美国生产小型砌块按所使用的骨料大体上可分为两类。一类是用硬质岩石集料如河砂、砾石、破碎的花岗岩、玄武岩和石灰石等生产的称之为普通重骨料砌块;另一类使用浮石、炉渣、膨胀矿渣、陶粒和火山灰渣等轻骨料生产的称之为轻骨料砌块。而且后者在过去25年中所占的比例较大,约为美国全国小型砌块总产 The production of small blocks in the United States is generally divided into two categories based on the aggregates used. One is the use of hard rock aggregates such as river sand, gravel, broken granite, basalt and limestone, etc., which are called ordinary heavy aggregate blocks; the other uses pumice, slag, expanded slag, ceramsite and volcanic ash. Lightweight aggregates such as slag are called lightweight aggregate blocks. And the latter has accounted for a large proportion in the past 25 years, which is about the total production of small blocks in the United States.