Masonry Mortars grades and its Technical specifications ,Storage of cement bags, Strength of Mortar ,specifications of plaster work,Grades of cement, Initial and final settling time and physical requirements of Fly ash

Cement bags shall be stacked (or stored)  at least 450 mm clear off the walls and in rows of two bags leaving in a space of atleast 600 mm between two consecutive rows. 

Welcome friends ,in this article we shall discuss the following topics. 
Technical Specifications and grades of masonry Mortars ,Storage of cement bags, Strength of Mortar ,specifications of  plaster work,Grades of cement, Initial and final settling time and physical requirements of  Fly ash 

So let's get start............. 

 GENERAL
                  Desirable properties of mortars for use in masonry are:
(a) Workability
(b) Water retentivity
(c) Rate of stiffing
(d) Strength
(e) Resistance to rain penetration
(f) Durability

A- MATERIALS

1- Cement

The cement used shall be any of the following grade and the type selected should be  appropriate for the intended use.

(a) 33 grade ordinary Portland cement conforming to IS 269-2013.

(b) 43 grade ordinary Portland cement conforming to IS 8112-2013.
(c) 53 grade ordinary Portland cement conforming to IS 12269-2013.
(d) Rapid hardening Portland cement conforming to IS 8041-1990, Reaffirm Apr 2014
(e) Portland slag cement conforming to IS 455-1989, Reaffirm Apr 2014.
(f) Portland Pozzolana cement (flyash based) conforming to IS 1489 (Part 1)-1991, Reaffirm Apr  2014.
(g) Portland Pozzolona cement (calcined clay based) conforming to IS 1489 (part 2)-1991,
Reaffirm Apr 2014.
(h) Hydrophobic Portland cement conforming to IS 8043-1991, Reaffirm Apr 2014.
(i) Low heat Portland cement conforming to IS 12600-1989, Reaffirm Apr 2014.
(j) Sulphate resisting Portland cement conforming to IS 12330-1988, Reaffirm Apr 2014.
(k) White cement conforming to IS 8042-1989, Reaffirm Apr 2014.

Different types of cement shall not be mixed together. In case more than one type of cement is used in any work, a record shall be kept showing the location and the types of cement used.

 (i )Caution in Use of Cement Grade 53 in Construction: Because of the faster hydration process, the concrete releases heat of hydration at a much faster rate initially and release of heat is the higher in case of Grade. 53. The heat of hydration being higher, the chances of micro-cracking of concrete is much  greater. Thus, during initial setting period of concrete, the higher heat of hydration can lead to damaging micro-cracking within the concrete which may not be visible at surface. This cracking is different from shrinkage cracks which occurs due to faster drying of concrete in windy conditions.

The situation can be worse when we tend to increase the quantity of the cement in the concrete with a belief that such increases are better for both strength and durability of concrete. Thus, it is very  essential to be forewarned that higher grade cement specially grade 53 should be used only where such use is warranted for making higher strength concrete and also where good Quality Assurance measures are in place, by which proper precaution are taken to relieve the higher heat of hydration through chilling of aggregates or by proper curing of concrete. There are instances where higher grade cement is being used even for low strength concrete, as, mortar or even for plastering. This can lead to unnecessary cracking of concrete/ surfaces.

Another issue to be cautioned against is the tendency of the manufacturers to project Grade 53 cement as stronger cement, whereas Grade 33 or 43 are enough to produce the concrete of desired characteristic strength. The scenario of method of production of cement by various manufacturers should also be kept in mind while ordering various grades of cement. The ability to produce cements of particular fineness get fixed by the machinery installed by the manufacturers, and thus the ability to produce other various grades of cement by a particular manufacturer also gets limited. Whereas tendency today is to supply the consumer what he orders for by the manufacturers by simply stamping such grades on the bags. Thus, it is often observed that cement bags marked as grade 33 or 43 may really be containing cements of much higher grade.

