Assessment criteria for binding characteristics of foundry bentonites

The paper presents laboratory test results for an assessment of the binding characteristics of two grades of calcium bentonite compounds for casting moulds. The bentonite compounds were chemically modified with sodium carbonate at several different percentage ratios of the modifier. Samples were selected as the specimens and assessed for certain physical and chemical characteristics, including compressive strength, swelling factor, and montmorillonite content. The test results allowed the so-called bentonite activation curves to be plotted. Some of the specimens had their physical and chemical characteristics tested at high temperatures. The entirety of the laboratory tests of bentonite activation and heat resistance enabled an optimised selection of the sodium carbonate percentage fraction for a bentonite compound modification which would produce the best binding properties of foundry bentonite.

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