Construction Material Testing
Core Cutting of Asphalt Pavements and Concrete
In-situ strength and thickness verification of pavements and structural concrete
ASTM D3549
IS 516 Part 1/Sec 1
IS 5816
Core cutting is a direct method of extracting cylindrical specimens from existing asphalt pavements or hardened concrete structures to verify in-situ thickness, density, and compressive or tensile strength. It is the most reliable technique for confirming that constructed layers meet design specifications.
What Is Core Cutting of Asphalt Pavements and Concrete?
Core cutting of asphalt pavements and concrete involves drilling a diamond-tipped rotary core cutter into the finished surface to extract a cylindrical sample. For bituminous pavements, cores are taken to measure layer thickness and bulk density per ASTM D3549, confirming that the laid thickness matches the design requirement and that adequate compaction has been achieved. For concrete structures such as slabs, beams, columns, and bridge decks, cores are tested for compressive strength per IS 516 and splitting tensile strength per IS 5816 to assess the in-situ strength of hardened concrete.
Core diameters of 75 mm, 100 mm, and 150 mm are used depending on the maximum aggregate size and structural element thickness. Length-to-diameter (L/D) ratio corrections are applied per IS 516 when cores are not of standard proportions. MoRTH specifications mandate core cutting at defined frequencies for quality assurance of highway pavements — typically one core per 500 metres per lane for bituminous layers.
NKMPV provides complete core cutting and testing services covering extraction, measurement, density determination, and strength testing. Our reports are accepted by NHAI, state PWDs, and independent design consultants. We also perform Rebound Hammer testing as a complementary non-destructive assessment and bitumen testing on extracted binder from asphalt cores when required.
Test Parameters & Acceptance Criteria
The following parameters are evaluated during core cutting and subsequent laboratory testing. Acceptance criteria depend on whether the core is from an asphalt pavement or a concrete structure, and are governed by project-specific MoRTH, IRC, or IS code requirements.
| Parameter | Value / Range | Unit | Standard |
|---|---|---|---|
| Core Diameter | 75 / 100 / 150 mm | mm | IS 516 Cl. 7.1 / ASTM D3549 |
| Bituminous Layer Thickness | As per design (typically 25-200 mm) | mm | ASTM D3549 / MoRTH Cl. 501-509 |
| Bulk Density of Bituminous Core | >= 97% of Marshall density | g/cc | ASTM D3549 / MoRTH Table 500-14 |
| Compressive Strength of Concrete Core | >= 85% of design fck | N/mm² | IS 516 Part 1/Sec 1 Cl. 7 |
| L/D Ratio Correction Factor | 0.87-1.00 (for L/D 1.0 to 2.0) | IS 516 Part 1/Sec 1 Table 1 | |
| Splitting Tensile Strength | Typically 1/10th of compressive strength | N/mm² | IS 5816 |
| Air Voids in Bituminous Core | 3-5% (Dense graded mixes) | % | MoRTH Cl. 501-509 |
| Concrete Core Density | 2200-2600 (normal concrete) | kg/m³ | IS 516 |
Applicable Indian & International Standards
ASTM D3549
Standard Test Method for Thickness or Height of Compacted Asphalt Mixture Specimens
IS 516 Part 1/Sec 1
Hardened Concrete — Methods of Test — Compressive, Flexural and Split Tensile Strength
IS 5816
Method of Test for Splitting Tensile Strength of Concrete
MoRTH 5th Revision
Specifications for Road and Bridge Works — Section 500 (Bituminous Courses)
IS 456:2000
Plain and Reinforced Concrete — Code of Practice (Clause 17.4 — Acceptance Criteria for Cores)
ASTM C42
Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
Equipment Used
Diamond Core Cutting Machine
Hilti DD 200 / DD 350
Core diameters 50-350 mm; wet drilling with water-cooled diamond bits
CalibratedDiamond Core Bits
Hilti DD-BI series (75 mm, 100 mm, 150 mm)
Suitable for asphalt, reinforced concrete, and plain concrete up to 500 mm depth
CalibratedCompression Testing Machine (CTM)
AIMIL AIM-311-D
2000 kN capacity, digitally controlled with automatic pace rate
CalibratedVernier Caliper & Measuring Instruments
Mitutoyo digital caliper (0-300 mm)
Least count 0.01 mm for diameter and length measurement
CalibratedCore Capping Equipment
Sulphur capping set / Neoprene pad system
For preparing plane and parallel end surfaces per IS 516
CalibratedWeighing Balance
Essae DS-252 (high precision)
30 kg capacity, least count 0.1 g for density determination
CalibratedTesting Process
1
Site Survey & Core Location Marking
2-4 hoursThe project engineer identifies core cutting locations based on MoRTH frequency requirements or structural investigation needs. For bituminous pavements, locations are typically at 500-metre intervals per lane, away from edges and joints. For concrete structures, locations are selected to avoid reinforcement using a rebar detector (cover meter). Each location is marked and documented with chainage or structural member reference.