(ii )Compressive Strength : Compressive strength requirement of each type of cement for various grades when tested in accordance with IS 4031 (part 6) shall be as under:

(iii) Setting Time: Setting time of cement of any type of any grade when tested by Vicat apparatus method described in IS 4031 (Part-5)-1988 (Reaffirm-2014) shall conform to the following requirement:

(a) Initial setting time: Not less than 30 minutes 

(b) Final setting time: Not more than 600 minutes 

( iv )Supply : The cement shall be packed in jute sacking bags conforming to IS 2580, double hessian bituminized (CRI type) or woven HDPE conforming to IS 11652. Woven polypropylene  conforming to IS 11653, jute synthetic union conforming to IS: 12174, or any other approved composite bags, bearing the manufacturer’s name or his registered trade mark if any, with grade batch no. and type of cement, with date of manufacturing of batch of cement.

Every delivery of cement shall be accompanied by a producer’s certificate conforming that the supplied cement conforms to relevant specifications. These certificates shall be endorsed to the Engineer-in-Charge for his record.

Every consignment of cement must have identification marks on packages indicating date of manufacturing grade and type of cement batch no. etc. Cement brought to works shall not be more than 6 weeks old from the date of manufacture.

Effective precautionary measures shall be taken to eliminate dust-nuisance during loading or transferring cement.

( V) Stacking and Storage : Cement in bags shall be stored and stacked in a shed which is dry,leakproof and as moisture-proof as possible. Flooring of the shed shall consists of the two layers of dry bricks laid on well consolidated earth to avoid contact of cement bags with the floor. Stacking shall be done about 150 to 200 mm clear above the floor using wooden planks. Cement bags shall be stacked at least 450 mm clear off the walls and in rows of two bags leaving in a space of atleast 600 mm between two consecutive rows. In each row the cement bags shall be kept close together so as to reduce air circulation. Stacking shall not be more than 10 bags high to avoid lumping under pressure. 

In stacks more than 8 bags high, the cement bags shall be arranged in header and stretcher fashion i.e. alternately lengthwise and crosswise so as to tie the stacks together and minimise the danger of toppling over.

A typical arrangement for storing and stacking of cement is shown in fig.

Different types of cement shall be stacked and stored separately.Cement bags shall be stacked in a manner to facilitate their removal and use in the order in which they are received.

For extra safety during monsoon, or when cement is expected to be stored for an unusually long period, each stack shall be completely enclosed by a water proofing membrane, such as polyethylene, which shall cover the top of the stack. Care shall be taken to see that the water proofing membrane is not damaged at any time during use.

Storage of cement at the work site shall be at the contractor’s expense and risk. Any damage occurring to cement due to faulty storage in contractor’s shed or on account of negligence on his part shall be the liability of the contractor.

2 - Fine Aggregate

Aggregate most of which passes through 4.75 mm IS sieve is known as fine aggregate. Fine aggregate shall consist of natural sand, crushed stone sand, crushed gravel sand stone dust or marble dust,  fly ash and broken brick (Burnt clay) . It shall be hard, durable, chemically inert, clean and free from adherent coatings, organic matter etc. and shall not contain any appreciable amount of clay balls or pellets  and harmful impurities e.g. iron pyrites, alkalies, salts, coal, mica, shale or similar laminated materials in such form or in such quantities as to cause corrosion of metal or affect adversely the hardening, the strength, the durability or the appearance of mortar, plaster or concrete. The sum of the percentages of all deleterious material shall not exceed 5%. Fine aggregate must be checked for organic impurities such as decayed vegetation humps, coal dust etc. in accordance with the procedure prescribed in Appendix ‘A’ (Given at last) .

(I)  Silt Content : The maximum quantity of silt in sand as determined by the method prescribed in Appendix ‘C’ (Given at last) shall not exceed 8%.

Fine aggregate containing more than allowable percentage of silt shall be washed as many times as directed by Engineer-in-charge so as to bring the silt content within allowable limits for which nothing extra shall be paid.

(II) Grading : On the basis of particle size, fine aggregate is graded in to four zones. The grading when determined in accordance with the procedure prescribed in Appendix ‘B’  shall be within the limits given in Table - 1 below. Where the grading falls outside the limits of any particular grading zone of sieves, other than 600 micron IS sieve, by a total amount not exceeding 5 per cent, it shall be regarded as falling within that grading zone.
                                                                 Table - 1
                                                    Fine Aggregate

Note 1: For crushed stone sands, the permissible limit on 150 micron sieve is increased to 20 per cent. This does not affect the 5 per cent allowance permitted in (Fine Aggregate (III) (e) (1) ) applying to other sieves.

