Category Archives: SCM

Coal Ash: Its Origin, Disposal, Use and Potential Health Issues

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Millions of tons of coal ash are produced worldwide each year. EPRI and others have done extensive studies over many years of the nature of coal ash and its possible effects on the environment and human health. This Environmental Focus feature summarizes this information applicable regulations that govern the handling and use of coal ash and the benefits that can result from its use. EPRI concludes that the health risks from coal ash are minimal that the general public does not encounter coal ash in such proportions that it would present health risks and that radiation from fly ash and products made with fly ash is well below the Environmental Protection Agency s action standards. Further EPRI argues that use of fly ash as a recycled material can have economically and environmentally beneficial results.

Technical Report Author: Electric Power Research Institute (EPRI)

Self Compacting Concrete Incorporating High Volumes of Class F Fly Ash: Preliminary Results

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In recent years self-compacting concrete -SCC- has gained wide use for placement in congested reinforced concrete structures with difficult casting conditions. For such applications the fresh concrete must possess high fluidity and good cohesiveness. The use of fine materials such as fly ash can ensure the required concrete properties.

This paper presents the initial results of an experimental program aimed at producing and evaluating SCC made with high-volumes of fly ash. Nine SCC mixtures and one control concrete were investigated in this study. The content of the cementitious materials was maintained at 400 kg/m 3 while the water/cementitious material ratios ranged from 0.35 to 0.45. The self-compacting mixtures had a cement replacement of 40 50 and 60% by Class F fly ash. Tests were carried out on all mixtures to obtain the properties of fresh concrete in terms of viscosity and stability. The mechanical properties of hardened concretes such as compressive strength and drying shrinkage were also determined. The self-compacting concretes developed 28-day compressive strengths ranging from 26 to 48 MPa. The results show that an economical self-compacting concrete could be successfully developed by incorporating high-volumes of Class F fly ash. Includes tables and figures detailing the results.

This paper was originally published in Cement and Concrete Research Vol. 31 No. 3 Mar. 2001.

Technical Report Author: Nabil Bouzoubaa, M. Lachemi

Performance of Mortars Incorporating Finely-Ground Fly Ash

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This paper presents results on the compressive strength of mortars in which 10 and 20% of ASTM Type I cement has been replaced by ground fly ash from two different sources. The results are compared with those of the mortars made with ASTM Type I cement and with the mortar in which 10% of portland cement has been replaced by silica fume. The results show that the mortars made with 20% replacement of cement by the fine Sundance fly ash that had been ground for 2 hours achieved a 28-day compressive strength that was 90 to 93% of the strength of the mortars incorporating 10% silica fume as cement replacement. However for the coarse fly ash the results were not encouraging: even increasing the grinding times of the fly ash up to 10 hours did not yield the compressive strengths approaching that of the silica fume mortars. The report includes tables and figures that detail the results of the study.

Technical Report Author: Nabil Bouzoubaa, V.M. Malhotra, CANMET Energy Technology Centre, Natural Resources Canada,

The Potential Use of Natural Pozzolans in British Columbia as Supplementary Cementing Materials

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Based on a review of existing information the team examined the technical environmental and economic benefits and costs of using naturally pozzolanic materials from provincial deposits as compared with those associated with the use of fly ash from coal-fired thermal electrical power plants as a supplementary cementing material in British Columbia. Based on their findings the team concludes that there is no indication that the natural pozzolans from any of the identified sources in British Columbia have any apparent technical advantage relative to the fly ashes being imported into the province and used as portland cement replacement materials. Further in terms of the present supplementary cementing materials market in British Columbia there would be no environmental benefit derived from using a natural pozzolan instead of fly ash. Finally the delivered cost of a natural pozzolan suitable for use as a supplementary cementing material will be of the same order of magnitude but possibly higher than the price of fly ash in the Greater Vancouver Area market.

Consequently it is recommended that no further investigation of this issue be carried out by the EcoSmartâ„¢ Concrete Project until it can be demonstrated that there is a demand for portland cement replacement materials in the province that cannot be satisfied by the importation of fly ash form Washington State and/or Alberta at an acceptable cost.

Technical Report Author: Robert Gray, Ph.D., P.Eng., James Atwater, P.Eng., W. Dunbar, Ph.D., P.Eng., CMP Technologies Ltd.,