poor concrete

例句：

1. 1. The construction of the new bridge was made with poor concrete.
   新桥的建设使用了劣质混凝土。
2. 2. The builders used poor concrete to save costs.
   建筑工人使用劣质混凝土以降低成本。
3. 3. The poor concrete in the foundation cracked under the weight of the building.
   地基中的劣质混凝土在建筑物的重量下开裂了。