Note 2: Allowance of 5% permitted in (Fine Aggregate (III) (e) (1) )  can be split up, for example it could be 1% on each of three sieves and 2% on another or 4% on one sieve and 1% on another.

Note 3: Fine aggregate conforming to Grading Zone IV shall not be used in reinforced cement concrete unless tests have been made to ascertain the suitability of proposed mix proportions.

Note 4: Sand requiring use for mortar for plaster work shall conform to IS 1542 and for masonry work shall conform to IS 2116.

 (III) Type and grading of fine aggregate to be used shall be specified. Use of sea sand shall not be allowed, unless otherwise specified. Fine aggregate may further be sub-divided into following parts:-

(a) Coarse sand shall be either river sand, pit sand, crushed stone sand, crushed gravel sand or a combination of these. It shall be clean, sharp, angular, gritty to touch and composed of hard  siliceous material. Its grading shall fall within the limits of grading zone I, II, III of Table -1. Grading of sand shall conform to IS 2116 -1980 (Reaffirm-2012) for use in Masonry work.

(b) Fine sand shall be either river sand or pit sand or a combination of the two. Its grading shall fall within the limits of Grading zone IV of Table -1. As a guideline, fine sand conforming to grading Zone IV can be generally obtained in Delhi by mixing one part of Badarpur sand and two parts of jamuna Sand (by volume). Grading of sand shall conform to IS 1542 for use in plaster work. 

(c) Stone dust/Gravel dust shall be obtained by crushing hard stones or gravel. Its grading shall fall within the limits of grading Zone, I, II, III or IV of Table-1.

(d) Marble dust shall be obtained by crushing marble. Its grading shall fall within the limits of Grading  Zone IV of Table-1. Grading of Marble dust for use in Mortar shall be as per following table.

(e) Sand for Masonry Mortar and for Plaster- Sand shall consist of natural sand, crushed stone sand or crushed gravel sand or a combination of any of these. Sand shall be hard durable, clean and free from adherent coating and organic matter and shall not contain the amount of clay, silt and fine dust more than specified as under. 

Deleterious Material: Sand shall not contain any harmful impurities such as iron, pyrites, alkalis, salts,coal or other organic impurities, mica, shale or similar laminated materials, soft fragments, sea shale in such form or in such quantities as to affect adversely the hardening, strength or durability of the mortar. The maximum quantities of clay, fine silt, fine dust and organic impurities in the sand / Marble dust shall not exceed the following limits.

shall not exceed the following limits:
(1) Clay, fine silt and fine dust when determined in accordance within IS 2386 (Part II). In natural sand or crushed gravel sand & crushed stone sand : Not more than 5% by mass
(2) Organic impurities when determined in accordance with IS 2386 (Part II): Colour of the liquid shall be lighter than that indicated by the standard specified
in IS 2386 (Part II)

Grading of sand for use in masonry mortar shall be conforming to IS: 2116 -1980 (Reaffirm-2012) (Table-2 below).
Grading of sand for use in plaster shall be conforming to IS 1542 (Table-2 below):
                                                                 Table - 2

Note: For crushed stone sands, the permissible limit on 150 micron IS Sieve is increased to 20%, this does not affect the 5% allowance as per IS 2386 (Part 1).

(IV)  Bulking: Fine aggregate, when dry or saturated, has almost the same Volume but dampness causes increase in volume. In case fine aggregate is damp at the time of proportioning the ingredients for mortar or concrete, its quantity shall be increased suitably to allow for bulkage, which shall be  determined by the method prescribed in Appendix ‘D’  Table - 3 gives the relation
between moisture content and percentage of bulking for guidance only.
                                                        Table - 3

(V)  Stacking: Fine aggregate shall be so stacked as to prevent dust and foreign matter getting mixed up with it as far as practically possible. Marble dust in dry condition shall be collected in bags and properly staked so as not to form lumps, suitable arrangements shall be made to protect it from moisture similar to those adopted for stacking of cement bags.

(VI) Measurements: As the fine aggregate bulks to a substantial extent when partially wet,measurements shall be taken when the stacks are dry or appropriate allowance made for bulking.

