Scholarly record

STUDIES BASED ON CEMENT MORTAR COMPOSITES WITH BLAST FURNACE SLAG POWDER AND ULTRAFINE SILICA

Liliana Maria Nicula

Abstract

The purpose of this paper is to study some mix design on different mortar mixtures whose results aim at obtaining high mechanical strengths, especially for flexural strength, with low water absorption, to prevent material degradation due to the action of various environmental factors and also to ensure their durability. From the category of cement additions widely used in the current practice due to their pozzolanic and hydraulic activity in latent condition, we refer to silica fume (SF) which is a mineral addition from industry with a high content of silicon dioxide amorphous (over 85%), used in high-performance and ultra-high-performance concrete. Another cement admixture used in this mortar composition study is granulated and ground blast furnace slag (SP) as a fine powder with dimensions up to 63 ?m and with a lower amorphous dioxide silica content (below 36.50%), derived from the steel industry as a secondary by-product which presently shows the interest to be used in special concrete composition for road covering. From this point of view, two new mortar mixtures were designed by partial replacement of Portland cement CEM I 42,5R only with fine slag powder (20% SP), of local origin in the first mixture and partial replacement of cement Portland CEM I 42,5R both with fine powder from blast furnace slag (10% SP) and also with silica fume (10% SF) in the second mixture. The physical and mechanical characteristics of the two new blends were analysed in comparison to those of a mortar mix made from Portland CEM I 42,5R cement. For this experiment, the study on cement mortar samples was performed by laboratory and macroscopic tests, maintaining consistency, density, absorption, porosity, mechanical strength and freeze-thaw resistance and analysing the physical and mechanical characteristics which influence the behaviour of composite materials as cement mortars to aggression of the environment. The results show us that water absorption decreases in new mortar mixes made from fine powder of blast furnace slag (SP) and silica fume (SF), while bending tensile strength and freeze-thaw resistance increase relative to reference mortar. This experiments and studies will reduce the harmful environmental impact of cement production by reducing carbon dioxide (CO2) emissions, will contribute to lowering the costs of concret cement production, but will also contribute to the development of research into the use of materials based on cement with various mineral additions.

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