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QUALITY ASSURANCE OF CONCRETE BASED ON TESTING OF THE FRESH, STILL PLASTIC MATERIAL

Objective

The objective is to develop a system for Quality Assurance of Concrete and to test and verify this system based on petrographical analysis in combination with testing of permeability and diffusivity of the hardened concrete using traditional testing methods.

It is a further goal to produce demoversions of testing equipment and manuals for the testing methods developed.
The following test methods have been developed during the research:

1. Prediction of the paste density

The water cement ratio of a concrete with known theoretical composition can be determined with an accuracy of +/-0.02 corresponding to determination of the water content with an accuracy of +/-5 kg/m{3}.

Two principles proved feasible:

- Sampling of mortar, drying out and fast chemical testing;
- Radar detection;

2. Prediction of the quality of an entrained air void system.

Based on principles of separation of air voids from paste and succeeding recording of their size and number through buoyancy recordings an intensive documentation of the accuracy of the method has been carried out.

The outcome has been that the specific surface and the spacing factor of a given air void structure may be determined with an accuracy of +/-10% assuming that an average of 5 measurements of the same properties performed according to ASTM C457 represents the 'true' air void structure.

3. Prediction of the permeability and diffusivity of concrete.

The research has resulted in a test procedure which in the pre-testing phase enables the researcher to predict essential properties of the concrete. Under normal circumstances it may take up to one year to produce the same results.

In the following field the research did not yield fully operational test method statements; However, in this area it is expected that further research or documentation will lead to test methods and equipment which will be industrially feasible.

4. Determination of degree of consolidation by ultrasound.

During the research it was recorded that the degree of consolidation could be monitored by ultrasound measurements. The industrial potential for such tests is enormous and studies of the accuracy of the test were concluded. These proved that at present the scatter is too big.
Quality Assurance and Quality Control of concrete are today in its advanced form carried out in separate stages :

-Quality verification of the concrete components, i.e. cement, water, aggregates and additives.
-During batching and mixing it is assured that the composition of concrete is in accordance with the specifications.
-Strength testing of laboratory produced specimens.
-Petrographic analysis of hardened concrete.

Generally it can be stated that the above mentioned methods and procedures are excellent for the control of the hardened concrete and for the documentation of the properties achieved as to durability as well as strength performance. The methods are also excellent to assure that harmful alkali-aggregate reactions will not appear in the concrete structure.

Coordinator

Dansk Beton Teknik A/S
Address

2900 Hellerup
Denmark

Participants (4)

CUR Centre for civil engineering and codes
Netherlands
Address
Po Box 420
2800 AK Gouda
Centre Scientifique et Technique de la Construction-Wetenschap.en Technisch Centrum voor het Bouwbedrijf CSTC/WTCB
Belgium
Address
Rue De Lombard 41
1000 Brussels
Danish Welding Institute
Denmark
Address
Park Alle 345
2605 Brondby
Instituut voor materiaal - en milieu - onderzoek BV
Netherlands
Address
Dr. Nolenslaan 126
6130 PD Sittard