Disclosure to Promote the Right To Information

Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public.

इंटरनेट मानक

“!ान $ एक न' भारत का +नम-ण”Satyanarayan Gangaram Pitroda

“Invent a New India Using Knowledge”

“प0रा1 को छोड न' 5 तरफ”Jawaharlal Nehru

“Step Out From the Old to the New”

“जान1 का अ+धकार, जी1 का अ+धकार”Mazdoor Kisan Shakti Sangathan

“The Right to Information, The Right to Live”

“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता है”Bhartṛhari—Nītiśatakam

“Knowledge is such a treasure which cannot be stolen”

“Invent a New India Using Knowledge”

है”ह”ह

IS 4925 (2004): Concrete Batching and Mixing Plant [MED 18:Construction Plant and Machinery]

IS 4925:2004

n

((114-Jm-??7

%%wiRJT’skf%wrfim( ~5@-@

Indian Standard

—Rf$Tfk

CONCRETE BATCHING AND MIXING PLANT —SPECIFICATION

( First Revision

ICS 91.220

0 BIS 2004

BUREAU OF IN DIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

August 2004 Price Group 4

Construction Plant and Machinery Sectional Committee, ME 18

FOREWORD

This Indian Standard (First Revision) was adopted by the Bureau of Indian Standards, after the draft finalizedby the Construction Plant and Machinery Sectional Committee had been approved by the MechanicalEngineering Division Council.

At civil construction sites where considerable quantity of concrete is required, central batching plants orbatching and mixing plants are generally deployed. These plants are erected at sites to deliver either the mixedconcrete or dry mix of concrete.

These plants are usually specially designed to suit the local conditions and the output required. Small plantsmay have an output of as low as 10 m3 of mixed concrete per hour, medium plants may have the output in therange of 30 to 100 m3 of mixed concrete per hour and large plants may have an output of over 100 m3 of mixedconcrete per hour. The plants may be manually controlled, semi-automatic or fully automatic (see 6.1). Thecomposition of the plant may also vary depending upon the type and composition of aggregates, cement,admixtures for concrete, and various other requirements, such as temperature control of aggregates, mixingwater and concrete and above all the quality of concrete expected from the plant.

This standard was first published in 1968 covering general requirements and guidelines for centralized batchingplants of capacities above 100 m3/h of mixed concrete. This revision has been taken up to incorporate themodifications considered necessary as a result of continuous developments since then in the areas of controlsof batching plants, and also to cover plants of lower capacity.

In view of intricate nature of such plants and of the variety of combination of ancillary equipment that mayberequired under different conditions, information on many aspects may have to be supplied both by the user forthe guidance of the manufacturer and by the manufacturer to the prospective user, to obtain a true comparativeassessment of different plants available and to ensure that the plant selected is suited to the conditions prevailing.For this reason, the standard contains clauses which call for agreement between the purchaser and the supplierand which permit the purchaser to use his option for selection to suit his requirements. A specimen enquiryformat to be supplied by the user for the guidance of manufacturer is given in Annex A.

For the purpose of deciding whether a particular requirement of this standard is complied with, the final value,observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance withIS 2:1960 ‘Rules for rounding off numerical values (revised)’. The number of significant places retained inthe rounded off value should be the same as that of the specified value in this standard.

IS 4925:2004

Indian Standard

CONCRETE BATCHING AND MIXING PLANT —SPECIFICATION

( First Revision)

1 SCOPE

This standard covers the requirements of concretebatching and mixing plant with manual, semi-automatic and fully automatic controls.

2 REFERENCES

The standards listed below contain provisions whichthrough reference in this text, constitute provisions ofthis standard. At the time of publication, the editionsindicated were valid. All standards are subject torevision and parties to agreement based on thisstandard are encouraged to investigate the possibilityof applying the most recent editions of the standardsindicated below:.

IS No.

