MS 76-1972

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MS 76 : 1972 ICS : 91.100.15

SPECIFICATION FOR BRICKS AND BLOCKS OF FIRED

BRICKEARTH, CLAY OR SHALE

PART 2 : METRIC UNITS

MALAYSIAN

STANDARD

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BRICKS AND BLOCKS OF FIRED

BRICKEARTH, CLAY OR SHALE

PART 2. METRIC UNITS

MS 76:1972

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This Malaysian Standard, which had been approved by the Civil Engineering and Building Construction Industry Standards Committee and endorsed by the Standards Council, was published under the authority of the Standards Council in June, 1972.

SIM wishes to draw attention to the fact that this Malaysian Standard does not purport to include all the necessary provisions of a contract.

Malaysian Standards are subject to periodical review to keep abreast of progress in the industries concerned. Suggestions for

im-provements will be recorded and in due course brought to the notice of the Committee charged with the revision of the Standards to which they refer,

The following SIM references relate to the work on this standard: Committee Reference: SIM/I/7/018

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Test

... ... ... ... ... ... 53

43. Compliance ... ... ... ... ... ... ... 55

44. Procedure in the Event of Dispute ... ... ... 55

45. Cost of Testing ... ... ... ... ... ... 56

Appendix A. Application of Works Quality Control Scheme

for Dimensions ... ... ... ... ... 57

Appendix B. Choice of Limits and Acceptance Clauses for

Dimensions of Bricks ... ... ... ... 64

Table 1. Standard Formats (Bricks) ... ... ... ... 17

Table 2. Standard Formats (Blocks) ... ... ... ... 17

Table 3. Dimensional Tolerances (Bricks) ... ... ... 1 8

Table 4. Dimensional Tolerances (B!ocks) ... ... ... 19

Table 5. Maximum Deviations on Dimensions 21

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Table 7. Standard Formats (Floor Blocks) ... ... ... 27

Table 8. Limits for Use With Gauge Board ... ... 63

Table 9. Limits for Use With Alternative Scale for

Gauge Board ... ... ... ... ... ... 63

Figure 1. Arrangements for Measuring Clay Building Bricks

(a) for Length, (b) for Width, (c) for Depth ... 66

Figure 2. Determination of ‘Out of Squareness’ and

‘Bowing or Twisting’ of Hollow Blocks ... 67

Figure 3. Apparatus for Vacuum Absorption Test ... 68

Figure 4. Apparatus for Efliorescence Test ... ... ... 68

Figure 5. Gauge Board for Measuring Bricks ... ... 69

Figure 6. Double Bricks Referred to in Note 3,

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Committee Representation

The Civil Engineering and Building Construction Industry Stand-ards Committee under whose supervision this Malaysian Standard was prepared, comprises representatives from the following Government Ministries, trade commerce and manufacturer Association and scientific and professional bodies.

Association of Consulting Engineers (Malaysia) Cement & Concrete Association, Malaysia Federation of Malaysian Manufacturers Institution of Engineers (Malaysia)

Institution of Surveyors, Malaysia Malaysian Institute of Architects Malaysian Scientific Association Master Builders Association

Ministry of Agriculture and Lands Ministry of Commerce and Industry Ministry of Education

Ministry of Technology Research, & Local Government Ministry of Works, Posts and Telecommunications

(Public Works Department) United Chambers of Commerce University of Malaysia

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FOREWORD

This Malaysian Standard has been prepared under the authority of the Civil Engineering and Building Construction Industry Standards Committee. It is based on BS 3921: Part 2: 1969 which has been published in metric units, in view of the fact that the country is contemplating changing over to metric. In the interim, however, values given in imperial units within brackets may be used. But one system of units should be adhered to throughout for consistency, and the values within brackets have been extracted from the corresponding BS 3921 : 1965 which has become Part 1 of the corresponding British Standard.

The technical difficulties in the way of a standard which shall give useful guidance on the quality of all the many varieties of fired clay bricks and blocks are so great that it is still not possible to specify completely every point of importance. Nevertheless, the com-mittee considered that the standard should provide as much guidance as possible, even though some of the quality clauses will require re-vision in the light of further knowledge. The main issues raised by this standard are discussed in the following paragraphs.

Attempts to ascertain the quality of clay bricks and blocks by infrequent sampling and testing to a specification of isolated batches are subject to uncertainty because the properties of clay products, like those of other manufactured products, are liable to variations over a long period, as a result of changes in the naturally variable raw materials, as well as process variations of products made at any one time, it is therefore good manufacturing technique to sample and test products regularly and to record the results in the form of control charts on the principles discussed in BS 2564, ‘Control chart technique when manufacturing to a specification’ and in Appendices A and B. Such

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charts display the variation of properties with time and thus give more information about a product than can be obtained by tests made on a single occasion. It is recommended that manufacturers should make their control charts available for inspection by users and that users should recognize their value. This recommendation shall not preclude users from taking samples in accordance with Clauses 33 and 34 for testing in accordance with the remaining Clauses of Chapter 3. Any such samples that users may require shall be taken before the bricks or blocks are built into work, especially where tests for soluble salts content or liability to efflorescence are in question.

The treatment of strength in the specific clauses reflects the fact, still not as widely appreciated as it should be, that strength is not necessarily an index of durability and may be very misleading if used as such. The main use of the strength test is as a guide to permissible pressure in brickwork.

In the past, the permissible pressures on brickwork have been calculated, in accordance with British Standard CPI 11: 1948, ‘Struc-tural recommendations for loadbearing walls’, in terms of the mean strength of samples of twelve bricks taken at random and of the mortar composition. Variation in the strength of bricks and mortar and in workmanship have been allowed for by using high load factors. Re-cently, calculated loadbearing brickwork has begun to be treated like other structural engineering materials and designed to finer limits. Where this is to be done, it is desirable that the bricks used should be manufactured under a system of quality control on a sound statistical basis which enables the manufacturer to satisfy the user that he can supply consignments such that, when a sample is tested in accordance with Clause 39, there is a specified probability, normally of not more than I in 40, that the arithmetic mean of the sample will be below a specified limit of compressive strength.

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The water absorption test also is given less prominence than has often been accorded to it. A low water absorption figure can be used in defining engineering bricks and bricks for damp-proof courses but water absorption, like strength, is not a general index of durability. With many, but not all, clays, the more durable bricks absorb less water than those that are not so durable, so long as a single variety of bricks is considered. No limit can be set, however, that will dis-criminate generally between durable and non-durable bricks. Recent work has shown that the saturation coefficient, or ratio or 24-how cold absorption to a total absorption by the boiling or vacuum methods, is less useful as an index of durability than was formerly thought. II has not, therefore, been included. The vacuum method has been spe-cified as an alternative to the boiling method, since some laboratories regard it as more convenient and the results are approximately equivalent. The method of measuring 24-hour cold absorption has also been included in Clause 40, since this may occasionally he found useful for works control, but no specific requirements based on this test are in-cluded in Section Two of Chapter 1.

The committee has given serious consideration to the problem of framing a specification which is based on the knowledge that bricks containing undue amounts of calcium, magnesium, potassium and sodium suiphates are liable to produce complaints about walls built with them. The complaints may be of two kinds: sulphate expansion of Portland cement mortar and efflorescence on brickwork.

