这里所提及的混凝土建筑砖石,主要是指用波特兰水泥混凝土生产的混凝土砌块和混凝土砖,它自1897年问世以来,已在美国广泛应用。今天由于它具有经济、实用、耐久、防火及一定的强度等优点,故在美国建材市场上仍保持较好的地位,得到广泛的应用,近十二年来每年平均产量均超过33亿块。(见 The concrete building bricks mentioned here mainly refer to concrete blocks and concrete bricks produced from Portland cement concrete. Since its inception in 1897, it has been widely used in the United States. Today, due to its advantages of economy, practicality, durability, fire prevention, and certain strength, it still maintains a good position in the US building materials market and is widely used. In the past 12 years, the average annual output has exceeded 3.3 billion. (see