The use of recycled concrete aggregate in a dense graded aggregate base course.

692393802Final report; 1/2007-3/2008.PDFTech ReportFHWA-NJ-2008-002AggregatesBase course (Pavements)Concrete pavementsRecyclingWaste productsNew JerseyNew Jersey. Dept. of TransportationBennert, ThomasMaher, AliNew Jersey. Dept. of TransportationUnited States. Federal Highway AdministrationNTL-HIGHWAY/ROAD TRANSPORTATION-MaterialsNTL-HIGHWAY/ROAD TRANSPORTATION-Soils and GeologyUS Transportation CollectionThe research project was broken up into 2 different parts. The first part involved evaluating the potential use of the TimeDomain Reflectometry, TDR (ASTM D6780), as a non-nuclear means for determining the dry density and moisture content ofgranular base and subbase aggregates during quality control. Just prior to the study, Humboldt Equipment Company provideda device called the Electrical Density Gauge (EDG) that also claimed to be a non-nuclear means of determining dry density andmoisture content. Both units were used on five separate field trials (5 sections for the TDR and 3 sections for the EDG) andcompared against the NJDOT\ue2\u20ac\u2122s nuclear density gauge. The field trials indicated that the TDR test method, as it currentlystands according to ASTM D6780, does not compare well with the nuclear density gauge readings. This was mainly attributedto the TDR\ue2\u20ac\u2122s soil constant calibration procedure. There also appeared to be a lack of sensitivity with the TDR method whencompared to the nuclear gauge. The EDG showed a better correlation to the nuclear gauge, although this was expected sinceat the time of the study, the EDG device required field calibration. A newer version of the EDG now incorporates a laboratorycalibration procedure that would eliminate the need for field calibration with a nuclear gauge.The second part of the research study was to evaluate potential methods of increasing the permeability of recycled concreteaggregate (RCA), while attempting to maintain its structural integrity (i.e. \ue2\u20ac\u201c California Bearing Ratio, CBR). Before laboratorytesting began, a survey was developed, sent to various state agencies, and tabulated to determine if other state agenciescurrently utilized RCA, and if so, what experience did they have regarding the drainage characteristics of the material. After thesurvey results were tabulated, laboratory testing was conducted on RCA blended with different aggregates; dense-gradedaggregate (DGA), NJDOT I-3, and poorly graded sand. Work was also conducted on RCA material which was processed overa coarser sieve size (2 inches), as opposed to the finer 1.5 inches currently specified by NJDOT, in an attempt to include alarger, coarser fraction that could open up the internal structure of the RCA. This was in an attempt to meet some of the stateagency specifications of the various states who responded to the survey saying they did not have any current issues with thepermeability/drainage of their RCA materials. The results of the laboratory testing showed that the best performingmodification to the RCA was when blended with 50% DGA. This increased the permeability to levels considered average,while still providing excellent bearing strength. The attempts of using the NJDOT I-3 and poorly graded sand did notdramatically increase the permeability, while a decrease in bearing strength was still reported. Increasing the top size of theprocessed/screened RCA from 1.5 inches to 2.0 inches helped to increase the permeability, while achieving the same bearingstrength properties (CBR)