Although cause and effect have been established broadly, conS siderable difficulty has arisen when trying to decide what are suitable maximum limits for the permissible contents or calcium, magnesium, potassium, sodium and sulphate individually or in toto. In some cir-cumstances it would appear that bricks with a total soluble sulphate

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content of well under 1% have given severe trouble in sulphate expan-sion: in others, bricks with soluble salt contents of as much as three times this amount have been used without arousing comment. The same sort of evidence has been forthcoming on particular salts, e g

potassium sulphate. For instance there has been complete absence of complaints over extended periods when bricks containing 0.25% soluble potassium have been used. Elsewhere trouble has arisen with bricks containing less than 0.25%. In these circumstances it has been con-sidered unreasonable to set a maximum of 0.25% of soluble potassium for bricks in general.

The explanation of this conflicting evidence remains a matter of conjecture. It is well known, for example, that for sulphate

ex-pansion to occur it is necessary to have soluble suiphates, tricalcium aluminate, and water in juxtaposition. Thus, sulphate expansion does not occur in brickwork where the bricks have negligible sulphate content, or the mortar has a low triealcium aluminate content, as in mortar made from sulphate-resisting cement, or when water is largely excluded by sound methods of building construction. Thus it is easy to visualize service and other conditions in which bricks of less salt content could have performed badly. There are many other factors too, which obscure this issue.

The incidence of efflorescence is subject to similar uncertainties. it has, however, been observed that the sulphates of sodium or magnesium are more troublesome than those of calcium or potassium.

Bearing all these factors in mind the committee felt that, for bricks of ordiiiary quality (Clause 3.1 (c)(ii)

),

although the etilorescence test should be retained, it could not recommend the setting of limits for the content of soluble salts.

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However, for bricks of special quality (Clause 3.! (c)(iii), for which higher standards of manufacture can be reasonably expected, the com-mittee felt that the maximum quantity of soluble salts permissible should be stated, although the limits must necessarily be tentative.

The provision in Clause 3.1 (d)(i) that bricks containing up to 25% of holes are to be considered as ‘solid’ requires explanation It has been included because it is known that bricks with not more than this modest degree of perforation can be treated in the same way as bricks without holes when calculating permissible pressures on brick-work from the strengths of the bricks determined in accordance with Clause 39, and this artifice should ensure that such bricks are auto-matically so treated. It need not be concluded that similar relations between the strength of bricks and the strength of brickwork do not subsist when the bricks contain more than 25% of holes, but where a designer feels any doubt it is always open to him to require tests on walls in accordance with MS * “Structural Recomniendations

for Loadbearing Walls”. Possibly on a future revision of the codes it may be more appropriate to deal with this situation in the code rather than in the standard, but on the present occasion the method adopted has seemed expendient.

The method of overall measurement of 24 bricks, which wt~s used in BS 657 in checking conformity with the dimensional clauses

of the standard, has been retained for standard bricks and is recom-mended for non-standard bricks.

The minimum strength for blocks for structural floors and roofs, specified in Clause 29, differs from the minimum strength specified for blocks for walling because the method of testing and the method of expressing the results are different. The limit of 14 MNIm2 (2,000

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lbf/in2) is one that can reasonably be attained by most manufacturers. It is lower than the limit 17.0 MN/rn2 (2,500 lbf/in2) set in BS 1190, but it is open to the structural engineer who wishes to take the strength of the blocks into consideration in his design to specify a higher strength where this is likely to be useful.

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SPECIFICATION

1. SCOPE

1. This Part of the Malaysian Standard specifies bricks and blocks manufactured from brickearth, clay, or shale.

CHAPTER 1. BRICKS AND BLOCKS FOR WALLING

SECTION ONE: GENERAL

2. GENERAL

2.1 Bricks and blocks for walling are units designed to be laid in a bed of mortar.

3. DEFINITIONS

3.1 For the purposes of this Malaysian Standard the following definitions apply:

(a) Bricks and blocks.

(I) Brick. A walling unit not exceeding 337.5 mm (131 in) in length, 225 mm (9 in) in width, or

112.5 mm (41 in) in height.

(ii) Block. A walling unit exceeding in length, width or height the dimensions specified for bricks.

(b) Different varieties of brick and block may be more parti-cularly defined as follows:

(i) Common. Suitable for general building work but

having no special claim to give an attractive appearance.

(ii) Facing. Specially made or selected to give an

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or plaster or other surface treatment of the wall. (iii) J~ngineering. Having a dense and strong

semi-vitreous body conforming to defined limits for absorption and strength.

(c) Different qualities of brick and block may be defined as follows:

(i) Internal quality. Bricks and blocks suitable for internal use only.

Note: Bricks and blocks not attaining quality 3.1 (c)(iii) may be suitable for internal use only.

(ii) Ordinary quality. Less durable than special quality but normally durable in the external face of a building.

(iii) Special quality. Durable even when used in situa-tions of extreme exposure where the structure may

become saturated, e g retaining walls, sewerage plants or pavings.

Note: Engineering bricks and blocks normally attain this standard of durability. Facing and common bricks or blocks may do so, but this should not be assumed unless claimed by the manufacturer. (d) Different types of brick and block may be defined as

follows:

(i) Solid. In which small holes passing through, or nearly through, a brick or block do not exceed 25% of its volume, or in which frogs (depressions in the bed faces of a brick) do not exceed 20% of its volume. For the purposes of this definition, a small

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hole is a hole less than 20 mm (~ in) wide or less than 500 mm2 (0.8 in2) in area. Up to three larger holes, not exceeding 3250 mm2 (5 in2) each. may be incorporated as aids to handling, within the total of 25%.

(ii) Perforated. In which holes passing through the

brick or block exceed 25% of its volume, and the holes are small as defined in (i) above. Up to three larger holes, not exceeding 3250 iiiiii2 each, may he

incorporated as aid to handling.

(iii) Hollow. In which holes passing through the brick or block exceed 25% of its volume, and the holes are not small, as defined in (i) above.

(iv) Cellular. In which holes closed at one end exceed 20% of the volume of the brick or block.

Note: Cellular bricks and blocks are normally made by pressing, whereas perforated and hollow bricks and blocks are normally made by extrusions. Per-forations and hollows may be either perpendicular to the bed face (V type) or parallel to the bed face (H type).

(v) Special shapes. Shapes other than the normal rec-tangular prism.

(vi) Standard specials. Special shapes that are in general

use may be available from stock.

4. FORMATS

4.1 The formats of bricks and blocks shall be designated in terms of their nominal dimensions which, with the exception of the widths of blocks include the thickness of a mortar joint. This is taken, for the purposes of this Standard, as equal to 10 mm

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(~

in). The standard brick format is given in Table 1 and the block formats in Table 2. Sonic considerations affecting the design of any additional formats that may be required are mentioned in Appendix C.

TABLE 1. STANDARD FORMATS (BRICKS)

(Dimensions are in millimetres, inches in brackets)

Designation Actual dimensions

Length Width Height

225 x 112.5 x 75 (9 x 41~x 3) 215 (8*) 102.5

(4k)

65 (2*)

Note 1: In accordance with modern terminology ‘Actual di-mensions’ should be replaced by ‘Work sizes’.

TABLE 2. STANDARD FORMATS (BLOCKS) (Dimensions are in millimetres, inches in brackets)

t

See Note 1 to Table 1.

Designation Actual dimensioust

Width Height 300 x 62.5 x 225 (12 x 21 x 9) 300 x 75 x 225 (12 x 3 x 9) 300 x 100 x 225 (12 x 4 x 9) 300 x 150 x 225 (12 x 6 x 9) Length 290 (11

~)

290 (1 l~) 290 (111) 290 (1l~) 62.5 (2 ~) 75 (3) 100 (4) 150 (6) 215 (8 ~) 215 (Q5 215 (8k) 215 (8k)

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In addition, half blocks, 140 mm (5~in) long, and three-quarter blocks, 215 mm (8~~in) long, shall be available for bonding.

