Contractor Variability in Construction of Cement Treated Base Layers

• Main Author: Rogers, Maile Anne
• Format: Others
• Published: BYU ScholarsArchive 2006
• Subjects: FDR; full-depth recelamation; CTB; cement-treated base; construction; Construction Engineering and Management; Manufacturing
• Online Access: https://scholarsarchive.byu.edu/etd/503; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=1502&context=etd

The primary purposes of this research were to identify construction factors most correlated to specific mechanical properties of cement-treated base (CTB) layers and to determine which construction factors exhibit comparatively high variability within individual construction sections of the two pavement reconstruction projects included in this study. In addition, differences between construction sections tested in this research were evaluated. The research focused on the construction of CTB layers in two pavement reconstruction projects in northern Utah, one along Interstate 84 (I-84) near Morgan and one along U.S. Highway 91 (US-91) near Richmond. The significant predictor variables associated with California bearing ratio (CBR), Clegg impact value (CIV), 7-day unconfined compressive strength (UCS), and 28-day UCS at the I-84 sites include reclaimed asphalt pavement (RAP) content; cement content; amounts of aggregate particles finer than the No. 8, No. 50, and No. 200 sieves; 7-day moisture content, and 28-day moisture content. The significant predictors of the same response variables on US-91 were in-situ moisture content, cement content, amount of aggregate particles finer than the No. 50 sieve, time between mixing and compaction in the field, dry density in the field, 7-day dry density, 7-day moisture content, 28-day dry density, and 28-day moisture content. The factors that were found to be the most variable on both I-84 and US-91 were CBR, cement content, time between mixing and compaction in the field, and time between mixing and compaction for each of the manually compacted specimens. On I-84, 16 of 27 factors were found to be significantly different between the sites, while 17 of 26 factors were found to be significantly different between the sites on US-91. The results of this research suggest that tighter specifications are warranted with respect to RAP content, cement content, and time between mixing and compaction. Concerning full depth recycling (FDR) projects, milling plans should be utilized to achieve improved uniformity in RAP content, and inspection protocols for encouraging improved control of cement content should be implemented during construction to ensure high-quality work. Compaction should be performed as soon as possible after mixing to minimize the adverse effects of cement hydration on the ability to achieve maximum dry density in the field.