2
Core Extraction
15-30 minutes per coreA diamond-tipped rotary core cutter is anchored to the surface and operated with continuous water cooling. For bituminous pavements, 100 mm or 150 mm diameter cores are drilled through the full pavement thickness. For concrete, the core diameter is selected to be at least 3 times the maximum aggregate size (typically 100 mm or 150 mm). Cores are carefully extracted, labelled with location ID, orientation (top marked), date, and placed in protective packaging to prevent damage during transport.
3
Visual Examination & Measurement
Day 1At the laboratory, each core is visually inspected for segregation, honeycombing, voids, layer delamination (in bituminous cores), and crack patterns. The diameter is measured at three locations along the height using a digital caliper, and the average is recorded. The length (height) is similarly measured at three points. For bituminous cores, individual layer thicknesses are measured to verify compliance with design cross-section.
4
Density & Thickness Analysis (Bituminous Cores)
Day 1-2For asphalt cores, the bulk specific gravity is determined by weighing the core in air and in water (saturated surface dry method per ASTM D2726). The bulk density is compared against the Marshall mix design density to calculate the degree of compaction. Layer thickness is compared against the design requirement with MoRTH tolerance limits. Air void content is computed from the bulk specific gravity and the maximum theoretical specific gravity of the mix.
5
Strength Testing (Concrete Cores)
Day 2-3Concrete cores are trimmed to the required length using a diamond saw. End surfaces are capped with sulphur compound or ground plane using a lapping machine to ensure uniform load distribution. The L/D ratio is recorded and the appropriate correction factor is determined per IS 516. The core is tested for compressive strength in a 2000 kN CTM at a loading rate of 14 N/mm2/min. Where required, splitting tensile strength is tested per IS 5816 by applying a diametral compressive load through plywood strips.
6
Calculation & Reporting
Day 3-7For concrete cores, the equivalent cube compressive strength is calculated by applying the L/D correction factor. The result is compared against the acceptance criteria of IS 456 Clause 17.4 — the average of three cores must be at least 85% of the specified grade strength, with no individual core below 75%. For bituminous cores, the report includes measured thickness, bulk density, degree of compaction, and air voids. The NABL-accredited test certificate is issued with all raw data, photographs, and compliance assessment.
Where This Test Is Used
Core cutting is the definitive method for verifying the quality of constructed pavements and concrete structures. On highway projects, MoRTH mandates core cutting of bituminous layers to confirm laid thickness and compaction density for every 500 metres per lane. For concrete structures, core testing per IS 516 is performed when cube test results are doubtful, when structural adequacy is in question, or during forensic investigation of distressed structures. The Rebound Hammer test is frequently used as a preliminary screening tool before deciding core locations. Core cutting is also essential for bitumen extraction and recovery from asphalt layers to verify binder content and grading of reclaimed material.
Bituminous pavement thickness verification per MoRTH Section 500
In-situ compressive strength assessment of concrete structures per IS 516
Splitting tensile strength determination of concrete per IS 5816
Quality audit and third-party verification for NHAI highway projects
Forensic investigation of structural distress in buildings and bridges
Compaction density verification of asphalt layers per ASTM D3549
Dispute resolution and arbitration — court-admissible NABL test reports
Pavement condition evaluation prior to overlay or rehabilitation design
Detailed Information
Core cutting of asphalt pavements and concrete
Core cutting is a vital technique in civil engineering used to assess the quality, durability, and overall structural integrity of asphalt pavements and concrete structures. By extracting cylindrical samples of pavement or concrete from an in-situ structure, engineers can perform detailed tests that offer insight into the material's performance under real-world conditions. These tests play a pivotal role in ensuring that materials meet specific quality standards, adhere to design requirements, and are capable of withstanding traffic loads, weather conditions, and other environmental stressors over time. Core cutting is one of the most effective non-destructive methods available for evaluating the performance of both asphalt and concrete pavements. The data obtained from core cutting tests help guide construction quality control, maintenance planning, and future design improvements.Testing of Core Cutting in Asphalt Pavements
2.1 Description of Core Cutting in Asphalt Pavements Core cutting for asphalt pavements involves extracting cylindrical samples from the pavement using a specialized core drill. The process is conducted on the finished pavement after it has cured to assess its quality, material composition, and the structural integrity of the asphalt layers. Core cutting helps determine critical properties, such as the binder content, air voids, aggregate gradation, and density of the asphalt mixture. This technique provides an accurate and direct assessment of how the pavement was constructed and whether it meets the required standards. Additionally, it helps identify construction defects such as insufficient compaction, improper layer thickness, or non-compliance with the binder content specifications. 2.2 Core Cutting Procedure for Asphalt Pavements The core cutting procedure typically includes the following steps:- Preparation: The pavement surface is cleaned of any debris, oil, or loose materials before drilling to prevent contamination of the sample. The drilling location is selected to represent different areas of the pavement, ensuring that the core samples are representative of the entire structure.
