Concrete Pumps in Precast Plants - Current Scenario, Opportunities and Prospects

Bernd Maerkert, Head of Precast Concrete Applications, Putzmeister Concrete Pumps GmbH, Germany

In a conventional construction site setting, the efficiency of concrete pumps that are used as flexible equipment to convey most diverse types of concrete is undisputed. At precast plants, however, such pumps continue to be considered rather an exception to the rule despite several decades of technical innovation in the precast industry. This is due to the approach taken by the precast industry itself but also a result of the concrete pump manufacturers’ neglect of this market. Manufacturers were hesitant in taking the step towards concrete pumping processes that form an integral part of production.

The recent past has shown that concrete pumps are indeed an attractive option for precast operations. On the technical side, the trend towards more flowable concrete mixes should be mentioned as a key milestone in this direction although concrete need not be flowable to be pumped. In addition, the rationale behind the introduction of integrated systems based on concrete pumps is mostly of an economic or production-specific nature: High labor costs and a decline in prices seen especially in conventional precast prompt many businesses to seek more flexible solutions based on complete systems that require fewer people, which is where concrete pumps do open up opportunities for optimization.

Photo 1. Stationary pump design with mechanical distributor shown here for the production of manhole elements

From a production point of view, too, solutions based on concrete pumps provide particularly interesting options: For instance, complex moulds can easily be filled from the bottom whilst ensuring premium surface quality. Pumps also provide a continuous concrete flow that can be utilized to increase production output to many times the previous level and to achieve a better, more effective mixing of the individual concrete batches (i. e. the mix becomes more homogeneous). Unlike the conventional mould filling process using buckets operated by a crane, this approach frees up crane capacity and enables simultaneous efficient workflows.

Reference projects have demonstrated that it is possible, and useful for precast plants to integrate concrete pumping systems in the production line regardless of the concrete volume to be processed per day and of the product range manufactured (walls, pipes, manholes, custom-made elements etc.).These examples show that comprehensive, pump-based solutions can be useful for small businesses with a daily concrete flow of approx. 20m³ (picture 1) but also for large producers with a daily flow of several hundred cubic metres (picture 2). Among other factors, such as conveying distance and planned flow rate, the implementation of an entire system based on concrete pumps is heavily dependent on the type and quality of the concrete. If the concrete can be pumped (for this purpose, consider, among other relevant parameters, its grading curve, maximum aggregate size, powder ratio, additives/admixtures, w/c ratio), the choice of an appropriate pump type is of crucial importance to the entire production process. Rotor pumps (picture 3) are characterized by their low-noise operation, accurate batching capability and short to medium conveying distances whereas piston pumps are particularly well-suited to conveying larger volumes over longer distances and at higher pressures. The great variety of available pump types and specifications results in a wide range of system component options that come at most diverse cost levels and are suitable for various fields of application. Precast businesses that are determined to retain their competitive edge in the future will be required to use efficient and flexible concrete conveying and mould filling systems. Since integrated concrete pump systems are one of the options fulfilling these requirements- as demonstrated in reference projects - whilst also opening up additional options for production, we should assume that the growing appreciation of concrete pump systems in the precast industry will result in an increasingly broader use and acceptance of these systems.