Bruce W. Ramme

MECHANICAL PROPERTIES AND DURABILITY OF CONCRETE MADE WITH BLENDED FLY ASH

This study focused on evaluating the effects of blended fly ash on mechanical properties and durability of concrete. In this investigation two reference mixtures were used. One was a mixture without fly ash, and the other contained 35% ASTM Class C fly ash. Additional mixtures were composed of three blends of ASTM Class C and Class F fly ash while maintaining a total fly ash content of 40% of the total cementitious materials. Mechanical properties such as compressive strength, tensile strength, flexural strength, and modulus of elasticity were determined. Durability related properties determined were drying shrinkage, abrasion resistance, salt scaling resistance, and electrical prediction of chloride ion penetration. The results showed that blending of Class C fly ash with Class F fly ash showed either comparable or better results than either the reference mixture without fly ash or the unblended Class C fly ash. Blending of fly ash, therefore, leads to comparable or better quality and reduced cost, attributed to the use of Class F versus Class C fly ash in concrete.

HIGH-STRENGTH CONCRETE CONTAINING LARGE QUANTITIES OF FLY ASH

The paper presents research performed to indentify and recommend mix designs for high fly ash content 3000 and 4000 psi (21 and 28 MPa) structural grade concrete utilizing Class C fly ash. The fly ash was produced at Wisconsin Electric Power Plant.

PRECAST CONCRETE PRODUCTS USING INDUSTRIAL BY-PRODUCTS

This work aimed to help establish the use of high volumes of fly ash, bottom ash, and used foundry sand in manufacture of precast molded concrete products such as wet-cast concrete bricks and paving stones. ASTM Class F fly ash was used as a partial replacement for 0 (reference), 25, and 35% of portland cement. Bottom ash combined with used foundry sand replaced 0, 50, and 70% of natural sand. Tests for compressive strength, freeze-thaw resistance, drying shrinkage, and abrasion resistance were conducted on the wet-cast concrete masonry units manufactured at a commercial manufacturing plant. It was concluded that all wet-cast bricks could be used for both exterior and interior walls in regions where freezing and thawing is not a concern, and for interior walls in regions where freezing and thawing is a concern. No wet-cast paving-stone mixtures, including the reference mixture, met all ASTM requirements for paving stones.

Long-Term Performance of High-Volume Fly Ash Concrete Pavements

This investigation was undertaken to evaluate the long-term performance of concrete pavements made with high volumes of Class F and Class C fly ash (FA). Six different mixtures, three mixtures with Class C fly ash up to 70% cement replacement and three mixtures with Class F fly ash up to 60% cement replacement, were used. Long-term performance tests were conducted for compressive strength, resistance to chloride-ion penetration, and density using specimens from in-situ pavements. Long-term results showed greater pozzolanic strength contribution of Class F fly ash relative to Class C fly ash. Generally, based upon long-term data, mixtures containing Class F fly ash exhibited higher resistance to chloride-ion penetration relative to mixtures containing Class C fly ash. Compressive strengths of core specimens taken from in-situ pavements ranged from 45 to 57 MPa (6,600 to 8,300 psi) at seven to 14 years of age. The highest long-term compressive strength (57 MPa, 8,300 psi) was achieved for the high-volume fly ash mixture incorporating 67% Class F fly ash at the age of 7 years. Visual observations (in 2000) revealed that the pavement sections containing high volumes of Class F fly ash (40 to 67% FA) performed well in the field with only minor surface scaling. All other pavement sections have experienced very little surface damage due to the scaling.

EFFECTS OF HIGH-LIME FLY ASH CONTENT ON WATER DEMAND, TIME OF SET, AND COMPRESSIVE STRENGTH OF CONCRETE

The paper presents research performed to report the effect of high-lime (Class C) fly ash on water demand, workability, time of set, and compressive strength of concrete. Tests were carried out on nominal 3000, 4000, and 5000 psi structure grade concrete utilizing fly ash produced at Wisconsin Electric Power Companys Pleasant Prairie Power Plant. Fly ash replacement improved workability, decreased water demand, and increased strength. The initial and final set times were not significantly different when fly ash replacement for cement was increased up to levels of 5 %.

