$($b$)$ The Young's modulus E $13\mathrm{.}5$GPa, compressive strength $=135$MPa and critical energy release rate G $=1\mathrm{.}851$KJ$/$m$^2$ of a concrete with an overall porosity P $=20\%$ and a maximum crack length a $=5$mm$.$ Estimate the compressive strength and tensile strength of a concrete with an overall porosity P$=4\%$ and a maximum crack length a $=1$mm$,$ respectively. $(10\%)($b$)$ The Young's modulus $E_C=13\mathrm{.}5$GPa, compressive strength ${}_C=135$MPa

and critical energy release rate $G_C=1\mathrm{.}851K\frac{J}{m^2}$ of a concrete with an

overall porosity $P=20\%$ and a maximum crack length $a=5mm.$

Estimate the compressive strength and tensile strength of a concrete with an

overall porosity $P=4\%$ and a maximum crack length $a=1mm,$

respectively.