Building Materials
Asbestos

Contains iron oxide and alumina
Is composed of hydrous silicates of calcium and magnesium (CaSiO3, 3MgSiO3)
Is a natural fibrous mineral substance
All of these

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Building Materials
The basic purpose of a retarder in concrete is

To increase the initial setting time of cement paste in concrete
To improve the workability of concrete mix
To decrease the initial setting time of cement paste in concrete
To render the concrete more water tight

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