3- Water

 Water used for mixing and curing shall be clean and free from injurious quantities of alkalies,acids, oils, salts, sugar, organic materials, vegetable growth or other substance that may be deleterious to bricks, stone, concrete or steel. potable water is generally considered satisfactory for mixing. The Ph value of water shall be not less than 6. The following concentrations represent the  maximum permissible values: (of deleterious materials in water).

(a) Limits of Acidity: To neutralize 100 ml sample of water, using phenolphthalein as an indicator,  it should not require more than 5ml of 0.02 normal NaOH. The details of test shall be as given  in IS 3025 (part 22). 

(b) Limits of Alkalinity: To neutralize 100ml sample of water, using mixed indicator, it should not require more than 25ml of 0.02 normal H2SO4. The details of tests shall be as given in IS 3025 (part 23)-1986 (Reaffirm 2003).

(c) Percentage of Solids: Maximum permissible limits of solids when tested in accordance with IS  3025 shall be as under: 

Organic 200mg/ litre

Inorganic 3000 mg/ litre

Sulphates 400 mg/ litre

Chlorides 2000 mg/ litre.for concrete not containing embedded steel and 500 mg./ltr.for reinforced concrete work.

Suspended matter 2000 mg/ litre

The physical and chemical properties of ground water shall be tested along with soil investigation  and if the water is not found conforming to the requirements of IS 456-2000, the tender documents  shall clearly specify that the contractor has to arrange good quality water for construction indicating the source.

 Water found satisfactory for mixing is also suitable for curing. However, water used for curing shall not produce any objectionable stain or unsightly deposit on the surface.

Sea water shall not be used for mixing or curing.

Water from each source shall be tested before the commencement of the work and thereafter once in every three months till the completion of the work. In case of ground water, testing shall also be done for different points of drawdown. Water from each source shall be got tested during the dry  season before monsoon and again after monsoon.

4 - Broken Brick (Burnt Clay) Fine Aggregate

(I) Broken Brick (Burnt Clay) Fine Aggregate, also known as Surkhi, shall be made by grinding well burnt (but not under or over burnt) broken bricks as specified in IS 3182-1986 (Reaffirm-2014). It shall not contain any harmful impurities, such as iron pyrites, salts, coal, mica, shale or similar laminated or other materials in such form of quantity as to adversely affect hardening, strength,durability or appearance of the mortar. The maximum quantities of clay, fine silt, fine dust and organic impurities in surkhi (all taken together) shall not exceed five per cent by weight. The particle size grading of surkhi for use in lime mortars shall be within the limits specified in Table - 4.
                                                 Table - 4

(II) Stacking: Surkhi shall be stacked on a hard surface or platform so as to prevent the admixture of clay, dust, vegetation and other foreign matter. It shall be also protected form rain and dampness  and kept under adequate coverings.

(III)  Measurements: Surkhi shall be measured in regular stacks in cubic metres. Alternatively it may be measured by weight when supplied in bags.

5- Fly Ash

Fly ash is finely divided residue resulting from the combustion of pulverized coal in boilers. Fly ash is the pulverized fuel ash extracted from the flue gases by any suitable process such as cyclone 

separation or electrostatic precipitation. The ash collected from the bottom of boilers is termed as bottom ash. Fly ash is finer than bottom ash. Siliceous fly ash (ASTM Class F) containing calcium oxide less than 10% by mass is normally produced from burning anthracite or bituminous coal and 

possesses pozzolanic properties. Calcareous fly ash (ASTM Class C) is produced by burning lignite or sub-bituminous coal and contains calcium oxide more than 10% by mass; the content could be as high

as 25%. This fly ash has both hydraulic and pozzolanic properties. It shall be clean and free from any contamination of bottom ash, grit or small pieces of pebbles. It is obligatory on the part of supplier/ 

manufacture that the fly ash conforms to the requirements if mutually agreed upon & shall furnish a certificate to this effect to the purchaser or his representative.

(I) Characteristics: The physical requirements of fly- ash shall be as specified in Annexure ‘E’ . The chemical properties of fly ash shall be as per IS 3812 (part 1 & 2) depending on the usage.

(II)  Stacking: Fly ash shall be protected from dirt collecting on it.

(III)  Measurements: Fly ash shall be measured in regular stacks in cubic metres. Alternatively it may be measured by weight when supplied in bags.

