द्वितीय श्रेणी की ईंटों (2nd class bricks) की औसत संपीड़न सामर्थ्य (compressive strength) किससे कम नहीं होनी चाहिए?

Which of the following artificial stones is produced by moulding a mixture of iron slag and Portland cement?

Enamel paint is generally prepared by adding:

Dorry's testing machine is used for which test on building stones?