ASTM C39 is the go-to standard for determining concrete’s compressive strength. In the following article, you’ll learn exactly how this test is conducted and why its outcomes are crucial for construction quality and safety.
Key Takeaways for ASTM C39
- ASTM C39 is a standard test method used to measure the compressive strength of cylindrical concrete cylinders and specimens. This test ensures structural integrity, compliance with specifications, and the effectiveness of the concrete mix.
- The test involves preparing concrete cylinders and applying an axial load. Factors like initial curing conditions, temperature, and air content in the concrete mix can significantly affect the results.
- ASTM C 39 test results are crucial for quality control in concrete proportioning and placement, acceptance testing, and evaluating the performance of concrete mixes in construction.
Overview: The Importance of Compressive Strength Testing
In construction, the compressive strength of concrete is crucial for its ability to withstand loads and maintain structural integrity. The ASTM C39 standard is widely used in the industry to measure this parameter. It involves testing concrete the compressive strength of cylindrical concrete specimens as part of a rigorous testing regime to verify the soundness and load-bearing ability of concrete elements.
The standard includes both molded cylinders and drilled cores and requires performance demonstration. Key terms are cylindrical concrete specimens, axial load, and compressive strength. These refer to the samples tested, the type of load applied, and the material’s capacity to resist the load. The ASTM C39 test ensures concrete cylinders meet the required standards by evaluating their compressive strength.
ASTM C39 testing contributes to the reliability and durability of concrete structures by:
- Establishing standards for quality control of concrete proportioning, mixing, and placing operations
- Assessing compliance with specifications
- Evaluating the effectiveness of admixtures.
ASTM C39: Purpose
Evaluating the compressive strength of cylindrical concrete specimens is the primary purpose of the ASTM C39 test. This assessment offers valuable insights into the structural integrity and load-bearing capacity of concrete, crucial in the building industry. The test ensures that the concrete meets the necessary strength criteria for structural purposes. The ASTM C39 test method evaluates concrete cylinders to determine their compressive strength, ensuring they meet the required criteria for structural applications.
Furthermore, the precise objectives of conducting ASTM C 39 compressive strength testing on concrete extend beyond merely measuring strength. They include:
- Quality control of concrete proportioning, mixing, and placing operations
- Determination of compliance with specifications
- Control for evaluating the effectiveness of admixtures
- Similar applications
Key Terminologies and Definitions
Understanding specific terms and definitions is crucial for grasping the ASTM C39 standard. The primary term in this standard is the compressive strength of cylindrical concrete specimens, which includes molded cylinders and drilled cores. According to ASTM C39, ‘compressive strength’ is the maximum load achieved during the test, divided by the cross-sectional area of the specimen. This measure is a key factor in controlling concrete quality. ASTM C39 tests concrete cylinders to ensure they meet the required quality specifications.
In ASTM C39, ‘concrete cylinders’ are cylindrical specimens used to measure compressive strength. The term ‘axial load’ refers to the compressive load applied to these specimens at a specific rate until failure occurs. This is the final concept I wanted to cover.
Performing Test: Guidelines and Procedures
The ASTM C39 test involves a series of clearly defined steps, from preparing concrete cylinders to applying a compressive axial load. Each stage is crucial for ensuring reliable results. The test method determines the compressive strength of concrete cylinders by following this sequence to ensure accurate.
The process starts with preparing the surface of the concrete cylinders, setting up the testing machine, and then applying the compressive axial load.
Preparing Concrete Cylinders
Proper preparation of concrete cylinders for the ASTM C 39 test involves the following steps:
- Remove the cylinders from the moisture room while keeping them covered with wet burlap to preserve moisture.
- Measure the diameter of each cylinder.
- Position the cylinder on the lower plate of a compression testing system, ensuring precise alignment with the loading axis.
- Thoroughly inspect the cylinders for any defects before testing.
These steps are crucial for ensuring the accuracy of the test results. Proper preparation is crucial as the ASTM C39 test method tests concrete cylinders to determine their compressive strength.
The typical dimension of such cylinders is usually 4×8 inches or 100×200 mm. The preparation of a concrete cylinder for ASTM C39 testing also involves the use of capping compounds such as sulfur mortar.