B- PREPARTATION OF MORTARS AND ITS GRADE

(1)  Grade of Masonry Mortar

The grade of masonry mortar will be defined by its compressive strength in N/mm2 at the age of 28 days as determined by the standard procedure detailed in IS 2250.

(I)  For proportioning the ingredients by volume, the conversion of weight into volume shall be made on the following basis:

                                                         Table - 5

For details of grades and criteria for selection of Masonry mortars see Appendix ‘F’ .

(2) Cement Mortar

(I)  This shall be prepared by mixing cement and sand with or without the addition of pozzolana in specified proportions as per Appendix ‘F’.

(II) Proportioning: Proportioning on weight basis shall be preferred taking into account specific gravity of sand and moisture content . Boxes of suitable size shall be prepared to facilitate proportioning on weight basis. Cement bag weighting 50 kg shall be taken as 0.035 cubic metre. Other ingredients in specified proportion shall be measured using boxes of size 40 x 35 x 25 cm. Sand shall be measured on the basis of its dry volume in the case of volumetric proportioning.

 (III) Mixing

The mixing of mortar shall be done in mechanical mixers operated manually or by power as decided by Engineer-in-Charge. The Engineer-in-Charge may, however, permit hand mixing at his discretion taking into account the nature, magnitude and location of the work and practicability of the use of mechanical mixers or where item involving small quantities are to be done or if in his opinion the use of mechanical mixer is not feasible. In cases, where mechanical mixers are not to be used, The
contractor shall take permission of the Engineer-in-Charge in writing before the commencement of the work.

(a) Mechanical Mixing: Cement and sand in the specified proportions shall be mixed dry thoroughly in a mixer. Water shall then be added gradually and wet mixing continued for at least three minutes. only the required quantity of water shall be added which will produce mortar of
workable consistency but not stiff paste. Only the quantity of mortar, which can be used within 30 minutes of its mixing shall be prepared at a time. Mixer shall be cleaned with water each time before suspending the work.

(b) Hand Mixing: The measured quantity of sand shall be leveled on a clean masonry platform and cement bags emptied on top. The cement and sand shall be thoroughly mixed dry by being turned over and over, backwards and forwards, several times till the mixture is of a uniform colour. The quantity of dry mix which can be used within 30 minutes shall then be mixed in a
masonry trough with just sufficient quantity of water to bring the mortar to a stiff paste of necessary working consistency. 

(IV) Precautions: mortar shall be used as soon as possible after mixing and before it begins to set,and in any case within half hour, after the water is added to the dry mixture.

3 - Cement Flyash Sand Mortar

This shall be prepared by mixing cement, flyash and sand in specified proportions as per Appendix G. Mixing shall be done in a mechanical mixer (operated manually or by power) unless other￾wise permitted by the Engineer-in-Charge in writing. The Engineer-in-Charge may, however, permit
hand mixing at his discretion, taking into account the nature, magnitude and location of the work and practicability of the use of mechanical mixer or where items involving small quantities are to be done or if in his opinion the use of mechanical mixer is not feasible. In case, where mechanical mixer is not to be used, the contractor shall take permission of the Engineer-in-Charge in writing before the commencement of the work.

(I) Proportioning: Proportioning on weight basis shall be preferred taking into account specific gravity of Fly Ash, sand and moisture content. Boxes of suitable size shall be prepared to facilitate
proportioning on weight basis. Cement bag weighting 50 kg shall be taken as 0.035 cubic metre. Other ingredients in the specified proportions shall be measured using boxes of suitable sizes. Sand and
flyash shall be measured on the basis of their dry volume in the case of volumetric proportioning.

(II)  Mixing

(a) Mechanical Mixing: Sand and flyash in the specified proportions shall be mixed dry in a mixer and then the specified quantity of cement shall be added and mixed dry thoroughly. Water shall
then be added gradually and wet mixing continued for atleast one minute. Water shall be just sufficient to bring the mortar to the consistency of a workable paste. Only the quantity of mortar which can be used within 30 minutes of its mixing shall be prepared at a time.

(b) Hand Mixing: The measured quantity of sand and flyash shall be mixed dry on a clean masonryplatform before adding specified quantity of cement to it. The resulting mixture of cement, sand and flyash shall then be mixed thoroughly being turned over and over, backward several times till the mixture is of a uniform colour. The quantity of dry mix which can be used within 30 minutes shall then be mixed in a clean watertight masonry trough with just sufficient quantity of water, to bring the mortar to a stiff paste of necessary working consistency.