1791:1985

2062:1999

2932:1993

4634:1991

3 CAPACITY

Title

General requirements for batchtype concrete mixers (secondrevision)

Steel for general structural pur-poses — Specification @fthrevision)

Enamel synthetic, exterior: a)undercoating, b) finishing —Specification (second revision)

Methods for testing performanceof batch type concrete mixers (@wrevision)

The maximum capacity of the plant shall be calculatedusing the minimum cycle time of the mixer after thematerials to be mixed are fed into the mixer. Thecapacity of the plant, as calculated above, shall be forconcrete with 80 mm slump.

4 COMPOSITION OF THE PLANT

4.1 The plant shall be capable of accurate (see 6.1.1and 6.3.1) batching and mixing of aggregates, sand,cement, additives, ice flakes, etc. It is necessary forthe purchaser to specify following details as an aid formanufacturer to select/design the appropriate batchmixing plant:

a) Information Regarding Materialsi)

2)3)

4)

Number ‘of cement and cementitiousmaterials;Numbers of coarse and fine aggregates;Types of water (chilled water/iceflakes); andDesirable dispensing arrangement ofadditives such as, air entraining agen~water reducing and set retarding agent,etc, in liquid or powder form.

b) Type of Plant1) Storage arrangement for sand and ag-

gregates:i)

ii)

iii)

iv)

Boom scraper plant, that is openstorage with retaining walls;Ground storage hopper (forsmaller plants);Ground storage hopper with weigh-ing facility at belt conveyo~ andOverhead storage hopper indicat-ing total storage capacity re-quired for aggregates and sandand number of aggregate compart-ments required.

2) Storage arrangement for cement:Cement silo, indicating its capacity andnumber of compartments.

c) Weighing Arrangements1)”

2)

3)

4)

5)

6)

7)

Single weighing system for aggregatesand cement;Independent weighing arrangement forcement as well as for all aggregatestogether;Independent weighing arrangement foreach type of aggregate;More than one weighing arrangementfor cement to cater to the different typesof cements;Arrangement for measurement of waterthrough flowmeter or through weigh-ment;Additional arrangements for weighmentof ice flakes; andNumber of admixtures and whetherweighing arrangement is required forany of them.

1

IS 4925:2004

d)

e)

f)

Type of Mixer1) Non-tilting reversible drum concrete

mixer,2) Double conical tilting mixer,3) Pan mixer,4) Turbo panmixer, and5) Single shafthwint shaft compulsory

mixer/pug mill.

NOTE — For plants up to 30 m3 /h capacity, onlyone mixeris required. t%plaots txyond30m3/lr, thecustomers have option for one or more than one mixer.

Controls.

1)

2)

3)

Manual control through individual leversfor opening of gates (recommended forbatching plants up to 20 m3/h capacity);Semi-automatic control through in-dividual push buttons for opening ofvarious gates by electro-pneumaticallyor hydraulically operated actuators(recomme~ded for batching plantsbelow 30 m /h capacity);Fully automatic control through a singlepush button for batching of all ag-gregates, cement, water and additives(recommended for batching plants of30 m3/h and above capacity);

Ready Mixed Concrete PlantsReady mixed concrete (RMC) plants shall beequipped with computer (containing minimum15 recipes), monitor and printer. Delivery slipsof RMC plants shall contain the followinginformation:

1)

2)3)4)5)6)7)8)9)

10)

11)

12)13)14)15)16)

17)

Name of RMC plant supplier with logoand address,Delivery note No.,Name of receiving p~y,Ordered quantity in m ,Recipe number,Number of batches,Batch size in m3,Date,Starting time,Moisture percentage of each material atthe time of batching,Weighing chart for each type of com-ponent with total for each componentindependently,Total quantity delivered in m3,Remarks column,Transit mixer number and capacity,Transit mixer driver’s name,Representative of RMC plant (signaturecolumn), andRepresentative of customer (signaturecolumn).

