सदंर्भ: डब्‍ल्लयलू डलड0ल /टील–43ल ल ददन ंक: 05/06/2017

लल

तकनीक समितत : ब धंलऔडलस्पिलवे ववषय समितिलडब्‍ल्लयूल डलड0ल प्रेषिती

1. ब ॉंध और स्पिलवे षविय समितत डब्‍ ् यू र डी 09 के सभी सदप य । 2. जल सॉंसाधन षवभाग िररिद् (डब्‍ ् य ू र डीलसी) के सदप य । 3. रूचि रखने वाले सभी तनकाय ।

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धन् यवाद ।

डलएसलजुनेज ü

व।0 एो एवॉं प्रि खú(जल सॉंसाधन षवभाग)

प्रतत : उिमलािखत

(जल सॉंसाधन षवभाग) ( WATER RESOURCES DEPARTMENT)

व्यािक िररिालन िसौदा

नोट : कृिय लधय् नलदेंलककलयिलिसौद ल िकीलसिि्तिय लंिेिुलिैंलिथ लइसक प्रयोगलककस0लअनय्लउद्वेशय्लकेलमलएलनिींलकडेलक्योंककलयेलक ि0ड इटलकेलिििलिैंल।

सदंर्भ: डब्‍ल्लयलू डलड0ल /टील–43 ददन ंक: 05/06/2017 Technical Committee: Dams And Spillways Sectional Committee, WRD 09

Addressed to:

1. All Members of Dams And Spillways Sectional Committee, WRD 09

2. All interested Members of WRDC

3. All others interested.

Dear Sir(s)/Madam(s),

As per the decision taken in the 16th meeting of the sectional committee, the following

documents is hosted on the BIS website www.bis.org.in :

DOC. NO. TITLE

WRD 9 (689) Colgrout Masonry in Dams-Code of Practice

Kindly examine this draft and forward your views stating any difficulties which you are likely to

experience in your business or profession, if this is finally adopted as a national standard and

kindly provide your specific suggestion for revising the same in view of latest technology.

Last Date for Comment is 31 July 2017

Comments, if any, may please be made in the format as annexed and mailed to the undersigned at

the above address. Comments will be appreciated in electronic form at the e-mail address

‘wrd@bis.org.in. In case you have any difficulty in accessing the document at our website,

please write to us for a hard copy.

In case no comments are received or comments received are of editorial nature, you will kindly

permit us to presume your approval for the above document as finalized. However, in case of

comments of technical in nature are received then it may be finalized either in consultation with

the Chairman, Sectional Committee or referred to the Sectional committee for further necessary

action if so desired by the Chairman, Sectional Committee.

Thanking you, Yours faithfully,

(R.S. Juneja)

Sc.F & Head (WRD)

Encl: as above. Note: Please note that the documents attached are for your comments only and shall not be used for any other purpose as they

are under copy right.

(जल सॉंसाधन षवभाग) (WATER RESOURCES DEPARTMENT)

FORMAT FOR SENDING COMMENTS ON BIS DOCUMENTS

(Please use A4 size sheet of paper only and type within fields indicated.

Comments on each clauses/sub-clauses/table/fig. etc be started on a fresh box.

Information in Column 5 should include reasons for the comments and

Column 6 for suggestions for modified wording of the clauses when the

existing text is found not acceptable. Adherence to this format facilitates

Secretariat’s work)

Doc. No.: WRD 09(689)C

Title: Colgrout Masonry in Dams-Code of Practice

LAST DATE OF COMMENTS: 31/07/2017

NAME OF THE COMMENTATOR/ORGANIZATION: _________________________

Sl.

No.

(1)

Clause/Sub-clause/

para/table/fig. No.

commented

(2)

Commentator/

Organization/

Abbreviation

(3)

Type of Comments

(General/Editorial/

Technical)

(4)

Justification

(5)

Proposed

change

(6)

For official use only Doc. WRD 09 (689) June 2017

BUREAU OF INDIAN STANDARDS

Draft Indian Standard

र् डि0यलि नकल

ब धंोलिेंलक ग्र उडलचिन ईल-लडीतिलसंदिि Indian Standard

COLGROUT MASONRY IN DAMS- CODE OF PRACTICE

(Not to be reproduced without the Last date for receipt

permission of BIS or used as a of comments is 31 July 2017

Standard)

FOREWORD

(Formal clauses will be added later)

Uncoursed rubble masonry for dams is extensively used till date. With a view to keep

pace with construction speed and to get expected performance from masonry work, more

advanced techniques are required to be researched, experimented & implemented.

