shall be of ball or roller type and protected from ingress of grit or dust. The horizontal displacement of the centre of the table as caused by the play of the pivot shall not exceed 1 mm. The lug and the stop shall be made of through-hardened steel of at least HV 500 Vickers hardness value (see IS0 409-I). The curvature of the lug shall be about 0,Ol mm -1. In operation, the table is raised by a cam and allowed to fall freely from a height of 15 mm IL 0,3 mm before the lug strikes the stop. The cam shall be made of steel of at least HV 400 Vickers hard- ness value and its shaft shall be mounted in ball bearings of such construction that the free drop requirement of 15 mm 91 0,3 mm is always satisfied. The cam follower shall be of a construction which ensures least wear of the cam. The cam shall be driven by an electric motor of about 250 W through reduction gear at a uniform speed of 1 r/s. A control mechanism and a counter shall be provided which ensure that one period of jolting of 60 s IL 3 s comprises exactly 60 jolts. The position of the mould on the table shall be such that the longitudinal dimension of the compartments is in line with the direction of the arms and perpendicular to the axis of rotation of the cam. Suitable reference marks shall be provided to facilitate the positioning of the mould in such a way that the centre of the central compartment is directly above the point of impact. The apparatus shall be firmly mounted on a concrete block of about 600 kg mass and of about 0,25 msvolume and of dimen- sions giving a suitable working height for the mould. The entire -,-,- IS0 679: 1989 (E) 38 H: height of hopper a) Large spreader Dimensions in millimetres b) Small spreader cl Straightedge (approximate dimensions) Figure 3 - Typical spreaders and metal straightedge base of the concrete block shall stand on an elastic pad, e.g. natural rubber, having a suitable isolation efficiency preventing external vibrations from affecting the compaction. The bases of the apparatus shall be fixed level to the concrete base by anchor bolts and a thin layer of mortar shall be placed between the base of the apparatus and the concrete base to en- sure overall and vibration-free contact. 4.2.6 Flexural strength test machine The test machine for the determination of flexural strength shall be capable of applying loads up to 10 kN, with an accuracy of the type of material used for the bags shall have no effect on the results of the strength test. 5.2 Cement When the cement to be tested is kept for more than 24 h be- tween sampling and testing, it shall be stored in completely filled and air-tight containers made from a material which does not react with cement. 5.3 Water Distilled water shall be used for reference testing. For other tests, drinking water may be used. 6 Preparation of mortar 6.1 Composition The proportions by mass shall be one part of the cement (5.2). three parts of Standard sand (5.11, and one half part of water (5.3) (water/cement ratio = 0,5). Each batch for three test specimens shall consist of 450 g f 2 g of cement, 1 350 g IL 5 g of sand, and 225 g IL 1 g of water. 6.2 Batching The cement, sand, water and apparatus shall be at the laboratory temperature (see 4. I). Carry out weighing by means of a balance accurate to rt 1 g. When water is added from automatic 225 ml pipettes, they shall be accurate to + 1 ml. 6.3 Mixing Mix each batch of mortar mechanically using the mixer (4.2.3). With the mixer in the operating position, proceed as follows. Pour the water into the bowl and add the cement. Then start the mixer immediately