NOTE — Besides chalkm. there area number of other facilitieswhich can be provided. The necessary software maybe designedas per customer requirements.

g) Additional Facilities1)

2)

3)

4)5)6)7)

Automatic cement /water correctionarrangementMimic display panel showing high andlow position of various storage hoppers;Material consumption report on annual,monthly and daily basis;Customer report;Accounting;Stock maintenance; andPlant scheduling.

4.1.1 If so desired by the purchaser, plants of30 m3/h capacity and above shall have suitablearrangements for cooling or heating of concrete. ‘I%eactual details of the cooling or heating arrangementsshall be as agreed to between the purchaser and thesupplier.

4.2 Unless otherwise agreed to between thepurchaser and the supplier, the plant shall consist ofthe following components of suitable size related tothe capacity of the plant:

a)

b)c)d)e)

f)

4.2.1

Storage arrangement for different types ofaggregates and cement;Batching equipmentConcrete mixe~Control panel;Material feeding and elevating arrangement;andHopper for mixed concrete.

The various components shall conform to therequirements as specified in this standard.

5 STORAGE

5.1 Storage shall be provided either on the groundor in the bins for different sizes of fine and coarseaggregates and cement. The compartments for eachtype of aggregates shall approximately be equal orof sizes to suit the requirement as defined by thepurchaser for specific job applications. For plantsupto 30 m3/h capacity, a cement hopper of suitablecapacity with sctew conveyor/manttal arrangementshall be provided. For ptints of 30 m3/h capacity andabove, cement weigh hatcher shall be providedseparately with independent structure and the cementcompartment shall be water-tight and provided withnecessary air vent, aeration fittings for proper flow ofcement and emergency cement cut off gate. For plantsof 30 m3/h capacity and above, cement silo may beprovided as per agreement between the purchaser andthe supplier.

5.1.1 In case of scrapper type plant, based on therecommendations of the supplier, the purchaser shallprovide aggregate storage capacity required forcontinuous plant operation of one hour duration.

2

-“l

5.2 Wherever a separate cabin is provided for thecontrol panel, the cabin and it’s door shall becompletely sealed to prevent entry of dusthainwater.

6 BATCHING EQUIPMENT

6.1 Batchers shall be manual or semi-automatic orautomatic in accordance with the requirements givenbelow:

a)

b)

c)

Manual hatcher—Manual hatcher shall becharged by devices which are actuatedmanually. In such batching systems, the ac-curacy of batching operation is dependent onthe operator’s visual observation of a scale orvolumetric indicator. The various elements ofthe batching plant may be actuated by hand orby pneumaticlhydraulic cylinders..Senzi-autornatic butcher — Semi-automatichatcher shall be charged by devices which areseparately actuated manually to allow thematerial to be weighed but are actuated auto-matically when the designated weight of eachmaterial has been reached. The weighingaccuracy shall be within the tolerancesspecified in 6.1.1.Automatic ba(cher — Automatic hatcher shallbe charged by devices which, when actuated

by a single starter switch, will automaticallystart the weighing operation of each materialand stop automatically when the designatedweight of each material has been reached.Automatic hatcher shall be interlocked in sucha manner that:

1)

2)

3)

4)

Charging device cannot be actuated untilthe weighing scale has returned to zero.(within f 0.3 of 1 percent of the scalecapacity);Charging device cannot be actuated, ifthe discharge device is open;Discharge device cannot be actuated, ifthe charging device is open; andThe discharge device cannot be actuateduntil the indicated material is within theapplicable tolerance.

Automatic plants of 30 m3/h capacity and above shallhave eleckonic display and p-rinter attachment, ifspecifically agreed to by the purchaser and thesupplier.

6.1.1 For individual hatcher, the following tolerancesshall apply, based on the required weight of materialbeing weighed:

Type of Material Tolerance inPercentage

Cement and other cememntitious * 1materials

Sand aggregates &’2

IS 4925:2004

Type of Material Tolerance inPercentage

Water *1

Admixture *3

6.1.2 For cumulative hatcher, interlocked sequentialcontrols shall be provided and the above tolerancesshall apply to the required cumulative weight ofmaterial as batched.

