Selection of Design Factors for the Use of Gravel in CRC Paving
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Gravel aggregates have been used for many years in the construction of continuous reinforced concrete (CRC) pavements in Texas. However, these pavements are in many instances subject to delamination and spoiling distresses, and thus costly to maintain and repair. Evidence collected from extensive field studies has indicated that the bond of the aggregate-mortar interface at an early age is one of the most significant factors affecting the development of delamination and eventual spalling. In this research, a fractional factorial design (the Taguchi method) was applied to investigate the methodology for improving delamination resistance of CRC pavements. Four factors (i.e., aggregate type, water/cementitious ratio, replacement of ultra-fine fly ash, and curing method) with three levels for each factor based on the orthogonal array were considered. A fracture mechanics parameter, fracture toughness (K If), was used to represent the aggregate-mortar bond strength. The significances of each factor to achieve better K If were determined, and the optimum design combination was subsequently chosen and validated. The consistency between the results from the experimental design and laboratory validation provides highway agencies valuable recommendations and aid in selecting design factors for the use of gravel in paving construction to relieve delamination and further spalling distresses. A comprehensive investigation on overall aggregate contribution to pavement bonding performance will be considered in future research to ensure the integrity of the evaluation and analysis.