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Why is the 28-days compressive strength of concrete generally specified?
It is attributed to two reasons: 1. Strength of concrete grows faster in initial days and this process of gaining strength slow down with time. This can be said as stabilization in value of gained strength of concrete. After approximately 20 or some more days, strength value get stabilize and does not change too much with time. Therefore, compressive strength is taken after approximatley 3 weeks time. 2. These tests have to performed practically and date record is needed to be maintained. Therefore, if test duration is a multiple of 7 (7 weekdays) then it is more easy to remind. It is the reason we have 28=7x4 days to note down compressive strength of concrete. for ex: if we start test on monday then we know that after 4 weeks on same time on monday we can finish the compressive strength test.
What is the compressive strength of M10 concrete at 7 days?
The compressive strength of M20 concrete at 28 days typically falls in the range of 20 to 25 megapascals (MPa), which is equivalent to 2900 to 3600 pounds per square inch (psi). M20 is a mix designation for concrete, where "M" stands for "mix" and the number 20 represents the characteristic compressive strength of the concrete mix in MPa. Please note that the actual compressive strength of M20 concrete can vary depending on several factors, including the quality of materials used, the water-cement ratio, the curing conditions, and the testing procedures. To ensure the desired strength, it's essential to follow the recommended mix proportions and proper construction practices during the preparation, placing, and curing of the concrete. Additionally, testing of concrete samples is typically conducted in a laboratory environment to determine the 28-day compressive strength accurately.
How do you calculate the compressive strength of concrete cubes?
Concrete specimens are tested using the ASTM39 Test Standard Test Methodfor Compressive Strengthof Cylindrical Concrete Specimens by using two samples made from the same test at the same age, usually at strength of 28 days old.Design engineers use the specified strength ƒ´c to design structural elements. This specified strength is incorporated in the job contract documents. The concrete mixture is designed to produce an average strength (ƒ´cr) higher than the specified strength, such that the risk of not complying with the strength specification is minimized.Cylindrical specimensfor acceptance testing should be 6 x 12 inch (150 x 300 mm) size or 4 x 8 inch (100 x 200 mm) when specified. The Concrete strength is calculated by dividing the maximum load at failure by the average cross sectional area.Concrete compressive strength requirements can vary from 2500 psi (17 MPa) for residential concrete to 4000 psi (28 MPa) and higher in commercial structures. Higher strengths up to and exceeding 10,000 psi (70 MPa) are specified for certain applications.Cylinders are placed in a Compression testing machine and loaded to failure from 20 to 50psi. The type of break should be recorded by a Certified Technician.Example 1:For a concrete sample that is broken after 28 daysThe cylinder is 6” diameter, so it has an area of 3.14 x Diameter squared /4A = 3.14 x 6 x 6/4A = 28.26 square inchesIf the force required to break the cylinder was 97,500 poundsThen the compressive strength is 97,500 pounds / 28.26 square inches = 3,450 psi.3,450psi needs to be compared to the Design strength determined by the Design Strength determined by the Design Engineer.Example 2:Given: f 'c = 3000 psiConcrete test cylinders averaged 2800 psi.PSICore 1 =2900Core 2 =2850Core 3 =2450Average compressive strength of 3 cores = 2730 psi.Find: Is the concrete in the structure adequate under CDOT specifications?Solution:Test Evaluation:f 'c = 3000 psiAverage compressive strength of 3 cores - 2730 psiDo any compressive strengths differ from the average by more than 10%?10% of Average compressive strength = 273 psiCore 1: 2900 - 2730 = 170 psi, < 273 therefore OKCore 2: 2850 - 2730 = 120 psi, < 273 therefore OKCore 3: 2730 - 2450 = 280 psi, > 273 therefore -discard core and re-compute average compressive strength using two remaining cores.New average compressive strength = 2875 psi
How many days does cement take to cure completely?
Generally 30 days brings concrete to to specified compression strength. Concrete may take 30 years to cure.AnswerConcrete will harden to about 80% strength in 2-3 days and close to 100% strength in 28 days. Concrete driveways should be towards the latter end prior to driving on them. AnswerAs a former concrete inspector, I would agree with the first answer. AnswerConcrete takes 50 years to completely cure and then takes 50 years to break down
Maxing ratio in M20 Concrete?
Mix ratio for M5 concrete is 1:1.5:3compressive strength is 20N/mm2 @ 28 days.1 part of cement, 1.5 part of sand, 3 parts of coarse aggregate.
What is the Compressive strength of M 50 concrete at seven days?
2/3 times the 28 days strength
Why is the 28-days compressive strength of concrete generally specified?
It is attributed to two reasons: 1. Strength of concrete grows faster in initial days and this process of gaining strength slow down with time. This can be said as stabilization in value of gained strength of concrete. After approximately 20 or some more days, strength value get stabilize and does not change too much with time. Therefore, compressive strength is taken after approximatley 3 weeks time. 2. These tests have to performed practically and date record is needed to be maintained. Therefore, if test duration is a multiple of 7 (7 weekdays) then it is more easy to remind. It is the reason we have 28=7x4 days to note down compressive strength of concrete. for ex: if we start test on monday then we know that after 4 weeks on same time on monday we can finish the compressive strength test.
