Method Statement for Concrete Sampling and Testing

This method statement is applicable for collecting samples for concrete before and during concrete pouring activities and doing the standard tests.

The aim of this civil works method statement is to provide and maintain effective quality control procedures and to execute the work in compliance to standard and good practice at all stages and activities in the concrete sampling and testing.

Abbreviations

MS – Method Statement

ITP – Inspection & Test Plan

ITR – Inspection & Test Request

ITL – Independent Testing Laboratory

PM – Project Manager

CM – Construction Manager

PPE – Personal Protective Equipment

Applicable Standards/References

• BS 1881Part 5, Methods of Testing Hardened Concrete for Other Than Strength
• BS EN 12350-1: 2000,  Methods of Sampling Fresh Concrete
• BS EN 12350-2: 2000, Methods of Testing Fresh Concrete.
• BS EN 12350-6: 2000 Part 108 to Part 113 Part 124, Method for Determination of Density of Compacted Fresh Air Methods of Making & Curing Test Specimens Analysis of Hardened Concrete.
• BS EN 196, Methods of Testing Cement
• ASTM C 94/BS 5328, Ready Mixed Concrete

Necessary Equipment

• Concrete Mixers
• Slump measurement cone and  equipments
• Concrete cube moulds for concrete sampling
• Thermometer
• Meter tape
• Curing pool
• Cube crushing and testing equipment
• Equipment for Durability test and moisture content
• Safety Equipment As applicable

Concrete Sampling Procedure

Pre-Sampling Activities:

Full details of all materials shall be submitted, which is proposed to use for making concrete. No concrete shall be placed in the Permanent Works until the consultant has approved the materials of which it is composed. Approved materials shall not thereafter be altered or replaced by other materials without the consent of the consultant.

All equipments used for concrete testing and concrete sampling shall be calibrated. All testing and sampling activities to be carried out at site/ in ITL by ITL representative or in presence of ITL representative.

Sampling Steps

• Sample shall be taken for each class of concrete in production at each plant for use for a project.
• Samples of concrete shall be taken at the point of mixing or of deposition as instructed by the consultant.
• All samples shall be taken in  the presence of a representative from the contractor/consultant/client as applicable in accordance with the sampling procedures described in BS EN 12350-1:2000 (Testing fresh concrete).
• Samples shall be taken on the basis of one for each 20 cubic meter of concrete placed or more often dependent on concrete grade and location as agreed. In any case not less than one sample per day or one sample for each pour of concrete placed shall be taken, whichever is the more frequent.
• From each sample 6 x 150mm cubes shall be casted, cured and tested as set out in BS EN 12390-1:2000.
• When the concrete contains aggregate with a nominal size of 75mm, all aggregate retained on a 50mm sieve shall be removed before casting cubes or making slump measurements. Six 200mm test cubes shall be casted from each sample and cured as set out in BS EN 12390-1:2000 [Testing hardened concrete, Shape, dimensions and other requirements for specimens and moulds]. In this instance, samples shall be taken on the basis of one for each 100 cubic meter of concrete placed but in any case not less than one sample per day or one sample for each pour of concrete placed, whichever is the more frequent.

Testing of Concrete

For all classes of concrete in production three cubes shall be tested at 7 days and three at 28 days or as required by the consultant/client.

The average strength of the three cubes crushed at & or 28 days shall be referred to as one test result.

Concrete shall be deemed to comply with the strength specified if:

Any one test result is not less than 85% of the final trial mix strength for that class of concrete.

The average of any 6 successive test results for the same class of concrete is not less than 90% of the final trial mix strength for that class.

No single cube result is less than 75% of the final trial mix strength for that class of concrete.

All the tests shall be conducted by an approved testing agency which should have previous track record for doing the concrete testing.

Slump Test

The slump or compacting factor of the concrete shall be determined for each batch from which samples are taken and in addition for other batches at the frequency agreed between all parties.

The slump of each sample shall be carried out in accordance with BS EN 12350-2:2000 at the time of sampling.

Concrete may only be accepted for placement if its workability is within one of the following limits at the time of placement:

The slump of the concrete in any batch shall not differ from the value established by the trial mixes by more than 25mm or one third of the value, whichever is the greater.

The variation in value of the compacting factor, if used in place of a slump value, shall be within the following limits:

• For value of 0.9 or more ±0.03
• For value between 0.8 and 0.9 ±0.04
• For values of 0.8 or less ±0.05

Water/ Cement Ratio:

The water/cement ratio as estimated from the results of slump test section as above, or when required by the client, determined by samples from any batch shall not vary by more than 5% from the specified maximum value or the value established during the trial mixes, whichever is the lower.

