4/17/2021 0 Comments Concrete Compressions Strength
If one concrete is cured continuously in water and the other is curved wet and then stored in dry environment and tested.This implies a fixed relation between the compressive and tensile strength of concrete.
In fact there is a close relation but not a direct proportionality. The ratio of tensile to compressive strength is lower for higher compressive strengths. The ratio of tensile strength to compressive strength depends upon the strength of concrete. Thus higher the compressive strength, higher the tensile strength, but the rate of increase of tensile strength is of decreasing order. The tensile strength of concrete is more sensitive to improper curing than the compressive strength. The uses of pozzolanic materials have shown the increase in tensile strength. The strength is found to vary with the nature and size of aggregate. In general the ratio was found slightly higher for natural gravel than for crushed stone. ![]() In the calculation of modulus of rupture, it is assumed that stress is proportional to the distance from the neutral axis of the beam, while the shape of the actual stress block under loads nearing failure is known to be non-triangular, but parabolic. The modulus of rupture thus overestimates the tensile strength of concrete and gives a higher value than would be obtained in direct tensile test or splitting test. However the actual values may vary depending on the properties of concrete. The alteration in this ratio was found to alter the flexural strength. The change in the span to depth ratio by 1 induced 3 change in the flexural strength when tested by third point loading and 2.5 change when tested by central point loading. With the increase in span to depth ratio, the flexural strength was found to decrease. If the rate of application of stress is increased from the standard rate of application of 0.7 MPa per minute, the flexural strength was found to increase upto 25. The average value for both may be taken as 8.3 and the value of n may vary from 0.5 to 0.75. It has been observed that vertical cracking in a specimen subjected to uniaxial compression starts under a load equal to 50 to 75 of the ultimate load. The stress at which the cracks form depends to a great extent on the properties of coarse aggregate. It has been observed that concrete made from smooth surfaced gravel cracks at much lower stress than concrete made with rough and angular crushed rock aggregate. This may be due to mechanical bond and shape of the coarse aggregate. ![]() The properties of coarse aggregate have been found to have little effect on direct and splitting tensile strength, but flexural strength is found greater with the use of crushed and angular crushed rock aggregate than the rounded gravel.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |