Fireclay bricks; refractory bricks containing chrome-corundum; refractory bricks containing zircon oxide; refractory bricks containing alumina and magnesia spinel; acid resisting bricks; pre-cast blocks, namely, bricks as building units; refractory components, namely, refractory bricks, refractory cement, refractory concrete, refractor blocks not of metal, and refractor construction materials not of metal, as building materials; insulating fire bricks