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I ndian StandardPREPARATIONANDUSEOFMUD MORTAR

INMASONRY -GUIDE

UDC 691532 : 6932

0 BIS 1991BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002July 1991 Price Growp 1

( Reaffirmed 1997 )

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Building Construction Practices Sectional Committee, BDC 13

.FOREWORDIhis Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized bythe Building Construction Practices Sectional Committee had been approved by the CivilEngineering Division Council.One of the strategies of the new housing policy is to promote use of locally available low costbuilding materials. As both material and skill for mud mortar are locally available, its use inbrick masonry will be a small step towards saving scarce material like cement which is also energyintensive and keeping the cost of construction on lower side. Further, mud mortar being thermalinsulating material, helps in saving energy cost during usage of dwelling.This standard is intended to serve as a guide in selecting proper type of raw material and usingproper method for preparation and use of mud mortar for quality construction.

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IS 13077 1991

Indian StandardPREPARATIONANDUSEOFMUDMORTAR

INMASONRY- GUIDE1 SCOPE1.1 This standard covers the selection of clayfor mud mortar, methods of its preparation anduse in masonry.2 REFERENCES2.1 The Indian Standards listed in Annex A arenecessary adjuncts to this standard.3 TERMINOLOGY3.1 For the purpose of this standard, definitionsgiven in IS 2809 : 1972 shall apply.4 SELECTION OF CLAY FOR MUDMORTAR4.1 The clay or mixture of clays should pre-ferably conform to the following mechanicalcomposition.Grain size analysis shall be done in accordance6;: the methcd given in IS 2720 (Part 4 > :

Clay 18-22 percent by weightSilt 40-45 per cent by weightSand 30-40 percent by weight

4.2 The total content of clay and silt be pre-ferably not less than 60 percent by weight.NOTE - In case of soils which are more sandy orclayey than the limits specified above, the sameshould be blended with more plastic clay or non-plastic materials as the case may be so as to bringthe mechanical composition within the abovespecified limits.

4.3 Plasticity IndexThe plasticity index shall be determined inaccordance with the method given in IS 2720( Part 5 ) : 1970 for large and important projectsand it should range between 12-15. However,in case of projects of lesser importance andsmaller size, the field test as given in 7 may besufficient.5 DESIGN CONSIDERATIONS5.1 The durability of masonry mortars dependsupon the volume changes during the process ofsetting, hardening and later due to temperaturevariations, moisture movement in the surround-ing, changes in its own moisture content and theextent to which mortar will internally accom-modate the stresses induced by these volumetricchanges before yielding.

5.2 The bond between the mortar and masonryunits if ruptured by the volumetric changes andthe structural movements results not only inreduction in strength of masonry but also information of channels of seepage of water andother solutions into the masonry. This wouldaggravate the process of deterioration andaffect resistance to chemical attack in aggressiveenvironment.5.3 The compressive and bond strength ofmud mortar decreases with the increase inmoisture content in it. The compressive strengthdecreases by 08 to 1 N/mm at 6-10 percentmoisture content ( see Fig. 1 ).

SOIL ACLAY 20*2 1.SILT 117* 8 */aSAND 32.0 10

MOISTURE CONTENT(PERCENT)

FIG. 1 STRENGTH OF MUD MORTARDIFFERENT MOISTURE CONTENTS

AT

5.3.1 Moisture to the extent of 5 to 8 percentby weight is likely to penetrate in the mudmortar even after plastering or pointing theexposed surface of masonry.5.3.2 Since the mud mortar is susceptible toweathering, mud mortar masonry may be usedfor temporary structures and low rise structureshaving adequate lateral stability.5.3.3 Basic stress in masonry with bricks of 7 to10 N/mm2 and 3.5 N/mm? shall not exceed02 N/mm2 and 01 N/mm2, respectively.5.3.4 Thickness of mud mortar should not bemore than 20 mm in case of brick masonryworks and 30 mm in case of stone masonryworks.

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fS 13 077 : 19915.3.5 The masonry should preferably beplastered or pointed by cement or lime mortarexternally to avoid erosion of mortar from joints.5.3.6 Concentrated load should be distributedby providing plain concrete or RCC bed blocksor by using cement mortar masonry below theconcentrated loads.