5. PATTERNS

5.1 Bricks and blocks may be solid, perforated, hollow or cavity. Perforated and hollow bricks and blocks may be either V-type or H-type.

6. COMPLIANCE FOR DIMENSIONS (BRICKS)

6.1 The bulk supply or load of bricks shall be deemed to comply with Clause 4 if the overall measurements of the sample of 24, taken in accordance with Clauses 33 and 34 and tested in accordance with Clause 35 do not fall outside the tolerances given in Table 3. ‘If the measurements of the sample fall outside those tolerances the bulk supply or load shall be deemed not to comply. No testing of a second sample shall

be permitted.

TABLE 3. DIMENSIONAL TOLERANCES (BRICKS)

Specified dimension (Fable 1) Ovei~alI measurement of 24 bricks mm in 65 ‘ 2* 102.5 4* 215 8* mm in 1560

(

+ 60 63 ± 1* ( — 30 2460 ± 45 99 ±l~ 5160 ±75 207 ±3

Note 1: This method of measurement is also recommended

for non-standard bricks. The tolerances applied to the length, width and height dimensions should then

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be directly proportional to those specified for the corresponding dimensions of the standard brick. Note 2: In the past certain manufacturers have, by special

arrangement, supplied bricks to closer tolerance than those quoted. Where for special reasons closer tolerances are required it is therefore suggested that this can best be done by agreement between the user and the manufacturer on the basis of the latter’s routine control charts of. brick dimensions. See also Appendixes A and B.

Note 3: For building construction the use of the term ‘tolerances’ is likely to be restricted to the per-missible range between the maximum and minimum limit of size, and the term ‘permissible deviation’ more accurately describes the permissible variations in this Table

TABLE 4. DIMENSIONAL TOLERANCES* (BLOCKS)

Specified dimension (Fable 2 or Table 7)

Tolerance for single units

mm in

Less than 125 Less than 5

125 to 225 5 to 9

Greater than 225 Greater than 9,

mm in

± 2.5 ± 3/32

+ 3.0 ± 1/8 ± 5.0 ± 3/16 Note 1: This method of measurement is also recommended

for non-standard blocks. *See Note 3 to Table 3.

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7. COMPLIANCE FOR DIMENSIONS (BLOCKS)

7.1 If 3 or more of the 10 blocks selected in accordance with Clauses 33 and 34 and tested in accordance with Clause 36 fail to meet the tolerances specified in Table 4, the bulk supply or load shall be deemed not to comply. If 1 or 2 blocks fail to meet the tolerance specified a further 10 blocks shall be selected from the batch represented and the test repeated. Failure of one of the blocks in the repeat test shall be taken to indicate that the bulk supply or load does not comply with this Standard.

8. COMPLIANCE FOR OUT OF SQUARENESS (BLOCKS)

8.1 Where adjacent faces are intended to be at right angles, the amount by which they deviate shall be measured in accordance with Clause 37. The distance between the inner edge of the straight edge and the face of the block shall not exceed 5 mm (3/16 in) per 300 mm (I ft) run.

The measurement shall be made on 10 blocks, and the method described in Clause 7 shall be used to determine whether or not the bulk supply complies.

9. COMPLIANCE FOR BOWING OR TWISTING (BLOCKS)

9.1 When measured in accordance with Clause 42, the deviation from a straight line shall not exceed the figures shown in Table 5. These measurement refer to the deviations at or near the centre if the face is concave, and two equal measure-ments between the straight edge and the corners of the block if the face is convex.

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method described in Clause 7 shall be used to determine whether or not the bulk supply complies.

TABLE 5. MAXIMUM DEVIATIONS ON DIMENSIONS

of block Max. deviation from.

a straight line

mm in

225 x 150 (9 in

measured faces 3 1/8

the above but not

300 (9 in x 12 in) 5 3/16

225 x 300 (9 in x

6 1/4

10. STRENGTH AND ABSORPTION

10.1 In accordance with MS * or to comply with building

regulations, the classification given in Table 6 shall apply: interpolation of classes of Ioadbearing bricks not given in the above Table’ may be used for bricks having average crushing strengths intermediate between those given in the Table. Thus for instance ‘Class 4.5’ may be used to describe bricks with an average strength of 31.0 MN/rn2 (4500 lbf/in2) and Class 11 to describe bricks with an average strength of 76 MN/rn2 (11,000 lbf/in2).

Bricks to 5.2 MN/rn2 (750 lbf/in2) and blocks to 2.8 MN/rn2 (400 lbf/in2) in Clauses 12, 17 and 22 can also be loadbearing e g as used in one- and two-storey dwelling houses, the

* MS , “Structural Recommendations for Loadbearing Walls”, In

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TABLE 6. STRENGTh AND ABSORPTION Designation Class Average compressive strength MN/m~ not less th~ Average absorp-tion boiling or vacuum percent weight not greater han Engineering brick A B 69.0 (10,000 lbf/in2) 48.5

(

7,000 lbf/in2) 4.5 7.0 Loadbearing brick 15 10 7 5 4 3 2 1 103.0 (15,000 lbf/in2) 69.0 (10,000 lbf/in2) 48.5

(

7,000 lbf/in2) 34.5

(

5,000 lbf/in2) 27.5

(

4,000 lbf/in2) 20.5

(

3,000 lbf/in2) 14.0

(

2,000 Ibf/in2) 7.0 (1,000 lbf/in2) No specific requirements

Bricks for damp-proof courses

D P C as required 4.5

5.2 MN/rn2 (750 lbf/in2) brick is not limited to non-loadbearing uses.

Compliance with the requirements of the Clause shall be checked by the methods set out in ~Clauses 39 and 40.

If the manufacturer works a quality control system that includes strength testing, the results of the quality control tests may be made the basis of acceptance.

Where loadbearing brickwork is not calculated, the only strength requirements of this standard are those of Clauses 12, 16 and 20.

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SECTION TWO: SPECIFIC CLAUSES

SUB-SECTION 4: FACING AND COMMON BRICKS

AND BLOCKS OF ORDI1NARY QUALITY

11. FINISH

11.1 Facing and common bricks and blocks of ordinary quality shall be well-fired and shall be reasonably free from deep or extensive cracks and from damage to edges and corners, from pebbles and expansive particles of lime. They shall also, when a cut surface is examined, show a reasonably uniform texture.

Note: It is not possible to define ‘well-fired’ in a way that would apply unambiguously to all types of brick and blocks, though people with experience of particular types soon come to recognize what is meant. It is known that a brick or block has been ‘well-fired’ when an adequate ceramic bond has been formed within the body, but it is not possible precisely to determine by appearance or other simple test whether or not such a bond has been formed, without reference to the type of clay, the method of manufacture, and the format. To people very familiar with a specific product, colour can be a guide when considering that particular pro-duct, but to the layman, colour alone can be completely misleading. Similarly, hardness and hence ‘ring’ when struck can be a good guide to the expert, but clearly this criterion cannot be applied to all bodies such as, for example, those of low density.