Colgrout Masonry is one of them which satisfies the requirement of strength and

durability and at the same time, being impervious, is particularly suitable for water

retaining structures in Indian conditions. It has been used in upstream septum of gravity

dams in Maharashtra and results are encouraging. Its use for modern structures is

increasing steadily. Need was, therefore, felt to formulate a standard to serve as a useful

guide to field engineers.

In preparation of this standard, valuable assistance has been derived from the practices

followed for construction of various colgrout masonry dams in Maharashtra.

For the purpose of deciding whether a particular requirement of this standard is complied

with, the final value, observed or calculated, expressing the results of a test or analysis,

should be rounded off in accordance with IS 2:1960 “Rules for rounding off numerical

values (revised)”. The number of significant places retained in the rounded off value

should be the same as that of the specified value in this standard.

Doc. WRD 09 (689)

June 2017

Draft Indian Standard

र् डि0यलि नकल

ब धंोलिेंलक ग्र उडलचिन ईल-लडीतिलसंदिि Indian Standard

COLGROUT MASONRY IN DAMS- CODE OF PRACTICE

1 SCOPE

1.1 This standard covers requirements regarding quality of material and general

construction practices for colgrout masonry used in dams & other massive structures

(generally for small and medium height dams). The code aims at control of colgrout work

with a view to ensuring strength, durability, impermeability and uniformity. This standard

requires to be supplemented by special instructions, if any, for each job.

2. REFERENCES

The following standards contain provisions which through reference in this text,

constitute provisions of this standard. At the time of publication, the editions indicated

were valid. All standards are subject to revision, and parties to agreements based on this

standard are encouraged to investigate the possibility of applying the most recent editions

of the standards indicated below:

IS No. Title

269:2015 Ordinary portland cement (Sixth Revision)

383:2016 Coarse and fine aggregates for concrete (Third Revision)

455:2015 Specification for Portland slag cement (Fifth Revision)

456:2000 Plain and reinforced Concrete – Code of Practice (Third

Revision)

460(Part 1):1985

Specification for test sieves : Part 1 Wire cloth test sieves

(Third revision)

1121(Pt 1):2013 Determination of strength properties of natural building

stones: Method of test Part 1 Compressive strength (Second

Revision)

1124:1974 Method of test for determination of water absorption,

apparent specific gravity and porosity of natural building

stones (First Revision)

1126 : 2013 Determination of durability of natural building stones -

Method of test (Second Revision)

1489(Part 1):2015 Specification for portland pozzolana cement Part 1 Flyash

based (Fourth Revision)

1597 (Part 1):1992 Construction of stone masonry – Code of practice – Part 1:

rubble stone masonry (First Revision)

2116 :1980 Specification for sand for masonry mortars (First Revision)

2250 : 1981 Code of practice for preparation and use of masonry mortars

(First Revision)

3085:1965

Method of test for permeability of cement mortar and concrete

6909: 1990 Specification for supersulphated cement

9103:1999 Concrete admixtures – Specification (first revision)

11155:1994 Construction of spillways and similar overflow structures –

Code of Practice (first revision)

11216 :1985

Code of practice for permeability test for masonry (during and

after construction)

11223:1985 Guidelines for fixing spillway capacity

3 TERMINOLOGY

For the purpose of this standard, the following definitions should apply -

a) Bond – An interlocking arrangement of structural units in the masonry to ensure

stability.

b) Bond stone – Selected long stones used to hold the masonry together transversely.

c) Coefficient of permeability – The rate of flow of water under laminar flow

conditions through a unit cross sectional area of porous medium under a unit

hydraulic gradient and at a standard temperature of 270 C.

d) Colgrout double drum mixer – The mixer used for preparing colgrout mortar.

e) Colgrout flow meter – Flow meter used for measuring the flow of colgrout mortar.

f) Colgrout masonry – Resultant masonry by injection of colgrout mortar in

pre-packed stones.