Use of High Volumes of Class C and Class F Fly Ash in Concrete

This paper reports the results of research performed in the development and use of high volumes of Class C and Class F fly ash in concrete mixes for roadway paving projects. Mix proportions were developed for paving roadway concrete with 20 and 50% Class C fly ash and 40% Class F fly ash replacements for Portland cement. These mixes were used to demonstrate their potential for highway paving work. Actual application test results are presented including fresh concrete data, compressive strength, flexural strength, tensile strength, and freezing and thawing durability data. The test results indicate that high volumes of Class C and Class F fly ash can be used to produce high-quality pavements in concrete with excellent performance.

DETERMINATION OF THE WATER CONTENT OF CONCRETE BY THE MICROWAVE METHOD

Abstract This paper presents a rapid (15 minutes or less) method for determining the water content of fresh concrete by using a microwave oven. By combining this information with the cement content used, the water to cement ratio can be obtained. The microwave overn was also used successfully to determine natural moisture content, percent absorbtion (S.S.D.) and bulk specific gravity values of aggregates in a short period of time.

Design and Testing Controlled Low-Strength Materials (CLSM) Using Clean Coal Ash

The major objective of this project was to develop mixture proportions for controlled low-strength material (CLSM) using clean coal ash obtained from atmospheric fluidized bed combustion (AFBC). A clean coal ash is defined as the ash derived from SO{sub x} and NO{sub x} control technologies. The specific ashes used for this project were: (1) circulating fluidized bed boiler fly ash and bottom ash and (2) stoker-type boiler fly ash and bottom ash. These two coal ash samples were characterized for physical and chemical properties. Chemical properties and water leaching tests were also performed on the hardened CLSM. Many initial CLSM mixtures were developed by blending the two types of ash. Tests conducted on the final three selected CLSM mixtures included compressive strength, bleeding, setting and hardening, settlement, length change of hardened CLSM, permeability, mineralogy, and chemical water leach testing. Results show that acceptable CLSM material can be developed by blending the fluidized bed boiler ash with the stoker boiler ash. Recommendations for a pilot scale manufacturing application of the three CLSM mixtures were made based upon the lab test results.

Low cement content high strength concrete

The fundamental objective of this research project was to develop mix design information for structural grade concrete using high fly ash content. The fly ash used in this project was produced by Wisconsin Electric Power Company (WEPCO), in Pleasant Prairie, Wisconsin. The WEPCO fly ash in Class C fly ash in accordance with the ASTM C618 designation. The concrete mix designs developed were consistent with good quality concrete production and good quality concrete construction needs.

A pilot study of mercury liberation and capture from coal-fired power plant fly ash

Abstract The coal-fired electric utility generation industry has been identified as the largest anthropogenic source of mercury (Hg) emissions in the United States. One of the promising techniques for Hg removal from flue gas is activated carbon injection (ACI). The aim of this project was to liberate Hg bound to fly ash and activated carbon after ACI and provide high-quality coal combustion products for use in construction materials. Both bench- and pilot-scale tests were conducted to liberate Hg using a thermal desorption process. The results indicated that up to 90% of the Hg could be liberated from the fly ash or fly-ash-and-activated-carbon mixture using a pilot-scale apparatus (air slide) at 538 °C with a very short retention time (less than 1 min). Scanning electron microscope (SEM) evaluation indicated no signifi-cant change in fly ash carbon particle morphology following the thermal treatment. Fly ash particles collected in the baghouse of the pilot-scale apparatus were smaller in size than those collected at the exit of the air slide. A similar trend was observed in carbon particles separated from the fly ash using froth flotation. The results of this study suggest a means for power plants to reduce the level of Hg in coal-combustion products and potentially recycle activated carbon while maintaining the resale value of fly ash. This technology is in the process of being patented.