- Drilling: A core drilling machine is used to extract samples, often with a diamond-tipped drill bit. The drill bit is typically between 100 mm to 150 mm in diameter. The core is extracted with minimal disturbance to the surrounding material.
- Handling and Transport: After extraction, the core is immediately labeled with vital information such as the location, depth, and date of extraction. The core is then transported to the laboratory under controlled conditions to avoid damage and ensure accurate test results.
- Binder Content: The binder content is measured by dissolving the bitumen in a solvent and comparing the mass of the binder to the total mass of the core. The appropriate binder content ensures the pavement’s durability and flexibility.
- Air Voids: The air void content of the sample indicates the level of compaction. A lower air void content generally indicates better compaction and resistance to deformation.
- Aggregate Gradation: The aggregate mix’s particle size distribution is tested to verify whether it matches the required specifications. Well-graded aggregates enhance the pavement's stability and durability.
- Density: The density of the extracted core is measured, and its compactness is compared to the standard values specified in the design. Proper density indicates that the pavement will resist deformation from traffic loads.
- Verification of Material Quality: Ensures that the asphalt mix used is of high quality and meets the specified standards for binder content, aggregate gradation, and density.
- Identification of Construction Issues: Core cutting identifies construction-related issues such as poor compaction, improper layer thickness, or the presence of excess air voids, which can lead to early deterioration of the pavement.
- Assessment of Pavement Longevity: By examining core samples, engineers can predict the expected lifespan of the asphalt pavement and make recommendations for repairs or adjustments in future projects.
- Guiding Maintenance Plans: Core cutting helps identify areas that require maintenance or rehabilitation, facilitating timely intervention and prolonging the life of the pavement.
- IS 3386: This code specifies the methods for sampling and testing asphalt mixtures. It includes guidelines for core extraction, testing procedures, and result interpretation.
- IS 15642: Provides specifications for hot-mix asphalt (HMA), covering the mix design, quality control, and testing processes used in the production and construction of asphalt pavements.
- IS 1203: This standard outlines the testing methods for bitumen, which is crucial in determining the binder content in the asphalt mix.
Testing of Core Cutting in Concrete
3.1 Description of Core Cutting in Concrete Core cutting in concrete is the process of extracting cylindrical samples from hardened concrete structures. The core samples obtained from these structures provide essential data regarding the compressive strength, quality, and integrity of the concrete. This testing method is commonly used in structures such as bridges, buildings, and pavements, particularly when assessing existing structures or verifying compliance with design specifications. Core cutting allows engineers to evaluate how the concrete has performed in situ, enabling them to make decisions about maintenance, rehabilitation, or even demolition if the structure does not meet the necessary standards. 3.2 Core Cutting Procedure for Concrete The procedure for core cutting in concrete is as follows:- Selection of Locations: Core samples should be taken from critical locations within the structure, such as areas exposed to heavy loads or aggressive environmental conditions. Multiple samples may be needed to ensure the core results are representative of the overall condition of the structure.
- Drilling: A diamond-tipped core drill is used to cut cylindrical samples from the concrete. The size of the core typically ranges from 100mm to 150mm in diameter, depending on the project requirements. Cores are cut with water to avoid excessive heat, which could alter the properties of the concrete.
- Core Extraction and Handling: The extracted cores are carefully labeled with relevant details and transported under controlled conditions. Proper handling is essential to prevent cracking or dehydration, which could skew the test results.
- Compressive Strength: Compressive strength is the most critical parameter for concrete. Cores are subjected to compressive loading in a testing machine to determine their strength. This is compared to the specified design strength to ensure that the concrete meets the structural requirements.