12. STRENGTH

12.1 Unless a higher strength is agreed in accordance with Clause 10 the compressive strength of bricks of ordinary quality when

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tested in accordance with Clause 39, shall be not less than 5.2 MN/m2 (750 lbf/in2) and of blocks of ordinary quality shall be not less than 2.8 MN/rn2 (400 lbf/in2). These minimum strengths are acceptable provided the bricks and blocks are satisfactory in other respects.

13. SOLUBLE SALTS CONTENT

13.1 No requirements.

14. LIABILITY TO EFFLORESCENCE

14.1 When tested in accordance with Clause 42 no sample shall develop efflorescence worse than moderate.

SUB-SECTION B: FACING AND COMMON BRICKS

AND BLOCKS OF SPECIAL QUALITY

15. FINISH

15.1 Facing and common bricks and blocks of special quality shall be hardfired and shall be reasonably free from cracks and from damage to edges and corners, from pebbles and expansive particles of lime. They shall also, when a cut surface is examined, show a reasonably uniform texture with no very coarse particles.

Note: In interpreting the qualitative requirements of Clauses 11 and 15, a more exacting standard may reasonably be set for bricks of special quality than for those of ordinary quality

16. STRENGTH

16.1 Unless a higher strength is agreed in accordance with Clause 10. the compressive strength of bricks of special quality, when tested

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in accordance with Clause 39, shall be not less than 5.2 MN/m~ (750 lbf/in2) and of blocks of special quality shall be not less than 2.8 MN/ni2 (400 lbf/in2). These minimum strengths are acceptable provided the bricks and blocks are satisfactory in other respects.

17.1 When tested in accordance with Clause 41, the contents by weight percent of soluble sulphate, calcium, magnesium, potassium and sodium radicals shall not exceed respectively 0.30, 0.10, 0.03, 0.03 and 0.03%. The sulphate figure to be used for the purpose of this Clause shall be the acid soluble sulphate determined in accordance with Clause 41 (c).

18.1 When tested in accordance with Clause 42 no sample shall develop elflorescence worse than moderate.

SUB-SECTION C: BRICKS AND BLOCKS FOR

INTERNAL WALLS

19. FINISH

19.1 Bricks and blocks for internal walls (loadbearing) and partitions shall be reasonably free from deep or extensive cracks, from damage to edges and corners, and from expansive particles of lime. They shall also, when a cut surface is examined, show a reasonably uniform texture.

Note: Such units unless otherwise specified will be suitable for rendering but not necessarily for fair faced work. 20. STRENGTI-I

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the compressive strength of bricks for loadbearing internal walls when tested in accordance with Clause 39, shall be not less than 5.2 MN/rn2 (750 Ibf/in2) and of blocks for load-bearing internal walls shall be not less than 2.8 MN/m2 (400 lbf/in2). The compressive strength of bricks and blocks for non-loadbcaring partitions shall not be less than 1.4 MN/rn2 (200 Ibf/ in2). These minimum strengths are acceptable pro-vided the bricks and blocks are satisfactory in other respects.

22.1 When tested in accordance with Clause 42 no sample shall develop efflorescence worse than moderate.

CHAPTER 2. HOLLOW BLOCKS FOR

STRUCTURAL FLOORS AND ROOFS

23. GENERAL

23.1 The hollow blocks for structural floors and roofs covered by this Standard are blocks designed to be used as filler blocks

in reinforced concrete floors.

24. FORMATS

24.1 The formats of blocks for structural floors and roofs shall be designed in terms of their nominal dimensions which differ from their actual dimensions except in the depth. The actual length and width are 5 mm (3/16 in) less than the nominal length and width. ‘The standard formats are given in Table 7.

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TABLE 7. STANDARD FORMATS (FLOOR BLOCKS)

(Dimensions are in millimetres, inches in brackets)

Designation

Actual climensions*

Length Width Depth

300x 300x 75 (l2x12x3) 295 (11 13/16) 295 (11 13/16) 75 (3) 300x 300x 100 (12x12x4) 295 (11 13/16) 295 (11 13/16) 100 (4) 300 x 300 x 125 (12 x 12 x 5) 295 (11 13/16) 295 (11 13/16~ 125 (5) 300 x 300 x 150 (12 x 12 x 6) 295 (11 13/16) , 295 (11 13/16) 150 (6) 300x 300x 175 (12x12x7) 295 (11 13/16) 295 (11 13/16) 175 (7) 300 x 300 x 200 (12 x 12 x 8) 295 (11 13/16) 295 (ii 13/16) 200 (8) 300x 300x 225 (12x12x9) 295 295 225 (11 13/16) (11 13/16) (9) 300x 300x 250 (12x12x10) 295 295 250 (11 13/16) (II 13/16) (10)

Note: Length is measured along the direction which is

normally parallel to the concrete reinforcing ribs when the block is in the floor. Width is measured in the direction which is normally at right angles to the concrete ribs when the block is laid in the floor.

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25. COMPLIANCE FOR DIMENSIONS

25.1 Blocks for structural floors and roofs shall be measured in-dividually by the method laid down in Clause 36 for blocks for walling.

The measurement shall be carried out on 10 blocks and the

method described in Clause 7 shall be used to determine whether or not the bulk supply complies.

26. COMPLIANCE FOR OUT OF SQUARENESS

26.1 Where adjacent faces are intended to be at right angles, the amount by which they deviate shall be measured in accordance with Clause 37. The distance between the inner edge of the straight edge and the face of the blocks shall not exceed 5 mm (3/16 in) per 300 mm (1 ft) run.

The measurement shall be carried out on 10 blocks and the method of Clause 7 used to determine whether or not the bulk supply complies.

27. COMPLIANCE FOR BOWING OR, TWISTING

27.1 When measured in accordance with Clause 38, the deviation from a straight edge shall not exceed the figures shown in

Table 5. These measurements refer to the deviations at or

near the centre if the face is concave, and two equal measure-ments between the straight edge and the corners of the block if the face is convex.

The measurement shall be carried out on 10 blocks and the method of Clause 7 used to determine whether or not the bulk supply complies.

28. FINTSH ~

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from deep or extensive cracks, from damage to edges and corners and from expansive particles of lime. They shall also, when a cut surface is examined, show a reasonably uniform texture.

29. STRENGTH

29.1 The compressive strength of blocks for structural floors and roofs, when tested in accordance with Clause 39, shall be not less than 14.0 MN/rn2 (2000 lbf/in2). Higher strengths may be agreed between the supplier and the user if it is desired to make use of the block strength when calculating the strength of the floor for design purposes.

31. LIABILITY TO EFFLORESCENCE

CHAPTER 3. SAMPLING PROCEDURE AND

TEST METhODS

32. GENERAL

32.1 Testing shall be carried out on samples which are taken in accordance with Clauses 33 and 34.

33. SAMPLES

33.1 Samples may be required for:

(a) Routine quality control tests carried out by the manufac-turer. For this purpose the number of units to be taken as samples shall be at the discretion of the manufacturer and shall be based on sound statistical principles*.

* Suitable expositions of statistics for this purpose are given in Appendix

A and in BS 2564, “Control Chart Technique When Manufacturing to a Specification”.

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(b) Tests carried out by the manufacturer or the customer to determine compliance with specification. For this purpose the number of units required for specific tests shall be as follows:

(i) Compressive strength 10 (ii) Water absorption 10 (iii) Soluble salts 10 (iv) Efflorescent testt I 0 40

(v) Dimensions of bricks 24 (vi) Dimensions of blocks 10

Since the dimensional test can be carried out on units which are used subsequently for other tests and since the 10 bricks or blocks used for the water absorption test may be used subsequently for the compressive strength test, the minimum number of units required when all tests are to be made is 30, but a sample of 50 units provides a reasonable margin to allow for loss and breakage and for simultaneous testing. When it is known that only certain of these tests are to be made then the appropriate number of units required shall be sampled instead of the 50 units.

t

When the sample for soluble salts analysis is prepared by the method of Clause 33.1(b)(iii), the 10 bricks or blocks from which the sample has been taken may be used subsequently for the efflorescence test.

