Porosity and Permeability Studies of Virginia Aggregates: Final Report

About the report:

It is generally recognized that the volume and geometry of included pores within a mineral aggregate have a significant effect on the physical and chemical behavior of the aggregate when used as a structural material. However due to the technical difficulties involved in measuring pore parameters, accurate correlation of field behavior with pore characteristics has not readily evolved. This study was proposed to provide accurate data on pore characteristics for a variety of Virginia aggregates with the expectation that future durability studies would attempt to correlate these findings with field performance. All of the aggregates studied showed relatively low porosities ranging from a high of 3.66% to a low of 0.19% with most values being less than 1%. Pore size distributions showed carbonate aggregates to have pores of nearly all one size while igneous and metamorphic rocks contain several sizes. Permeabilities of all rocks fell in the range of 10-1 to 10-5 millidarcys. A set of equations was developed to relate porosity and permeability values. Finally in order to investigate the feasibility of a rapid test method to predict aggregate water absorption, a correlation between porosity determined high pressure mercury injection and porosity determined by long-term water was attempted. The results ranged from poor to fair. Incorporation of other parameters such as rate of water uptake, pore size, and rock grain size served to make only modest improvements in the correlation. In view of this lack of strong correlation no recommendation concerning a rapid test method is offered at this time.

Authors