g) Colgrout mortar or Colloidal grout – A mixture of cement, fine aggregate and water

and admixture, if any, mixed at high speed in colgrout double drum mixer.

h) Colgrouting – Inserting colloidal grout with some suitable pressure to fill up voids,

in the prepacked stones or in the body of dam.

i) Hammer dressing – Rough surfacing to a stone by means of a spall hammer.

j) Interstice – Void or space between adjacent placed stones.

k) Laitance – An extremely fine film of material of little hardness which may form on

the surface of freshly laid masonry.

l) Lugeon – It is the water loss in litre per minute per meter depth of the drill hole

under a pressure of ten atmosphere maintained for ten minutes in a drill hole of 46

to 76mm diameter.

m) Sand – Natural sand or sand prepared from crushed stone, gravel or such other inert

materials.

n) Pozzolana – An essentially siliceous material which in itself possessing no

cementitious properties, in finely divided form and in the presence of water, react

with calcium hydroxide at ordinary temperature to form compound possessing

cementitious properties.

o) Stretcher stones (Pin header) – Selected long stones embedded vertically in the

interior of colgrout masonry to form a bond between successive courses.

p) Slurry – Paste of cement and water.

4 MATERIALS

4.1 Cement

Ordinary Portland cement, Portland slag cement, Portland pozzolona cement and

Super Sulphated cement used for colgrout masonry work in dams and other massive

structures should comply with the requirements of IS 269, IS 455, IS 1489 and IS 6909

respectively. Special cements may also be specified for use in dam masonry.

4.2 Admixture

Admixture including pozzolanas, air entraining agents, wetting agents, etc. should be used

only under specific authorization and wherever so permitted, the proportions and methods

of use should be specified by the engineer-in-charge. The chemical admixtures should

conform to IS : 9103.

4.2.1 Materials permitted as admixtures should have established merit for improving any

specific quality of the mortar without causing deleterious effects.

4.3 Sand

The sand should conform to IS 2116 and IS 383.

4.4 Stone

4.4.1 Stone for Masonry - The stones for masonry should be hard, dense, durable, tough,

sound and clean. They should be free from decay, weathered faces, soft seams, adhering

coatings, sand holes, veins, flaws, cracks, stains and other defects and should have as far

as possible, uniform colour and texture. Stones not uniform in colour, texture and/or with

stains may be permitted after proper tests. The stone should be taken from quarries

approved from geological and engineering considerations. The size of stones should

normally vary from 0.05to 0.01 cum. No stone should weigh less than 25 kg. No stone

weighing between 75 kg and 150 kg should be less than 225 mm in any direction and no

stone weighing between 25 kg and 75kg should be less than 150 mm in any direction.

4.4.1.1 Spalls – Spalls with the minimum dimension of 200 mm to 100 mm should be

used to wedge into the interstices of stones. They should not normally exceed 10 percent

of the volume of colgrout masonry.

4.4.2 Stone for Coursed Face Work – The height of the stone for face work should be

uniform and is recommended to be 300 mm including mortar joint. The length and depth

of the face stone should not be less than the height of the stone. At least 50 percent of the

stones should have length more than twice the height of the stone. At least one third of the

remaining stones should be bond stones projecting not less than 2½ times the height into

the masonry. The remaining should be header stones with depth not less than 1½ times the

height of the stone. The stones should be hammer dressed on face and one line chisel

dressed on bed, top and sides for a minimum depth of 75 mm up to which the stones

should be true and rectangular. Beyond 75 mm depth, the stones may be tapered but the

tail end of the stones should have at least half the area of the faces. Bushing on the faces

of the stones should not project more than 40 mm.

4.4.2.1 Header stones – The header stones should not be less than 300 mm in length and

one and half times the height in depth.

4.4.2.2 Stretcher stones – The stretcher stones should not be less than 600 mm in length

and not less than its height in depth.

4.4.2.3 Bond stones – The bond stones should not be less than 300 mm in length

and two and half times the height in depth.

4.4.3 Stone for Uncoursed Face Work – Stones for uncoursed face work should be of

selected stones meeting the requirement of stones for coursed face work masonry (Ref

4.4.2) except that the stones should be hammer dressed and nearly rectangular.