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When dimensional tests only are to be carried out on blocks, since ten additional units may be required under the terms of Clause 7, these must be taken at the same time as the first sample of ten, unless it is known that the whole delivery will be available for further sampling when the first part of the test has been completed.

The required number of units shall be sampled from a discrete delivery of not less than 2000 or more than 10,000 bricks, or not less than 500 or more than 2,500 blocks.

When all tests are to be carried out, units for any one specific test shall be taken at random from the sample of 50 units if the latter are originally sampled at random from the delivery, or where statistical representative sampling of the delivery is carried out the required number of units shall be taken at random from each of the representative sub-samples (See Clause 34, Method of sampling).

Sample units remaining after allocating units for specific tests shall be reserved either for reference or for other tests which may be required.

34. METHOD OF SAMPLiNG

34.1 TI required sample may be drawn by: (a) Random sampling.

(b) Representative sampling.

In random sampling the sample is taken in such a way that

every unit in the bulk has an equal chance of appearing in

the sample.

In representative sampling the bulk is divided into convenient sections (real or imaginary) and the sample is taken so that

(34)

of the sample. The units in each of these portions must be taken in a random manner (See (a) below).

The word Representative applied to sampling does not mean that the sampler is to select units which lie thinks represent the different colours, sizes, strengths, etc., of the bulk supply. Any person bias in selection must be avoided.

The samples shall be taken by one of the methods set out below, sampling being arranged SO as to yield the number

of units required.

(a) Sampling in motion. Whenever practicable a sample shall be taken whilst the units are being moved, for example during loading or unloading. 1n this case 2, 3, 4 or 5 units shall be taken at random from each of 10 ap-proximately equal sections of the bulk to be tested de-pending on whether one, two, three or four of the tests (i), (ii), (iii), (iv) are to be carried out, with or without test (iv).

If only test (v) is to be carried out it will be more con-venient to take 2 units at random from each of 12

ap-proximately equal sections of the bulk.

if test (v) is to be carried out and one, two, three or four of the tests (i), (ii), (iii), (iv), then 24, 24, 30 or 40 is the minimum number of units required. To allow for loss and breakage the number sampled shall there-fore be 30, 30, 40 or 50. These units shall be obtained by taking 3, 3, 4 or 5 units at random from each of 10 approximately equal sections of the bulk to be tested. The sample of 24 units required for test (v) shall be obtained by taking 2 units at random from each of 6 portions selected at random from the tO portions

(35)

corn-prising the main sample and 3 units at random from each of the remaining 4 portions.

When 2 or more multiples of 10 units are sampled from a bulk supply the sample of 10 units required for one specific test shall be obtained by taking one unit at random from the units in each of the 10 portions of the sample. When sampling it will therefore be neces-sary to identify the units in any 1 portion of the sample by the same letter or mark which should be different from the letters or marks given to the other 9 portions of the sample.

(b) Sampling from a stack. When it is necessary to take a

sample from a stack the following procedure shall be adopted:

The stack shall be divided into a number of real or imaginary sections and the required number of units drawn from each section as indicated under (a). For this purpose units in the upper layers of the stack shall be moved to enable units to be sampled from places within the stack. Units shall also be sampled from

accessible sides of sections which are at the edge of the

stack.

Sampling from stacks may not be satisfactory when testing for soluble salts and efflorescence because con-tarnination from the ground and other sources may occur.

(c) Sampling from lorries or trucks. When for any reason

sampling cannot be carried out in motion, units shall be taken from a number of sections of the load as indicated

(36)

35. DETERMINATION OF DIMENSIONS (BRICKS)

35.1 When standard bricks are to be checked for dimensions the method shall be the overall measurement of 24 bricks placed in contact in a straight line upon a level surface in each of the arrangements indicated in Fig. 1 Any blisters or small projections or ‘loose particles of clay adhering to the face of a brick shall be removed before they are assembled for measure-ment. The overall dimensions of the assembled bricks shall be measured with. a steel tape or other suitable inextensible measure long enough to measure the whole row at once. Measurement by repeated application of a short rule or measure shall not be considered satisfactory.

if for any reason, it is found impracticable to measure 24 bricks in one row, the samples may be divided into two rows of 12, or three rows of 8, which shall be measured separately to the nearest 2 mm and their measurements added. The measurement of one row of 12 or 8 units and multiplication by 2 or 3 shall not be considered satisfactory, because of the probability that the mean dimensions of so small a sample differ appreciably from the mean dimensions of the bulk supply.

36. DETERMINATION OF DIMENSIONS (BLOCKS)

36.1 Standard blocks shall be measured individually, a sample of 10 units being measured. Each of the 3 linear dimensions shall be measured with a ruler graduated at intervals of 1 mm (1/32 in) and the results noted. The measurements shall be carried out for each of the 10 units in turn.

37. DETERMINATION OF OUT OF SQUARENESS (BLOCKS) 37.1 The amount by which the angle between adjacent faces of

(37)

the block differs from a right angle ~haIl be determined by placing a builder’s steel square against one edge and measuring the distance between the inner edge of the square and the face of the block (See Fig. 2).

38. DETERMINATION OF BOWiNG OR TWISTING (BLOCKS) 38.1 The blocks shall be placed between two parallel straight edges running diagonally across the two faces of the unit as shown in Fig 2. The distance between the straight edge and the face of the block shall be measured at a point near the centre on the side which is concave, and two equal measurements shall be taken between the straight edge and the corners of the opposite face of the block on the convex side.

39. DETERMINATION OF COMPRESSIVE STRENGTH

(a) Test specimens. Ten whole units, taken as directed in

Clauses 33 and 34, shall be used for determining com-pressive strength.

(1) Bed face area. Bricks and blocks for walling. When

testing bricks and blocks for walling, the overall dimensions of each bed face shall be measured to the nearest 1 mm (0.05 m) and the area of the smaller of the two shall be taken as the area of the unit for calculating the compressive strength. This applies to all types of bricks and blocks,

in-cluding the divided-joint type, i e, the gap between the twin strips of mortar on which the latter are

bedded is included in the overall area.

(ii) Bed face area. Blocks for structural floors and roofs.

When testing flooring blocks the ends in which the cavities appear shall be treated as the bed faces.

(38)

The net area of the material in the bed face shall

be obtained by subtracting the area of the cavities

from the overall area of the bed face, and shall be taken as the area of the block for calculating the compressive strength.

(b) Preparation of specimens.

(i) Solid bricks without frogs, bricks with frogs intended to be laid frog downwards, perforated bricks and cavity bricks. Bricks of standard size. including solid bricks without frogs, perforated bricks and cavity

bricks, shall be immersed in water at room

tem-perature for not less than 24 hours or saturated under

vacuum or by boiling, before testing.

The same method shall be used for bricks with

ordinary frogs that are to be laid frog downwards.

When, for this purpose, the strength of bricks is determined with the frog unfilled, this fact shall be prominently stated in the test report.

(ii) Bricks with frogs intended to be laid frog upwards.

