通常拌制混凝土是将水泥、砂、石子与水一次投入搅拌机,同时搅拌。这种搅拌方法的缺点是:水泥颗粒易聚成团块,不能充分水化,各组分材料之间易形成大量气泡,残存于混凝土中,影响混凝土的质量。混凝土分次投料搅拌是将水泥、砂、石子和水分次投入搅拌机,先将骨料与部分水拌和,使骨料表面达到湿润饱和,再投入水泥搅拌,使骨料表面粘附一层较小水灰比的水泥外壳,这种状态叫“造壳作用”。然后加入剩余水搅拌,使骨料周围的水泥皮壳与水充分混合糊化。经过 Concrete is usually mixed with concrete, sand, gravel and water into the mixer, while stirring. Disadvantages of this mixing method are: cement particles easily aggregated into clumps, can not be fully hydrated, the formation of a large number of bubbles between the various components of the material, remaining in the concrete, affecting the quality of concrete. Concrete grading feed mixing is the cement, sand, gravel and water into the mixer times, the first aggregate and part of the water mixing, so that the aggregate surface moist and saturated, and then put into cement mixing, the aggregate surface of a small layer of adhesion Water cement ratio cement shell, this state is called “shell effect.” Then add the remaining water, stirring, so that the cement around the aggregate skin and water mixed thoroughly gelatinized. after