What is compressive strength of M15 in 7 days as per IS?
3/4 of its strength
What is the compressive strength of M10 concrete at 7 days?
The compressive strength of M20 concrete at 28 days typically falls in the range of 20 to 25 megapascals (MPa), which is equivalent to 2900 to 3600 pounds per square inch (psi). M20 is a mix designation for concrete, where "M" stands for "mix" and the number 20 represents the characteristic compressive strength of the concrete mix in MPa. Please note that the actual compressive strength of M20 concrete can vary depending on several factors, including the quality of materials used, the water-cement ratio, the curing conditions, and the testing procedures. To ensure the desired strength, it's essential to follow the recommended mix proportions and proper construction practices during the preparation, placing, and curing of the concrete. Additionally, testing of concrete samples is typically conducted in a laboratory environment to determine the 28-day compressive strength accurately.
Different between cube and cylinder in concrete compressive test?
The difference in compressive strength is due to the difference between the modulus of elasticity of concrete and that of the steel which is used to apply the compressive force on the concrete. The pressure applies a lateral confinement pressure which is equal to d/3 meaning that for the cylinder, 2d/3 is confined leaving d/3 unconfined whereas for the cylinder 2d/3 is confined means all of the cube is confined. This leads to the cube having a higher compressive strength that the cylinder. For more information, try to read about the triaxial test and the effect of confinement on the compressive strength of soil samples.
What is high performance of concrete in civil engineering?
Normal use concrete has a compressive strength of 3-5 ksi (concrete is essentially useless in tension). Though in skyscrapers, they are beginning to use concrete with strengths upto 14 ksi.
How much is the compressive strength of cement mortar cube in proportion 1 each to 3?
it should be around 3.0 N/mm2 in 2 days.
How do you calculate the compressive strength of concrete cubes?
Concrete specimens are tested using the ASTM39 Test Standard Test Methodfor Compressive Strengthof Cylindrical Concrete Specimens by using two samples made from the same test at the same age, usually at strength of 28 days old.Design engineers use the specified strength ƒ´c to design structural elements. This specified strength is incorporated in the job contract documents. The concrete mixture is designed to produce an average strength (ƒ´cr) higher than the specified strength, such that the risk of not complying with the strength specification is minimized.Cylindrical specimensfor acceptance testing should be 6 x 12 inch (150 x 300 mm) size or 4 x 8 inch (100 x 200 mm) when specified. The Concrete strength is calculated by dividing the maximum load at failure by the average cross sectional area.Concrete compressive strength requirements can vary from 2500 psi (17 MPa) for residential concrete to 4000 psi (28 MPa) and higher in commercial structures. Higher strengths up to and exceeding 10,000 psi (70 MPa) are specified for certain applications.Cylinders are placed in a Compression testing machine and loaded to failure from 20 to 50psi. The type of break should be recorded by a Certified Technician.Example 1:For a concrete sample that is broken after 28 daysThe cylinder is 6” diameter, so it has an area of 3.14 x Diameter squared /4A = 3.14 x 6 x 6/4A = 28.26 square inchesIf the force required to break the cylinder was 97,500 poundsThen the compressive strength is 97,500 pounds / 28.26 square inches = 3,450 psi.3,450psi needs to be compared to the Design strength determined by the Design Strength determined by the Design Engineer.Example 2:Given: f 'c = 3000 psiConcrete test cylinders averaged 2800 psi.PSICore 1 =2900Core 2 =2850Core 3 =2450Average compressive strength of 3 cores = 2730 psi.Find: Is the concrete in the structure adequate under CDOT specifications?Solution:Test Evaluation:f 'c = 3000 psiAverage compressive strength of 3 cores - 2730 psiDo any compressive strengths differ from the average by more than 10%?10% of Average compressive strength = 273 psiCore 1: 2900 - 2730 = 170 psi, < 273 therefore OKCore 2: 2850 - 2730 = 120 psi, < 273 therefore OKCore 3: 2730 - 2450 = 280 psi, > 273 therefore -discard core and re-compute average compressive strength using two remaining cores.New average compressive strength = 2875 psi
What is the mix ratio for each grade of concrete?
1:2:4
Why is steel good in tension?
It depends on its strength. Usually, concrete is 6.7 to 9 times stronger in compression.To be exact, tensile strength of concrete is equal to 0.7 times square root of its compressive strength. For common concretes with compressive strength of 20 to 40 MPa, it is about 3 to 4.4 MPa of tensile strength respectively.
What is c35 grade concrete in psi?
It is the bearing capacity in N/mm2 when tested on 21 day on a hydraulic testing m/c When we tested this grade concrete cubes on 28th day the compressive strength value have to come 35 N/mm2.
How many days does cement take to cure completely?
Generally 30 days brings concrete to to specified compression strength. Concrete may take 30 years to cure.AnswerConcrete will harden to about 80% strength in 2-3 days and close to 100% strength in 28 days. Concrete driveways should be towards the latter end prior to driving on them. AnswerAs a former concrete inspector, I would agree with the first answer. AnswerConcrete takes 50 years to completely cure and then takes 50 years to break down