6.1.3 The minimum weight of any material weighedto which the above tolerances shall apply isdetermined by the following formula:

~= 0.3x RT

where

W = minimum weight in kg;R = scale capacity in kg; andT = weight tolerance in percent.

6.2 The batching equipment shall be such so as toaccurately determine and control the prescribedquantities of various constituent materials ofconcrete, that is, water, cement, admixtures sandand aggregates. For plants of capacity 20 m3/h andabove, cement shall be weighed separately. Howeverfor plants of capacity below 20 m5/h, cement andaggregate can be weighed in one weigh hatcher. Insuch case, a separate compartment in the weighhatcher shall be provided so that the cement does notcome into contact with aggregate or sand. Water canbe fed through a water meter of suitable size or byweigh hatcher. The quantity of each admixture shallbe determined by- volu-metric measurement/weighment for each batch.

6.2.1 Equipment for carrying batched material fromthe batch hoppers or other suitable arrangement to andinto the mixer shall be such that there will be nospillage of the batched materials or overlap of batches.Equipment for handling cement in the batching plantshall be such as to prevent noticeable increase of dustin the plant during measuring and discharge of eachbatch of material.

6.3 Batching system shall have rated capacity (interms of concrete in a single batch) to match themaximum rated size of the mixer that could beadopted for use with the plant. Semi-automatic orautomatic hatcher shall be operated from the centralcontrol panel. Respective scales, hatcher and dialindicators shall be provided for the aggregates,cement, water, air entraining agent and waterreducing agent. Cement hatcher shall be completewith dust preventive arrangements. To achievegreater efficiency, the weighing ‘cut off’ shall be intwo stages, that is, ‘initial’ and ‘final’ with necessaryjogging action for treble feed as the final weightapproaches. All the weights shall be indicated on

“‘1

k

3

IS 4925:2004

respective indicator on the central control panel. Thescales shall be calibrated in kilograms. If agreed bythe purchaser and the supplier, the weighing hoppersor other suitable arrangement shall permitobtaining representative samples of each material.Scale system shall have provision for necessaryadjustment, levelling, aligning, balancing andcalibration from time to time.

6.3.1 Each weighing unit shall be equipped with avisible indicator which shall register the load at anystage of the weighing operation. The weighinghoppers shall permit the convenient removal ofoverweight materials in excess of the prescribedtolerances. The scales shall be interlocked so that anew batch cannot be started until the weighing hoppershave been completely emptied of the last batch andthe scales are in balance.

6.3.2 The equipment shall be capable of controllingthe delivery of material for weighing or volumetricmeasurement so that the combined inaccuracies infeeding the material during normal operation shallnot exceed 1 percent for water, 1 percent for cement,3 percent for admixtures, 2 percent for sand and3 percent for aggregates.

6.4 Batching of water shall be by weight but maybe b volume in case of plants upto and including

J30 m /h capacity. A reservoir tank for storage of watershall be provided with the batching plant and its sizeshall be as agreed to between the purchaser and thesupplier. Reservoir shall be complete with waterpiping, float valves and other fittings for directdelivery to mixers without coming in contact withcement or the aggregate prior to the mixingoperations. Water hatcher shall be such that it canmeasure and discharge full batch of specified quantit yof water simultaneously and within the same time asset for the rest of the batch.

6.4.1 In case of small plants where water batching isprovided by volume, water metering arrangementshall be so constructed that the flow may be cut offautomatically after a predetermined quantity ofwater. Suitable arrangements shall be included inwater meter system so that variations in the watersupply pressure do not affect the rate of delivery andaccuracy of the meter.