Bricks with frogs shall be immersed in water at room temperature for not less than 24 hours, or

saturated under vacuum or by boiling. They shall then be removed and allowed to drain for about five minutes, wiped free from surplus moisture, and their frogs filled with mortar. (The requirement that

frogs shall be filled shall not be taken as requiring

the filling of perforations in perforated bricks or of the deep frogs in cavity bricks which are made to give a lightweight wall when bedded frog down-ward. These are to be prepared as prescribed in

(39)

(h)(i) above). Not less than four, and preferably six cubes, approximately 75 mm (3 in) on side, shall be made from each batch of mortar and shall

he stored under the same conditions as the bricks. The mix used shall be capable of attaining the strength specified below and, when set, there shall he no concavity in the mortar filling (See Note 1).

Singlc-frogged bricks shall be stored under damp sacking or similar material for 24 hours after their

frogs have been tilled and then immersed in water until they are ready for testing.

Double-frogged bricks shall be prepared in two stages not less than four nor more than eight hours being allowed to elapse after filling the first frog before

filling the second, using a mortar with the same

composition as before. They shall be stored under damp sacking or similar material for 24 hours after filling the second frog, and then immersed in water

until ready for testing.

Bricks with ‘frogs shall be considered ready for testing when tests on the cubes show that the com-pressive strength of the mortar is not less than

28.0 MN/rn2 (4000 lbf/in2) and not more than 42.0

MN/rn2 (6000 lbf/in2). Single cubes may be used

to indicate the growth of mortar strength, but the

final test shall be made with three cubes for each

batch of mortar, the average strength of the three

cubes being taken as the strength of the mortar.

(iii) Hollow blocks, including floor blocks, and bricks larger than 22S x .112.5 mm (9 x 4~in) (on bed face).

(40)

temperature for not less than 24 hours, or saturated

under vacuum or by boiling. They shall then be removed and allowed to drain for about five minutes, wiped free from surplus water and bedded in a mortar capable of attaining the strength specified

below (See Note 1). Not less than four, and pre-ferably six, cubes of mortar approximately 75 mm (3 in) side, shall be made from each batch of mortar and shall be stored under the same con-ditions as the specimens.

The bedding shall be carried out in the following manner. Each specimen shall be bedded on a

smooth rigid plate, at least 40 mm (13 in) longer and wider than the specimen, which, does not depart

from a true plane surface by more than 0.05 mm

(0.002 in) pieces of Plate glass, or machined steel

plates, are the most suitable materials. The plate

shall be firmly supported with the machined face uppermost and levelled in two directions at right angles by means of a spirit level. It shall be coated

with a film of mould oil to prevent mortar adhering,

or alternatively a sheet of thin paper can be used for the same purpose. A layer of mortar 20 him ~ in) and 40 mm (11 in) to 50 mm (2 in) longer and wider than the specimen shall then be placed on the plate and one bed face of the specimen firmly

pressed into it so that the vertical axis of the

speci-men is perpendicular to the plane of the plate and so that the bed is approximately 10 mm

(~

in) thick and nowhere less than 5.0 mm

(~

in) thick (See Note 2). Th~ surplus mortar shall be trimmed off flush with the sides of the block after it has

(41)

hardened sufficiently (See Note 1). The block shall then be stoi ccl under damp sacking or similar ma-terial for 24 hours before being carefully removed

from the plate, without damaging the mortar, and

inverted.

The second bed face shall then be bedded in the same way as the first using a mortar with the same composition as before. The specimen shall be placed on the bed of mortar and the face now uppermost levelled in two directions at right angles by means of a spirit level to ensure that the two mortar-faces

are parallel. After bedding the specimen shall again he covered with damp sacking or similar material for 24 hours and then immersed in water until tested. The specimen shall he considered ready for testing when tests on the cubes show that the compressive strength of the mortar is riot less than 28.0 MN/rn2

(4000 lbf/in2) and not more than 42.0 MN/rn2 (6000 lbf/in2). Single cubes may be used to indicate the growth of ‘ mortar strength, but the final test

shall be made with three cubes for each batch of mortar, the average strength of the three cubes being taken as the strength of the mortar.

(iv) Divided-joint bricks and blocks. Bricks and blocks designed to give a single-leaf wall with the mortar joints divided into two strips (See Note 3) shall be immersed in water at room temperature for not less than 24 hours, or saturated under vacuum or by

boiling. They shall then be removed and allowed to drain for about five minutes, wiped free from surplus water and bedded in mortar. The method

(42)

of bedding shall be generally as described in (iii)

above, but instead of bedding the whole face of the brick or block, the bedding mortar shall be placed in two parallel strips of a uniform thick-ness of 20 mm

(~

in) formed with the help of a simple guide, described below. These strips of mortar shall correspond with the parts of the brick or block designed to carry the mortar bed, and the brick or block shall be accurately placed on them and pressed down to form a bed as uniform as possible approximately 10 mm

(~

in) thick and nowhere less than 5.0 mm

(~

in) thick.

The guide mentioned in the preceding paragraph shall consist of a rectangular strip of wood of 20 mm

(~

in) finished thickness, of width equal to the de-signed gap between the mortar strips (for the V double brick shown in Fig. 6. it may be taken as 75 mm (3 in) and 50 mm (2 in) to 100 mm (4 in) longer than the brick. In use, the guide shall be placed across the machined plate on which the bedding is done, and level mortar strips somewhat longer and wider than their finished dimensions placed on either side of it. The guide shall be carefully re-moved with the least possible disturbance of the mortar bed before the brick or block is pressed into position.

(c) Apparatus. The testing machine shall have adequate capacity to crush all the test specimens but the scale used shall be such that the ultimate loads on the specimens exceed one-fifth of the full scale reading. The machine shall be provided with a load-pacer or equivalent means to enable the load to be applied at the rate specified

(43)

in (d) (iii). It shall meet the requirements for accuracy of Grade B of BS 1610, “Verification of Testing Machines”, Part I. The testing machine shall be equipped with two steel bearing-platens with hardened faces. The platen that normally will bear on the upper surface of the specimen shall be fitted with a ball seating in the form of a portion of a sphere. the centre of which coincides with the centre of the face of the platen. The movable portion of the hall—seated platen shall be held on its scat ‘hut shall he

free to rotate and to tilt through small angles in any direction. The other platen shall be a plain rigid hearing block. The bearing faces of both platens shall be at least as large as, and preferably larger than, the nominal size of the specimen. The bearing surfaces of the platens shall not depart from a plane by more than 0.05 mm (0.002 in). (To meet this requirement, the platens, when new, should be somewhat more accurate to allow for wear and should be refaced when they approach this limit.) (d) Testing procedure.

(i) General. When the requirements of Clause (b) have been satisfied, the specimens shall be tested immedi-ately on removal from the water.

(ii) Placing specimen in the testing machine. The bearing surfaces of the testing machine shall be wiped clean and any loose grit removed from the bed faces of the specimen. The load shall be applied to the specimen in the same direction as in service, and the axis of the specimen shall be carefully aligned with the centre of the ball-seated platen. As the latter is brought to bear on the specimen the niov-able portion shall be guided gently by hand so that a uniform seating is obtained. Specimens

(44)

pre-pared in accordance with (b)(i) and (b)(ii) shall be tested between two 3 mm plywood sheets which shall be at least as long and as wide as the specimen and shall be used once only. Specimens prepared in accordance with (b)(iii) and (b)(iv) need not be tested between sheets of plywood.