NOTE - For mud mortar construction in seismiczones refer 1s 4326 : 1976.6 PREPARATION OF MORTAR6.1 The soil for preparation of mud mortarshould be processed so as to be free from gravelcoarse sand ( particle size greater than 2 mm )lime and kankar particles vegetable matter, etc.6.2 Coarse grit, karkar, etc, if present shouldbe removed by wet sieving.6.3 The sieved clay should be allowed to dryand then blended with plastic clay or a non-plastic locally available material ( like rice husk,jute waste, wheat husk, etc ) as the case may be,so as to bring the mechanical composition withinthe limits specified under 4.1 above.Where wet sieving is not necessary, the soil shallbe lightly broken up and wetted. The wet massshall be tempered over under the feet, repeatedlyturned over big spades and then thoroughly

kneaded. The kneaded mass shall than be leftfor Tempering for at least 24 hours with thesoil being prefeGbly covered with wet gunnybags.6.4 Immediately before use in the masonry asmall quantity of the prepared soil shall bemixed with a further quantity of water to obtainthe desired consistency and workability. Thetotal moisture content of the prepared mortarshall be in the range of 35 to 40 percent byweight of soil.7 FIELD TEST7.1 For quick field observation and intermittentchecks, sample test as given in Annex B may bemade.7.1.1 If the ball prepared as given in Annex Bhas deformed on drying and crumbles easilywhen pressed lightly, it may be inferred thatsand content is excessive.7.1.2 If the ball is hard but shows cracks on thesurface, then the sand content is insufficient.7.1.3 If the soil is not found suimble, as inferredabove, the test should bs repeated after modi-fying the composition of the soil, such as bymixing different proportions of two soils or byaddition of sand or clay whichever is needed,for checking the stability.

ANNEX A( Clause 2.1 )

LI ST OF REFERRED INDIAN STANDARDSIS No.

2720( Part 4 ) : 19862720( Part 5 ) : 1970

T i t l e IS No.Method of test for soils: Part 2809 : 19724 Grain size analysis ( secondrevi sion )Method of test for soils: 4326 : 1976Part 5 Determination ofliquid and plastic limits(first revision )

T i t l eGlossary of terms andsymbols relating to soilengineering (first revi sion )Code of practice for earth-quake resistant design andconstruction of buildings(first revi sion )

ANNEX B( Clause 7.1 )

FIELD TESTS FOR SOIL FOR MASONRY MUD MORTARB-l The soil should be ground to a fine powder and form into a ball of about 80 mm diameter.and mixed with sufficient water, added in smallquantities. The mix should then be kneaded B-3 Keep the ball in the sun for drying. Wheninto a plastic mass of the required consistency. dried, examine the ball for loss of shape andsurface cracks, if any.B- 2 Take a handful of the soil prepared in B-l

2

http://../link/15to30/2720_4.Bishttp://../link/15to30/2720_4.Bishttp://../link/15to30/2720_4.Bishttp://../link/15to30/2720_4.Bishttp://../link/15to30/2720_5.Bishttp://../link/15to30/2720_5.Bishttp://../link/15to30/2720_5.Bishttp://../link/15to30/2809.Bishttp://../link/15to30/2809.Bishttp://../link/15to30/2809.Bishttp://../link/31to60/4326.Bishttp://../link/31to60/4326.Bishttp://../link/31to60/4326.Bishttp://../link/31to60/4326.Bishttp://../link/15to30/2809.Bishttp://../link/15to30/2720_5.Bishttp://../link/15to30/2720_4.Bis

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.

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Boreao of India&StandardsBIS is a statutory institution established under the Bureau of ndi an St andard3 Act, I 986 to promoteharmonious development of the activities of standardization, marking and quality certification ofgoods and attending to connected matters in the country.Copyright .BIS has the copyright of all its publications. No part of these publications may be reproduced inany form without the prior permission in writing of BIS. This does not preclude the free use, inthe course of implementing the standard, of necessary details, such as symbols and sizes, type OFgrade designations. Enquiries relating to copyright be addressed to the Director ( Publication ), BIS.Revision of Indian StandardsIndian Standards are reviewed periodically and revised, when necessary and amendments, if any,are issued from time to time. Users of Indian Standards should ascertain that they are inpossession of the latest amendments or edition. Comments on this Indian Standard may be sentto BIS giving the following reference :Dot : No. CED 13 (4688 )

Amendments Issued Since PublicationAmend No. Date of Issue Text Affected

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