Master of Science / Department of Civil Engineering / Major Professor Not Listed / With recycled concrete aggregates (RCA) becoming a more popular and cost effective alternative to virgin aggregate, the Kansas Department of Transportation (KDOT) looks to incorporate these aggregates into Portland cement treated base (PCTB). KDOT currently practices a freeze-thaw method that includes 90 days of curing and a maximum of 660 freeze-thaw cycles to determine the durability of its concrete pavements and bases. An experimental study was conducted to determine if lower quality RCA would be an adequate replacement for virgin aggregates within PCTB. Two sources of D-cracked aggregate from “D” cracked pavements, were acquired and used to batch the PCTB. Control samples were batched using virgin aggregates following the gradation of the two sources of RCA. Following the procedure laid out by KDOT, both the RCA and control samples were tested for durability. The results showed that increasing the total amount of cementitious binder in the PCTB increased the durability. Also at lower binder contents, the type of RCA had an impact on the performance of the base containing RCA. In addition, the RCA and control samples had similar performance, and as a result RCA could be a viable aggregate source for PCTB. Finally, it was determined that different criteria need to be developed for the freeze-thaw durability of PCTB as mass loss was an important factor for PCTB with D-cracked aggregates

Master of Science / Department of Industrial & Manufacturing Systems Engineering / Malgorzata J. Rys / Before year 2012 the US States must implement and continue using an assessment or management method to maintain traffic signs’ retro-reflectivity at or above the minimum levels adopted by FHWA. Overhead guide signs are a particular problem because past research has shown that with available sheeting types, external illumination may still be necessary. Newer sheeting types and more energy efficient and cost-effective lighting systems are currently available. Over the next several years there is potential for savings of tens of thousands of dollars if the states don’t have to use external illumination for their overhead guide signs, or, if more energy efficient, low cost lighting systems are used when necessary. A detailed literature review was conducted on minimum retro-reflectivity values for overhead guide signs, the legibility distance under reduced sign luminance and the lighting systems available for external illumination. There is no agreement found in the previous research studies as to what is the optimum or minimum luminance of the guide signs. In addition, a survey was sent to all state DOTs. This survey was focused on finding states’ policies regarding the use of sheeting type and external illumination requirement, and methods and lighting systems for maintaining minimum values for overhead guide sign luminance. The total response rate was 56% (28 out of 50 state DOTs responded). Out of 28 respondents 19 said that they have usage policy for the type of sheeting material used for overhead guide signs and 18 of them provided details about their policy. An equipment to control the illumination levels from vehicle headlamps was built and pilot tests were conducted in the laboratory. A pulse-with-modulation dimming circuit designed around the Atmel ARM-based microcontroller board and power MOSFETs was used to control the brightness of the headlights for the high- and low-beams. Field tests were conducted in the later stages during nighttime to evaluate three different types of sheeting materials using 10 human subjects from age group 18-34. The materials DG3 and Type IV were found to perform better than Type I material for nighttime visibility but they were not significantly different from each other.

Master of Science / Department of Civil Engineering / Kyle Riding / Concrete is most widely used material in construction industry, which is made up of cement, water and aggregates as its major ingredients. Aggregates contribute to 60 to 75 % of the total volume of concrete. The aggregates play a key role in the concrete durability. The U.S Midwest has many aggregates that can show distress in the field under freezing and thawing conditions. The objective of this research was to determine if the Test Method for the Resistance of Unconfined Coarse Aggregate to Freezing and Thawing, method CSA A23.2-24A, could be used to differentiate good from poor performing aggregates in concrete. In this study fifty one KDOT aggregates (including twelve ledge and thirty nine production samples) were tested for freeze thaw resistance using CSA A23.2-24A test method and were compared to the results of the standard KDOT aggregate qualification tests. In addition to performing the CSA test method using a 3% sodium chloride solution, a subset of the aggregates were tested using either a 3% magnesium chloride or calcium chloride solution to determine the effects of the salt type on the aggregate performance. No correlation was found between the CSA A23.2-24A test method results and the standard KDOT aggregate qualification tests. The results also indicated that the mass loss in the CSA A23.2-24A was similar for the aggregate sizes tested. The use of alternate salt solutions like MgCl2 and CaCl2 resulted in increased freeze thaw mass loss in limestone aggregates.