The American Concrete Institute (ACI) provides a standard classification for concrete mixes based on their compressive strength. Here are some common concrete grades and their corresponding strengths measured in pounds per square inch (psi):

**1. Normal Weight Concrete:**

● 2,500 psi (17 MPa)

● 3,000 psi (21 MPa)

● 4,000 psi (28 MPa)

**2. High-Strength Concrete:**

● 6,000 psi (41 MPa)

● 8,000 psi (55 MPa)

● 10,000 psi (69 MPa)

These values represent the compressive strength of cylindrical specimens tested at 28 days of curing.

According to American standard (ACI), American concrete Institute, as per ACI code standard, concrete grade represented as concrete mix 2000, 3000, 4000, 5000, 6000, 8000 and 1000. For example, 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**

American Standard (ACI) codes concrete grade generally refers cylinder test, compression test is carried on cylinder shaped concrete block, when tested with 15cm dia and 30cm length of cylinder for finding out compressive strength of different mix of concrete at 28 days after mixing. In this article we read about types of concrete grade and their compressive strength as per American Standard or ACI code.

**Types of concrete grade and their compressive strength as per American Standard (ACI)**

According to American standard (ACI) code, there are three types of concrete grade, 1) normal concrete grade is indicated as Concrete mix 2000 and 3000, 2) standard concrete grade, indicated as 4000, 5000 and 6000 and 3) high strength concrete grade, indicated as 8000 and 10000. For example, Concrete mix 2000, this 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.

**What are the grades of concrete and their compressive strength as per American standard (ACI)**

As we know that concrete are made of mixing of cement, sand and aggregate in required proportion. What are the grades of concrete, according to ACI (American standard), according to ACI code concrete grade is three types, 1) normal concrete grade, 2) standard concrete grade and 3) high strength concrete grade. the grades of concrete represented as 2000 and 3000 is known as normal grade of concrete, 4000, 5000 and 6000 is known as standard grade of concrete which are generally used and 8000 and 10000 is known as high strength concrete grade used for special construction.

**Concrete mix 2000**

● Concrete mix 2000:- This is normal grade of concrete have secondary uses for flooring, according to American standard ACI codes, strength of concrete and mix of Portland stone cement, fine aggregate and coarse aggregate, design according to cylinder test. In 2000 concrete mix, numerical figure 2000 represent it’s characteristics of compressive strength (fck) on cylinder test that is 2000psi (13.8MPa or 13.8N/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 2000psi based on cylinder test.

According to American standard (ACI), fck (characteristics of compressive strength) value for concrete mix 2000 is 2000psi (13.8N/mm2 or 13.8MPa) on cylinder test at 28days after mixing, when tested with 15cm dia and 30cm length of cylinder.

**Concrete mix 3000**

● Concrete mix 3000:- This is normal grade of concrete, it is used for flooring, pcc slab formation of garage, parking, etc, according to American standard ACI codes, strength of concrete and mix of Portland stone cement, fine aggregate and coarse aggregate, design according to cylinder test. In 3000 concrete mix, numerical figure 3000 represent it’s characteristics of compressive strength (fck) on cylinder test that is 3000psi (20.7MPa or 20.7N/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 3000psi based on cylinder test.

According to American standard (ACI), fck (characteristics of compressive strength) value for concrete mix 3000 is 3000psi (20.7N/mm2 or 20.7MPa) on cylinder test at 28days after mixing, when tested with 15cm dia and 30cm length of cylinder.

**Concrete mix 4000**

● Concrete mix 4000:- This is normal grade of concrete, it is used for RCC work, according to 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.

**Concrete mix 5000**

● Concrete mix 5000:- This is normal grade of concrete, it is used for RCC work, construction of RCC structure like column, beam, slab, Foundation, footing, according to American standard ACI codes, strength of concrete and mix of Portland stone cement, fine aggregate and coarse aggregate, design according to cylinder test. In 5000 concrete mix, numerical figure 5000 represent it’s characteristics of compressive strength (fck) on cylinder test that is 5000psi (34.5MPa or 34.5N/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 5000psi based on cylinder test.

According to American standard (ACI), fck (characteristics of compressive strength) value for concrete mix 5000 is 5000psi (34.5N/mm2 or 34.5MPa) on cylinder test at 28days after mixing, when tested with 15cm dia and 30cm length of cylinder.

**fck value for concrete mix 6000, 8000 and 10000**

According to American standard (ACI), fck (characteristics of compressive strength) value for concrete mix 6000 is 6000psi (41.3N/mm2 or 41.3MPa) on cylinder test at 28days after mixing, when tested with 15cm dia and 30cm length of cylinder.

According to American standard (ACI), fck (characteristics of compressive strength) value for concrete mix 8000 is 8000psi (55.2N/mm2 or 55.2MPa) on cylinder test at 28days after mixing, when tested with 15cm dia and 30cm length of cylinder.

According to American standard (ACI), fck (characteristics of compressive strength) value for concrete mix 10000 is 10000psi (68.9N/mm2 or 68.9MPa) on cylinder test at 28days after mixing, when tested with 15cm dia and 30cm length of cylinder.

Concrete mix 6000 8000, 10000 are higher strength concrete are used in extreme environmental condition, sea side condition, formation of septic tank and water tank, and basement formation, bridge & dams formation and heavy loaded structural commercial and industrial building, mostly high rise building, it is used for special uses.