concrete works (main one)

8/12/2019 Concrete Works (Main One)

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CONCRETE WORKS (PRODUCTION,HAULAGE AND PLACING)

Objective

To define the standard procedures for production, transportation,

placement/compaction, curing and protection of plain and reinforced

structural concrete

Scope

This methodology covers all plant, labor, equipment, materials to be

used in performing all operations in connection with the furnishing,

manufacturing, transportation, placement, vibration, finishing and

curing of plain & reinforced concrete as per applicable codes and

standards given there in the contract documents. All concrete work will

conform to requirements of ACI 318-08 and modifications.

Procedures

Concrete Materials and Arrangements

Submittals Samples of specified materials such as cement,

admixtures, coarse and fine aggregates including names of sources

and their description along with relevant literature, delivery and

storage record, details of construction plant, shop drawings ,

method statements, certificates and mill test data, results of routine

tests and daily reports, bar bending schedules and concreting

record will be submitted for approval.


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Cement Ordinary Portland cement and slag cement as specified

conforming to ASTM C-150-98 type - 1 standard shall be brought,

stored in dry place, and tested whenever required. Only one brand

of each type of cement will be used for concrete in any individual

member of the structure and will be used as early as possible after

delivery at site. The mixing of different types of cements shall not be

adopted. Mill testing certificates will be produced from time to time.

Admixtures Admixtures such as air entraining agents, water

reducing admixtures including plasticizers or super plasticizers or

retarders will be used as approved and required by the Engineer.Admixtures will be well agitated to ensure uniformity before use in

concrete. Admixtures will comply with ASTM Designation C-494

Type D and will not contain calcium chloride. Admixture will be

handled and stored in accordance with the manufacturers

recommendations.

Coarse Aggregates Specified coarse aggregate will be obtained

and used of sizes given in mixed design from the approved sources.

The grading of the aggregates used will be conforming to ASTM C-

33-74 standards as specified in specifications. The size of the

aggregates will fall within the range of 3/16of an inch to 3 inches.

Coarse aggregate will consist of natural deposits or quarried and

crushed rock or boulders. The sum of the percentages of all the

deleterious substances will not exceed three percent, by weight.

Fine Aggregate - Fine aggregates will be hard coarse sand, crushed

stone or gravel obtained from approved quarry/source and shall

conform to requirements of ASTM C-33-99. The sum of the


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percentages of all the deleterious substances will not exceed five

percent, by weight.

Water - Potable water will be used for cleaning of aggregates,

mixing in concrete, mortar and grout and their curing. Water will be

obtained from source approved by the engineer and would be free

from injurious amounts of oil, acid, salt, alkali, organic matter. The

water for curing shall have PH value of 6 to 8 and shall not contain

impurities which cause de-coloration of concrete. The contaminated

water may only be used having specified impurities with their

permissible limits in unavoidable circumstances. Delivery and Storage Record comprising details of cement,

aggregates, chemicals/admixtures delivered at Batching Plant will

be maintained for any time inspection. Deliveries of different types

of concrete supplied at site shall also be recorded in details.

Covered Sheds (if required) will be installed to protect aggregates

from direct sun-heat. Separate stockpiles will be provided for each

size or classification of aggregates.

Constructional PlantDetails of major constructional plants such as

batching plants, mixers, concrete pumping equipment, hoists and

cranes along with general layout plans and flow diagram will be

submitted for the review and approval of the Engineer.

Inspection of Concrete Pouring Arrangements Verification and

approval of formwork and rebar fixing will be assured before the

preparation of delivery of any type of concrete. Batching Plant

operators will be very well conversant with the Concrete Mix

Designs of all required types of concrete.


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Quality Assurance ICPL will furnish certificates, mill-test-data,

calibration certificates of scales and machines.

Concrete Records ICPL will submit record of daily poured

concrete on approved format and pour slips.

Proportioning of Concrete

Trial mixes and tests will be carried out for the purpose of designing

the mixes and for quality control with regard to the required

strength, density and durability. It is pertinent to mention here that

different compressive strengths of concrete are required keeping in

view the size and load carrying capacity of the structural members.

Material Engineer will conduct trial mixes as directed by the

Engineer and cylinders samples will be casted with complete testing

record such as mix proportions, temperature, slump etc. The trials

will be done using at least 03 different w/c ratios which will produce

a range of strength required for the works. For each w/c ratio cylinders will be casted and tested. From

compressive strength test results, curve for strength vs w/c ratio will

be drawn to ascertain accurate w/c ratio required for desirable

compressive strength.

The cement contents and mixed proportions to be used will be such

that w/c ratio is not exceeded when maximum slump is permitted.

Concrete mixes will be designed to use the larger size and

maximum amount of coarse aggregate to produce the proper place-

ability, durability, compressive strength and other required

properties.


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Aggregates will be batched by weight. The weighing machine will be

accurate within 2% limits. In case of volumetric measurement,

control on volume shall be assured. The measuring boxes should

be deep and narrow and fitted with handle.

Calculated water will be added within 25 % of specified mixing time.

Approved Design Mixes will be conveyed to all lab & Production

control staff to avoid any mistake in the mix proportion handling.

Before raising formal inspection request, ICPL QA/QC Engineer

shall inspect the works and if found satisfactory, shall proceed with

the Engineers representative for final inspection & approval.

Concrete Production & Transportation

Batching Plant of sufficient capacity will be set up as per the

requirements of the project.

All types of concrete specified in the contract documents shall be

designed, produced and supplied by the in-house batch plants. Allconstructional plant will be set up as per approved Layout plan.

