Impact of Fines on Various Base Material Properties

Abstract

The performance of the unbound aggregate base is affected by moisture content and fines (materials finer than No. 200 sieve) content. Proper moisture content and the proper amount of fines in a base material contribute to long-lasting pavements. This study evaluated an unbound aggregate base under different moisture contents and fines contents. The evaluation included the measurements of the electrical and electromagnetic properties with moisture content and fines content. The dielectric constants were measured with a percometer, and the resistivity values were measured using a Wenner probe. These measurements were correlated with the moisture content for all fines contents used in the study. Strength and modulus tests were also performed on the specimens using the unconfined compressive strength (UCS) tests and a lightweight deflectometer (LWD). The variations in these parameters with moisture content are also presented here for all fines content. A normalization scheme was used to allow for the data to be compiled and analyzed more easily. The dielectric constant increased as moisture was added with some dispersion, but no clear trend was seen among different fines contents. The resistivity decreased consistently as the moisture content increased. The peak UCS normally occurred at moisture contents of about 1% dry of optimum moisture content (OMC); specimens prepared with 1% less than optimum had higher UCS. LWD modulus tended to peak when prepared drier than OMC. The optimum strength and modulus were obtained with 5% and 10% fines contents for the unbound granular base used.