The precise quantity of water is essential to be further in the mixture to whole the chemical reaction or hydration. If the concrete dry out earlier than conclusion of the reaction, it reasons cracking.
Lack of control joint or control joint with wrong dimension of thickness causes cracking.
When the extra quantity of water freezes in winter, the volume enlarges, and cracking happens.
Dissimilar concrete will have dissimilar strengths. If the concrete mix with essential strength is not bent throughout the job, it can reason cracking.
Once an extra of water is additional to the concrete growing its w/c ratio, the strength of the concrete also will decrease. Throughout summer, vaporization of additional water takings place that reasons shrinkage. Owing to this shrinkage, cracking in concrete take place.
Find the Modulus of rupture (fr): fr= 7.5√ƒc, Where ƒc = The compression strength of the concrete (e.g. 4 ksi, 6 ksi)
Find yt: yt is the distance from the center of gravity of the beam to the extreme fiber of the tension side (this neglects reinforcement). Therefore for a rectangular section, yt = h/2.
Find Ig: Ig is the gross Moment of Inertia for the beam. Ig = bh3/12.
The Moment at Which These Cracks Begin to Form—that Is , When the Tensile Stress in the Bottom of the Beam Equals the Modulus of Rupture—is Referred to as The