InstroTek
2
1. Introduction
Increasing use of coarse and open graded mixes has created a need for more
reliable and accurate method of measuring the bulk specific gravity of
laboratory and field specimens. Open graded mixes readily absorb water and
drain quickly when removed from the water tank. The lack of control over the
penetration and drainage of water in and out of asphalt samples creates a
fundamental problem with the water displacement measurement method using
the current procedure (ASTM D2726 or AASHTO T 166) for determination of
specific gravity.
The most efficient and accurate method of correcting for this problem is to seal
the samples prior to testing in water. The current sealing methods, namely,
Paraffin and Parafilm are optimized for 100-mm diameter samples. They are
difficult to impossible to use effectively for 150-mm samples and cause large
measurement variability. The new system explained in this manual provides an
advanced and automatic solution to sealing asphalt samples.
The CoreLok system is a vacuum chamber that is used with specially designed
polymer bags to completely seal field and laboratory asphalt samples from
water during the bulk specific gravity measurements.
The CoreLok is a versatile density system with many different applications. This
device can be used for determination of bulk gravity of compacted asphalt
samples (ASTM D6752 & AASHTO T331), maximum gravity of loose asphalt
samples (ASTM D6857), porosity or permeability of compacted field or laboratory
samples (ASTM D7063), and gravity and absorption of fine and coarse
aggregates (ASTM D7370).
