696207184

Technical report; Sept. 2003-Aug. 2006.

Texas Transportation Institute

NTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and Performance ; NTL-HIGHWAY/ROAD TRANSPORTATION-Materials ;

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Fracture toughness (KIC) value at early ages of concrete was used to represent the interfacial bond between

aggregate and mortar of a variety of coarse aggregates types and concrete mixtures. A fractional factorial design based

on Taguchi’s orthogonal array using four factors (i.e., aggregate type, w/cm, replacement of ultra-fine fly ash, and

curing method) was selected to conduct the detailed laboratory study. The statistical analysis indicated the following

decreasing rank order with respect to the relative importance of each factor to KIC: aggregate type, curing method,

w/cm, and ultra-fine fly ash content. A comprehensive investigation of aggregate properties relative to physical,

geometric, and chemical characteristics was conducted. The research findings indicated that the aggregate-mortar

interfacial bond for a given cement paste was found not to be a simple function of any one of the aggregate properties,

but a function of all three properties aggregated together. The application of utility theory to the evaluation of overall

contribution of aggregate properties to the bonding performance of concrete, and feasibility of design combinations

enables agencies to select the best aggregate type, modify aggregates by blending different aggregates, and optimize

the design combinations for concrete paving construction, to relieve delamination and further spalling distresses.

The interfacial fracture energy can be predicted once a design combination is known based on the linear

relation with both concrete and mortar fracture energy. A fracture mechanics based approach was proposed with the

facilitation of numerical analysis to predict the occurrence of delamination. The criterion for predicting early age

delamination occurrence is that delamination occurs when KI > KIC. Through examples of practical design and

construction methods, this approach is able to assess the probability of delamination occurrence, which will facilitate

selection and evaluation of the effectiveness of pavement design methods to prevent delamination and spalling

problems in concrete paving.

Test sections of both winter and summer were established based on the research finding from laboratory

investigations, theoretical modeling, and numerical analysis. Future performance of these sections will determine if

t he measures taken to arrest delamination were successful or not.

US Transportation Collection

0-4826