Testing Machine Setup
According to ASTM C 39, setting up the testing machine involves:
- Measuring the specimen at three separate locations and recording the average calculation.
- The loading rate should ideally be within the range of 0.14 to 0.34 MPa/sec (20 to 50 psi/sec).
- For safe test viewing during the setup, it is recommended to use Lexan safety doors.
Proper setup of the testing machine is essential as the ASTM C39 test method tests concrete cylinders to determine their compressive strength.
Calibration and periodic maintenance are also crucial to ensure the accurate functioning of the testing machines. Lastly, adherence to the safety precautions detailed in the Manual of Aggregate and Concrete Testing is paramount to prevent accidents during the testing machine setup.
Applying Compressive Axial Load
Applying compressive axial load is the central component of the ASTM C 39 test. This load is applied to the prepared concrete cylinders or cores until failure occurs, thereby assessing the specimen’s ability to withstand loads and determining its compressive strength. The testing machine and equipment used in this process include:
- Steel bearing blocks, which enable uniform load distribution on the surfaces of the specimen
- Hydraulic or mechanical loading systems, which apply the compressive axial load
- Load cells, which measure the applied load
- Displacement transducers, which measure the deformation of the specimen
Applying compressive axial load is crucial in the ASTM C39 test method, which measures the compressive strength of concrete cylinders.
Tools, software, and equipment are essential for applying the compressive load and collecting data on the specimen’s behavior under stress. This information helps assess the material’s load-bearing capacity and make informed decisions about its use in construction projects.
When applying a compressive axial load, users need to adhere to the recommended safety precautions:
- Proper alignment of the specimen within the test frame
- Gradual and uniform application of the load
- Following the manufacturer’s safety guidelines for the testing equipment.
Factors Affecting Compressive Strength Results
Various factors influence the compressive strength test results from ASTM C 39. Primarily, the initial curing conditions, temperature range during testing, and air content in the concrete mix can significantly impact the results. Controlling these factors is crucial as the ASTM C39 test method tests concrete cylinders to determine their compressive strength.
Initial Curing Conditions
The compressive strength test results can be significantly affected by initial curing conditions. Variations in temperature and humidity during the initial curing can lead to different strength outcomes. For instance, curing at 37 ˚F and 100% RH had no effect on the 28-day compressive strength while curing at 73 ˚F and 60% RH resulted in approximately a 10% loss of strength. Factors such as specimen size, shape, and friction at its ends during initial curing also play a crucial role in altering the compressive strength results.
Curing plays a fundamental role in ASTM C 39 concrete compressive strength testing by creating the ideal conditions required for the hydration process and the formation of strength in concrete samples. To manage initial curing conditions for ASTM C 39 testing, it is advisable to ensure that the concrete samples are controlled, protected, and retrieved for final laboratory curing within 48 hours. Proper initial curing conditions are essential as the ASTM C39 test method tests concrete cylinders to determine their compressive strength.
Temperature Range: ASTM C39
The accuracy of ASTM C39 testing results is also heavily influenced by the temperature range. The recommended temperature range for conducting ASTM C39 concrete compressive strength testing is between 60 and 80°F (16 and 27°C). A deviation from this range may compromise the concrete’s compressive strength. For instance, a rise to 100°C may result in a 10-20% reduction in the original compressive strength. Maintaining the correct temperature range is crucial as the ASTM C39 test method tests concrete cylinders to determine their compressive strength.
Maintaining the correct temperature during ASTM C39 testing, including adhering to prescribed curing room conditions and conforming to ASTM C511 standards, is crucial. If the temperature deviates from the specified range, it can lead to suboptimal curing conditions and potentially inaccurate test results.
Air Content
The air content in the concrete mix also plays a significant role in influencing the results of ASTM C39 testing. It significantly impacts the workability and durability of concrete mixtures, rendering it a crucial factor in evaluating the overall quality of concrete. In the context of ASTM C 39 testing, accurate evaluation of air content is essential for assessing compressive strength as it directly affects the behavior of concrete under load. Variability in air content can have an impact on the compressive strength of the concrete being tested, resulting in variations in ASTM C39 test results. Controlling air content is essential as the ASTM C39 test method tests concrete cylinders to determine their compressive strength.
