MaBo - material saving in bored piles - a contribution to reducing CO2-emissions in the construction industry

Starting point / motivation

The research project aims to reduce CO2 emissions in the construction industry. This is to be achieved through material savings in foundation structures in building construction, with the project focusing on material savings in the production of bored piles.

The construction sector is responsible for around 40% of global CO2 emissions. Over a quarter of these emissions are caused directly by the construction industry – excluding transportation emissions from raw materials.

Foundations are an essential component of buildings which are predominantly made of reinforced concrete in accordance with the applicable rules of technology. Bored piles are regularly used, especially for deep foundations, but also for securing excavations.

In Austria alone, around 80,000 to 90,000 linear meters of bored piles with diameters between 90 and 120 cm are produced every year, resulting in an average material requirement of around 74,000 cubic meters of concrete per year. According to industry estimates, around half of these bored piles are suitable for optimization in terms of concrete consumption.

This is also the motivation for carrying out the project "MaBo - Material savings in bored piles - A contribution to reducing CO2 emissions in the construction industry", with the aim of sustainably improving the production of bored piles in terms of resource efficiency and climate impact.

Contents and goals

The direct aim of the research project is to develop a concept that can be applied in practice very quickly. Practical solutions should already support structural engineers in the design process of bored pile foundations in order to solve construction tasks with less material input.

These could be, for example, guidelines/tables that define the arrangement of hollow bodies within the foundation bodies at an early planning stage. A lower material requirement for bored piles not only has a positive impact on the climate and decarbonization, but an efficient use of resources also leads to an efficient use of the energy required in the production of concrete.

Methods

To this end, numerical investigations (FEM) are first carried out to determine the cross-sectional areas of conventional bored piles that are not required. The reduced components are recalculated with regard to their load-bearing capacity and interaction with the subsoil and verified by means of component tests. I.e.: "Same load transfer behavior with reduced material expenditure".

In a second part of the project, the manufacturing process is examined and a prototype is developed and tested. The steps of borehole production, insertion of the reinforcement, installation of displacement bodies, concreting and pulling the pipes are taken into account.

The recess and displacement bodies are 3D concrete-printed hollow bodies. This means that a reinforced concrete structure without plastic components can be assumed in the life cycle phase of the demolition. When manufacturing the recess formers, particular attention must be paid to a suitable geometry.

This should not, or not negatively, influence the internal force flow of the bored pile. In addition, the cubature of the recess body should have the largest possible volume in order to ensure maximum resource efficiency.

Expected results

Depending on the type of foundation and soil conditions, material savings of up to 40% are expected in terms of concrete.

The guidelines/tables on material savings developed in the research project enable a practical approach to the design of foundation bodies - in particular for bored piles. This makes a necessary contribution to reducing CO2 emissions in the construction industry.

Project management

Graz University of Technology - Institute of Structural Design

Project or cooperation partners

• Carinthia University of Applied Sciences
• Keller Grundbau Ges.mbH

Technische Universität Graz – Institut für Tragwerksentwurf
Univ.Prof. Dr.-Ing. Stefan Peters
Technikerstraße 4/4
A-8010 Graz
Tel.: +43 (316) 873 6211
E-mail: stefan.peters@tugraz.at
Web: ITE - Home (tugraz.at)