Trade Journals for the Concrete Industry

In precast concrete production the most important requirement is a fast early strength development with adequate workability of fresh concrete. To facilitate sufficient early strength development appropriate concrete mixtures and procedures are applied, i.e. low water to cement ratios, high cement content and heat treatment are essential. In some cases the addition of superplasticizers is necessary to ensure good workability. The disadvantage of highly efficient superplasticizers is the induced delay in the hydration progress and early strength development. Appropriate strength development can be achieved by adding accelerating admixtures and/or heat treatment. Unfortunately both methods may induce durability risks (corrosion effects, delayed ettringite formation), if they are not properly applied. Furthermore, heating of formworks disagrees with recent economic and ecologic requirements. The present study discusses the capability and challenges of power ultrasound application in concrete production. The main aim is to accelerate early strength development of cementitious materials by applying 20 kHz power ultrasound.