High air content and inaccuracies in the testing process can cause inconsistencies in data confirming the strength of the concrete specimen.
Quality Control and Compliance: Ensuring Accurate Test Results
The integrity of the ASTM C39 test depends significantly on quality control and compliance. Concrete laboratory service technicians, performance demonstrations, and the role of an independent examiner all contribute to accurate test results. Quality control and compliance are essential because the ASTM C39 test determines the compressive strength of concrete cylinders.
Concrete Laboratory Technician Requirements: ASTM C39
A concrete laboratory technician’s qualifications and responsibilities are crucial to the success of ASTM C39 testing. Certified technicians under the ACI Concrete Laboratory Testing Technician—Level 1 program, are qualified to perform, record, and report the results of compressive strength tests on concrete specimens. These technicians must possess an understanding of ASTM practices and test methods, including C617/C617M – 15 (Capping Cylindrical Concrete Specimens) and C1231/C1231M, which are crucial for evaluating the compressive strength of concrete cylinders. Qualified technicians are essential as the ASTM C39 test method tests concrete cylinders to determine their compressive strength.
Certification programs like the ACI Concrete Laboratory Testing Technician—Level 1 certification are available to validate a technician’s training and understanding of ASTM and AASHTO practices and tests, encompassing details related to ASTM C 39 compressive strength testing of concrete specimens.
Performance Demonstration and Independent Examiner
Performance demonstration and the role of an independent examiner are crucial aspects of the ASTM C39 testing protocol. The performance demonstration involves determining the compressive strength of cylindrical concrete specimens, including molded cylinders and drilled cores. An independent examiner, ideally certified as an ACI Concrete Laboratory Technician Level I or ACI Concrete Strength Testing Technician, oversees this process. They ensure that concrete proportioning, mixing, and placing operations follow the established procedure. These components are essential because the ASTM C39 test method measures the compressive strength of concrete cylinders.
This process collectively contributes to the verification of the accuracy and reliability of the test results.
ASTM C39: Analyzing and Interpreting Test Results
A key part of the ASTM C39 test process is analyzing and interpreting the test results. This includes determining the maximum load, calculating compressive strength, and identifying failure patterns. Accurate analysis and interpretation are crucial because the ASTM C39 test method measures the compressive strength of concrete cylinders.
Determining Maximum Load
In the ASTM C39 test, the maximum load is found by dividing the peak load by the specimen’s cross-sectional area. A compression machine is the main equipment used to determine this load. However, errors can occur, such as omitting key details in the test report, including the cylinder’s diameter, cross-sectional area, maximum load, compressive strength, and type of fracture. Accurately determining the maximum load is essential, as the ASTM C39 test measures the compressive strength of concrete cylinders.
Calculating Compressive Strength
In ASTM C39 testing, compressive strength is calculated by dividing the maximum load by the specimen’s cross-sectional area, determined by averaging measured diameters or cube side dimensions. The loading rate can impact compressive strength measurement. For instance, high loading rates exceeding ASTM C39 limits can increase the compressive strength of high-strength concrete by up to 20%.
It is essential to consider the size and shape of the cylinder to ensure accurate calculation of the compressive strength. However, it is crucial to be mindful of common mistakes, such as the failure to adhere to the standard test method, ASTM C39, for evaluating the compressive strength of cylindrical concrete specimens. Accurate calculations are essential as the ASTM C39 test method tests concrete cylinders to determine their compressive strength.
Identifying Failure Patterns
The identification of failure patterns plays a significant role in the analysis and interpretation of ASTM C39 compressive strength test results. Various failure patterns, such as cone failure, side fractures, and shearing off at corners, can offer valuable insights into specimen and test conditions that could impact the compressive strength of concrete. Identifying failure patterns is crucial as the ASTM C39 test method tests concrete cylinders to determine their compressive strength.
