Grading of aggregate in a concrete mix is necessary to achieve

$$IS$$ $$456$$-$$2000$$ recommends providing certain minimum steel in a $$RCC$$ beam

A prestressed concrete rectangular beam of size $$300\,\,mm \times 900\,\,mm$$ is prestressed with an intial prestressing force of $$700$$ $$kN$$ at an eccentricity of $$350$$ $$mm$$ at midspan. Stress at top due to prestress alone, in $$N/m{m^2}$$ is

The state of two dimensional stresses acting on a concrete lamina consists of a direct tensile stress, $${\sigma _x} = 1.5\,\,N/m{m^2},$$ and shear stress, $$\tau = 1.20\,N/m{m^2},$$ which cause cracking of concrete. Then the tensile strength of the concrete in $$N/m{m^2}$$ is