Effect of Waterproofing Admixture Ipanex on Concrete Durability (includes Addendum), MLR-98-2, 1999

The concrete admixture Ipanex (Registered trademark) manufactured by IPA Systems Inc. was submitted to the Iowa Department of Transportation (Iowa DOT) New Products Committee on April 15, 1998. The New Products Committee requested that the Iowa DOT Materials Laboratory evaluate the durability, corrosion inhibiting and concrete permeability reduction effects of this admixture. This report is intended to present the results of testing in Iowa DOT materials laboratories, review a Pennsylvania State University report, as well as review the IPA Systems Inc. marketing literature. The objective is to provide the New Products Committee with a recommendation concerning approval of this product based on the information gathered. The portland cement concrete admixture Ipanex (Registered trademark) did not show any significant benefit in terms of improvement in areas of permeability, chloride resistance and strength in the testing performed at the Iowa DOT. The literature and reports reviewed did not provide enough credible evidence to refute this conclusion. Additionally, the benefits ascribed to this product can be more economically achieved using other currently available products such as slag and silica fume. The recommendation is that this product not be approved for use on State projects in Iowa.

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.

Evaluation of Dense Bridge Floor Concrete Using High Range Water Reducer, May 1983

The objectives of this research project are: (1) To determine the feasibility of proportioning, mixing, placing and finishing a dense portland cement concrete in a bridge floor using conventional mixing, placing and finishing equipment. (2) To determine the economics, longevity, maintenance performance and protective qualities of a dense portland cement concrete bridge floor when using a high rangewater reducing admixture. The purpose of a high range water reducing admixture is to produce a dense, high quality concrete at a low water-cement ratio witj adequate workability. A low water-cement ratio contributes greatly to increased strength. The normal 7 day strength of untreated concrete would be expected i n 3 days using a superplasticizer. A dense concrete also has the desirable properties of excellent durability and reduced permeability. It is felt that a higher quality, denser, higher strength portland cement concrete can be produced and placed, using conventional equipment, by the addition of a high range water reducing admixture. Such a dense concrete, w i t h a water/cement ratio of approximately 0.30 to 0.35, would be expected to be much less permeable and thus retard the intrusion of chloride. With care and attention given to obtaining the design cover over steel (2% inches clear), it i s hoped that protection for the design life of the structure will be obtained. Evaluation of this experimental concrete bridge floor included chloride content and delamination testing of the concrete floor five years after construction. A comparitive evaluation o f a control section o f concrete without the water reducing admixture was conducted. Other items o f comparison include workability during construction, strength, density, water-cement ratio and chloride penetration.

Concrete Pavement Mixture Design and Analysis (MDA): Assessment of Air Void System Requirements for Durable Concrete, TPF-5(205), 2012

Concrete will suffer frost damage when saturated and subjected to freezing temperatures. Frost-durable concrete can be produced if a specialized surfactant, also known as an air-entraining admixture (AEA), is added during mixing to stabilize microscopic air voids. Small and well-dispersed air voids are critical to produce frost-resistant concrete. Work completed by Klieger in 1952 found the minimum volume of air required to consistently ensure frost durability in a concrete mixture subjected to rapid freezing and thawing cycles. He suggested that frost durability was provided if 18 percent air was created in the paste. This is the basis of current practice despite the tests being conducted on materials that are no longer available using tests that are different from those in use today. Based on the data presented, it was found that a minimum air content of 3.5 percent in the concrete and 11.0 percent in the paste should yield concrete durable in the ASTM C 666 with modern AEAs and low or no lignosulfonate water reducers (WRs). Limited data suggests that mixtures with a higher dosage of lignosulfonate will need about 1 percent more air in the concrete or 3 percent more air in the paste for the materials and procedures used. A spacing factor of 0.008 in. was still found to be necessary to provide frost durability for the mixtures investigated.

Characterization of Fly Ash for Use in Concrete, HR-225, 1983

Recent construction of new generation power plants burning western coal within Iowa has resulted in fly Ash production on the order of 760,000 tons annually. Although fly ash has long been accepted as a valuable replacement for portland cement in concrete, most experience has been with fly ash generated from eastern bituminous coals. A few years ago, fly ash in Iowa was not a significant factor because production was small and economics dictated disposal as the better alternative than construction use. Today, the economic climate, coupled with abundance of the material, makes constructive use in concrete feasible. The problem is, however, fly ash produced from new power plants is different than that for which information was available. It seems fly ash types have outgrown existing standards. The objective of this study was to develop fundamental information about fly ashes available to construction in Iowa such that its advantages and limitations as replacement to portland cement can be defined. Evaluative techniques used in this work involve sophisticated laboratory equipment, not readily available to potential fly ash users, so a second goal was preliminary development of rapid diagnostic tests founded on fundamental information. Lastly, Iowa Department of Transportation research indicated an interesting interdependency among coarse aggregate type, fly ash and concrete's resistance to freeze-thaw action. Thus a third charge of this research project was to verify and determine the cause for the phenomena. One objective of this project was to determine properties of Iowa fly ashes and evaluate their relevance to use of the material as an admixture of PCC. This phase of the research involved two approaches. The first involved the development of a rapid method for determining quantitative elemental composition while the second was aimed at both qualitative and quantitative determination of compounds. X-ray fluorescence techniques were adapted for rapid determination of elemental composition of fly ash. The analysis was performed using a Siemens SR-200 sequential x-ray spectrometer controlled by a PDP-11-03 microcomputer. The spectrometer was equipped with a ten sample specimen chamber and four interchangeable analyzing crystals. Unfiltered excitation radiation was generated using a chromium tube at 50 KV and 48 ma. Programs for the spectrometer were developed by the Siemens Corporation.