(iii) Loading. The load shall be applied without shock and increased continuously. Initially the loading

may be at any convenient rate up to 35.0 MN/m2 (5000 lbf/in2) per minute but, when about half the expected maximum load has been applied, the rate shall be adjusted to 15.0 MN/rn2 (2000 lbf/in2) per

minute and maintained until the maximum failing load is reached. With some specimens the recorded load may fluctuate before the maximum failing load is reached. This will be indicated by a reduction in

load as the specimen yields followed by an increase

to a new maximum as loading is continued. This

temporary reduction may occur several times before

the specimen finally fails. The maximum failing load shall be taken as the load at which the specimen no longer produces any further increase in the in-dicator reading (See Note 4).

(iv) Calculation of results. The compressive strength of

the specimen shall be calculated by dividing its

maximum failing load by its area as defined in (a) and shall be expressed in MN/in2 (lbf/in2) to the nearest 0.5 MN/rn2 (70 lbf/in2) for strengths of 7.0 MN/rn2 and above and to the nearest 0.1 MN/rn2

(10 lbf/in2) for strengths less than 7.0 MN/rn2. The arithmetic mean of the compressive strength of the ten specimens is the best unbiased estimate

(45)

of the true consignment mean and shall be taken as the compressive strength of the consignment sampled, for purposes of Clauses 10, 12, 16, 20 and 29.

It. should be noted that manufacturers who use quality control schemes for strength testing have detailed information on the compressive strength of their bricks and their variability, which can be made available to users.

Note ‘1: The strength of mortar required for this test may be obtained within a reasonable time (3 to 7 days) by using a I : 1~ mix of ordinary Portland cement or rapid-hardening Portland cement complying with MS

~,

with clean well-graded sand, 3 mm (-~ in) down. The water/cement ratio will usually be not greater than 0.35 and, if the bricks are of an open texture so that water drains from them

readily, it may be necessary to use a lower water/ cement ratio

If the sand available is relatively fine and/or contaminated with silt or clay, a higher water/cement ratio will be required to obtain satisfactory workability. It will then be difficult to attain the required strength within a reasonable time when using a 1 : l- mix with Portland cement. A 1 : 1 mix with ordinary Portland cement or rapid-hardening Portland cement or a 1 3 mix with a high-alumina cement complying with MS

t

will then be found more satisfactory.

To obtain the specified strength without difficulty it is necessary to use cement in fresh condition. This means that, if it is

* MS

,

“Portland Cement (Ordinary and Rapid-Hardening)”.

(46)

not used very shortly after manufacture, it should be preserved in an airtight container.

When the mixes give the required strength in 3 to 7 days, the mortar is usually sufficiently set to enable reversal of bricks to be carried out in 4 to 8 hours as mentioned in (b)(ii) above and trimming in accordance with (b)(iii) above.

To ensure that, as required in (b)(ii), there shall be no con-cavity in the mortar filling of frogs, the mortar should not be trowelled off flush with the surface of the brick immediately, but after allowing it to stand for a period judged by experience, usually between two and four hours.

Note 2: When bedding hollow blocks in mortar, (b)(iii), it will be found an advantage to place a layer of mortar about twice the required finished thickness and to shape it so that it is a little thicker in the middle than at the edges. This will ensure that air is not trapped under the block when it is pressed into the mortar. Some laboratories have found it convenient to restrain the flow of the mortar by a removable metal rim or frame slightly larger than the block, but this is not necessary if the layer of mortar is initially of the thickness indicated and extends about 25 mm beyond the edges of the block in all directions.

Note 3: The instructions for bedding divided-joint bricks and

blocks in (b)(iv) have been drafted with the double bricks illustrated in Fig. 6 chiefly in mind. Divided-joint hollow blocks (H blocks) in which the width

of the strips of bedding mortar is defined by de-pressions in the bed faces of the blocks, arc also manufactured. These can be prepared for testing by

(47)

the method of Clause (b)(iii), the mortar beds being divided into two strips by cutting away the surplus with a strip of nietal when the mortar is trimmed 10 the edges of the blocks.

Note 4: Determination of the end point of the test presents no difficulty to the person experienced in the strength testing of bricks. The less experienced operator should however appreciate that the indicator needle may fall back at certain stages during the loading operation, before the point of final collapse is

reached. Should this occur considerable judgement is required in resetting the controls of the machine in order to maintain smoothly the specified rate of loading. At the final point of collapse, the indicator needle will continue to fall back rapidly even though

every effort is being made to maintain the loading specified. The pattern of final collapse will vary with the type and thickness of the sample being tested. With solid bricks of 65 mm (2~ in) thick-ness, for example, the final collapse occurs by shear and is easily recognizable. With highly vitreous vertically perforated specimens, however, final failure is characterized by a complete shattering of the sam pie.

40. WATER ABSORPTION TESTS

40.1 Two alternative standard methods are specified for the deter-mination of water absorption, the 5-hour boiling test (B) and the vacuum test (V). The two forms of test give acceptable agreement with the great majority of bricks, and the choice of method is a matter of convenience. Either method may be used for the purposes of Clause 10. A method of test

(48)

by 24-hour cold immersion (C) is also specified for use as works control test only. The results by this method are always lower than, and are not proportional to, those by the standard methods.

(a) Test specimens. The test specimens shall normally con-sist of whole bricks or’ blocks, but representative portions being approximately a half or a quarter of the brick or block may be used when testing large units. Ten whole specimens, or representative portions from each of them shall ‘be tested.

(b) Accuracy of weighings. Specimens shall be weighed to

an accuracy. of 0.1% of the weight of the specimen, using

a suitable balance.

(c) Preparation of specimens. The test specimens shall be

dried to constant weight in a ventilated oven at I 10°C—

115°C. When cool, each Specimen shall be weighcd*.

(d) Procedure for 5-hour boiling test. (B). The Specinlens

shall be placed into a tank of water immediately after

weighing so that water can circulate freely on all sides of them. The tank shall be provided with a grid to ensure free circulation of water between bricks and the bottom of the tank. The water shall be heated to boiling in

* it can be assumed that heating f~. at least 48 hours at 110°C will

assure constant weight, but it should be noted that several hours may be required before the specimens reach 110°C if they are wet when put into the oven. The 48 hours shall be reckoned from the time the

specimens reach 110°C. Storage of bricks, unstacked, with spaces between them, in a ventilated room for a period of 4 hours, with a current of air from an electric fan passing over them continuously for at

(49)

approximately one hour, boiled continuously for 5 hours, and then allowed to cool to room temperature by natural loss of heat. for not less than 16 or more than 19 hours.

The specimens shall be removed, the surface water wiped oil with a damp cloth, and the specimen weighed. When wiping perforated bricks, water that might otherwise be left

in the perforations shall be displaced by shaking.

Weighing of any one specimen shall be completed within 2 minutes after its removal from the water.

The test may be carried out either on dry bricks, or following the 24-hour cold immersion test if desired, pro-vided that the specimens were in the first instance dried and weighed in accordance with Clauses (b) and (c).

(e) Procedure ~or vacuum test. (V). The apparatus consists of a cast-iron or other suitable tank capable of holding the required number of specimens connected through stop-cocks to a vacuum pump and water tank (See Fig 3). Greased ground surfaces on the tank and lid ensure an air-tight fit. The dry specimens, which have previously been weighed, shall be placed on end in the tank, separated from the base by a perforated zinc platform or similar method, and so arranged generally as to allow free access to all surface as far as possible.

