Question

Which of the following cannot be used repeatedly for making moulds?

(a) Sillimanite

(b) Dolomite

(c) Natural Sand

(d) Silica Sand

I have been asked this question in an internship interview.

My doubt stems from Types of Binders in the Moulding Sand, Types of Base Sand topic in chapter Casting Processes of Foundry and Forging

Answer 1

The correct option is (c) Natural Sand

The explanation is: The Natural Sands are to be used for making moulds as soon as it is received from the source. The content of the binding particles is less which makes it unsuitable for the making of moulds which are needed repeatedly.