The recommended approach for analyzing and interpreting failure patterns in ASTM C39 testing involves examining the various forms of failures observed in the concrete cylinders. This provides crucial insights into the specimen and test conditions, including:
- Atypical crack patterns that might have emerged during testing
- Friction at the testing machine platens
- High sand content in the concrete
- Size and geometry of the specimen
Understanding the typical reasons behind these failure patterns is essential for comprehending and addressing issues for subsequent tests.
Practical Applications of Test Results
In the construction industry, the ASTM C39 test results find multiple practical applications. The ASTM C39 test serves as a foundation for quality control in concrete proportioning, mixing, and placing operations, ensuring compliance with design specifications and structural integrity. The test results quantify the compressive strength of concrete, providing a standard measure for evaluating its quality and dependability in construction.
By applying a compressive axial load to concrete samples, the ASTM C39 test results help assess the effectiveness of a concrete mix, ensuring it meets the specified strength criteria. These practical applications are crucial for determining the mix’s suitability for construction projects.
Engineers can utilize the results of the ASTM C39 test to:
- Ascertain whether the concrete meets the necessary strength for its intended application
- Guarantee compliance with specification requirements
- Confirm the suitability of the concrete for the intended structural application.
Concrete Proportioning
Concrete proportioning refers to the method of determining the quantities of cement, sand, coarse aggregate, and water in concrete. The compressive strength of concrete is affected by the proportioning of aggregates, specifically the compressive strength of the aggregates utilized. Furthermore, the water-cement ratio plays a crucial role in determining the strength of concrete. Concrete proportioning is crucial as the ASTM C39 test method tests concrete cylinders to determine their compressive strength.
In ASTM C39 testing, the maximum load is determined by testing the cylinders in compression and plotting the results to create a strength versus water-cement ratio curve. This curve helps to determine and optimize the cementitious material content in the concrete mixture to achieve the desired compressive strength.
The findings from the ASTM C39 test are essential for quality control in concrete proportioning and mixing, contributing to the safety and durability of concrete structures.
Acceptance Testing
In ASTM C39, acceptance testing entails applying a compressive axial load to molded cylinders or cores at a defined rate until failure. Subsequently, the compressive strength of the specimen is determined using the maximum load recorded during the test and the cross-sectional area of the specimen.
The criteria for acceptance testing for concrete as per ASTM C39 dictate that the concrete strength tests should be the average of at least two 6 x 12 in. (150 x 300 mm) cylinders. Acceptance testing plays a pivotal role in ensuring the quality of concrete. It verifies that the concrete adheres to the specifications of the purchaser and fulfills the quality assurance standards for ready mixed concrete. Acceptance testing is crucial as the ASTM C39 test method tests concrete cylinders to determine their compressive strength.
The construction utilizes acceptance testing results to validate that the project meets specified requirements for client or owner acceptance. Testing under ASTM C39 standards should occur at specific intervals: two cylinders at 7, 14, and 28 days.
Evaluating Mix Effectiveness
Effectiveness assessment of a concrete mix via ASTM C39 testing takes into account factors like:
- Specimen size and shape
- Batching and mixing procedures
- Sampling
- Molding and fabrication methods
- Age, temperature, and moisture conditions during curing
Evaluating mix effectiveness is crucial in the ASTM C39 test, which measures the compressive strength of concrete cylinders.
The ASTM C39 test evaluates the quality of a concrete mix by measuring the compressive strength of cylindrical specimens, such as molded cylinders and drilled cores.
If the test results fall below the specified strength, f’c, it may indicate a poor concrete mix. Engineers use these results to determine if the concrete meets the necessary strength for its intended use and to ensure compliance with specifications.
ASTM C39: Common Challenges and Solutions in Testing
Several challenges can arise during the ASTM C39 test, including handling molded cylinders and drilled cores, ensuring proper placement operations, and maintaining specimen integrity. Each challenge has potential solutions that involve following the detailed guidelines in ASTM C39. These guidelines cover specimen preparation and handling, correct placement methods, and maintaining specimen integrity. Addressing these challenges is crucial because the ASTM C39 test method measures the compressive strength of concrete cylinders.