In case mixing machines are to be used, they must have sufficient

capacity to produce the concrete continuously without having any

cold joint. Minimum mixing time of 2 min shall be used for mixers

with 0.25 to 0.2 cum capacity.

Preferably computerized scales for weigh measurement of raw

material at batching plant will be installed and maintained. An

accurate recorder will be provided that shows batching weights.

Imprint made by a calendar type showing day, time etc.


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Approved Design Mixes will be conveyed to all lab & Production

control staff to avoid any mistake in the mix proportion handling.

Concrete will be transported from production to final deposit location

as rapidly as practicable to control the segregation and any loss of

required workability. The concrete will not be dropped more than

900 mm for transportation to prevent the segregation.

The w/c ratio shall be adjusted such that concrete with suitable

workability, density, impermeability, durability and required strength

could be obtained without the use of excessive amount of cement.

Addition of water to compensate the stiffening of concrete will not beadopted. Uniformity in concrete consistency from batch to batch

shall be assured.

Concrete will be transported with concrete pumps directly in contact

with batching plants and through transit mixers to the remote work

locations or any other arrangement like hoists or bucket operated

with tower crane.

Concrete Placing

After production and transportation of concrete all type of

confirmatory tests will be managed by Q/A & Q/C staff. This will

include slump test at batch plant & site, temperature control, lead

time control & homogeneity of concrete.

Concrete will be placed only after the approval of formwork, steel

fixing, embedded parts installation, bracing of form etc by the

Engineer. The concrete will be placed in such a manner which will

require as little re-handling as possible.


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Immediately before placing concrete, all surfaces upon or against

which the concrete is to be places will be free from standing water,

mud, debris or loose material. The surfaces of all absorptive

materials against which the concrete is to be placed shall be

thoroughly moistened in order to avoid any suction of water from

freshly placed concrete.

Placing will be carried out at such a rate that the concrete which is

being integrated with fresh concrete is will plastic. Concrete will be

places and compacted well within the initial setting time. Concrete

will be deposited as close as possible to its final position in the formand avoiding to maximum its horizontal movement.

The concrete will be consolidated by vibration so that concrete is

thoroughly worked around reinforcement, embedded items, into

corners of form eliminating all air and stone pockets which may

cause honeycombing and planes of weakness. Internal vibrators

shall have sufficient frequency and amplitude to achieve

consolidated concrete. At each insertion of vibrating shaft for 5 to 15

sec time shall be given for thorough consolidation.

The time between the mixing and placing will be reduced for rich

mixes or if the work is carried out at high temperature or exposed to

dry weather. In any circumstances this time span shall not exceed

30-45 minutes.

During placement care will be taken not to disturb rebar, have

proper walkways / passages, standby vibrators (mechanically or

electrically operated), temperature observation, approved

construction joints, avoiding cold joints & stability of embedded


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mass concrete & 32 C for Normal concrete) in addition to the

approval of the Engineer.

The water for mixing concrete will be cooled by the use of crushed

ice & chillers. The ingredients will also be cooled before mixing with

water.

The aggregates may be stacked under shade if required. This will

be further cooled by sprinkling cold water on coarse aggregate.

Curing of Concrete

Freshly placed concrete will be protected against any premature

drying, excessively hot and cold temperature and will be maintained

with minimum moisture loss at constant temperature for the period

necessary for hydration of cement consequently hardening of

concrete.

Curing of concrete surfaces not in contact with form will be done

with water sprinkling, wet hessian cloth, covering with waterproofsheet or application of curing compound (if necessarily required).

Horizontal members like raft, foundations and slabs will be cured

with ponding on their top surface. Vertical members like walls,

columns and vertical sides of the beams will be cured with water

sprinkler and hessian cloth periodically is wetted.

Moisture loss from surfaces in contact with form shall be

continuously wet for controlling the temperature till the form is safely

removed. Curing will be continued for 14 days for all types of

concrete


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Curing period may be terminated earlier if the cylinders casted from

the relevant concrete member are placed in the vicinity with all

similar conditions shows 70% of average compressive strength on

their early testing (usually after 07 days).

During the curing period concrete will be protected from damaging

due to mechanical disturbances and excessive vibrations.

Testing of Concrete

During placement of concrete, cylinders will be casted for

compressive strength test as per the standards mentioned in the

specifications. ICPLs QA& QC engineer shall assist to the

Engineers staff from casting to crushing of cylinders at every stage.

After 07 & 28 days testing of the samples, report will be submitted

for approval of the Engineer. Generally one test sample consisting

of 06 # cylinders shall be prepared from any one class of concrete

per day or 50 cum of concrete whichever is greater. All six sampleswill be tested with division of 02# each on 03 days, 07 days & 28

days. Test cylinders will be clearly marked with date identification

mark and location of concrete.

A test sample data sheet for record purposes will be prepared for

each set of samples. For any concrete mix, compressive strength of

any one specimen or average compressive strength of three

specimens is not less than specified strength or the difference

between the greatest and least strengths is not more than 20% of

that average value.


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The test results will be compiled on monthly basis for complete

recording and ready references.

TOOLS & EQUIPMENTS

Batching plant, Concrete pumps, Vibrators, Slump cones, Personal

Protective Equipment, Cylinders, Wheel-barrows etc

Related documents

Corrective Action Request (CAR) form

Quality of Coarse/Fine aggregate.

Survey Report

Weather record

Flat and elongated particles

Calculation Sheet Aggregate Combination for Concrete Design Mix.

Specific gravity test

Cement Soundness test

Unit weight (Loose / Rodded)

Summary of Daily Concrete

Concrete compression test

Monthly / Weekly summary of compression strength of concrete

Request/Report for Inspection/Test (RIT)

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