6.4.2 The operating mechanism in thewater-measuring device shall be such that leakageswill not occur when the valves are closed and thewater will be discharged quickly and freely into themixer without objectionable dribble from the end ofthe discharge pipe. In addition to thewater-measuring device, there shall be arrangementfor plants above 30 m3/h for measuring andintroducing small increments of water into mixerwhen ~quired for final tempering of the concrete.

6.5 Dispensers (if provided, for air-entraining, waterreducing, set-retarding agent) shall be of suftlcientcapacity to measure at one time the full quantity ofproperly diluted solution required for each batch andshall be maintained in clean and freely operatingconditions. Equipment for measuring shall bedesigned for convenient confirmation of accuracy ofthe measurement for each batch and it shall be soconstructed that the required quantity can be addedonly once to each batch.

6.5.1 Batching system for admixtures (see 4.1) shallbe volumetric and shall be such that the admixture isautomatically added to the mixing water. The quantitymay vary up to 400 mVm3 of concrete. This systemshall include a storage tank of adequate capacity foreach admixture solution at the hatcher floor forgravity feed, delivery pump from the ground storage,float switch with automatic start and stop control ofthe pump to maintain fixed levels. The feeding ofadmixtures shall be interlocked with the mixingwater feeding arrangement.

6.6 The range of each scale shall be as required bythe purchaser to suit the capacity of the batching plant(see 6.3). The purchaser shall indicate this range in hisenquiry or in order.

7 MIXERS

7.1 The mixers shall be non-tilting reversible drumtype/double conical tilting type/pan type/singleshaft/twin shaft compulsory type/pug mill typeconforming to the performance requirements ofIS 1791. The number and sizes of the mixers shallbe commensurate with the rated output of the plantbased on the mixing time indicated in 7.1.1. The mixerdrum and blades shall be made of highmanganese/abrasion resistant steel. Alternatively,these items may be carbon steel with replaceable linersof cast iron or abrasion resistant steel.

7.1.1 Minimum mixing time for each batch (after allmaterials, except the full quantity of water have beenadded in the mixer drum) shall be as follows providedthat all the mixing water shall be introduced beforeone-fourth of the mixing time has elapsed.

Capacity of Mixerlitre

375,500,750,1000,1500,20001000,2000,3000,4000,5000375,500,750,1000,1500,2000,3000500,750,1000,1250,

Type MinimumMixing

Times

Non-tilting 40reversible drum typeDouble conical tilting 30typePan type 30

Single shafthwin 301 fi, 2060, 25(X),3 fMO, shah compulsory3500,4000,5 ~, 6000 typdpug mill type

NOTE — Capacity of the mixer indicated above is for wet mixconcrete.

4

IS 492S :2004

7.1.2 The minimum mixing periods specified aboveare based on standard speed of rotation of the mixer.Mixing time shall be increased if and when thecharging and mixing operations fail to produce aconcrete batch which conforms throughout with theforegoing requirements with respect to adequacy bfmixing.

7.2 The concrete as discharged from the mixer shallbe uniform in composition and consistencythroughout the mixed batch and from batch to batch,except where changes in composition or consistencyare required.

7.3 Mixer shall be so located in the plant that itsoperation can be observed conveniently by thebatching plant operator.

7.4 Each mixer shall be equipped with a mechanicallyor electrically operated timing and signaling (orlocking) device which shall indicate and assure thecompletion of the required mixing period.

7.5 Each mixer shall be complete with electric drivemotor and starter, air or hydraulic operated controls,consistency indicators, etc. The operation of the mixershall be controlled from the central control panel ofthe plant having necessary indication lights for theentire operation and adjustable mixing timers foreach mixer. The arrangement for feeding the mixersshall not have any spillage or leakage of water orcement. Each mixer shall hold a full capacity batchconcrete of the required consistency without unduespilling during rotation. The height of discharge asrequired by the purchaser shall be provided.

7.6 In case wet concrete hopper is provided, it shallhave an arrangement for concrete sampling devicefor taking samples of wet concrete for the laboratorytests.