An Investigation of Concrete Setting Time, R-265 (MLR-75-4), 1975

A water reducing and retarding type admixture in concrete is commonly used on continuous bridge deck pours in Iowa. The concrete placed in the negative moment areas must remain plastic until all the dead load deflection due to the new deck's weight occurs. If the concrete does not remain plastic until the total deflection has occurred, structural cracks will develop in these areas. Retarding type admixtures will delay the setting time of concrete and prevent structural cracks if added in the proper amounts. In Section 2412.02 of the Standard Specifications, 1972, Iowa State Highway Commission, it states, "The admixture shall be used in amounts recommended by the manufacturer for conditions which prevail on the project and as approved by the engineer." The conditions which prevail on the project depend on temperature, humidity, wind conditions, etc. Each of these factors will affect the setting rate of the plastic concrete. The purpose of this project is to provide data that will be useful to field personnel concerning the retardation of concrete setting times, and how the of sets will vary with different addition rates and curing temperatures holding all other atmospheric variables constant.

Drying Shrinkage in P.C. Concrete, MLR-89-5, 1990

Crack formation has been a problem on some recently constructed bridges in Iowa. Drying shrinkage has been considered a contributing factor in that cracking. The study was undertaken to evaluate some of those material properties that contribute to the magnitude of drying shrinkage. Cement content, cement composition, fly ash and retarding admixture were the factors studied. Concrete prisms were cast for seven mixes and, after curing, were exposed to 100 deg F heat at ambient humidity for 280 days. The following were observed from the testing: (1) Higher C3A content cement concrete produced larger shrinkage; (2) Use of fly ash increased shrinkage; (3) Use of retarder increased shrinkage; and (4) Lowering the cement content reduced the shrinkage.

Evaluation of High-Slump Concrete for Bridge Deck Overlays, TR-427, 2005

The Iowa Method for bridge deck overlays has been very successful in Iowa since its adoption in the 1970s. This method involves removal of deteriorated portions of a bridge deck followed by placement of a layer of dense (Type O) Portland Cement Concrete (PCC). The challenge encountered with this type of bridge deck overlay is that the PCC must be mixed on-site, brought to the placement area and placed with specialized equipment. This adds considerably to the cost and limits contractor selection, because not all contractors have the capability or equipment required. If it is possible for a ready-mix supplier to manufacture and deliver a dense PCC to the grade, then any competent bridge deck contractor would be able to complete the job. However, Type O concrete mixes are very stiff and generally cannot be transported and placed with ready-mix type trucks. This is where a “super-plasticizer” comes in to use. Addition of this admixture provides a substantial increase in the workability of the concrete – to the extent that it can be delivered to the site and placed on the deck directly out of a ready-mix truck. The objective of this research was to determine the feasibility of placing a deck overly of this type on county bridges within the limits of county budgets and workforce/contractor availability.

Mix Design Development for Pervious Concrete in Cold Weather Climates

Portland cement pervious concrete (PCPC) is being used more frequently due to its benefits in reducing the quantity of runoff water,improving water quality, enhancing pavement skid resistance during storm events by rapid drainage of water, and reducing pavement noise. In the United States, PCPC typically has high porosity and low strength, which has resulted in the limited use of pervious concrete, especially in hard wet freeze environments (e.g., the Midwestern and Northeastern United States and other parts of the world).Improving the strength and freeze-thaw durability of pervious concrete will allow an increase in its use in these regions. The objective of this research is to develop a PCPC mix that not only has sufficient porosity for stormwater infiltration, but also desirable strength and freeze-thaw durability. In this research, concrete mixes were designed with various sizes and types of aggregates, binder contents, and admixture amounts. The engineering properties of the aggregates were evaluated. Additionally, the porosity, permeability, strength, and freeze-thaw durability of each of these mixes was measured. Results indicate that PCPC made with single-sized aggregate has high permeability but not adequate strength. Adding a small percent of sand to the mix improves its strength and freeze-thaw resistance, but lowers its permeability. Although adding sand and latex improved the strength of the mix when compared with single-sized mixes, the strength of mixes where only sand was added were higher. The freeze-thaw resistance of PCPC mixes with a small percentage of sand also showed 2% mass loss after 300 cycles of freeze-thaw. The preliminary results of the effects of compaction energy on PCPC properties show that compaction energy significantly affects the freeze-thaw durability of PCPC and, to a lesser extent, reduces compressive strength and split strength and increases permeability.