Department of Administrative Services Four Year Strategic Plan, FY 2012-2015

Through the strategic initiatives outlined in this plan, and incorporation of those initiatives into the department’s business plans, DAS believes other departments will be able to concentrate their resources on core missions and rely on DAS for the administrative expertise for their operations. This realignment of effort will result in both an increase in efficiency and a reduction in overall cost to State government. Areas of human resources, information technology, financial services, and general services will be provided statewide in a comprehensive, cohesive, and manageable form with opportunity to make those services available to other public entities outside of state government where efficiency and economics support that cooperation.

Reducing the Adverse Effects of Transverse Cracking, HR-217, 1984

This research was initiated to identify methods of reducing the occurrence of transverse cracking. Eight (four repetitive) research sections were established to study three variations in the asphalt concrete pavement. The first variation was the comparison of low- and high-temperature-susceptible asphalt cement (AC) from two different sources. The second variable was to saw and seal transverse joints at spacings varying from 40 to 100 ft. The third variable was to increase the AC content in the asphalt treated base by 1 percent. The research sections were constructed with relatively few problems. Crack and joint surveys have been conducted on all research sections at intervals of less than 1 year since construction. No cracking was identified after the first winter season. The sawed joints also remained sealed through the first winter. At an age of approximately 1 1/2 years there was substantial cracking of the high-temperature-susceptible AC sections and substantial failure of the sealant material in the sawed joints. After almost 4 years, the asphalt pavement constructed with the high-temperature-susceptible AC produced a crack interval of 35 ft, the low-temperature-susceptible AC yielded an interval of 170 ft, and the low-temperature-susceptible AC with an increased AC content yielded an interval of 528 ft. The Pen-Vis number is an effective measure of temperature susceptibility of asphalt cements. The frequency of transverse cracking is affected by the temperature susceptibility of the AC. An increased AC content also reduces the frequency of transverse cracking.

Performance of Randomly Oriented, Fiber-Reinforced Roadway Soils, HR-211, 1982

Several primary techniques have been developed through which soil aggregate road material properties may be improved. Such techniques basically involve a mechanism of creating a continuous matrix system of soil and/or aggregate particles, interlocked through the use of some additive such as portland cement, lime, or bituminous products. Details by which soils are stabilized vary greatly, but they are dependent on the type of stabilizing agent and nature of the soil, though the overall approach to stabilization has the common feature that improvement is achieved by some mechanism(s) forcing individual particles to adhere to one another. This process creates a more rigid material, most often capable of resisting the influx of water during freezing, loss of strength due to high moisture content and particle dispersion during thawing, and loss of strength due to migration of fines and/or water by capillarity and pumping. The study reported herein, took a new and relatively different approach to strengthening of soils, i.e., improvement of roadway soils and/or soil-aggregate materials by structural reinforcement with randomly oriented fibers. The purpose of the study was to conduct a laboratory and field investigation into the potential of improving (a) soil-aggregate surfaced and subgrade materials, including those that are frost-prone and/or highly moisture susceptible, and (b) localized base course materials, by uniting such materials through fibrous reinforcement. The envisioned objective of the project was the development of a simple construction technique(s) that could be (a) applied on a selective basis to specific areas having a history of poor performance, or (b) used for improvement of potential base materials prior to surfacing. Little background information on such purpose and objective was available. Though the envisioned process had similarities to fibrous reinforced concrete, and to fibrous reinforced resin composites, the process was devoid of a cementitious binder matrix and thus highly dependent on the cohesive and frictional interlocking processes of a soil and/or aggregate with the fibrous reinforcement; a condition not unlike the introduction of reinforcing bars into a concrete sand/aggregate mixture without benefit of portland cement. Thus the study was also directed to answering some fundamental questions: (1) would the technique work; (2) what type or types of fibers are effective; (3) are workable fibers commercially available; and (4) can such fibers be effectively incorporated with conventional construction equipment, and employed in practical field applications? The approach to obtaining answers to these questions, was guided by the philosophy that an understanding of basic fundamentals was essential to developing a body of engineering knowledge, that would serve as the basis for eventual development of design procedures with fibrous products for the applications previously noted.

Embankment Quality Phase II Final Report, TR-401, 1999

Phase II research included the following: (1) develop and evaluate alternative soil design and embankment construction specifications based on soil type, moisture, density, stability, and compaction process; (2) assess various quality control and acceptance procedures with a variety of in-situ test methods including the Dual-mass Dynamic Cone Penetrometer (DCP); and (3) develop and design rapid field soil identification methods. At the start of the research, soils were divided into cohesive and cohesionless soil types, with each category being addressed separately. Cohesionless soils were designated as having less than 36% fines content (material passing the No. 200 sieve) and cohesive soils as having greater than 36% fines content. Subsequently, soil categories were refined based not only on fines content but soil plasticity as well. Research activities included observations of fill placement, in-place moisture and density testing, and dual-mass DCP index testing on several highway embankment projects throughout Iowa. Experiments involving rubber-tired and vibratory compaction, lift thickness changes, and disk aeration were carried out for the full range of Iowa soils. By testing for soil stability the DCP was found to be a valuable field tool for quality control, whereby shortcomings from density testing (density gradients) were avoided. Furthermore, critical DCP index values were established based on soil type and compaction moisture content.

Methods to Increase Durability of Reactive ("D" Cracking) Coarse Aggregate in Portland Cement Concrete, MLR-73-01, 1973

The coarse aggregates used for Portland Cement concrete in southwest Iowa have exhibited a poor serviceability. This early failure is attributed to a characteristic commonly referred as "D" cracking. "D" line cracking is a discolored area of concrete caused by many fine, parallel hairline cracks. "D" line cracking is primarily caused by the movement of water in and through coarse aggregate with a unique pore structure. The presence of the water in the aggregates at the time of freezing causes the "D" cracking to occur and early failure. By making the pore structure less permeable to moisture, it is thought the durability factor of the concrete should increase. By drying the aggregate before mixing and then mixing with the cement, the particles of cement should enter the outer pore structure, and upon hydration make the pore structure less permeable to moisture.