Ready mix concrete is a critical material used in construction, and it is essential to verify that it meets the specified conditions before it is used. This verification involves rigorous inspection and testing to ensure that the concrete meets the required standards. Ready mix concrete is produced in batching plants and transported to construction sites using truck-mounted mixers. To ensure that the concrete meets the applicable standards, it is commonly inspected and tested according to industry standards, such as those set by ASTM International. These standards help ensure that the concrete is of high quality and meets the necessary criteria for use in construction projects.
Inspect Ready Mix Concrete
Batching Plant Inspection
The initial task at hand is to scrutinize the facilities, scales, and truck mixers to determine whether they meet the project’s specified requirements. This involves a thorough assessment of these elements to ensure that they are up to par with the project’s expectations.
The storage areas of all materials must also undergo inspection to ensure that they are free of contamination, properly protected from the effects of freezing, and kept clean. This is a crucial step in ensuring that the materials used in the project are of high quality and meet the necessary standards.
Furthermore, it is important to conduct coarse and fine aggregate gradation tests in accordance with applicable standards such as ASTM C 136. These tests help to verify that the aggregate materials used in the project meet the necessary requirements. The results of these tests must also be carefully examined to ensure that they are in line with the project’s expectations.
Overall, it is crucial to conduct thorough inspections and verifications of all aspects of the project, from the facilities and equipment used to the materials stored and used. This helps to ensure that the project is completed to the highest standards and meets all the necessary requirements.
Onsite Inspection of Ready Mix Concrete
To ensure that the correct designation of concrete mixture is delivered, it is essential to inspect every delivery ticket thoroughly. This is a crucial step in maintaining quality control and ensuring that the appropriate mixture is delivered to the construction site.
Once the concrete is delivered to the site, it is necessary to inspect it to verify that it is uniform and adequately mixed before discharge. This is to ensure that the concrete’s properties are consistent throughout the mixture and that it will perform as intended.
Monitoring the addition of water, admixtures, and fiber reinforcement on-site is also essential. This step ensures that these elements are added correctly and that the concrete mixture will have the desired properties.
Finally, it is important to monitor the delivery and placement time of the concrete. This helps to determine whether the concrete was delivered and placed within the specified time constraints. By monitoring the process, potential issues can be identified and corrected, ensuring that the project is completed on time and to the desired standard.
Fig. 1: Inspection of ready mix concrete onsite
Testing Ready Mix Concrete
1. Onsite Tests
At construction sites, it is necessary to carry out various tests on ready mix concrete to ensure its quality and suitability for use in construction projects. Table 1 outlines the different types of tests that are required to be performed on ready mix concrete upon its arrival at the construction site. These tests are essential to assess the properties of the concrete, such as its compressive strength, workability, and durability, and to verify that it meets the required specifications and standards. Conducting these tests helps to ensure that the ready mix concrete is of adequate quality and can perform as intended in the construction project.
| Type of tests | ASTM international for testing procedures | Test frequencies | Purpose of the test |
| Slump | ASTM C 143/C 143M | First truck load, whenever the consistency of the concrete appears to vary. | Measure fresh concrete consistency, check its workability, and use as an indicator of poor mixed batch |
| Air content | ASTM C 173, ASTM C 231 | Performed on all samples taken to measure concrete strength | To check air entrained concrete |
| Temperature | ASTM C 1064 | At the time of sampling for each strength test | to make sure that concrete comply with certain specifications that define a certain allowable temperature range |
| Density | ASTM C 138, ASTM C 567 | Whenever required by project specifications | To estimate concrete density |
Fig. 3: slump test on first batch of ready mix concrete
2. Laboratory tests
To evaluate the properties of ready mix concrete, it is necessary to conduct tests on concrete specimens in a laboratory. Table 2 outlines the list of tests that need to be performed to assess the quality of the concrete. These tests provide crucial information about the physical and mechanical properties of the concrete, including its compressive strength, density, durability, and workability.
The results of these tests help to determine whether the concrete meets the required specifications for its intended use. For example, the compressive strength test provides information about the maximum load the concrete can withstand before it fails, which is important for structures such as buildings and bridges. The density test provides information about the weight of the concrete, which is important for transportation and placement.
The durability test provides information about the ability of the concrete to resist damage caused by weathering, chemical attacks, and other environmental factors, while the workability test provides information about the ease with which the concrete can be mixed, placed, and finished.
Overall, these tests are critical for ensuring the quality and performance of ready mix concrete, and they play an essential role in the construction industry.
Table 2 laboratory tests conducted on ready mix concrete specimens
| Type of tests | ASTM international for testing procedures | Test frequencies | Purpose of the test |
| compressive strength | ASTM C 39/C 39M | Minimum two specimens are test at each age | To estimate concrete compressive strength and determining conformance with the specified strength |
| Flexural strength | ASTM C 78 or ASTM C 293 | To estimate concrete flexural strength and determining conformance with the specified strength | |
| Test results shall be compared with values provided in ACI 318/318R to find out whether the concrete confirm with specifications or not. | |||
Sampling of Ready Mix Concrete
To ensure accurate representation of concrete conditions, it is required to record certain information for each specimen. This includes the date, time, placement location, truck number, and ticket number. These details are important for identifying and tracking each specimen during testing.
For each test age, it is necessary to cast a minimum of three strength specimens. This ensures that there are enough specimens available for testing and to account for any anomalies that may arise during the testing process. If in-place concrete strength verification is required before removing forms, shoring, or placing the structure in service, additional specimens should be casted for field curing.
To ensure adequate coverage, at least one set of strength test specimens must be casted for each 76 cubic meters of each class of concrete placed in any one day. This ensures that there are enough specimens available for testing, and it provides a representative sample of the concrete used in the project. This process follows ASTM C 31/C 31M standards, which outline specific requirements for casting and testing concrete specimens.
Fig. 4: Ready mix concrete sampling
Curing and Handling Specimens
For the purpose of acceptance testing, it is necessary to store and cure samples that have been casted for up to 48 hours after molding on the project site. In order to ensure that the curing process is carried out properly, it is important to follow applicable standards such as ASTM C 31/C 31M. The storage temperature of the specimens should be maintained within the range of 16 to 27 ºC, and any loss of temperature or damage to the specimens should be prevented.
Once the specimens have been cured and stored for the appropriate period of time, they should be transported to the laboratory within 16 to 48 hours after molding. It is crucial to ensure that the transportation time does not exceed 4 hours, in order to prevent any further damage to the specimens during transportation. Following these guidelines will help to ensure that accurate and reliable test results are obtained, and that the project can proceed smoothly.