Low-Cost Rural Surface Alternatives Phase III: Demonstration Project TR-721

(2022) Low-Cost Rural Surface Alternatives Phase III: Demonstration Project TR-721. Transportation, Department of

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Abstract

The goal of this project was to identify effective and economical methods for stabilizing Iowa granular-surfaced roads to reduce freeze-thaw-related damage using materials and construction equipment that are readily available to county engineer’s offices. To study a range of representative Iowa aggregate sources, subgrade soil types, and weather conditions, 31 test sections were constructed and/or monitored in four counties across Iowa. The test sections included one control section in each county and several mechanical and chemical stabilization methods. The performance of the stabilized and control sections was evaluated over two years using extensive field and laboratory tests, as well as digital image surveys and surface condition rating reports completed by the grader operators. The field tests included falling weight deflectometer (FWD), lightweight deflectometer (LWD), dynamic cone penetrometer (DCP), and nuclear density gauge (NDG) tests. Samples of the surfacing materials were collected on several occasions before and after each winter and were evaluated through laboratory tests including sieve analysis, Atterberg limits, compaction, shear strength, and durability tests. The construction costs and maintenance costs were tracked with the assistance of the county engineers, and an economic analysis was conducted to compare the relative cost effectiveness of the different stabilization methods. Among the stabilization methods examined, the most economical and potentially effective were optimized gradation with clay slurry (OGCS), 4 in. cement-treated surface course, and the liquid chemical stabilizers BASE ONE, EMC SQUARED, and Claycrete.