With stop-cock B closed and stop-cock A open (See Fig. 3) the pump shall be started, continuing until the residual pressure is less than 2700 N/rn2 (0.39 lbf/in2) (20 mmHg). Stop-cock A is then closed, and stop-cock B opened. After the bricks have become completely immersed and the water has ceased to flow, a period of 10 minutes shall be allowed to ensure that penetration is complete.

(50)

The lid of the tank shall then be removed, and the bricks wiped and weighed in the manner prescribed for (d).

(f) Procedure for 24-hour F cold immersion test (for works control). (C). The dry specimens, which shall be at room temperature,, shall be completely immersed, without zpre-liminary partial immersion, in water at room temperature. The water shall have free access to all surfaces as far as possible. After immersion for 24 ± I hours the speci-mens shall be removed and wiped and weighed in the manner prescribed for (d).

(g) Calculation o. water absorption. The absorption results shall be reported in terms of percentage increase by weight on the dry specimens and shall be calculated to the nearest 0.1%.

The arithmetic mean of the absorptions of the ten speci-inens is the best unbiased estimate of the true consign-ment mean and shall be taken as the absorption of the consignment.

41. SOLUBLE SALTS ANALYSIS

(a) Preamble. The preparation of a powdered sample of

mineral substance such as brick for chemical analysis is

a well understood technique, as is the analytical

deter-mination of the radicals present in an aqueous solution. It is the preparation of an aqueous solution from the powdered bricks as a preliminary to soluble salts analysis that calls for standardization, because widely divergent amounts of soluble salts may be taken into solution

de-pending on the methods of extraction used.

(51)

or blocks a representative working sample of about 25 g ground to pass a 150 micron MS * “Test Sieve” shall

be prepared. The following are the alternative methods: (i) Fragments representative of the interior and exterior

of the bricks amounting to at least one-tenth of each brick or block are crushed in hardened steel equip-ment to produce about 5000 g of material passing a MS * “Test Sieve” with an aperture not greater

than 3.35 mm. This is mixed and then reduced by coning and quartering or other equivalent method to about 300 g which is then all ground to pass a MS * “Test Sieve” with an aperture not greater

than 710 micron. This finer sample is reduced to about 25 g by coning and quartering or other equivalent method and all is ground to pass a 150

nh,cron MS * “Test Sieve.”

A magnet is used to remove any iron that may have contaminated the sample during crushing. The sample shall then be dried at 110°C.

(ii) Holes are drilled in 10 bricks or blocks with a masonry drill not larger than 7 mm in diameter. The holes are approximately equally spaced over the bed-faces of each brick or the outer surface of the block. They are carried to a depth appro-ximately equal to half the depth of the brick or half the thickness of the web of the block. The number of holes is such as to give a sample of approximately 25 g of powder passing a 150 micron MS * “Test Sieve.” Material from the drillings

which does not pass the sieve immediately is ground

(52)

in a suitable mortar until (he whole sample passes through.

A magnet is used to remove any iron which may have contaminated the sample during drilling. The sample shall be dried at 110°C.

(c) Determination o acid-soluble sulphate. Weigh 2 g of’ the sample and transfer to a 250 ml beaker and cover with a clock glass. Through the lip of the beaker introduce 150 ml of hydrochloriê acid (1: 9) and heat to boiling add half a Whatman ashless tablet or equivalent and boil for 10 minutes, stirring to prevent bumping. Cool, filter through a sintered glass buchner funnel and wash thoroughly five or six times with hot distilled water. Add one or two spots of methyl red indicator and ammonia

(1 : I) dropwise till just neutral then add immediately 25 drops hydrochloric acid (sp gr I .1 8) followed by 3 ml

of bromine water (saturated). Heat to boiling, boil for 2 minutes and, while boiling, slowly add from a pipette 10 ml of barium chloride solution (10%). Continue boiling for about 2 minutes, transfer to a steam bath for I hour and allow to cool. Stand overnight and filter through a slow filter papcr**. Wash with hot water until free of chlorides. Transfer the precipitate and paper to a weighed platinum crucible, heat gently to dry the residue and char the paper, and finally ignite to 1000°C for 30 minutes, cool and weigh.

Weight of BaSO4 x 0.4115 = weight of SO4

Note: The ‘acid soluble sulphate’ may be assumed to

cor-respond fairly closely to the total quantity of sulphate

(53)

which could be obtained from the brick sample on long continued extraction with water. This quantity is therefore relevant to an assessment of the liability of the brick material to cause sulphate expansion in

Portland cement

(d) Extraction of water-soluble salts The extraction of soluble salts shall be carried out at room temperature, 10

-i--0.05 g of the sample shall be weighed and transferred to a 150 ml polythenc bottle,., 100 ml of cold distilled water shall be added, the bottle closed with a screw-on polythene top and the bottle shaken for 60 minutes. (A rotary shaker revolving at about 30 revolutions per minute is suitable or alternatively the contents of the bottle may be stirred for 60 minutes by a magnetic stirrer using a polythene covered follower). The suspended sample shall be filtered and the filtrate collected in a clean dry flask. The residue on the filter shall not be washed. •Alterna-tively a centrifuge may be used. The filtering means employed shall be used dry. The alternatives are either:

(i) Sintered glass buchner funnel1’~, porosity grade 4, with suction.

(ii) Centrifuge.

(iii) Filter candle with suction.

(iv) Ordinary filter with. e g, a No. 42 Whatman or equivalent filter paper.

It is essential that the filtrate shall be clear.

(54)

(e) Determination of radicles. Recognized analytical methods shall then be used to determine the following radicles:

Calcium (Ca+ +), Magnesium (Mg~

~)

Sodium (Nat), Potassium (K~)

The following analytical procedure has been found con-venient and is recommended though it is not mandatory. The results shall be reported to the nearest 0.01% by weight.

Calcium. Pipette a 10 ml aliquot of the soluble salt extract into a 500 ml conical flask. Add 20 drops of hydrochloric acid (sp gr 1.18), followed by 10 ml of potassium hydroxide solution (approximately 4 N), and dilute to about 200 ml with water. Add about 0.015 g of calcein indicators. Titrate with standard EDTA solution from a 10 ml semi—micro burette, the colour change being from fluorescent green to pink.

Magnesium. Pipette a 10 ml aliquot of the soluble salt extract into a 500 ml conical flask. Add 20 drops of hydrochloric acid (sp gr. 1.18), followed by a 10 ml of ammonia solution (sp gr 0.880) and dilute with to about 200 ml. Add about 0.04 g of methyl thymol blue complcxonc indicator. Titrate with the standard EDTA solution from a 10 ml semi—micro burette, the colour change being from blue to colourless.

The volume of EDTA used lor the titration ol calciuiu is subtracted from the volume of EDTA used for this titration. The remainder represents the volume of EDTA required for the titration of the magnesium.

~ Screened Murexide or 2-hydroxyl- I -(2-hydroxy-4-sulpho- I -naphthylazo)-3-naphthoic acid are also suitable indicators.

MS 76-1972

SPECIFICATION FOR BRICKS AND BLOCKS OF FIRED

BRICKEARTH, CLAY OR SHALE

PART 2 : METRIC UNITS

MALAYSIAN

STANDARD

BRICKS AND BLOCKS OF FIRED

BRICKEARTH, CLAY OR SHALE

PART 2. METRIC UNITS

MS 76:1972

CONTENTS

Test

Committee Representation

FOREWORD

),

SPECIFICATION

(~

(4k)

t

~)

(

(

(

(

(

(

(

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