What Are Disadvantages of Concrete Pumps

Posted On: 17/12/2024 | Posted by: Haomei Concrete Pumps

In modern concrete construction, mini concrete pump is is widely used. Pumped concrete can achieve fast speed, high efficiency and shortened construction period. Does the small concrete pumps really have only advantages and no disadvantages?

Features and obvious defects of pumped concrete

Pumped concrete refers to the use of concrete pumps to transport and pour concrete mixtures along pipelines.It has developed with the advancement of modern construction technology. But it is by no means that modern construction is not possible without pumped concrete.

In fact, cracks in pumped concrete are common due to its own process characteristics and construction technology, which greatly affects the impermeability and durability of the structure.

Since the pumped concrete uses a large amount of cement, it has a high sand ratio, a difficult-to-control water-cement ratio, a small maximum particle size of gravel and a large need of pumping agent and admixture. If it is not well controlled, concrete cracks are extremely likely to occur.

Causes of cracks

The main cause of cracks in pumped concrete is: cement hydration is an exothermic chemical reaction process, during which a certain amount of hydration heat is generated. Each gram of cement releases 502J of heat. If calculated based on a cement dosage of 300-550kg/m3, each m3 of concrete will release 15500-27500KJ of heat, and most of the cement hydration heat is released within 3 days.

Concrete is a poor conductor of heat, especially large-volume concrete. The large amount of hydration heat generated is not easy to dissipate. The internal temperature continues to rise and , and the concrete surface dissipates heat quickly.

Temperature gradients are generated in the inner and outer sections of concrete, and pressure is generated by thermal expansion and deformation of the internal concrete, while tension is generated by cold shrinkage and deformation of the external concrete. Since the tensile strength of concrete is low at this time, when the tensile stress inside the concrete exceeds its tensile strength, cracks will appear in the concrete.

Economic benefits of construction

Pumped concrete, especially under high strength and high fluidity conditions, has a large amount of cement, large unit water consumption, high sand ratio and chemical admixtures, which causes concrete to dry and shrink, and has a high potential risk of cracks. Therefore, a lower slump should be selected according to construction requirements.

Under the conditions of meeting fluidity and pumpability, the unit water consumption should be reduced to below 170kg/m3, and the cement consumption should be reduced as much as possible under the conditions of meeting strength.

At the same time, a pumping agent with little effect on the drying shrinkage of concrete should be selected. If necessary, add an appropriate amount of expansion agent. Using secondary vibration during construction, strengthening plastering and wet curing are also essential technical measures.

In terms of economy, pumping concrete can save labor and speed up the construction progress, but pumping concrete also has its disadvantages, that is, the amount of cement used is relatively large, and the admixture accounts for a large proportion of the cost. In addition, the construction site and power conditions have high requirements, and the maintenance cost is not low, such as electricity (or diesel), various lubricants, and supporting pipelines. In addition, the one-time investment in isuzu concrete pump is large, and the equipment transfer fee and installation fee are not low.

Especially when pouring smaller units, processes such as ball pressing and pipe washing take longer than the main processes. In order to ensure that there is enough concrete in the warehouse, more concrete is generally delivered, which invisibly increases the pouring cost. But if you need, Haomei Machiney’s concrete pumps has a high cos performance.

Original source: https://www.concrete-pump-cn.com/a/what-are-disadvantages-of-concrete-pumps.html

Tags: small concrete pump,  

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