(III) Precautions

Mortar shall be used as soon as possible after mixing and before it begins to set,

and in any case within half hour, after the water is added to the dry mixture.

  

APPENDIX ‘A’

TEST FOR ORGANIC IMPURITIES

The aggregate must also be checked for organic impurities such as decayed vegetation humus, coal dust etc.

What is called the colour test is reliable indicator of the presence of harmful organic matter in aggregate, except in the area where there are deposits of lignite.

Fill a 350 ml clear glass medicine bottle upto 70 ml mark with a 3% solution of caustic soda or sodium hydroxide. The sand is next added gradually until the volume measured by the sandy layer is 

125 ml. The volume is then made upto 200 ml by addition of more of solution. The bottle is then stoppered and shaken vigorously and allowed to stand for 24 hours. At the end of this period, the 

colour of the liquid will indicate whether the sand contains a dangerous amount of matter. A colourless liquid indicates a clean sand free from organic matter. A straw coloured solution indicates some organic 

matter but not enough to be seriously objectionable. Darker colour means that the sand contains injurious amounts and should not be used unless it is washed, and a retest shows that it is satisfactory.

Add 2.5 ml of two per cent solution of tannic acid in 10 per cent alcohol, to 97.5 ml of three per cent sodium hydroxide solution. Place in a 350 ml bottle, fix the stopper, shake vigorously and allow to 

stand for 24 hours before comparison with the solution above the sand.

Note: A three per cent solution of caustic soda is made by dissolving 3 g of sodium hydroxide in 100 ml of water, preferably distilled. The solution should be kept in a glass of bottle tightly closed with a

rubber stopper. Handling sodium hydroxide with moist hands may result in serious burns. Care should  be taken not to spill the solution for it is highly injurious to clothing, leather, and other materials.

APPENDIX ‘B’

TEST FOR PARTICLE SIZE (SIEVE ANALYSIS)

Apparatus: Perforated plate sieves of designation 10 mm, 4.75 mm and fine mesh sieve of designation2.36 mm, 1.18 mm, 600 micron, 300 micron and 150 micron should be used.
The balance or scale shall be such that it is readable and accurate to 0.1 per cent of the weight of the test sample.

Sample: The weight of sample available shall not be less than the weight given in the table below. Thesample of sieving shall be prepared from the larger sample either by quartering or by means of a sample divider.

Test Procedure: The sample shall be brought to an air-dry condition before weighing and sieving. This may be achieved either by drying at room temperature or by heating at a temperature of 100 degree to 110 degree centigrade. The air dry sample shall be weighed and sieved successively on the appropriate sieves starting with the largest. Care shall be taken to ensure that the sieves are clean before use.

Each sieve shall be shaken separately over a clean tray until not more than a trace passes, but in any case for a period of not less than two minutes. The shaking shall be done with a varied motion, backwards and
forwards, left to right, circular clockwise and anti-clockwise, and with frequent jarring, so that the material is kept moving over the sieve surface in frequently changing directions. Materials shall not be forced through the sieve by hand pressure, but on sieves coarser than 20 mm, placing of particles is permitted, Lumps of fine
material, if present may be broken by gentle pressure with fingers against the side of the sieve. Light brushing of under side of the sieve with a soft brush may be used to clear the sieve openings.

Light brushing with a fine camel hair brush may be used on the 150 micron IS sieve to prevent segregation of powder and blinding of apertures. Stiff or worn out brushes shall not be used for this purpose and pressure shall not be applied to the surface of the sieve to force particles through the mesh.

On completion of sieving the material retained on each sieve, together with any material cleaned from the mesh, shall be weighed.

Reporting of Results: The results shall be calculated and reported as:

(a) The cumulative percentage by weight of the total sample passing each of the sieves, to the nearest whole number:

or

(b) The percentage by weight of the total sample passing one sieve and retained on the next smaller sieve, to the nearest 0.1 percent.

APPENDIX ‘C’

TEST FOR SILT CONTENT

The sand shall not contain more than 8% of silt as determined by field test with measuring cylinder.