Handling Molded Cylinders and Drilled Cores
Handling molded cylinders and drilled cores requires delicate care and precision. Cylinders intended for 28-day strength specifications should undergo the same curing process as the structural member until steam curing is complete. It is also essential to inspect the cylinders for imperfections, such as holes, cracks, and crumbliness before testing. Proper handling is crucial because the ASTM C39 test method determines the compressive strength of concrete cylinders.
Inadequate handling can compromise the integrity of these specimens. Adhering to the standard test method is essential for obtaining accurate and reliable results. When handling molded cylinders in ASTM C39 testing, it is important to:
- Ensure that the cylinders are stored in a dry and dust-free environment
- Regularly inspect them for indications of wear and tear, and replace any worn or damaged molds
- Thoroughly clean the molds before and after each use to prevent contamination
Following these guidelines will help ensure accurate and consistent results in your testing.
ASTM C39: Ensuring Proper Placing of Operations
Improper placement affects C39 testing. It impacts strength due to mishandling, curing, and testing issues. This can lead to inaccurate compressive strength values.
Applying effective techniques ensures proper placing operations. It involves adhering to relevant practices such as C31/C31M. This includes specimen preparation and curing. It also involves meticulously choosing, preparing, and mixing materials. This is done in the laboratory. The aim is to ensure precise and dependable results. Proper placement is crucial as the ASTM C39 test method tests concrete cylinders to determine their compressive strength.
ASTM C39: Maintaining Specimen Integrity
Maintaining specimen integrity is crucial for accurate and reliable results in ASTM C39 testing. The quality of mold selection, specimen handling, and proper curing procedures greatly influences the test quality, ensuring specimen integrity. Each step is vital for maintaining test accuracy and reliability, emphasizing the importance of attention to detail in the testing process. Human errors, mold quality issues, and procedural lapses can compromise ASTM C39 specimen integrity. Precision at every step is essential for accurate results. Vigilance throughout the testing process ensures reliable outcomes.
The prescribed methods for specimen preservation in ASTM C39 testing include proper batching, mixing procedures, sampling, and molding. Additionally, measurements should be taken at three locations on the specimen, and the average should be calculated and recorded. Handling and storage errors can significantly impact specimen integrity in ASTM C39 testing.
Summary
In conclusion, the ASTM C39 test is crucial for assessing the compressive strength of concrete, ensuring safety and quality in construction projects. This method tests concrete cylinders to determine their strength, offering valuable insights into the concrete mix’s quality. By following the standard’s guidelines, addressing challenges, and accurately interpreting results, engineers and construction professionals can ensure the durability and structural integrity of concrete structures. Despite its complexities, the ASTM C39 is a vital test in the construction industry, highlighting the importance of rigorous testing and quality control for building safe and reliable structures.
Frequently Asked Questions
What are ASTM C39 standards?
For over 80 years, the ASTM C39 standards have been the industry benchmark for testing the compressive strength of cylindrical concrete specimens, including molded cylinders and drilled cores. This standard ensures that concrete cylinders meet the necessary specifications for quality control by testing their compressive strength.
What is the difference between ASTM C31 and C39?
The main difference between ASTM C31 and C39 is that C31 is about making and curing concrete test specimens in the field, while C39 is about testing the compressive strength of cylindrical concrete specimens. These are two separate standards for different aspects of concrete testing. While ASTM C31 focuses on making and curing concrete test specimens in the field, ASTM C39 tests concrete cylinders to determine their compressive strength.
What is the ASTM for cylinders?
The ASTM standard for concrete cylinders, ASTM C39, determines the compressive strength of cylindrical specimens, including molded cylinders and drilled cores. This standard applies to concrete having a unit weight over 50 lb/ft³ (800 kg/m³). ASTM C39 tests ensure that concrete cylinders meet the required specifications for quality control.
How does the ASTM C39 test work?
The ASTM C39 test applies a compressive axial load to prepared concrete cylinders or cores until they fail. The compressive strength is calculated by dividing the maximum load by the specimen’s cross-sectional area.
What factors can influence the results of ASTM C39 testing?
The results of ASTM C39 testing can be influenced by factors like initial curing conditions, the temperature range during testing, and the air content in the concrete mix. To ensure accurate and reliable results, these factors must be carefully controlled.
