Concrete mixer commonly used raw materials include sand, cement, water, etc., they are put in different order, the production of concrete performance is also different. So what are the common concrete mixer feeding sequence?

一次投料法

One time feeding method

一次投料法是目前常见的方法，即将砂、石、水泥和水混合在一起加入搅拌筒中同时进行搅拌。混凝土搅拌机加料过程中为了减少水泥的飞扬和水泥的粘罐现象，先倒砂子（或石子）再倒水泥，然后再倒入石子（或砂子），也就是说将水泥加在砂、石之间，混凝土搅拌机由上料斗将干物料送入搅拌筒内，加水搅拌。

One time feeding method is a common method at present, that is, sand, stone, cement and water are mixed together and added into the mixing drum for mixing at the same time. In order to reduce the flying of cement and the sticking of cement in the process of concrete mixer feeding, first pour sand (or stone) and then pour cement, and then pour stone (or sand), that is to say, add cement between sand and stone, and the concrete mixer will send dry materials into the mixing drum from the upper hopper, and then add water for mixing.

二次投料法

Secondary feeding method

二次投料法又分为预拌水泥砂浆法和预拌水泥净浆法。预拌水泥砂浆法是先将水泥、砂和水加入搅拌筒内进行充分搅拌，成为均匀的水泥砂浆后，再加入石子搅拌成均匀的混凝土。国内一般是用强制式搅拌机拌制水泥砂浆约1-1.5min，然后再加入石子搅拌约1-1.5min。

The second feeding method is divided into premixed cement mortar method and premixed cement paste method. Premixed cement mortar method is to first add cement, sand and water into the mixing cylinder for full mixing to form uniform cement mortar, and then add stones to mix into uniform concrete. In China, cement mortar is generally mixed with a forced mixer for about 1-1.5min, and then stones are added for about 1-1.5min.

预拌水泥净浆法是先将水泥和水充分搅拌成均匀的水泥净浆后，再加入砂和石子搅拌成混凝土。国内外的试验表明，二次投料法搅拌的混凝土与一次投料法相比较，混凝土的强度可提高15%,在强度相同的情况下，可节约水泥15%-20%。

Premixed cement paste method is to fully mix cement and water into a uniform cement paste, and then add sand and stones to mix into concrete. The tests at home and abroad show that the strength of concrete mixed by twice feeding method can be increased by 15% compared with that by once feeding method, and the cement can be saved by 15% - 20% under the same strength.

水泥裹砂法

Cement sand wrapping method

水泥裹砂法又称SEC法，采用这种方法拌制的混凝土称为SEC混凝土或造壳混凝土。该法的搅拌程序是先加一定量的水使砂表面的含水量调到某一规定的数值后（一般为15%~25%），再加入石子并与湿砂拌匀，然后将全部水泥投入与砂石共同拌合使水泥在砂石表面形成一层低水灰比的水泥浆壳，将剩余的水和外加剂加入搅拌成混凝土。采用SEC法制备的混凝土与一次投料法相比较，强度可提高20%-30%，混凝土不易产生离析和泌水现象，工作性好。

The concrete mixed by this method is called sec concrete or shell concrete. The mixing procedure of this method is to add a certain amount of water to adjust the water content of sand surface to a specified value (generally 15% ~ 25%), then add stones and mix them with wet sand, and then put all the cement into mixing with sand and stone to form a cement slurry shell with low water cement ratio on the surface of sand and stone, and add the remaining water and additives to mix concrete. Compared with the one-time feeding method, the strength of concrete prepared by SEC method can be increased by 20% - 30%. The concrete is not easy to produce segregation and bleeding, and has good workability.