Friday Facts, December 3, 2010, Vol. 81

Bureau of Nutrition and Health Promotion part of the Iowa Department of Public Health produces of weekly newsletter about the Iowa WIC Program for the State of Iowa citizen.

Fly Ash Concrete Compressive Strength and Freeze-Thaw Durability, MLR-81-06, 1981

The current study investigated the effect of fly ash class, source and amount on the compressive strength and freeze-thaw durability of fly ash concrete. Concrete aggregates of varying quality were also included as test variables. The current results and those obtained from previous laboratory and field work indicate that compressive strength can·be affected by fly ash class, source and amount while aggregate quality is shown to have no effect on strength. Freeze-thaw durability of fly ash concrete is strongly affected by aggregate quality and to a lesser degree by fly ash class, amount and source.

Evaluation of the Concrete Admixture Gla-Zit, MLR-81-5, 1983

A concrete admixture, Gla-Zit, was evaluated in 1970 by the Iowa State Highway Commission and found to be lacking in providing beneficial effects to concrete. This current evaluation is similar to that conducted in 1970 with slight modifications in the actual concrete mixes studied. At the request of the manufacturer, all concrete mixes containing Gla-Zit were non-air entrained. Concrete properties examined were compressive strength, salt scaling resistance, absorption, resistance to chloride penetration, and freeze-thaw durability. The differences found in the mixes studied are much more attributible to air entrainment, or the lack thereof, than the influence of Gla-Zit. The study re-affirms that it is necessary to have properly air entrained concrete to lessen the detrimental effects of freeze and thaw and scaling caused by salting. There is no data in the study to suggest that Gla-Zit has any significant effect on any of the concrete properties examined.

Report on Fly Ash Variability, MLR-81-2, 1981

The physical-chemical testing of fly ashes indicates that, under normal operating conditions, a low variability of results can be expected from a particular generating plant unit. However, unannounced changes in coal source and/or plant operations do occur and they may result in an ash with undesirable properties. Since these properties can be detected by physical-chemical testing, it is recommended that this testing be performed on a lot-by-lot basis when a plant is supplying fly ash to a construction project.

Evaluation of Visibeads in Epoxy markings on I-235, HR-554, 1995

In recent years, the nighttime wet pavement retroreflectivity of pavement markings has become an important issue. In a effort to continue research in this area, the Iowa Department of Transportation evaluated the effectiveness of Visibeads in the Des Moines metropolitan area. Visibeads are three to four times larger in diameter then conventional glass beads. This larger size provides for better retroreflectivity under nighttime wet pavement conditions. The areas chosen for evaluation do not have roadway lighting, therefore, making them a good choice for Visibeads. Although the DOT has tested Visibeads in the past with moderate success, it is believed that using Visibeads with longer life markings such as epoxy will improve their performance.

Polk County, Township 81 North Range 24 West

Des Moines River Plat Maps.

Polk County, Township 81 North Range 25 West

Des Moines River Plat Maps.

Dallas County, Township 81 North Range 26 West

Des Moines River Plat Maps.

Dallas County, Township 81 North Range 27 West

Des Moines River Plat Maps.

Field Evaluation of Electro-Reflective Measuring Apparatus (ERMA), MLR-81-01, 1981

The Electro-Reflective Measuring Apparatus (ERMA) was developed by the Minnesota Department of Highways in 1974 to measure the retro-reflective characteristics of pavement marking materials. Minnesota researchers recommended that due to the increased cost of pavement marking materials and reduced availability of these materials, ERMA can and should be used as a maintenance management tool to determine when painting is necessary rather than according to a fixed time schedule. The Iowa DOT Office of Materials built an ERMA device patterned after Minnesota's design in 1976. Subsequent efforts to calibrate and correlate this ERMA device to District Paint Foremen ratings proved unsuccessful, and ERMA modification or abandonment was recommended in 1979. Lyman Moothart, Materials Lab. Tech. 4, modified the ERMA device in 1980 and correlation attempts to District Paint Foremen ratings conducted in November 1980 have been moderately successful. A Paint/No Paint ERMA value has been established which will identify about 90% of the painting needs but will also include about 40% of the marking lines not needing repainting. The Office of Maintenance should establish a trial ERMA program to study the accuracy and potential cost savings of using ERMA to identify pavement marking needs.

Report on Fly Ash as a Soil Additive, MLR-81-03, 1981

The addition of a selected self-cementing, Class C fly ash to blow sand soils improves their compacted strength greatly as opposed to the minimal strength improvement when fly ash is mixed with loess soil. By varying the percentage of fly ash added, the resulting blow sand-fly ash mixture can function as a low strength stabilized material or as a higher strength sub-base. Low strength stabilized material can also be obtained by mixing loess soils with a selected Class C fly ash. The development of the higher strength values required for subbase materials is very dependent upon compaction delay time and moisture condition of the material. Results at this time indicate that, when compaction delays are involved, excess moisture in the material has the greatest positive effect in achieving minimum strengths. Other added retarding agents, such as borax and gypsum, have less effect.

A Review of the Frictional Classification of Iowa Aggregates, MLR-81-04, 1981

The Iowa D.O.T. has a classification system designed to rate coarse aggregates as to their skid resistant characteristics. Aggregates have been classified into five functional types, with a Type 1 being the most skid resistant. A complete description of the classification system can be found in the Office of Materials Instructional Memorandum T-203. Due to the variability of ledges within any given quarry the classification of individual ledges becomes necessary. The type of aggregate is then specified for each asphaltic concrete surface course. As various aggregates become used in a.c. paving, there is a continuing process of evaluating the frictional properties of the pavement surface. It is primarily through an effort of this sort that information on aggregate sources and individual ledges becomes more refined. This study is being conducted to provide that needed up-to-date information that can be used to monitor the aggregate classification system.

Performance Evaluation of Concrete Pavement Granular Subbase - Pavement Surface Condition Evaluation, TR-554, 2008

This research project covered a wide range of activities that allowed researchers to understand the relationship between stability, pavement distress, and recycled portland cement concrete (RPCC) subbase aggregate materials. Detailed laboratory and field tests, including pavement distress surveys, were conducted at 26 sites in Iowa. Findings show that specific gravities of RPCC are lower than those of crushed limestone. RPCC aggregate material varies from poorly or well-graded sand to gravel. A modified Micro-Deval test procedure showed that abrasion losses of virgin aggregate materials were within the maximum Micro-Deval abrasion loss of 30% recommended by ASTM D6028-06. Micro-Deval abrasion loss of RPCC aggregate materials, however, was much higher than that of virgin materials and exceeded 30% loss. Modulus of elasticity of RPCC subbase materials is high but variable. RPCC subbase layers normally have low permeability. The pavement surfaces for both virgin and RPCC subbase across Iowa were evaluated to fulfill the objectives of this study related to field evaluation. Visual distress surveys were conducted to gather the detailed current pavement condition information including the type, extent, and severity of the pavement distresses. The historical pavement condition information for the surveyed field sections was extracted from the Iowa DOT's Pavement Management Information System (PMIS). The current surface condition of existing field pavements with RPCC subbase was compared with the virgin aggregate subbase sections using two different approaches. The changes in pavement condition indices (PCI and IRI) with time for both types of pavements (subbases) were compared.