But owing to its coarser grain, denser structure, smoother surface, higher hardness and melt point, so its proportioning rate was limited.

• 但海砂的粒度比较粗,颗粒形状比较规则、结构比较致密、表面比较光滑、硬度和熔点都比较高,使它的用量受到一定限制。