4.4.4 Tests – Samples of stone from approved quarry or new quarry should be tested for

compressive strength in accordance with IS 1121(Part 1). The compressive strength

testing should be conducted with the load parallel to the bedding plane and also

perpendicular to the bedding plane. The stone samples should also be tested for water

absorption in accordance with IS 1124 and for soundness in accordance with IS 1126 to

ensure suitability of stones for masonry.

4.5 Water

Water used for mixing mortar, grout and also for washing the stone and curing masonry

should conform to the requirements of IS 456.

4.6 Colgrout Mortar

4.6.1 The colgrout mortar should consist of cement, sand, water and other approved

admixtures, if any, each complying with its respective specifications in accordance with

4.1 to 4.3, mixed in the proportions as may be defined, by weight. The proportions of

materials entering into the mortar should be based on laboratory studies. The moisture

content of the sand should be taken into account in proportioning the mix. The fineness

modulus of sand should be 2.6 to 3.0. Pozzolanic material may also be mixed, if directed,

in proportions fixed by the engineer-in-charge. If directed, suitable air entraining agent

may be used to improve the quality and workability of the mortar. The exact proportion

of air-entrainment should be determined by actual tests.

4.6.2 All materials forming the mortar should be measured by mass except for water

which may be measured by mass or by equivalent volume. Where weigh-batching is not

possible, due consideration to bulkage of sand and its water content should be given.

4.6.3 The mortar should be mixed in a colgrout double drum mixer only. Single drum

mixer should not be allowed. Mixer should not be loaded in excess of the rated capacity

of mixer. Following general principles should be followed:

a) The speed of mixer should be 1500 to 2000 rpm.

b) The thoroughness of mixing and adequacy of mixing time so as to give colloidal

state to the mortar should be tested at the start of the job and at intervals as may be

considered necessary. The minimum mixing time generally specified is as follows:

1) Mixing cement and water in first drum – 15 to 20 seconds

2) Mixing of cement slurry and sand in second drum – 40 to 60 seconds.

3) Overall time for one mix of colgrout mortar – 60 to 90 seconds.

c) The compressive strength of colgrout mortar should be specified for the particular

job. The exact proportions for the cement, sand and water for the mortar should be

fixed after conducting test for compressive strength. Trial mixes should be run at

the project laboratory for obtaining the desired flow with the help of following

table.

Table 1 Water Cement Ratio & Water Requirement for Trial Mortar Mix

Cement : sand Water/Cement ratio Water for 50 kg cement in liters

1 : 2 0.62 to 0.70 31-35

1 : 3 0.76 to 0.84 38-42

Note: Consistency of the mortar should be such that it can flow 40 cm to 50 cm.

4.6.4 Testing of Mortar - Testing of mortar should be done in accordance with IS 2250. In

special cases where specimens of different sizes are used such as 15cmx30cm cylinder /

15 cm cube, necessary correlation should be established and such tests may be adopted for

quality control. Tests on mortar should be regularly conducted and should comprise

compressive, tensile and permeability tests.

4.6.5 Frequency of Sampling – The frequency of sampling of materials and colgrout

mortar during works should be as follows:

4.6.5.1 Cement - One sample for every 50 ton of cement.

4.6.5.2 Sand - One sample for every 500 cum of colgrout masonry or one sample in a

week, whichever is earlier.

4.6.5.3 Mortar flow -Minimum three flow meter tests per working shift per mixer.

4.6.5.4 Sampling of mortar cubes

i) Up to 100 cum of colgrout masonry work per day, one sample per shift per

mixer and

ii) For every additional 100 cum of colgrout masonry work per day, one

sample per shift per mixer.

4.6.6.2 Standard of acceptance

a) The strength of one sample should be taken as the average of at least three test

specimens taken from single batch of mortar. If the individual specimen result

differs by more than ± 15 percent of the average of three specimens, the average of

the remaining two specimens should be worked out. If the individual test results

of two specimens of mortar do not come within ± 15 percent of the average the

whole set of results should be rejected from analysis. Over a given period of time

as specified by Engineer-in-charge, not more than 10 percent of specimens tested

should have a compressive strength less than 80 percent of the required strength

and the average of all tests should equal or exceed the required strength.

