Power-Ultrasound as a tool for sustainable concrete production - first upscaling of laboratory experiments

点击翻译按钮获取中文摘要

DFG-funded basic research on "Impact of power ultrasound on the flow and solidification behavior of cement suspensions" showed that PUS has a great potential for the production of concrete The presentation of results at conferences and in journals encountered a great deal of interest from industry and research. Limiting must be said that all previous studies were performed on a laboratory scale. Up to date the ultrasonic processor available at the FIB /University of Weimar does not allow us to sonicate concrete mixes, i.e. so far only cement suspensions for preparing mortar formulations were sonicated. In order to provide sound information on the transferability of the results in the practice, trials at pilot scale and the transfer of technical tests in the precast and ready mix concrete production are missing (so called "upscale" - attempts). The proposed project will be carried out tests on a pilot scale. This means a high power ultrasound generator with a specially designed pump circuit is sought that allows to sonicate cement suspensions on bigger volumes, thus leading to an efficient and relevant way to produce concrete. From the sonicated cement suspensions concrete bars are casted and tested for workability, strength development, durability and deformation behavior. Comparing these results with those of the corresponding concretes mixed in a standard manner and by the known suspension technology enables us to evaluate advantages and maybe disadvantages on PUS on concrete characteristics. On this basis we will then decide whether PUS is a recommendable treatment for practice and if PUS should be applied to concrete in a technical test (i.e. in precasting plant and in ready mix concrete production).The first target in the proposed project is to optimize the PUS mixing parameters such as pressure in the pumping circuit, ultrasound power and amplitude to obtain a maximum acceleration of the concrete early strength. In the second section the properties of fresh concrete, the pore structure, the strength, the deformation behavior and the durability of concrete (by conventional mixing techniques, suspension and PUS-mixing method) are compared. In the third part of the investigations optimum sound regime (pump pressure and PUS - performance) as defined in the first part are used to increase the early strength of five standard concretes (at constant workability). The composition of the concrete is designed in such a way, that it can be evaluated whether PUS is capable to ensure constant concrete strength at reduced cement strength class (which allows saving of grinding energy). On the other hand, it will be considered whether PUS enables saving of Portland cement clinker by replacing it by fly ash, slag or limestone.