- Density and Air Voids: The density of the concrete is determined, and the volume of air voids is calculated. Air voids, if excessive, could lead to water penetration, freeze-thaw damage, and reduced durability.
- Cracking and Durability: Core samples are examined for signs of cracking, shrinkage, or early deterioration. These signs are often indicators of poor curing or inadequate mix design.
- Chloride Content: For concrete exposed to aggressive environments, such as marine exposure, chloride testing is performed to determine the potential for reinforcement corrosion.
- Accurate Evaluation of Concrete Strength: Core cutting allows for an accurate assessment of compressive strength, ensuring that the concrete can withstand the required structural loads.
- Compliance Verification: It helps verify whether the concrete mix used on-site complies with the project’s design specifications and quality standards.
- Detection of Structural Deficiencies: Core cutting can identify issues such as cracks, inadequate curing, and poor mix design, which could compromise the concrete’s integrity and lifespan.
- Guidance for Maintenance: By understanding the current condition of the concrete, engineers can recommend specific maintenance or repair strategies to prolong the service life of the structure.
- IS 516: "Methods of Tests for Strength of Concrete" outlines the procedures for testing the compressive strength of concrete cores and provides guidelines for evaluating the quality of concrete.
- IS 1199: "Sampling and Acceptance Criteria for Concrete" specifies the sampling and acceptance criteria for concrete cores, including the required number of samples and acceptable tolerances.
- IS 10262: This standard provides guidance for the mix design of concrete, which helps determine the suitability of the mix used in the concrete structure.
Why Core Cutting Tests Are Conducted
4.1 Verification of Material Properties Core cutting tests provide a reliable way to verify that the material properties, such as strength, density, and durability, meet the design specifications. For both asphalt and concrete, this ensures that the materials used are capable of performing as expected under real-world conditions. 4.2 Quality Control and Assurance Core cutting is an important tool for quality control during construction. By extracting cores from various locations, engineers can assess whether the construction methods are being followed correctly and whether the materials are of the required standard. Core cutting helps identify areas of poor construction, such as insufficient compaction in asphalt or improper curing in concrete. 4.3 Structural Integrity Assessment Core cutting tests are crucial for assessing the structural integrity of pavements and concrete structures. For example, by examining cores from an asphalt pavement, engineers can detect issues like cracking or rutting, which might be a result of poor compaction or inadequate binder content. Similarly, in concrete, core cutting can identify issues like voids or cracks, which can compromise the safety and stability of the structure.Conclusion
Core cutting test is a fundamental method that plays a pivotal role in ensuring the quality, integrity, and durability of both asphalt pavements and concrete structures. It provides a direct means of assessing the real-world performance of materials used in construction, offering detailed insights that go beyond theoretical or design predictions. By extracting cylindrical core samples from in-situ materials, engineers can gain accurate information regarding the strength, compaction, homogeneity, and overall condition of the materials used in the pavement or structure. The value of core cutting tests cannot be overstated, as they contribute to the overall safety, longevity, and efficiency of infrastructure projects. Through the results obtained from these tests, engineers are able to identify potential issues early in the construction process, such as poor compaction in asphalt or inadequate curing in concrete. This early identification can prevent costly repairs or premature failures in the future, ultimately leading to more reliable and durable infrastructures. In particular, core cutting helps in ensuring that the pavement or concrete structure is constructed according to the specifications and will continue to perform as expected throughout its lifespan. Moreover, core cutting tests support the decision-making process related to maintenance and rehabilitation. By analyzing core samples, engineers can determine whether certain areas of a structure require repair or whether the entire surface or structure needs to be resurfaced or replaced. This is especially crucial for infrastructure exposed to harsh environmental conditions or heavy traffic loads, as timely interventions can significantly extend the life of the pavement or concrete structure and improve its overall performance. In the context of regulatory compliance, core cutting tests provide assurance that construction projects are adhering to established standards and guidelines. Indian Standard codes, such as IS 3386 for asphalt and IS 516 for concrete, outline the accepted procedures for core extraction and testing, ensuring consistency and accuracy in the results. By following these standards, engineers can guarantee that the tests are performed correctly and that the results are meaningful, thereby reinforcing confidence in the constructed infrastructure’s ability to withstand the stresses and demands placed upon it. Core cutting tests also help engineers and construction teams build a feedback loop, allowing them to evaluate and improve the quality of materials and construction techniques. For example, if issues are identified in the core samples, engineers can revisit the mix designs, construction methods, or material sourcing processes to optimize future projects. This continuous feedback ultimately leads to improved practices and enhanced performance in subsequent infrastructure projects, benefiting the industry as a whole. Finally, core cutting is an essential practice in the ongoing maintenance and rehabilitation of roads, buildings, bridges, and other concrete or asphalt structures. It serves as a valuable tool not just for initial construction, but throughout the service life of the infrastructure. As structures age, core cutting provides critical information about their condition and helps plan for necessary repairs or upgrades, ensuring that public safety and operational efficiency are never compromised. In conclusion, core cutting testing stands as a cornerstone of modern civil engineering, ensuring the structural integrity and long-term durability of asphalt pavements and concrete structures. By providing vital information that informs design, construction, and maintenance decisions, core cutting helps engineers make informed, data-driven choices that contribute to the development of safe, sustainable, and reliable infrastructure. The adherence to standards like IS 3386, IS 516, and other relevant codes ensures that the testing process is robust and the results are dependable, enabling the industry to build infrastructure that stands the test of time. References- IS 3386: Method of Sampling and Testing of Asphalt.
