Advancements in Concrete Technology

In terms of advancements in concrete technology the driving forces have been durability and speed of construction. However the environmental impact of construction materials is becoming an increasingly important driver. In this paper Mehta evaluates concrete technologies using the criteria of construction speed durability and environmental impact. One of the technologies he examines is high volume fly ash and slag concrete particularly in terms of their use in structural concretes roller compacted concrete dams concrete pavement for highways and base courses and embankments.

Technical Report Author: P. K. Mehta

Current Situation of Supplementary Cementitious Materials (SCMs) in Canada

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

Concrete Incorporating Rice-Husk Ash: Compressive Strength and Chloride-Ion Penetrability

This report deals with the evaluation of the performance in concrete of an Indian sample of rice-husk that was burnt in an industrial furnace in Ontario and ground at the CANMET laboratories. This exploratory study was performed under contract with DCR Phoenix Development Corporation Ltd. Ottawa and is divided in two parts.

The first part deals with determining the optimum grinding time of the RHA in order to produce a highly-reactive product with a minimum energy of grinding. The performance of the RHA in concrete forms part II of the study. The results show that the rice-husk ash sample used in this study is principally composed of SiO2 -90.7 %- contains 4.7% loss on ignition and a relatively high K2O content of 2.2 %. The RHA ground for the optimum grinding time -140 seconds in a pulverizer with a capacity of 30 g- has a median particle size of ~ 8 µm a water requirement of ~ 104% and a pozzolanic activity index of ~ 100% in the mortar used for determining the pozzolanic activity of the RHA. The results also show that in general for similar W/CM -0.40- the replacement of 7.5 to 12.5% of the portland cement by the RHA did not affect significantly the compressive strength but improved significantly the resistance to the chloride-ion penetrability of the concrete with and without the entrained air.

Includes tables and figures detailing the study results.

Technical Report Author: Nabil Bouzoubaa, Benoit Fournier

Mechanical Properties and Durability of Concrete Made With High Volume Fly Ash Blended Cements Using a Coarse Fly Ash

This paper presents a study on the mechanical properties and durability of concrete made with a high-volume fly ash blended cement using a coarse fly ash that does not meet the fineness requirement of ASTM C 618. The results were compared with those of the HVFA concrete in which unground fly ash had been added at the concrete mixer. The properties of the fresh concrete determined included the slump air content slump loss stability of air content bleeding and setting time; those of the hardened concrete investigated included the compressive strength flexural- and splitting-tensile strengths Young’s modulus of elasticity drying shrinkage resistance to abrasion chloride-ion penetration freezing and thawing cycling and to de-icing salt scaling. The results show that except for the resistance of the concrete to the de-icing salt scaling the mechanical properties and the durability of concrete made with this blended cement were superior to the concrete in which the unground fly ash and the cement had been added separately at the mixer. The production of HVFA blended cements therefore offers an effective way for the utilization of coarse fly ashes that do not otherwise meet the fineness requirements of ASTM C 618.

This paper was originally published in Cement and Concrete Research Vol. 31 No. 3 Oct. 2001. It includes a list of tables and figures detailing the results of the studies.

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

Development of Ternary Blends for High-Performance Concrete

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,