8 CONTROL PANEL

8.1 Fully automatic plant shall have desk type, singleoperator, push-button operated control panelcompletely inter-wired and having the followingprovisions:

a) Panel mounted digital weight indicator/frontlocated weight dials — for each material, or asrequired.

b) Push buttons and indication lights for com-plete range of batching, master batch push-button, mixing and discharge push-buttons,etc. The operation of batching will be sodesigned that with a single master batchswitch, all the constituents of the batch, that isaggregates, cement, water, admixtures, ice,etc, shall be automatically batched and shall bedischarged into the mixer in the desired se-quence. Overriding manual control shall be

c)

d)e)

f)

g)

h)

j)

k)

m)

provided with necessary individual switchesfor manual batching and discharge of eachmaterial.Quick mix selector-unit shall comprise of atleast 6 pre-set selections. Pre-setting of variousmix constituents shall be simple and easy.Admixtures batch controls.Batch counters.Truck dump light (if required) — The lightshall be turned on from ground when a truck isin position and will automatically go offwhen the mix has been dumped. The dischargeof the mixer shall be interlocked with thedump light for this arrangement.Complete range ofpush buttons and indicatorlight for the mixers — The mixer shall auto-matically stop and give a ready light when ithas taken the pre-set mixing time.Separate mixing time — Timers having a rangeof O to 3 min minimum for each mixer.Mixer charging chute control push buttonsand position indicator light — for eachmixer if the plant has more than one mixer.Necessary interlocks for automatic and safeoperation of the plant — All relays, electroniccomponents and Programmable Logic Con-troller (PLC) used shall be enclosed in a dustproof cabinet. All the weighing scales, dialsand linkages shall have strong vibration freeconnection at the panel. The control panel andother controls shall be centralized in one con-trol room for the plant.Any other control or fittings asperlatest designand practice for mass concrete plants.

8.2 In case of manual or semi-automatic plants, thepurchaser shall specifically indicate as to which of theitems given in 8.1 would be required for the plant.

9 ICE FLAKES FEEDING ARRANGEMENT

When it is proposed to feed ice flakes, the necessaryice flaking machine complete with screw conveyor,bucket elevator, weighing machine and all otherauxiliaries shall be provided in the plant.

10 MATERIAL FEEDJNG AND ELEVATINGARRANGEMENT

Suitable arrangements shall be provided for elevatingcement to the cement silo/mixer of the batching plantand aggregates to the respective compartment binsof the batching plant.

11 GENERAL REQUIREMENTS

11.1 Irrespective of the foregoing specifications forthe plant, which are broad-based and generalized,the manufacturer or supplier shall ensure that the plantshall be complete with all the fixtures, steelstructures, platforms, ladders/stairs, railings, fittings,accessories and any other material required for proper

5

f-l

IS 4925:2004

running of the plant though nonspecifically detailedin the standards. The manufacturer or supplier shallnot be entitled for any extra amount in respect of suchaccessories required for the efficient operation of theplant, even though these have not been included in thestandards of the purchase order.

The mixer and all structural members shall bethoroughly cleaned/sand blasted prior to application oftwo coats of primer and one coat of synthetic enamelpaint of agreed shade conforming to IS 2932 at theworks of manufacturer.

11.2 The electrical equipment shall be completewith starters for various motors. All internal wiringand cables shall conform to the requirements ofrelevant Indian Standards. All motors shall be totallyenclosed fan cooled, squirrel cage or slip ringinduction type. The electric motors shall haveadequate protection against dust ingress and shall beable to perform to its specifications at an atmospherictemperatures up to 50”C. Entire equipment shall becapable of satisfactory operation in tropicalconditions. All solenoid and air valves of the plantshall be provided with automatic oiler unit and filtersin the air lines.

