BMT

4.8 QUALITY CONTROL OF CONCRETE (FRESH AND HARDENED)

Quality control of concrete ensures that the produced mix meets the desired performance criteria in terms of strength, workability, durability, and uniformity. The process includes control of constituent materials, mix proportioning, production, placement, and testing of fresh and hardened concrete as per relevant Indian Standards.

4.8.1 Objectives of Concrete Quality Control

• To ensure uniform and consistent quality of concrete at all stages.
• To maintain strength and durability as per design specifications.
• To detect deviations in mix proportions or workmanship.
• To ensure compliance with BIS codes and contract specifications.
• To reduce material wastage and achieve economical concrete production.

4.8.2 Stages of Quality Control

Stage	Control Activity	Relevant IS Codes
1. Before Construction	Checking cement, aggregates, admixtures, and water quality; mix design approval	IS 10262, IS 456
2. During Construction	Monitoring batching, mixing, transportation, placing, compaction, and curing	IS 4926, IS 7861
3. After Construction	Testing of hardened concrete cubes/cylinders; evaluation of strength	IS 516

4.8.3 Laboratory Tests on Fresh Concrete

S. No.	Test Name	Description / Objective	Typical Requirement / Acceptance Criteria	Standard Reference
1	Slump Test	Measures workability and consistency of concrete mix	25–75 mm (low), 75–100 mm (medium), 100–150 mm (high)	IS 1199
2	Compaction Factor Test	Determines the degree of compaction of fresh concrete (used for low workability mixes)	Compaction Factor: 0.75–0.95	IS 1199
3	Vee-Bee Consistometer Test	Measures workability of stiff mixes used in vibration-compacted concrete	Vee-Bee time: 5–10 sec (medium)	IS 1199
4	Flow Table Test (for SCC)	Determines the flowability and segregation resistance of self-compacting concrete	Flow spread: 650–800 mm	IS 9103, EFNARC Guidelines
5	Air Content Test	Determines the percentage of entrapped or entrained air	1–2% for vibrated concrete; up to 6% for air-entrained concrete	IS 1199
6	Temperature Measurement	Ensures control on heat of hydration and workability retention	≤ 32°C at placement	IS 7861

4.8.4 Laboratory Tests on Hardened Concrete

S. No.	Test Name	Description / Objective	Typical Requirement / Acceptance Criteria	Standard Reference
1	Compressive Strength Test	Determines crushing strength on standard cubes/cylinders	Minimum as per design grade (e.g., M25 = 25 MPa at 28 days)	IS 516
2	Split Tensile Strength Test	Measures tensile capacity indirectly using cylindrical specimens	≈ 10–15% of compressive strength	IS 5816
3	Flexural Strength Test (Modulus of Rupture)	Determines the bending strength of concrete beams	0.7–1.0 √fck (MPa)	IS 516
4	Density Test	Calculates hardened concrete density	Normal weight: 2300–2500 kg/m³	IS 1199
5	Water Absorption Test	Measures water uptake by immersion and drying	≤ 3% by mass for structural concrete	IS 516
6	Abrasion Resistance Test	Evaluates surface wear resistance of floors/pavements	Wear index ≤ 2 mm	IS 1237
7	Rebound Hammer Test (NDT)	Determines surface hardness and indicative compressive strength	±15% of actual strength	IS 13311
8	Ultrasonic Pulse Velocity (UPV) Test	Evaluates homogeneity and internal flaws	> 4.5 km/s – Excellent	IS 13311
9	Water Permeability Test	Determines resistance to water penetration under pressure	Depth of penetration ≤ 25 mm	IS 516

4.8.5 Acceptance Criteria for Compressive Strength

Concrete Grade	Characteristic Strength (fck, MPa)	Minimum Individual Test Result	Mean of 4 Consecutive Test Results
M15	15	≥ 12	≥ 15
M20	20	≥ 16	≥ 20
M25	25	≥ 20	≥ 25
M30	30	≥ 25	≥ 30
M35	35	≥ 28	≥ 35
M40	40	≥ 32	≥ 40

4.8.6 Field Quality Control Measures

• Use calibrated batching equipment and weigh-batching wherever possible.
• Maintain a daily record of slump and cube strength results.
• Ensure proper mixing time (minimum 2 minutes in batch mixers).
• Avoid segregation during transportation and placement.
• Maintain proper curing duration — 7 days (OPC), 10–14 days (blended cements).
• Record temperature and humidity during curing, especially for hot-weather concreting.

4.8.7 Frequency of Testing

Quantity of Concrete (m³)	Minimum Number of Samples
1 – 5	1
6 – 15	2
16 – 30	3
31 – 50	4
> 50	4 + 1 additional sample for each additional 50 m³

Each sample shall consist of 3 test cubes taken from a single batch of concrete.

4.8.8 Important BIS and ASTM Standards (Latest Revision)

Standard No.	Title / Description
IS 456	Plain and Reinforced Concrete – Code of Practice
IS 516	Methods of Tests for Strength of Concrete
IS 1199	Methods of Sampling and Analysis of Concrete
IS 10262	Concrete Mix Proportioning – Guidelines
IS 13311	Non-Destructive Testing of Concrete – UPV & Rebound Hammer
IS 4926	Ready-Mixed Concrete – Specification
ASTM C39	Compressive Strength of Cylindrical Concrete Specimens
ASTM C805	Rebound Hammer Test for Concrete
ASTM C597	Pulse Velocity through Concrete