Air Content Testing

The percentage air content determined from individual samples taken at the point of placing the concrete and representative of any given batch of concrete shall be within +1.5% of the specified value.

The average percentage air content from any four consecutive determinations from separate batches shall be within +1.0% of the specified value.

The air content shall be checked for each batch.

Total air content comprises entrained air plus entrapped air remaining after compaction.

Temperature Monitoring of Concrete

For each sample the temperature of the fresh concrete shall be measured and frequency of measurement shall depend on contractor/client requirements.

Durability Tests:

Samples of concrete shall be tested for durability properties by undertaking absorption and permeability tests as mentioned hereunder and shall coincide with samples taken from cube strength tests as appropriate.

Chloride Permeability: As per AASHTO T277. The maximum charge pass at 28 days shall be 3500 for normal concrete or 1500 for GGBS concrete. For other types respective standard can be referred.

Water Permeability to DIN 1048: The maximum penetration at 28 days shall be 10mm for silica fume concrete and 15mm for general concrete.

Initial Surface Absorption: As per BS 1881-208:1996 [Testing concrete.  Recommendations for the determination of the initial surface absorption of concrete] (ISAT). Maximum ISAT at 28 days (10 minute test) shall be 0.15ml/m2/sec for both silica fume concrete and for normal concrete.

30 Minute Absorption: BS 1881-122:1983 [Testing concrete. Method for determination of water absorption]. Maximum absorption shall be 1.5% at 21 days for silica fume concrete and 2.0% at 21 days for concrete generally.

Concrete Tests Frequency Rate:

Item	Requirement	Test Method	Test Frequency Rate
	FRESH CONCRETE
1	Sampling	ASTM C 31/C 172 and C 192	As required by individual test
2	Slump	ASTM C 143 or BS 1881	Every 20 m3 during production
3	Air content	ASTM C 173 or C 231	Every 100 m3 during production
4	Temperature	ASTM C 1064	Every 20m3 during production
	HARDENED CONCRETE
5	Sampling	ASTM C 823 and BS 1881 Part 101	As required by individual test
6	Strength (cubes)	BS 1881 Part 108	Six cubes every 20 m3. 3 Cubes for 7 days and 3 Cubes for 28 days.
7	Strength (drilled cores)	ASTM C 42	As required if cube tests do not meet acceptance criteria. No. of cores as instructed by engineer
8	Cement content	ASTM C 85/C 1084	As required if cube tests do not meet acceptance criteria. No. of cores as instructed by engineer
9	Rapid chloride permeability test (RCPT)	ASTM C 1202	Four tests every month for the first three months of production then every three months
10	Water penetration	DIN 1048	Three tests every month for the first three months of production then every three months
11	Porosity	RILEM CPC 113	Three tests every month for the first three months of production then every three months
12	Water absorption	ASTM C 642	Three tests every month for the first three months of production then every three months
13	Total chlorides	ASTM C 1152/C 1218 BS 1881 Part 124	Three tests every month for the first three months of production then every three months
14	Total sulphates	ASTM C 856 BS 1881 Part 124	Three tests every month for the first three months of production then every three months

Testing Agencies:

Testing Services shall be provided by one of the Approved Testing Agencies / Independent Test laboratory (ITL). The cost of Testing Services shall be borne by the Contractor.

Quality Control Procedure During Concrete Sampling

QA/QC Engineer is responsible for verifying all materials before incorporating to works and approved by the consultant.

The QA/QC Engineer/Inspector will verify the items listed on Check Sheets and make physical verification that the area is ready for the testing and sampling.

QA/QC Engineer after verifying all aspects, will forward ITR or information relevant to testing and sampling to consultant for inspection or witness.

In the event of any rectification required, QC Engineer will intimate the ITL/Site Engineer and get the issue rectified and a re-inspection/testing will be done.

After obtaining client approval, the testing or sampling of concrete will be done by ITL.

The ITL will check ambient temperature, concrete temperature, slump and mix details as per delivery note & specified testing frequency as per specification and method statement for concrete sampling and testing.

ITL will carry out the necessary testing and sampling for compression strength test as per specified testing frequency as per specification and method statement for concrete sampling and testing.

ITL will carry out 7 days compression strength tests followed by 28 days test (In case 7 days test is a failure, the matter shall be immediately conveyed to client).

After obtaining client approval, QA/QC Engineer will send ITR to witness/Test request to archive for the preparation of close out dossiers.

Attachments

• Quality Control Procedures
• Inspection & Test Plan
• Check Sheet
• Risk Assessment