Evaluating and modeling aggregate loss of Otta seal for low-volume roads

Abstract

Otta seal has gained significant interest from Iowa road engineers in search of a more economical surface alternative for low-volume road construction, preservation, and rehabilitation. This technology has not been sufficiently studied in the US, with the only available guideline for Otta seal construction based on field experience in Norway. Otta-seal specimens prepared using Iowa local aggregate were investigated in the laboratory by using sweep tests to measure the effect on aggregate loss of aggregate and binder types, application rate calculation method, and gradation. Methods such as Overby, McLeod, and modified McLeod were investigated to determine the optimum rates for both aggregate and binder application, with results indicating that material type variation did not significantly affect the aggregate loss of Otta seal specimens and that aggregate loss in specimens gradually decreased as grading was changed in from dense to open. Recycled aggregates (recycled concrete aggregate and slag) showed satisfactory performance, essentially the same as conventional aggregates, in the sweep tests; this encourages using recycled materials in Otta seal construction, considering the resulting economic and environmental benefits. Among the different methods tested for material application rate, the modified McLeod method produced the lowest aggregate loss for Otta seal specimens. Multiple linear regression (MLR) and artificial neural network (ANN) models for predicting aggregate loss of Otta seal from the ratio of binder to aggregate application rate (BR/AR), gravel content, and uniformity coefficient (Cu) were also developed. The model can be utilized to predict aggregate loss from easy-to-measure material properties.