backing concrete的用法和樣例：
例句
- But construction cracks in massive concrete frequently occur, which leads to lower ray-shielding efficiency.
但大體積混凝土施工中常會(huì )產(chǎn)生施工裂縫，以致降低了它防放射作用的效果。 - It is a difficulty to guarantee the high quality for bulk concrete construction in the high temperature weather.
在高溫天氣如何保證要求高的大體積混凝土的施工質(zhì)量是一個(gè)難題。
