4000 Psi concrete compressive strength at 3, 7, 21 and 28 days

According to ACI code standard, concrete grade is categorised according to their compressive strength represented as concrete mix 2000 Psi, 3000 Psi, 4000 Psi, 5000 Psi, 6000 Psi, 8000 Psi and 10000 Psi. For example, in concrete mix 2000, numerical figure is compressive strength of concrete is 2000psi (13.8MPa or 13.8N/mm2) after 28 days of mixing on axial compression test on cylinder shape with 15cm dia and 30cm length cylinder.

Characteristic strength of concrete is their compressive strength which can be determined by axial compression test on cubic concrete block or cylinder shape. If Compression test is carried on cubic concrete block, when tested with cube size 15cm × 15cm × 15cm, that’s known as Cubic test and their strength is called cubic strength. And compression test is carried on cylinder shaped concrete block, when tested with 15cm dia and 30cm length of cylinder, that is known as cylinder test and their strength is called cylinder strength.

Value of cube strength and cylinder strength are different for same mix. Value of cube strength is higher than cylinder strength. Using Thumb Rule, value of cube strength is is 1.25 times higher than cylinder strength.

**Cube strength = 1.25 × cylinder strength**

**Concrete mix 4000**:- this is standard grade of concrete used for flooring, pcc, rcc, footing, slab formation of garage, parking, etc. As per American standard ACI codes, strength of concrete and mix of Portland stone cement, fine aggregate and coarse aggregate, design according to cylinder test.

In 4000 concrete mix, numerical figure 4000 represent it’s characteristics of compressive strength (fck) on cylinder test that is 4000psi (27.6MPa or 27.6N/mm2) at 28 days after mixing, when tested with 15cm dia and 30cm length of cylinder. So compressive strength (fck) value of Concrete mix is 4000psi based on cylinder test.

According to American standard (ACI), fck (characteristics of compressive strength) value for concrete mix 4000 is 4000psi (27.6N/mm2 or 27.6MPa) on cylinder test at 28days after mixing, when tested with 15cm dia and 30cm length of cylinder.

**4000 Psi concrete compressive strength at 3, 7, 21 and 28 days**

As per ACI standard, compressive strength of concrete measured in Psi (Pounds per square inch). A higher psi means a given concrete mixture is stronger, so it is usually more expensive and lower Psi means a given concrete mixture is on average strength.

Compressive Strength of concrete can be estimated by strength of cement attained in 1,3, 7, 14, 21 and 28 days. However it would certainly depends upon no of factors such as- type of cement and their grade, cement & sand Mix Ratio, water ratio, gravel ratio, Concrete compactness (Vibrator) etc.

Concrete gain its strength with time after casting. The rate of gain of concrete compressive strength is higher during the first 28 days of casting and curing and then it slows down. The compressive strength gained by 4000 Psi concrete after 1, 3, 7, 14, 21 and 28 days of curing are 640 Psi (16% of total strength), 1600 Psi (40%), 2600 Psi (65%), 3600 Psi (90%), 3840 Psi (96%) and 4000 Psi (99%) respectively when tested with 15cm dia and 30cm length of cylinder of cylinder test.

**4000 Psi concrete strength at 1 day**:- compressive strength of 4000 Psi concrete at 1 day or after 24 hours of curing is about 640 Psi which is approximately equal as 16% of total strength gain in 28 days of curing after casting when tested with 15cm dia and 30cm length of cylinder of cylinder test.

**4000 Psi concrete strength at 3 days**:- compressive strength of 4000 Psi concrete at 3 days of curing is about 1600 Psi which is approximately equal as 40% of total strength gain in 28 days of curing after casting when tested with 15cm dia and 30cm length of cylinder of cylinder test.

**4000 Psi concrete strength at 7 days:**– compressive strength of 4000 Psi concrete at 7 days of curing is about 2600 Psi which is approximately equal as 65% of total strength gain in 28 days of curing after casting when tested with 15cm dia and 30cm length of cylinder of cylinder test.

**4000 Psi concrete strength at 14 days**:- compressive strength of 4000 Psi concrete at 14 days of curing is about 3600 Psi which is approximately equal as 90% of total strength gain in 28 days of curing after casting when tested with 15cm dia and 30cm length of cylinder of cylinder test.

**4000 Psi concrete strength at 21 days**:- compressive strength of 4000 Psi concrete at 21 days of curing is about 3840 Psi which is approximately equal as 96% of total strength gain in 28 days of curing after casting when tested with 15cm dia and 30cm length of cylinder of cylinder test.

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**4000 Psi concrete strength at 28 days:**– compressive strength of 4000 psi concrete at 28 days of curing is about 4000 Psi which is approximately equal as 99% of total strength gain in 28 days of curing after casting when tested with 15cm dia and 30cm length of cylinder of cylinder test.

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Finally, when its strength have reached 99% in 28 days, still concrete continues to gain strength after that period, but that rate of gain in compressive strength is very less compared to that in 28 days.

4000 Psi concrete compressive strength at 1, 3, 7, 14, 21 and 28 days of curing are 640 Psi, 1600 Psi, 2600 Psi, 3600 Psi, 3840 Psi and 4000 Psi respectively when tested with 15cm dia and 30cm length of cylinder of cylinder test. This is used for reference only their actual strength tested by CTM machine.