Aggregates generally contain pores; these may be of various size and extent. Some aggregates have pores within solid where other have opening to the surface. Dear reader we will discuss about pore size of different rock aggregates and their extent in our next post. Here we want to explain influence of porosity, absorption in aggregate on the properties of concrete. The porosity, permeability and absorption of aggregate have influence on following properties of concrete.
a. Bond between aggregates and surrounding hydrates paste of cement.
b. Chemical stability of concrete
c. Resistance of concrete against freezing and thawing of concrete
d. Resistance of concrete against abrasion
e. Apparent specific gravity of aggregate itself.
As specific gravity is affected, for a specific mass of aggregate, concrete production also affected.
It is obvious that a porous aggregate produce concrete of unit weight, as that of light weight aggregates. Now-a-days lightweight aggregate concretes are used for structural member, which yield significant strength with special treatment.
But when absorption is concerned, it will effect water demand with in concrete and should be adjusted for water/cement ratio while proportioning mix design. In our next post we will discuss about pore sizes of natural aggregates. Please stay with us.