A few days ago, a customer called us to inquire. The concrete sent to the construction site by their mixing plant was returned. I don't know how to deal with it. First of all, none of us wants such a thing to happen, but in case of such a thing, how should our concrete mixing plant deal with it? I believe this is a headache for many mixing plants.
今天我们就这个混凝土被退回的事情专门 说一下办法。
Today, let's talk about the solution to the return of concrete.
我们应该积极地处理被退回的混凝土，以达到科学合理地利用退回混凝土，减少废料，增加效益。退回站内的混凝土，均应考虑降低等级使用。 在无法降低等级使用时，应根据情况分清原因，判断混凝土的性能，然后进行合理的处理。
First of all, we should actively deal with the returned concrete, so as to make scientific and rational use of the returned concrete, reduce waste and increase benefits. For the concrete returned to the station, the grade shall be reduced first. When the grade cannot be reduced, the reason shall be distinguished according to the situation, the performance of concrete shall be judged, and then reasonable treatment shall be carried out.
因混凝土出站前未经检查或检查不严、判断失误等原因，致使不合格的混凝土发往工地，造成施工方拒收。退回后，应分以下两种情况处理：
The unqualified concrete is sent to the construction site and rejected by the construction party due to the reasons such as the concrete is not inspected before leaving the station, lax inspection, wrong judgment and so on. After returning, it shall be handled in the following two cases:
1、坍落度过大（或离析），应根据实际情况增加同配比的干料或稠砂浆，快速搅拌不少于90s，经检查无干料块，坍落度符合设计要求，且实际水胶比不大于理论 水胶比方可出站。如果处理后坍落度小于出站要求，应加入适量外加剂调整到满足施工要求的坍落度方可出站。
1. If the slump is too large (or segregation), the dry material or thick mortar with the same proportion shall be added according to the actual situation, and the rapid mixing shall not be less than 90s. After inspection, there is no dry material block, the slump meets the design requirements, and the actual water binder ratio is not greater than the theoretical water binder ratio, so it can leave the station. If the slump after treatment is less than the outbound requirements, an appropriate amount of admixture shall be added to adjust the slump to meet the construction requirements before outbound.
2、坍落度过小，应适当增加水泥，然后加外加剂，并强制搅拌，直到坍落度达到出站要求为止。但应注意，外加剂的掺量不得超过掺量的*大值。
2. If the slump is too small, the cement shall be added appropriately, then the admixture shall be added, and forced mixing shall be carried out until the slump meets the requirements of the station. However, it should be noted that the dosage of admixture shall not exceed the * maximum value of the recommended dosage.
因运输、泵送、浇筑等各种原因造成的退回混凝土，由罐车司机过磅，质检员根据罐车司机提供的过磅单及该罐车的皮重计算剩余方量，然后根据同等级或 降低等级使用，分别采用以下处理方法：
For the returned concrete caused by transportation, pumping, pouring and other reasons, the tank truck driver shall weigh it first, and the quality inspector shall calculate the residual volume according to the weighing sheet provided by the tank truck driver and the tare weight of the tank truck, and then use it according to the same grade or lower grade, and adopt the following treatment methods respectively:
1、同等级使用，延误时间在2h以内，处理后应保证水泥用量比原配合比提高10～15kg/m3，外加剂提高0.1%～0.3%。或直接降低一个强度等级，适当增加外加剂掺量 进行调整。延误时间在2～4h，处理后应保证水泥用量比原配合比提高20～40kg/m3，外加剂提高0.4%～0.6%。或直接降低两个强度等级，适当增加外加剂掺量进行调整。
1. For the same grade of use, the delay time is within 2H. After treatment, the cement dosage shall be increased by 10 ~ 15kg / m3 compared with the original mix proportion, and the admixture shall be increased by 0.1% ~ 0.3%. Or directly reduce one strength grade and appropriately increase the amount of admixture for adjustment. The delay time is 2 ~ 4H. After treatment, the cement dosage shall be increased by 20 ~ 40kg / m3 compared with the original mix proportion, and the admixture shall be increased by 0.4% ~ 0.6%. Or directly reduce two strength grades and appropriately increase the amount of admixture for adjustment.
2、降低等级使用，必须以降低等级后的混凝土与原等级混凝土所用原材料完全相同为基础，且仅适用于C40及C40以下的混凝土的处理。
2. The use of reduced grade must be based on the fact that the raw materials of the reduced grade concrete and the original grade concrete are exactly the same, and it is only applicable to the treatment of C40 and below.
3、延误时间超过4h，应报废或用作非承重低等级混凝土使用。
3. If the delay time exceeds 4h, it shall be scrapped or used as non load-bearing low-grade concrete.
4、若坍落度低于设计要求30～50mm，可按运输单上的方量，每方添加0.5kg泵送剂。把接料斗部位的泵送剂冲入罐内，开动罐体快速旋转3min，上车观察混凝土拌合物 是否合适，若符合要求，即可使用。混凝土在卸料槽中不流淌时，应先估计罐内混凝土方量，然后按每方加1kg计算加入泵送剂数量，加泵送剂后按上述方法要求的加水、 快转、观察等步骤操作。
4. If the slump is less than 30.5kg per cubic meter, it can be pumped according to the design requirement. Flush the pumping agent at the receiving hopper into the tank, start the tank to rotate quickly for 3min, get on the vehicle and observe whether the concrete mixture is suitable. If it meets the requirements, it can be used. When the concrete does not flow in the discharge tank, the concrete volume in the tank shall be estimated first, and then the amount of pumping agent added shall be calculated by adding 1kg per square. After adding pumping agent, the operation shall be carried out according to the steps of water addition, fast rotation, observation and so on required by the above method.
在初凝时间内的混凝土，由于气温较高、运距较远、压车时间较长等造成混凝土坍落度损失较大，可通过试验添加同型号的泵送剂或减水剂， 但添加与原先已加的总和掺量不能超过外加剂*大掺量的20%。应逐渐添加，先少加，掺入后，搅拌运输车必须快速转动2min左右，测定坍落度是否符合要求。 对超过初凝时间的混凝土应废弃，不能再使用。混凝土浇筑前停滞的时间越长，混凝土强度损失越严重，应当引起足够重视。
For the concrete within the initial setting time, due to the high temperature, long transportation distance and long rolling time, the concrete slump loss is large. The pumping agent or water reducing agent of the same model can be added through the test, but the total amount of added and previously added shall not exceed 20% of the large amount of admixture. It shall be added gradually and less at first. After mixing, the mixer truck must rotate quickly for about 2min to determine whether the slump meets the requirements. The concrete exceeding the initial setting time shall be discarded and cannot be used again. The longer the stagnation time before concrete pouring, the more serious the loss of concrete strength, which should be paid enough attention.
莱州聚峰机械http://www.zkzdsljbc.com有限公司是一家专门生产混凝土搅拌站设备，混凝土搅拌车设备，以及混凝土搅拌站所需的各种配套设备的厂家，产品研发经验丰富，设备性能 优良，使用寿命长久，业界口碑良好，案例遍布各地。如果您有设备需要，请及时拨打网站热线，联系我们！
Laizhou Jufeng Machinery Co., Ltd http://www.zkzdsljbc.com Ltd. is a manufacturer specializing in the production of concrete mixing plant equipment, concrete mixing truck equipment and various supporting equipment required by concrete mixing plant. It has rich product R & D experience, excellent equipment performance, long service life, good reputation in the industry and cases all over the world. If you need equipment, please call the website hotline in time and contact us!
