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MINIMAL STRUCTURES USING HIGH STRENGTH CONCRETE

Objective


Guidelines for design of CRC have been set up, and results have confirmed that the material is well suited for a plastic analysis. CRC columns have been designed without stirrups - with satisfactory test results, and the possibility of omitting shear reinforcement in beams has been established. In order to accomplish the task of preparing the design guidelines, it was decided at an early stage of the project to perform almost all tests with one particular CRC composition. For this reason a correlation between mix design and structural design is not well established, but the effect on mechanical properties of exchanging types of fibres has been investigated.

Tests on durability - corrosion as well as fire resistance - have also been encouraging, as even very rigorous testing have not led to active corrosion after more than two years of exposure. There is practically no danger of corrosion of reinforcing bars, even with a low thickness of cover to the reinforcement, due to the low porosity of CRC. Even with a chloride content in the mix water which is higher than the expected critical threshold value, no corrosion is observed. Chemical resistance is high, there is practically no effect of carbonation and light drying of structural components appear to prevent spalling under fire exposure.

Investigations with regard to production techniques were aimed at transferring the technology from laboratory level to full scale production, and one of the results was that mixing time has decreased from 18 minutes at the beginning of the project to 8 minutes used in production of specimens for full scale tests.

Procedures for in-situ casting has only been touched upon briefly as most of the production has been carried out as pre-cast. However, a CRC application has been implemented during the project, where the material was used for in-situ cast joints at Aalborg University. This application was part of another project led by the Carl Bro Group, which, however, supplemented the MINISTRUCT project well. As no problems were encountered in connection with the Carl Bro Group project, it has been decided to invest efforts set aside for this investigation of in-situ casting at other tasks.

Full scale tests - incorporating the knowledge gained in the project with regard to design, mixing and casting technology - have been carried out in the project, where large beams and columns have been produced and tested. Full scale joints have also been produced and tested.
The proposed research is directed at introduction of the concept of Minimal structures using ultra high strength concrete in civil engineering construction. In Minimal structures the material content is minimized by the use of a new ultra high strength concrete (CRC) with improved performance compared to contemporarily used materials, thus significantly reducing resource consumption (raw materials, energy) and environmental impact (refuse, pollution etc...). The major research tasks are:

- laboratory test on durability, i.e. corrosion and fire resistance

- laboratory tests on structural properties, i.e. creep and shrinkage, optimization of fibre content, anchorage and behaviour in bending

- production tests for large scale production and in situ casting

- structural analysis necessary for establishing guidelines

- design production, and testing of full scale prototypes .

Preliminary calculations have indicated that utilization of this new type of reinforced concrete in the manufacture of various structural members (beams, girders, columns, plates, etc...) may lead to considerable savings (up to app. 80%) in materials (and consequently in weight) as compared to the alternative uses of either conventional reinforced concrete or structural steel.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

AALBORG PORTLAND A/S
Address
Rordalsvej 44 - Po Box 165
9100 Aalborg
Denmark

Participants (3)

BOUYGUES SA
France
Address
1 Avenue Eugene Freyssine
78061 Paris
CARL BRO GROUP AS
Denmark
Address
Vermehrensvej,14
5230 Odense M
CSIC
Spain
Address
Galvache Apartado De Correas
28033 Madrid