11.3 All steel structure for the plant shall befabricated with the material conforming to IS 2062.Such structures shall generally comprise of thefollowing:

a)

b)

c)d)e)

f)

Complete bin structure of the plant with thesupporting columns;Supporting columns and suppotting structurefor the mixers;Concrete dump hopper (if provided);All stairs, ladders, platforms and railings;Feeding and weighing arrangement of iceflakes (if required); andAny other item the manufacturer may proposeto complete.

11.3.1 Notwithstanding the provision of 11.3, themanufacturer shall ensure that the plant forms acomplete working unit for achieving the desiredefficiency by using the items supplied by themanufacturer as well as those items specifically agreedfor manufacture/supply by the customer.

11.3.2 Partition walls, supporting structures of bins

(including hardwares) and foundation bolts shall beprovided by the customer. However, the sizes andtype thereof shall be intimated in advance by themanufacturer.

11.4 The manufacturer shall furnish a complete set intriplicate of operation and maintenance manuals,spare parts catalogue and any other relevantliterature required for the plant. The manufacturer

shall also supply duplicate set of drawings and erectiondetails, foundation plan. control wiring diagrams, etcfor the complete installation.

11.5 The manufacturer shall supply one set ofcomplete specifications of the plant and equipmentand also supply complete illustrations and technicalliterature thereof.

11.6 The manufacturer/supplier shall furnish pricelist of recommended spare parts for normal 2 yearoperation (5 000 working hours).

11.7 When erection of the plant and all civilengineering works including foundations of the plantare to be done by the purchaser. the manufacturer shallprovide technical guidance for the same. Themanufacturer shall also provide technical advice to thecustomer during erection, commissioning and trialruns of the plant.

11.8 The customer shall indicate in advance to themanufacturer/supplier, the characteristics of theavailable electric supply at the project. The customershall also indicate the pressure at which air would beavailable at the project, in case air compressor is notin the supply scope of manufacturer/supplier.

12 MIXING EFFICIENCY

12.1 The mixed concrete from the batching andmixing plant can be tested in accordance with themethod specified in IS 4634 with a view to checkingits ability to mix the ingredients to obtain a concretehaving uniformity within the prescribed limits. Theuniformity of mixed concrete shall be evaluated byfinding the percentage variation in quantity (mass inwater) of cement, fine aggregate and coarse aggregatein a freshly mixed batch of concrete.

12.2 The percentage variation between the quantitiesof cement, fine aggregates and coarse aggregates (asfound by weighing in water) in the two halves of abatch and the average of the two halves of the batchshall not be more than the following limits:

Cement 8 percent

Fine aggregate 6 percent

Coarse aggregate 5 percent

13 GUARANTEE AND WORKMANSHIP

Notwithstanding any qualification by the customer,the ultimate responsibility for supply of the completeplant and its satisfactory performance and output shallrest with the supplier. He shall guarantee against anydefect in the plant, either in design, material orworkmanship. The plant and equipment suppliedshall be a complete unit and shall conform to thehighest standards of engineering design andworkmanship.

6

IS 4925:2004

ANNEX A

( Foreword)

SPECIMEN ENQUIRY FORMAT

A-1 CAPACITY OF THE PLANT REQUIRED

The indentor should work out his requirementassuming 75 percent efficiency of the plant

A-2 TYPE OF PLANT REQUIRED

The indentor must indicate any of the following typebased on site requirement:

a) Central batching and mixing with overheadstorage (indicate storage capacity).

b) In line hoppers on ground with weighing arran-gement on belt conveyor.

c) Boom scraper plant with ground storage.d) Storage hopper above weigh hatcher (plant up to

20 ins/h).

A-3 TYPE OF MIXER REQUIRED

The indentor must indicate any of the following typeof mixer required based on site requirement:

a) Non-tilting reversible drum type,b) Double conical tilting type,c) Pan type,d) Single shaftftwin shaft compulsory typeiPug mill

type, ande) Any other type.

A-4 NUMBER OF AGGREGATES

Indicate number and sizes of aggregates to be used inaddition to sand.

