Destructive & non-destructive testing on concrete

Question 1

What do the numbers stand for in the concrete C40/50

Answer 1

40Mpa strength as a cylinder

50Mpa strength as a cube

Question 2

acceptable and unacceptable failure of concrete under compression

Answer 2

acceptable: “apple core”, vertical lines
unacceptable: cracking across the cylinder diagonally

Question 3

standardisation of cement, what do the sections stand for:

CEM II/A-V 42.5R

Answer 3

CEM II/A-V = flash blended cement
42.5 MPa at 28days
R- rapid strength development (N=normal)

Question 4

Mortar standard ratios of cement sand and water

Answer 4

1: 3 cement to sand

0. 5 water to cement

Question 5

describe the two standard mortar tests

Answer 5

1) slitting tensile test-ball crushed, splitting in half by tension
2) 3 point bending test: broken by three points then each bit tested in compression

Question 6

why is fly ash tested later than 28days?

Answer 6

because it takes longer to develop strength

Question 7

name 6 non destructive testing methods

Answer 7

1-air or water permeability
2-electrochemical testing
3-radiographic methods
4- surface hardness- rebound hammer and penetration probe
5-Ultrasonic pulse velocity
6-creep testing

Question 8

describe electrochemical testing

Answer 8

can detect corrosive currents and so the condition of the steel reinforcement

Question 9

describe what radiographic methods for testing is

Answer 9

can detect cracks and how far they penetrate towards the steel, x ray technique

Question 10

describe creep testing

Answer 10

applied load for a prolonged time, C-H-S nano particles slide over each other altering the size/shape
-it can release stresses

Question 11

describe ultrasonic pulse velocity testing

Answer 11

how well the microstructure can transmit ultrasound depending on time
-large cracks no signal received
small cracks prolong time and voids
travels faster through steel