6 Oct 2022

Development and Validation of a Balanced Mix Design Approach for CIR Mixtures Using Full-Scale Testing

Abstract: The main goal of this study was to improve the performance of cold in-place recycling (CIR) mixtures by using a balanced mix design (BMD) approach. This study involved preparing and testing CIR mixtures in the lab at varying contents of bituminous additives and constant content of 1% cement and 3% water. Eight combinations of CIR mixtures were produced for this study using two binders (emulsion and foamed asphalt), compaction efforts (30 and 70 gyrations), and curing processes (72 hours at 140°F and 50°F). Results showed that asphalt pavement analyzer, semicircular bend, and indirect tensile strength tests presented the highest correlation with the change of binder contents. The study successfully used the developed BMD for designing CIR mixtures and selecting their optimum binder contents. It then used three balanced CIR mixtures to construct full-scale pavement sections to validate the BMD approach in the field. A heavy vehicle simulator was used to apply different accelerated loadings on each section. Results showed that the CIR section with 2% binder presented the best rutting performance under truck loading and the highest rutting susceptibility under aircraft loading. Conversely, the CIR section with 3% binder presented the highest cracking resistance under both truck and aircraft loading.

27 May 2021

Long-term performance of sustainable pavements using ternary blended concrete with recycled aggregates

Abstract: Dwindling supplies of natural concrete aggregates, the cost of landfilling construction waste, and interest in sustainable design have increased the demand for recycled concrete aggregates (RCA) in new portland cement concrete mixtures. RCA repurposes waste material to provide useful ingredients for new construction applications. However, RCA can reduce the performance of the concrete. This study investigated the effectiveness of ternary blended binders, mixtures containing portland cement and two different supplementary cementitious materials, at mitigating performance losses of concrete mixtures with RCA materials. Concrete mixtures with different ternary binder combinations were batched with four recycled concrete aggregate materials. For the materials used, the study found that a blend of portland cement, Class C fly ash, and blast furnace slag produced the highest strength of ternary binder. At 50% replacement of virgin aggregates and ternary blended binder, some specimens showed comparable mechanical performance to a control mix of only portland cement as a binder and no RCA substitution. This study demonstrates that even at 50% RCA replacement, using the appropriate ternary binder can create a concrete mixture that performs similarly to a plain portland cement concrete without RCA, with the added benefit of being environmentally beneficial.

24 Sep 2020

Investigation of Testing Materials for the Chickamauga Lock and Dam Reconstruction Project

Abstract: In support of the U.S. Army Corps of Engineers (USACE) Nashville District, a preliminary investigation of concrete materials was conducted pursuant to re-construction at the Chickamauga Lock and Dam located near Chattanooga, TN. Local materials provided to the U.S. Army Engineer Research Development Center (ERDC) for testing included three different coarse aggregate gradations, two fine aggregate sources, two type I/II cements, a fly ash sources, a slag cement, a silica fume, and a limestone powder. Aggregate tests consisted of sieve analysis, specific gravity, absorption, materials finer than No. 200, organic impurities, soundness, LA abrasion, clay lumps and friable particles, flat and elongated particles, lightweight particles, petrography, and freezing and thawing. All cementitious and admixture materials were tested for chemical and physical properties based on appropriate specifications. This report presents the material characteristic results determined by laboratory testing in accordance with American Society for Testing Materials (ASTM) procedures or regulating specification criteria.