A-5 WEIGH BATCHERS

Whether common wejgh hatcher for aggregates andcement or separate weigh hatcher for each material isrequired.

A-6 TYPES OF CEMENTS/CEMENTITIOUS MATERIALS USED

Indicate whether one or more grade of cement to beused.

A-7 NUMBER AND SIZE OF SILO(S)

Available sizes are 20,30,45,60,75 t (bigger sizes ofsilos available for central storage of cement on groundlevel).

A-8 FEEDING OF CEMENT

Feeding of cement can be done through bucketelevator, screw conveyor, pneumatic system.

7

A-9 FILTER FOR SILO

Indicate whether filter on top of silo to avoid dust isrequired.

4-10 ADDITIVES REQUIRED

Indicate number of additives required. Also indicatewhether these are in liquid form or powder form.

4-11 WATER BATCHING (ANY OF THE FOLLOWING)a) Water meter (mechanical type),b) Water meter (electronic type), andc) Water weigh hatcher.

A-12 CAPACITY OF WEIGH BATCHERS

Indentor must indicate the capacity of each weighhatcher required.

A-13 COOLING OF AGGREGATE

In case the indentor wants aggregate coolingarrangement the same may be indicated.

A-14 NUMBER OF MIXERS

For plant up to 30 m3/h capacity, one mixer is enough.Indenters can have more than one mixer in a centralbatching and mixing plant.

A-15 OPERATION

Indentor to indicate type of controls required as per4.1 (e) and 8.1.

A-16 DISCHARGE HEIGHT

Depending upon transportation of mixed concrete bydumper or transit mixer, the indentor must indicate theheight of discharge required.

Bureau of Indian Standards

BI S is a statutory institution established under the Btireau of Indian Standards Act, 1986 to promoteharmonious development of the activities of standardization, marking and quality certification of goodsand attending to connected matters in the country.

Copyright

BIS has the copyright of all its publications. No part of these publications may be reproduced in any formwithout the prior permission in writing of BIS. This does not preclude the free use, in the course of

implementing the standard, of necessary details, such as symbols and sizes, type or grade designations.Enquiries relating to copyright be addressed to the Director (Publications), BIS.

Review of Indian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewed

periodically; a standard along with amendments is reaffirmed when such review indicates that no changes areneeded; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standardsshould ascertain that they are in possession of the latest amendments or edition by referring to the latest issue of‘BIS Catalogue’ and ‘Standards: Monthly Additions’.

This Indian Standard has been developed from Doc : No. MED 18 (0074).

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

BUREAU OF INDIAN STANDARDS

Headquarters :

Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002 Telegrams : ManaksansthaTelephones :23230131,23233375,2323 9402 (Common to all offices)

Regional Offices : Telephone

Central

Eastern

Northern

Southern

Western.“

Branches :

: Manak Bhavan, 9 Bahadur Shah Zafar Marg

{

23237617

NEW DELHI 110002 23233841

: 1/14 C.I.T. Scheme VII M, V. I. P. Road, Kankurgachi

{

23378499,23378561

KOLKATA 700054 23378626,23379120

: SCO 335-336, Sector 34-A, CHANDIGARH 160022

{

603843609285

: C.I.T. Campus, IV Cross Road, CHENNAI 600113

{

22541216,2254144222542519,22542315

: Manakalaya, E9 MIDC, Marol, Andheri (East)

{

28329295,28327858

MUMBAI 400093 2832 7~91 ,28327892

AHMEDABAD. BANGALORE. BHOPAL. BHUBANESHWAR. COIMBATORE. FARIDABAD.

GHAZIABAD. GUWAHATI. HYDERABAD. JAIPUR. KANPUR. LUCKNOW. NAGPUR.NALAGARH. PATNA. PUNE. RAJKOT. THIRUVANANTHAI%RAM. VISAKHAPATNAM.

Printed at Pcabhat Offset Press, New Dethi-2

I