Compressive strength of 15cm cube of colgrout mortar after 28 days should be equal or

higher than the stipulated values as given below:

S. No. Cement : Sand in Colgrout

mortar

Compressive strength in kg/cm2 of 15cm

size cubes at 28 days

lab. Strength Field Strength

1. 1:2 190 153

2. 1:3 150 117

b) Permeability of mortar as used on work should not give a coefficient of

permeability greater than 2.5 x 10-8 mm/sec as per IS 11216 when tested as per IS

3085(Part IV) for all proportions of mortar.

5. PREPARATION OF FOUNDATION

5.1 Colgrout Masonry in Contact with Rock Foundation

After completion of rough excavation of foundation, scaling and trimming for the final

removal of all slabby or drummy rock or any loosened mass should be done by chiseling

picking, barring and wedging. Any weathered or decomposed rock remaining should be

removed, the doubtful areas cleaned out to sufficient depth and back-filled with concrete

in richer proportion. If foundation conditions require consolidation grouting, then it may

be carried out after laying preferably two lifts of colgrout masonry. In case steps are

required to be provided in the foundation, those should conform to IS 11155.

5.1.1 Immediately prior to placing colgrout masonry, the foundation should be moistened

and coated by brush with a thick cement slurry (1 cement: about 2 or 3 water by

volume).This should be done within few minutes before building colgrout masonry. This

slurry should be spread only on a small area of about 1 m2 at a time and mortar spread

immediately thereafter. A layer of mortar 50 to 75 mm thick, should be spread over the

slurry and worked into all the irregularities of the rock surface, by trowels, bars or

brushes. The composition of this mortar should be the same as used in the colgrout

masonry work. The first course of stones should be carefully pressed in to the mortar so as

to force the mortar around the corners.

The layer of mortar should be made thicker, if required, to suit stones of sizes larger than

0.06 cum.

5.2 Colgrout Masonry in Contact with Fresh Colgrout Masonry

Surface of Colgrout masonry should be treated as follows before laying fresh Colgrout

masonry over it-

a) Loose stones, if any, should be removed;

b) Mortar joints should be scraped with iron rods and the exposed faces of the

stones should be wire brushed;

c) The surface should be cleaned with air-water jet;

d) The water collected in the depressions of masonry should be removed by sponge

or cloth, and;

e) Surface should be coated by thick slurry (1 cement : 2 or 3 water by volume) just

few minutes before laying the next lift.

5.3 Colgrout Masonry in Contact with Old Colgrout Masonry

Surface of old colgrout masonry which has been exposed for a long time that is more than

28 days should be treated as follows-

a) Loose stones, if any, should be removed;

b) Old mortar joints should be scraped to a depth of 15 mm or wet sand blasted and

washed with air-water jet, and;

c) Immediately prior to placing of colgrout masonry, the old masonry surface should

be treated in the same way as for rock foundation described in 5.1.1.

5.4 Colgrout Masonry in Contact with Concrete

Concrete surface, which has hardened should be roughened by chipping to a depth of 40

mm to 25 mm so as to remove top mortar film and get a rough surface for starting

masonry and surface should be treated in the same way as for rock foundation described

in 5.1.1.

6. COLGROUT MASONRY

6.1 General

The structure should be built true to line, plumb or curved or as directed in a workman

like manner, suitable aids like templates, scaffoldings etc. should be used. The

construction should be done in compartments of different size & shapes. The area of each

compartment should be so fixed that it can be colgrouted continuously in one shift of

working. It should not be more than 25 to 30 m2 and height not exceeding 1.0 m. For

Upstream & Downstream surfaces of dam, utmost care should be taken to face work. The

face work may be in wall compartment fashion or in colgrout masonry using shuttering.

In case of opening, the concrete of appropriate grade should be used instead of colgrout.

6.1.1 Colgrout masonry compartment (Block) should be constructed parallel to dam axis

in staggered fashion in vertical as well as in horizontal direction so that, formation of

horizontal and vertical joints as well as possibility of seepage through weakened portion

of the wall of a particular block can be avoided.

6.1.2 The maximum height of colgrout masonry allowed to be constructed at a time

should be 1 m. No fresh masonry should be laid within 24 hours over colgrout masonry

previously laid.

