ASTM C39 Compressive Strength of Cylindrical Concrete Specimens

What is ASTM C39?

ASTM C39 is a standard laboratory test method that is developed to measure the compressive strength of cylindrical concrete specimens. In the test, a concrete cylinder is loaded under compression in a compression testing machine set to deliver a continuous loading force that is applied until the cylinder shatters. The ultimate load that the specimen can bear is divided by the cross-sectional area of the specimen to obtain its compressive strength.

Compressive strength is one of the most critical mechanical properties of concrete, which directly influences the ability of concrete to carry the loads of the structure. Concrete companies, civil engineering laboratories, concrete producers, and quality assurance organizations use ASTM C39 to verify that concrete meets project specifications and design requirements. 

Get Certified ASTM C39 Testing for Reliable Concrete Strength Evaluation

Testing in accordance with ASTM C39 helps verify the compressive strength of concrete for quality control, construction acceptance, structural design verification, and compliance with applicable project specifications and regulatory requirements. Concrete specimens tested in accordance with ASTM C39 have been evaluated using the standardized compressive strength testing procedure described in the standard. 

ASTM C39 Equipment and Sample Preparation Guide

To obtain true compressive strength measurements, representative concrete samples and standard preparation procedures are crucial. Reliable and repeatable laboratory results are provided by well-prepared specimens and calibrated testing equipment. 

Testing Procedures and Requirements for Compressive Strength of Cylindrical Concrete Specimens

ASTM C39 is a test procedure that measures the strength of hardened concrete cylinders under axial compression. There are standardized laboratory procedures that provide reliable, repeatable, and comparable strength measurements of concrete. The testing process consists of the following: 

ASTM C39 Testing Process and Data Collection

Testing starts with casting samples of concrete in the form of representative concrete cylinders and curing these in standard laboratory conditions. The dimensions are taken, and bearing surfaces are prepared for uniformity before testing. Specimens are each placed at the center of a calibrated compression testing machine, under a steadily increasing axial load applied until the specimen fails. The maximum load, the compressive strength, specimen dimensions, curing age, failure mode, loading rate, and environment will be recorded and documented to meet the ASTM C39 requirements, which help in standardized reporting and reliable material evaluation. 

What is the Scope of ASTM C39 Test Standard?

ASTM C39 is a standard that specifies the methods for obtaining compressive strength of a cylindrical specimen of concrete by testing it under compression. The standard offers uniform ways to assess the quality of concrete, structural performance, and compliance with engineering requirements. The scope includes:

• Measures the compressive strength of cylindrical concrete specimens.
• Carries out evaluation of hardened concrete in structural applications.
• Determines the maximum compressive load sustained by the specimen and calculates its compressive strength.
• Assists with quality control and material verification on construction sites.
• Applies to concrete used in buildings, bridges, roads, dams, and infrastructure.
• Establishes a common basis for strength comparisons between concrete in different laboratories and construction projects. 

What are the Uses of ASTM C39 Testing?

ASTM C39 testing enables engineers, contractors, concrete producers, and quality control laboratories to verify that hardened concrete meets specified compressive strength requirements for structural applications. The results can be used for construction quality assurance, material acceptance, structural design verification, and regulatory compliance. Common applications include:

• ASTM C39 testing is used to verify that hardened concrete specimens achieve the specified compressive strength for structural and non-structural applications such as buildings, bridges, highways, and other infrastructure projects. This is to make sure that the structure is safe and will perform well over time.
• Concrete manufacturers regularly conduct ASTM C39 testing as a quality control measure to ensure consistency in the mix and to ensure that the concrete meets engineering requirements. The consistency of the results from regular testing reduces the variation in production lots.
• ASTM C39 is used in civil engineering laboratories to test new concrete mixtures, supplementary cementitious materials, and admixtures for research and development. Reliable strength comparisons can be obtained by using the standardized testing.
• Compressive strength results obtained using ASTM C39 may be used, when specified by project requirements, to support decisions regarding formwork removal, post-tensioning, or placing structures into service. Correct testing allows for efficient scheduling of projects while staying safe.
• ASTM C39 testing is used to ensure concrete quality for government structures, infrastructure, highways, tunnels, airports, dams, and public infrastructure. Standardized testing is one of the tools that can help with regulatory requirements and quality assurance of construction. 

What Materials Can Be Tested Under ASTM C39?

ASTM C39 is a standard that is mainly used for hardened concrete produced as cylinders. It is a widely adopted method for normal-weight concrete, lightweight concrete, high-strength concrete, fiber-reinforced concrete, self-consolidating concrete (SCC), roller-compacted concrete (RCC), and various other cementitious materials used in the construction of structures. ASTM C39 is intended for cylindrical concrete specimens. Mortar and grout are generally tested using other ASTM standards specifically developed for those materials. 

Why is ASTM C39 Important for Concrete Construction?

ASTM C39 is a standard test that is used to determine the compressive strength of hardened concrete and has become one of the most important parameters in structural engineering. Engineers use reliable compressive strength data to ensure structural safety, improve concrete mix design, ensure construction quality, meet building codes, and minimize the risk of structural failure. Standard testing is another benefit that allows for meaningful comparisons between various concrete mixtures, production batches, and construction projects. 

Common Challenges and Troubleshooting

Improper specimen preparation, inadequate curing, uneven specimen ends, incorrect machine alignment, loading rate deviations, equipment calibration errors, and/or operator inconsistencies may result in an inaccurate ASTM C39 test result. Accurate, repeatable, and reliable compressive strength measurements are made through standardized specimen preparation, controlled specimen curing, regular calibration of compressive testing equipment, proper alignment, and trained laboratory personnel.

Analysis Results and Interpretation

• The results of the tests are presented as the compression strength of the concrete specimen, usually in megapascals (MPa) or in pounds per square inch (psi).
• The compressive strength is the maximum load a concrete cylinder can withstand divided by the cross-sectional area of the cylinder.
• In general, the higher the compressive strength, the stronger and better the concrete quality.
• Failure patterns are examined to identify unusual specimen behavior or possible testing issues that may have affected the validity of the test results.
• The results are compared with project specifications, design requirements, and applicable acceptance criteria to determine whether the concrete meets the required compressive strength.

What are the Factors to Consider for ASTM C39 Testing?

• Speed: It takes time to cure specimens, but the compression test itself will only take a few minutes when the concrete has been cured to the specified testing age. 
• Expertise: The laboratory staff must be competent in the preparation of specimens, maintenance of curing conditions, operation of compression testing equipment, and accurate interpretation of compressive strength results. 
• Cost: ASTM C39 uses standard concrete testing equipment and offers valuable data to help optimize construction projects, minimize construction risks, and minimize costly project failures.

Link to ASTM C39

By Malhar Khole

Malhar Khole is a Material Testing Associate at MaTestLab Inc. and holds a postgraduate degree in Material Science and Technology from IIT...