This study was undertaken to determine the accuracy and reliability of portable, automatic, vehicle classification devices. Available classification equipment was identified, borrowed, and field tested against manual traffic classification to meet the objectives of the study. Field tests were conducted at both high-speed, high-volume and low-speed, low-volume sites.
It was found that portable, automatic vehicle classifiers are generally more accurate at low-speed sites and that when classification errors are made, the errors are in multiple-axle categories. Detection appears to be the biggest problem both in getting an impulse to the devices from the pneumatic road tubes and in securing the tubes in place in high-volume traffic areas.
A typical concrete pavement has expansion and contraction joints across and along the pavement surface. The joints allow the pavement to change in dimension with changes in temperature. A continuously reinforced concrete pavement (CRCP) does not have expansion or contraction joints. Random, closely spaced cracks are expected to develop naturally and allow for expansion and contraction due to temperature changes. The many random cracks eliminate expensive joint maintenance. This maintenance-free service life feature has not occurred in Minnesota.
During past years, an increasing number of CRCP s have exhibited deterioration where pieces of concrete separate from the surface of the pavement and potholes result. This is termed spalling. The frequency and extent of this deterioration has progressed from isolated and random to widespread and frequent. A comprehensive program was initiated by Mn/DOT to study this problem and develop possible solutions.
This CRCP inventory is a physical evaluation of the extent of corrosion on random, sections of pavement. It is related to concurrent efforts which will evaluate CRCP rehabilitation, techniques.
High quality aggregates for highway construction are in short supply in many parts of Minnesota. Although the current total supply is adequate, the distribution of sources results in localized shortages. In some areas, it is necessary to import high-quality aggregates from distant locations. Long haul distances can increase aggregate prices substantially, add significantly to the overall project cost, and require the expenditure of sizable amounts of energy. One available source of high-quality aggregate is existing portland cement concrete pavement currently in need of reconstruction. Re-using this aggregate would conserve natural resources, result in cost savings in areas experiencing aggregate shortages and conserve natural resources, result in cost savings in areas experiencing aggregate shortages, and conserve energy in the form off fuel savings when aggregates must be acquired from distant sources. A research study was undertaken to; Determine the feasibility of recycling portland cement concrete pavement; evaluate the new recycled pavement; determine the cost effectiveness of recycling versus conventional paving; and determine the amount of energy consumed and natural resources conserved. Economic and engineering factors led to the selection of a 16-mil (25.7 km.) segment of U.S. 59 from Worthington to Fulda in Southwestern Minnesota for :his study. The in place roadway which was constructed in 1955 and consisted of a 9-7-9 inch (23-18-23 cm.) thick, 24 foot (7.3 m) wide, non-reinforced "D"-cracked concrete pavement with soil shoulders was broken, salvaged, and crushed. Material passing the #4 sieve (0.187 in., 0.476 cm) was used for base stabilization and shoulder aggregate, and material retained on the #4 sieve but passing the 3/4 in. (1.905 cm) sieve was used] as the coarse aggregate for concrete paving. Pavement removal began May 15, 1980 and concrete paving was completed September 24. 1980.
