Tag Archives: Silica fume

EcoSmart Concrete in the Quebec Context: Mountain Equipment Co-op, Montreal

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The Mountain Equipment Co-op Montreal store is the Co-op s 8th retail store and the third -after the Ottawa and Winnipeg stores- to comply with Natural Resources Canada s C2000 Green Building Standard. It is the first C2000 compliant retail building in Quebec.

The decision to use EcoSmart concrete was based on the project s environmental objectives. The team initially hoped to use a 50% SCM concrete mix and was surprised to discover that the use of EcoSmart concrete in the MEC Montreal store would be a challenge both in terms of SCM percentage and in terms of cost. The cost premium for HVSCM -high volume supplementary cementing material- concrete in Quebec is related to the limited availability of SCMs in that province other than silica fume. Because most concrete plants do not have an extra silo for storing SCMs most SCM concrete in Quebec is made from preblended SCM cement based on an unvarying formula.

The goal of using a 50% mix was abandoned for budget reasons but MEC agreed to invest the extra money for the 27% mix. When the concrete bids were in the decision was made to use concrete made with Lafarge s Tercem 3000TM blended cement -a blend of 20-25% blast furnace slag 4-6% silica fume and 69-76% Portland cement- . The premium cost for this concrete was $20 / m3 which represents 11.3% of the total concrete cost.

Construction on the MEC store started in October 2002 and was completed in May 2003. The scheduling of the project suffered significant delays due to abnormally cold winter conditions. There was no perceived difference in curing time or workability. The quality of finishing was somewhat disappointing although this was mainly attributed to quality control of the finishing sub-trade rather than the concrete used.

Case Study Report Author: Studio MMA, Atelier d architecture

Current Situation of Supplementary Cementitious Materials (SCMs) in Canada

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The report details the current situation of supplementary cementing materials -SCMs- in Canada specifically in terms of production cost availability usage potential areas for increasing usage local barriers and relevant guidelines and specifications. The purpose of the study is to determine a strategy to increase the use of SCMs in Canada.

The data show that approximately 524 000 347 000 and 37 000 tonnes of fly ash Ground Granulated Blast Furnace Slag -GGBFS- and silica fume were used in cement and concrete applications in 2001. These amounts represent 11 90 and 185% of the quantity produced respectively. Thus fly ash appears to be the only material that is underused and that represents a potential for increased use of SCMs in Canada.

The investigation also shows that there are policy technical and economic barriers to the increased use of SCMs in Canada. The report suggests several solutions to overcome these barriers.

Includes an extensive list of tables.

Technical Report Author: Nabil Bouzoubaa, Benoit Fournier

Development of Ternary Blends for High-Performance Concrete

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The purpose of this study was to develop ternary blends with optimum amounts of fly ash and silica fume to be used in high-performance concrete. Two series of air-entrained concrete mixtures were investigated in the study: series 1 included concretes with a total cementitious materials content -CM- of 350 kg/m 3 and a water-to-cementitious materials ratio -W/CM- of 0.40 and series 2 included concretes with a total CM of 450 kg/m 3 and a W/CM of 0.34. In each series one silica fume and three fly ashes were used; these consisted of two ASTM Class F and one ASTM Class C fly ashes. Properties of the fresh and hardened concrete such as slump air content bleeding setting time autogenous temperature rise plastic shrinkage compressive strength drying shrinkage and the resistance to chloride-ion penetration were determined. The results show that the combined use of fly ash and silica fume in concrete are more advantageous in terms of the following parameters: the dosage of superplasticizer plastic shrinkage chloride-ion penetrability and the drying shrinkage. The report includes various tables and figures detailing the results of the study.

Technical Report Author: Nabil Bouzoubaa, Alain Bilodeau, Benoit Fournier, V. Sivasundaram, D.M. Golden, CANMET Energy Technology Centre, Natural Resources Canada,

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 Use of High Volume Fly Ash in Concrete

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This paper presents data from durability studies of concretes containing up to 60% fly ash; studies include carbonation chloride resistance permeability and strength. Data are also presented from a recent construction project in Toronto where high-volume fly ash concrete was used as part of a “Green Building Strategy”. Finally the paper presents recent data from studies using ternary blends of cement with high levels of fly ash -e.g. 56%- and small levels of silica fume -3 to 4%- . It is shown that the poor early-age performance that may be associated with high-volume fly ash can be offset by the inclusion of silica fume.

Technical Report Author: M.D.A. Thomas, D.S. Hopkins, Gurinder Girn, Robert Munro, Ernese Muhl