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Compressive strength of cement plaster9/18/2023 ![]() ![]() (100 x 200 mm) cylinders.Īdditional information on this topic can be found in on-demand courses Low Compressive Strength Test Results? What They Mean and Next Steps and Evaluating Test Results and Troubleshooting Low Compressive Strength. (150 x 300 mm) cylinders or at least three 4 x 8 in. Sections 26.5.3.2 and 26.12.1.1 of ACI 318-19, ACI 301-20 “Specifications for Concrete Construction”, and ACI 311.6-18 “Specification for Testing Ready Mixed Concrete” require concrete strength tests for acceptance to be the average of at least two 6 x 12 in. No strength test falls below the specified compressive strength by more than 500 psi (3.5 MPa) if the specified compressive strength is 5000 psi (35 MPa) or less or by more than 10 percent of the specified compressive strength if the specified compressive strength exceeds 5000 psi (35 MPa). ![]() Every arithmetic average of any three consecutive strength tests equals or exceeds the specified compressive strength.The acceptance criteria for the specified compressive strength according to section 26.12.3.1 of ACI 318-19 are as follows: However, 3- and 7-day test results are not commonly used for acceptance purposes. Aggregate / Cement Ratio Following points must be noted for aggregate cement ratio: If the volume remains the same and the proportion of cement in relation to that of sand is increased the surface area of the solid will increase. 3- or 7-day test results are used to monitor early strength gain, especially when high early-strength concrete is used. Since the water cement ratio has increased, the compressive strength will decrease. According to section 19.2.1.3 of ACI 318-19 the specified compressive strength shall be based on the 28-day test results unless otherwise specified in the construction documents. What ACI standard stipulates the percent of the specified compressive strength that the cylinder must meet in order to pass the compressive strength test at both the 7- and 28-day ages?Ī. Nowadays, wireless maturity sensors are used to monitor the strength gain of these ditched cylinders (those that failed the compression test), to monitor the strength over time.Īll standard-cured cylinders are made and tested on 28 days for acceptance purposes and strength with age is determined through maturity sensors.Standards for 7-day and 28-day strength test results If the sample still shows low strength, the mentioned causes must be studied and corrected. One way to avoid low-strength concrete breaks is to wait for the complete curing of the concrete and conduct the test on the next break day. Calculation Errorsīefore performing a compression test, the compression testing machine must be properly calibrated. The test specimen won’t break properly under the applied test load if the cured specimen is not prepared by grinding or capping its ends. If this is not corrected, the strength value of sample testing won’t be given by the real concrete structure. Improper Curing Conditionsįield-cured test specimens do not reflect the strength values of in-situ concrete samples. Improper handling and transportation of concrete test samples would result in cracking. The improper casting of concrete cylinders results in a test specimen that is not prepared for compression testing. This results in a compressive strength test value lower than expected. Preparing the wrong concrete mix results in delaying the concrete strength gain within the time that has been specified. The six key causes of low-strength concrete cylinder breaks are: 1. If the average of three consecutive tests is not equal to or exceeds the specified strength.The individual compressive strength test of one or two cylinders is more than 500 psi below the specified strength, or.Low-Strength Results of Concrete Cylinder- ACI 318 & ACI 301Īs mentioned in ACI Building Code ACI 318 and the Standard Specifications for Structural Concrete ACI 301, a concrete mix proportioned to meet the requirements of the standards and under compression test has chances of low-strength results about once or twice in 100 tests due to normal variability.Īs per ACI and CSA, a cylinder break during a compression test is considered to be of low strength when: Low-Strength Results of Concrete Cylinder- ACI 318 & ACI 301. ![]()
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