Challenges on pumping infra-lightweight concrete based on highly porous aggregates

Abstract

Infra-lightweight concrete (ILC) is the latest step in the development lightweight concrete mainly for the use in monolithic exterior walls. By optimizing the balance between reduced density, sufficient strength and the lowest possible thermal conductivity, ILC offers a competitive alternative to multilayer wall structures commonly used today. Pumping of fresh concrete is becoming increasingly important owing to further rationalization on the construction site and the increasing use of ready-mix concrete. However, pumping lightweight concretes is often associated with difficulties. This article presents the first study ever on pumpability of a record breaking ILC, using some of the most common concrete pumps. Therefore, an experimental study was carried out to determine whether the pressurization of the fresh concrete in the course of the pumping process influences fresh and hardened ILC properties. Based on the results, it can be concluded that ILC can be pumped. The delivery principle of the pumps has a particular influence on fresh ILC properties, especially in terms of abrasive stress on the porous aggregates and workability. No significant negative influences on hardened concrete properties were detected. Classification of the ILC can be accomplished in the same density and strength class before and after pumping. The study highlights challenges of pumping ILC with highly porous aggregates and provides practical approaches to its realization.