CUBE TEST METHOD - CIVIL ENGINEER VIJAY TECHNICAL

Compressive strengths of differents grade of concrete concrete at 3 days, 7 days and 28days of curing and compressive strengths test of concretes cube.

What is Compressive strengths  Compressive strengths is the capacity of materials or structures to resist or withstand under compressive load. The Compressive strengths is determined by the ability of the concretes materials to resist failure in the form cracks and fissure. The maximum loads at which the specimen breaks is taken as a compressive loads.

In compressive strengths test of concretes cube the push force applied on the boths faces of concrete specimen and the maximum compression that concrete bears without failure is noted.

Compressive Force acting on concretes testing specimen helps us to majorly focus on the Compressive strengths of concretes because it helps us to quantify the ability of concrete to resists Compressive stresses among structure where-as other stress such as axial stresses and tensile stresses are catered by reinforcements and other means.

Compressive strengths of concretes at 3 & 7  days

Generally strengths of concretes measured in psi (pound force per square inch in USA) & MPa (mega pascal) in India and other countrys. MPa in anothers term represented as N/mm2. And 1MPa = 145.038 psi.

Generally compressive strengths of concretes can vary from 2175 psi (15 MPa) to 4350 psi (30MPa) for constructions of residentials and commercials structures and may exceed higher upto 10000 psi (70MPa) for specified certains structures.

When compressives load acting on boths face of concretes cube, it resist or withstand under compressive load and causes compressions. Due to compressions diameters of concretes cube structures is increased and their lengths is decrease and developing stress known as compressive stress.

Compressives stress is represented by  which is equal to ratio of compressive loads to cross sectional area of concrete cube structures such that = P/A, where P = compressive loads and A = cross sectionals area of concrete cube specimens. Now understand with given diagram.

Compressive strengths is the maximums load at which the specimen breaks is taken as a compressive load represented by F or S, which is equal to ratio of compressive loads to cross sectional area of specimen,such as F=P/A, where F = compressive strengths = compressive load and A = area of cross section of specimen.

Compressive strength of different grade concrete at 3 days

Makings of at least 3 concretes cube size each 150mm×150mm×150mm in mould by cement sand and aggregate differents ratio for different grade of concretes  use tamping rod for levelling the surface of mould, it is kept for 24 hours setting afters water mix in concretes after 24 hours it is kept in water for curing for 3 days. And taken out just 30 minutes prior to start of test.

Now concretes cube test by CTM machine assuming 14N/mm2/ minutes load is applied on concrete cube specimens of different grade till the cube collapse. The maximums loads at which the specimen breaks is taken as a compressive loads. Now following results are obtained for compressive strengths of different grade of concretes at 3 days of curing given in table.

 Compressive strengths of concretes at 3 days measured in MPa (N/mm2) or psi.

     Conc. Grade MPa   psi

● M10 —- 4 MPa or 580 psi

● M15 —- 6 MPa or 870 psi

● M20 —- 8 MPa or 1160 psi

● M25 —- 10 MPa or 1450 psi

● M30 —- 12 MPa or 1740 psi

● M35 —- 14 MPa or 2030 psi

● M40 —- 16 MPa or 2320 psi

● M45 —- 18 MPa or 2610 psi

● M50 —- 20 MPa or 2900 psi

Compressive strengths of differents grade concretes at 7 days

Making of at least 3 concretes cube size each 150mm×150mm×150mm in mould by cements sand and aggregate differents ratio for different grade of concrete, use tamping rod for levelling the surface of mould, it is kept for 24 hours settings after water mix in concrete, after 24 hours it is kept in water for curing for 7 days. And taken out just 30 minutes prior to start of test.

Now concretes cube test by CTM machine,assuming 14N/mm2/minutes load is applied on concrete cube specimen of

different grade till the cube collapse. The maximums loads at which the specimens breaks is taken as a compressive loads.