6.1.3 In the same block (monolith) the difference in level of masonry layers should

normally be not more than 1.5 m.

6.2 Partition wall for compartments

Partition walls of compartment should be 45 cm thick uncoursed rubble masonry without

regular face work, height not exceeding 1 m and in mortar proportion as used in colgrout

masonry. This wall act as a shuttering for colgrout masonry which later becomes integral

part of colgrout masonry. Adequate headers and stretchers should be provided for

ensuring horizontal and vertical bond with the colgrout masonry. The minimum number

of headers should be at the rate of one per square meter of face work. Masonry walls

should be constructed in accordance with IS 1597(Part 1).

6.3 Laying of stones

The stones should be free from dirt and surface-dry before being placed. The quarried

stones should be thoroughly cleaned and watered before they are brought to the block for

placement. The stones should be placed in the work after knocking off weak corners and

edges with a mason’s hammer and after clearing scales of foreign matter, if any. Stones

should be placed manually and interlocking in a layer in the compartment so that bigger

dimension is along horizontal plane and they may not act as wedges and force out the

adjacent stone. If stones once kept in position are to be adjusted, they should be lifted

clear and reset; they should not be moved one over the other. Adequate headers should be

provided for proper horizontal and vertical bond with next surrounding layers. The

minimum number of headers should be more than one per 4 m2 area to be bonded. A row

of vertical stretcher stones should be erected at about 2 m center to center both ways so

that there is at least one vertical stone for every 4 m2 area for the bond with next lift.

Stone spalls of 200 mm to 100 mm size should be wedged in to the interstices between

the adjacent stones whenever necessary to avoid thick beds or joints and to achieve

maximum density. There should be a good collection of stones and spalls within easy

reach of each mason to enable proper selection of stones for laying and they should be

kept continuously replenished.

6.3.1 Layers - The thickness of layer should be 35 cm. Such layers should be continued to

be arranged till the predetermined height of the compartment is reached.

6.3.2 Placing of G.I. Pipes –

75mm diameter perforated GI pipes should be placed at 1.5 m center to center ( or at least

one pipe per 2.25 m2 area) and about 25 mm above the bottom while pre-packing the

stones. Pipes should be withdrawn simultaneously as colgrouting of each hole is in

progress.

6.4 Mortar Injection

The colgrout mortar should be injected with sufficient pressure by upward penetration

method through each perforated GI pipe. The insertion of mortar should proceed from one

end in direct sequence so as to achieve uniform height of the mortar in all pipes in any

section of colgrouted masonry and GI pipe should be raised as hole is getting filled up.

The mortar should not be brought up to the top level of the stones, but to about half the

height of the top stone so as to ensure a good key for next lift.

6.4.1 Colgrout masonry should invariably be done during day light hours.

6.5 Mortar Intake

Quantity of mortar in the colgrout masonry should normally be 40 percent to 45 percent.

6.6 Colgrout Masonry in U/S Septum

When colgrout masonry is used in upstream septum of dam the hearting masonry

downstream side of the septum should be constructed first. Adequate protruding headers

should be provided for proper horizontal bond with surrounding layers of colgrout

masonry in the septum so that question of separation of U/S septum from the hearting

masonry does not arise.

6.7 Cleaning of Laitance

On filling the compartment, the slurry should be roughened by rods, punja, wire brushes

etc. The laitance that comes to the surface after initial setting should be cleaned out by

wire brush and removed by water jetting the surface.

6.8 Protection

The fresh masonry should be protected against vibrations, any other movements and rains,

which might injure it before its final set. Stones should not be allowed to be dumped over

the masonry before its final set. Walkways for inspection, supervision, roughening at top

surface etc. should be provided to ensure that green masonry is not disturbed before it

sets.

6.9 Curing

Arrangements should be made to protect the fresh masonry against rapid drying and to

cure masonry. The masonry should be cured after 4 to 12 hours of construction and water

should be gently sprayed so as to avoid damages. All exposed surfaces of masonry should

be kept continuously moist for at least 21 days.

