10 resultados para 49B519961215-track

em Iowa Publications Online (IPO) - State Library, State of Iowa (Iowa), United States


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Just as the railroad tracks guide trains toward their destination, Iowa’s railroads play a vital role in keeping our state’s economic health and growth “on track” for the future.

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This report is a supplement to one issued in late summer 1986 which covered construction on U.S. 71, in Buena Vista County Iowa. The work involved rehabilitation of an older 20 feet wide pavement by placing a four inch thick bonded concrete overlay monolithically with two feet of widening on each side. The work was performed on one lane at a time while construction traffic and limited public traffic used the adjacent traffic lane. When work on the first lane was complete traffic was moved onto it and rehabilitation was completed on the second lane. This report covers the condition of the rehabilitated roadway in May 1987 after the first winter. The condition is described by visual observations, core conditions, and various test results including core compressive strength, direct shear tests on cores for bond strength, profilometer results and delamtect test results.

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In 1987, 1.5 km (0.935 mi.) of Spruce Hill Drive in Bettendorf, Iowa was reconstructed. It is an arteriel street with commercial usage on both termini with single family residential dwellings along most of the project. A portland cement concrete (PCC) pavement design was selected, but a 14 day curing period would have been an undue hardship on the residents and commercial businesses. An Iowa DOT Class F fast track concrete was used so the roadway could be used in 7 to 10 days. The Class F concrete with fly ash was relatively sticky and exhibited early stiffening problems and substantial difficulty in obtaining the target entrained air content of 6.5%. These problems were never completely resolved on the project. Annual visual field reviews were conducted through 1996. In November 1991, severe premature distress was identified on the westbound two lanes of the full width replacement. The most deteriorated section in a sag vertical, 152 m (500 ft.) of the westbound roadway, was replaced in 1996. Premature distress has been identified on a dozen other conventional PCC Iowa pavements constructed between 1983 and 1989, so the deterioration may not be related to the fact that it was fast track pavement.

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Two specialty cements are currently being marketed as a way to achieve portland cement concrete pavement opening strengths at less than 12 hours after placement. The cements are Pyrament from Pyrament/Lone Star Industries of Houston, Texas and Ideal Regulated-Set (RS) Portland Cement from Ideal Cement Company of Saratoga, Arkansas. The objective of the study was to evaluate the strength gain and durability of concrete produced with Pyrament and Ideal RS cement as Fast Track concrete. Mixes with 610 lb/cu yd (362 kg/cu m) cement were made and tested. Both Pyrament and Ideal RS are capable of producing pavement opening times less than 12 hours. Recent changes to Ideal RS cement have produced concrete flexural strengths of 550 psi (3792 kPa) at 4 hours in Iowa tests. Freeze/thaw durability of the concrete was not adversely affected by using either cement.

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There are projects where opening the pavement to traffic in less than the 5 to 7 days is needed, but an 8 to 12 hour opening time is not necessary. The study examined fast track concrete with Type I cement and admixtures. The variables studied were: (1) cure temperature, (2) cement brand, (3) accelerators, and (4) water reducers. A standard water reducer and curing blankets appear to be effective at producing a 24 hour to 36 hour opening strength. An accelerator and/or high range water reducer may produce opening strength in 12 to 24 hours. Calcium chloride was most effective at achieving high-early strength.

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In May 1950 a proposal for a research project was submitted to the newly formed Iowa Highway Research Board for consideration and action. This project, designated RPSl by the Board, encompassed the study, development, preparation of preliminary plans and specifications for the construction of a wheel track to be used in the accelerated testing of highway pavements. The device envisioned in the proposal was a circular track about seventy-five feet in diameter equipped with a suitable automobile-tired device to test pavements about five feet in width laid into the track under regular construction practices by small scale construction equipment. The Board, upon review, revised and expanded the basic concepts of the project. The project as revised by the Board included a study of the feasibility of developing, constructing and operating an accelerated testing track in which pavements, bases and subgrades may be laid one full lane, or at least ten feet, in width by full size construction equipment in conformity with usual construction practices. The pavements so laid are to be subjected, during test, to conditions as nearly simulating actual traffic as possible.

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Pavements have been overlaid with thin bonded portland cement concrete (PCC) for several years. These projects have had traffic detoured for a period of 5-10 days. These detours are unacceptable to the traveling public and result in severe criticism. The use of thin bonded fast track overlay was promoted to allow a thin bonded PCC overlay with minimal disruption of local traffic. This project demonstrated the concept of using one lane of the roadway to maintain traffic while the overlay was placed on the other and then with the rapid strength gain of the fast track concrete, the construction and local traffic is maintained on the newly placed, thin bonded overlay. The goals of this project were: 1. Traffic usage immediately after placement and finishing. 2. Reduce traffic disruption on a single lane to less than 5 hours. 3. Reduce traffic disruption on a given section of two-lane roadway to less than 2 days. 4. The procedure must be economically viable and competitive with existing alternatives. 5. Design life for new construction equivalent to or in excess of conventional pavements. 6. A 20 year minimum design life for rehabilitated pavements.

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Two lanes of a major four-lane arterial street in Cedar Rapids, Iowa, needed reconstruction. Because of the traffic volume and the detour problem, closure of the intersections, even for 1 day was not feasible. Use of Fast Track concrete paving on the mainline portion of the project permitted achievement of the opening strength of 400 psi in less than 12 hr. Fast Track II, used for the intersections, achieved the opening strength of 350 psi in 6 to 7 hr. Flexural and compression specimens of two sections each in the Fast Track and Fast Track II sections were subjected to pulse velocity tests. Maturity curves were developed by monitoring the temperatures. Correlations were performed between the pulse velocity and flexural strength and between the maturity and flexural strength. The project established the feasibility of using Fast Track II to construct portland cement concrete pavement at night and opening the roadway to traffic the next day.

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Contains information about the staff and athletes of the Iowa Hawkeyes Track and Field team for the 1984/85 academic school year. Also includes past year's results, team records, quick facts and schedule.

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Two lanes of a major four lane arterial street needed to be reconstructed in Cedar Rapids, Iowa. The traffic volumes and difficulty of detouring the traffic necessitated closure for construction be held to an absolute minimum. Closure of the intersections, even for one day, was not politically feasible. Therefore, Fast Track and Fast Track II was specified for the project. Fast Track concrete paving has been used successfully in Iowa since 1986. The mainline portion of the project was specified to be Fast Track and achieved the opening strength of 400 psi in less than twelve hours. The intersections were allowed to be closed between 6 PM and 6 AM. This could occur twice - once to remove the old pavement and place the base and temporary surface and the second time to pave and cure the new concrete. The contractor was able to meet these restrictions. The Fast Track II used in the intersections achieved the opening strength of 350 psi in six to seven hours. Two test sections were selected in the mainline Fast Track and two intersections were chosen to test the Fast Tract II. Both flexural and compression specimens were tested. Pulse velocity tests were conducted on the pavement and test specimens. Maturity curves were developed through monitoring of the temperatures. Correlations were performed between the maturity and pulse velocity and the flexural strengths. The project was successful in establishing the feasibility of construction at night, with no disruption of traffic in the daytime, using fast Track II. Both the Fast Track II pavements were performing well four years after construction.