- IS 516: Methods of Tests for Strength of Concrete.
- IS 1199: Sampling and Acceptance Criteria for Concrete.
Photos & Lab Images
Why Choose NKMPV for Core Cutting of Asphalt Pavements and Concrete?
NABL Accredited Results
Our core test reports carry NABL accreditation (ISO/IEC 17025:2017), accepted by NHAI, state PWDs, courts, and arbitration tribunals without additional verification.
On-Site Core Extraction
Our trained field crew arrives at your project site with Hilti diamond core cutters capable of extracting 75 mm to 150 mm diameter cores from asphalt, plain concrete, and reinforced concrete structures up to 500 mm depth.
Complete Testing Under One Roof
From core extraction to thickness measurement, density determination, compressive strength, and splitting tensile strength — all testing is performed in-house at our Pinjore laboratory. No sub-contracting, no delays.
Fast Turnaround for Bituminous Cores
Bituminous core results (thickness, density, air voids) are delivered within 2-3 working days. Concrete core compressive strength results follow within 5-7 days including end preparation and testing.
Detailed Photographic Documentation
Every core is photographed at the extraction site and in the laboratory. Reports include photographs showing layer structure, any defects, and measurement markings — invaluable for quality audits and dispute resolution.
Frequently Asked Questions
The core diameter must be at least 3 times the maximum size of aggregate used in the concrete. For concrete with 20 mm aggregate, a minimum 75 mm core is acceptable, but 100 mm or 150 mm cores are preferred for more representative results as per IS 516. For bituminous cores, a 100 mm (4-inch) diameter is standard. NKMPV extracts cores in 75 mm, 100 mm, and 150 mm diameters depending on project requirements.
As per IS 456 Clause 17.4, the concrete is considered acceptable if the average equivalent cube strength of three cores is at least 85% of the specified characteristic strength (fck), and no individual core has a strength less than 75% of fck. If the cores fail to meet these criteria, the structural element may require load testing or strengthening.
When the length-to-diameter ratio of a concrete core is less than 2.0, a correction factor is applied per IS 516 Part 1/Sec 1 Table 1. For an L/D ratio of 1.0, the correction factor is approximately 0.87; for L/D of 1.5 it is about 0.96; and for L/D of 2.0 no correction is needed (factor = 1.00). The corrected compressive strength is then multiplied by 1.25 to obtain the equivalent cube strength.
MoRTH specifications require a minimum of one core per 500 metres per lane for thickness and density verification of bituminous layers. For quality audit purposes, NHAI projects may require additional cores at random locations. Cores should be taken at least 300 mm from pavement edges and joints to avoid disturbed zones.
Core cutting is a destructive test that extracts a physical specimen for compressive strength testing — it gives the actual in-situ strength. The Rebound Hammer test is a non-destructive screening method that estimates surface hardness and provides only an approximate strength indication. For definitive strength assessment, core testing per IS 516 is the accepted standard. The Rebound Hammer is often used first to identify suspect areas before deciding where to extract cores.
Yes, with proper precautions. Before coring, a rebar detector (cover meter) is used to locate reinforcement bars, and core locations are selected to avoid cutting through main reinforcement. The core hole is later filled with non-shrink grout to restore structural continuity. For thin structural members or heavily reinforced sections, a smaller core diameter (75 mm) may be used to minimise the impact on the element.