6.10 Face work

The upstream and downstream face work in spillway, non-spillway and power dam

sections may be constructed either in wall compartment fashion or in colgrout masonry

using shuttering. Face side compartment wall should consists of face stones hammer-

dressed on face and one line chisel dressed on bed, top and sides for 75mm from the front

face built with the course normal to the face batter. This work can also be constructed in

uncoursed rubble masonry. The work should be built in header and stretcher fashion and

joints should be break in courses above and below by at least half the height of the course.

In case of uncoursed rubble masonry, the header stones should be placed at about 1 m

centre-to-centre. The joints in face work should not be thicker than 15mm for single-line

chisel-dressed stones or 20 mm for hammer dressed stones.

6.10.1 Bond stones in each course should be so provided that every sixth stone or third

header stone is a bond stone. In case of uncoursed face work, the bond stones should be

placed at about 2.5 m centre-to-centre. The bond stones should be staggered and marked

for identification.

6.10.2 The face work should be struck neatly and smoothed off with a trowel before the

mortar takes the final set.

6.10.3 All pointing should be done with cement sand mortar 1:3 or richer mix. The sand

should be fine, passing through 600-micron IS sieve (see IS 460) and conforming in all

respects to IS 2116.

The joints in masonry to be pointed should be raked square, for a minimum depth of two

times the thickness of the joint within 24 hour of laying of masonry. In special

circumstances this period may be released to 48 hours. The refilling and pointing should

be done within three days of raking of the joints so as to ensure good adhesion between

the two mortars. The joints should be finished neat, defined, regular and of uniform width.

The joints may be filled either flush or raised as required. The surface pointed should be

kept wet for 21 days after pointing is completed.

6.10.4 It is normal practice to use formwork for U/s and D/s sloping face instead of

masonry face work. Where formwork is used, it should confine the colgrout masonry and

shape it to the required line. The forms should have sufficient strength and rigidity to hold

masonry and sustain the pressure of colgrout mortar being injected without excessive

deflection from prescribed lines. Form work made up of only steel shuttering should be

allowed. It should be free from warping and fabricated true to line and shape. The inside

surface should be clean, rigid, watertight ,smooth and free from dirt, shavings, chipping or

other foreign matter. Inner surface should be treated with a suitable non-staining oil to

prevent adherence. The forms should fit tightly over the completed surface so as to

prevent leakage of slurry from the masonry. Removal of forms should never be started

until colgrout is thoroughly set and hardened adequately to sustain its own weight and live

load which is likely to come on the work for laying of next lift. In normal circumstances,

forms should be struck on expiry of 48 hours from injection of colgrout mortar. However

the length of time for which forms should remain in the place should be decided by

engineer-in-charge. All faces of masonry should be smooth and sound, free from voids

and air holes when formwork is struck. Any roughness or irregularity on the exposed

surfaces should immediately filled up while masonry is green with cement mortar 1:1½,

properly trawled and finished. Such patching of surface should be carried only with

permission of engineer-in-charge.

6.11 Tests for Colgrout Masonry

6.11.1 In situ Permeability test – Permeability tests on Colgrout masonry should be

carried out in accordance with IS 11216.

6.11.2 Laboratory Tests for drilling cores from colgrout masonry – For testing in

laboratory, core of 90 cm diameter and 90 cm depth should be drilled from colgrout

masonry. Drilling should be done after sufficiently hardening of masonry, preferably after

90 days. One core up to and for every ten thousand cum of colgrout masonry constructed

during the season should be taken.

6.11.3 Testing of core in laboratory for Permeability test – Permeability test should be

conducted by central injection method with double rubber packers placed at 60 cm apart

in central NX hole of the core. The maximum pressure allowed should be 3.5 kg/cm2.

Standard of impermeability aimed at, should be a water loss of not more than 2.5 lugeons.

6.11.4 Density – Density should be obtained by measuring the volume of core and

weighing the core. The density should not be less than 2.40 gm/cc.

6.11.5 Compressive strength - Compressive strength should be obtained by ultimate

crushing of core on 2000 Ton capacity Compression Testing Machine. The compressive

strength obtained on cylindrical core of 90cm x 90cm with L/D = 1 should be converted

for L/D = 2 using conversion curve given in IS 516. The compressive strength should not

be less than 90 kg/cm2 for L/D ratio as 2, for colgrout masonry.