The method of determining silt contents by field test is given below:

A sample of sand to be tested shall be placed without drying in a 200 ml measuring cylinder. The volume of the sample shall be such that it fills the cylinder upto 100 ml mark

Clean water shall be added upto 150 ml mark. Dissolve a little salt in the water in the proportion one tea spoon to half a litre. The mixture shall be shaken vigorously, the last few shakes being sidewise direction to level off the sand and the contents allowed to settle for three hours.

The height of the silt visible as settled layer above the sand shall be expressed as a percentage of the height of sand below. The sand containing more than the above allowable percentage of silt, shall be washed so as to bring the silt contents within allowable limits.


APPENDIX ‘D’

BULKING OF FINE AGGREGATES/SAND (FIELD METHODS)

Two methods are suggested for determining the bulking of sand/fine aggregate. The procedure may be suitably varied, if necessary. Both depend on the fact that the volume of inundated sand/fine aggregate is the same if the sand/fine aggregate were dry.

Method -1: Put sufficient quantity of sand loosely into a container until it is about two -third full. Level off the top of the sand and push a steel rule vertically down through the sand at the middle to bottom, measure the height. Suppose this is ‘X’ cm.

Empty the sand out of the container into another container where none of it is lost. Half fill the first container with water. Put back about half the sand and rod it with a steel rod, about 6 mm in diameter, so that its volume is reduced to a minimum. Then add the remainder and level the top surface of the inundated sand. Measure its depth at the middle with the steel rule. Suppose this is ‘Y’ cm.

The percentage of bulking of the sand due to moisture shall be calculated from the formula:

Percentage bulking = (X/Y -1) X 100

Method -2: In a 250 ml measuring cylinder, pour the damp sand, consolidate it by staking until it reached the 200 ml mark.
Then fill the cylinder with the water and stir the sand well (the water shall be sufficient to submerge the sand completely). It will be seen that the sand surface is now below its original level. Suppose the surface is at the mark of Yml, the percentage of bulking of sand due to moisture shall be calculated from the formula.

Percentage bulking= (200/Y – 1) x 100




APPENDIX ‘E’


PHYSICAL REQUIREMENTS OF FLY ASH

APPENDIX ‘F’

CRITERIA FOR SELECTION OF MASONRY MORTARS


(a) The selection of masonry mortars from durability consideration will have to cover both the loading and exposure condition of the masonry. The masonry mortar shall generally be as specified below
in (b) to (g).

(b) In case of masonry exposed frequent to rain and where there is further protection by way of  plastering or rendering or other finishes, the grade of mortar shall not be less than 0.7 MM but shall preferably be of grade MM2. Where no protection is provided, the grade of mortar for external wall  shall not be less than MM2.

(c) In case of load bearing internal walls, the grade of mortar shall preferably be MM 0.702 or more for high durability but in no case less than MM 0.5.

(d) In the case of masonry work in foundations laid below damp proof course, the grade of mortar for use in masonry shall be as specified below.
(i) Where soil has little moisture, masonry mortar of grade not less than MM 0.7 shall be used.
(ii) Where soil is very damp, masonry mortar of grade preferably MM 2 or more shall be used. But in no case shall the grade of mortar be less than MM 2.

(e) For masonry in building subject to vibration of machinery, the grade of mortar shall not be less than MM 3.

(f) For parapets, where the height is greater than thrice the thickness, the grade of masonry mortar shall not be less than MM3. In case of low parapets the grade of mortar shall be the same as used in the wall masonry.

(g) The grade of mortar for bedding joints in masonry with large concrete blocks shall not be less than MM 3.

(h) The compressive strength shall be determined in accordance with the procedure given in IS 2250.

(i) While mixing the pozzolanic material like fly ash in mortars Ordinary Portland cement only shall be
use.
         
                Grade of Masonry Mortar (IS 2250 )

Note:
* Pozzolana of minimum lime reactivity of 4 N/MM2
** This ratio by volume correspondence approximately to cement pozzolana ratio of 0.8:0.2 by weight. In this case, only ordinary portland cement is to be used (see IS 269). Specifications for ordinary rapid hardening and low heat Portland Cement (Third revision).
Note : Compressive strength shall be determined in accordance with the Appendix –A-IS 2550.

Thanks a lot 

Mukesh Kumar 

www.gyanofcivilengineering.com

Source of Content  : CPWD SPECIFICATIONS 2019