STUDIES OF THE INFLUENCE OF FINE SAND CONSTITUENTS ON THE COMPACTION PROPERTIES OF CONCRETE (RUBBERIZED CONCRETE)

UNTERSUCHUNGEN UEBER DEN EINFLUSS DER FEINSTSANDANTEILE AUF DIE VERDICHTUNGSWILLIGKEIT VON BETON (GUMMIBETON)

DURING MECHANICAL CONCRETE COMPACTION ON ROAD CONSTRUCTION SITES IT WAS OBSERVED THAT EVEN AFTER MECHANICAL SMOOTHING THERE ALWAYS REMAINED A WAVY CONCRETE SURFACE. IT MAY BE ASSUMED THAT THE COMPRESSIBILITY OF THE FRESH CONCRETE IS MAINLY INFLUENCED BY AIR-CONTAINING SAND CONSTITUENTS HAVING A PARTICLE DIAMETER OF LESS THAN 3 MM. TOGETHER WITH THE AIR VOIDS ADDITIONALLY INCORPORATED BY MEANS OF AIR-ENTRAINING AGENTS, THESE NATURAL AIR VOIDS SEEM TO EXPLAIN THE VISCOELASTIC BEHAVIOUR OF THE FRESH CONCRETE (SPRING EFFECT) . THEREFORE STUDIES ARE TO BE CARRIED OUT ON VARIOUS NATURAL SANDS USED FOR ROAD CONSTRUCTION TO DETERMINE THEIR PARTICLE COMPOSITION, THEIR NATURAL AIR VOLUME AND THEIR PARTICLE SHAPE. FOLLOWING THIS THE COMPACTIBILITY AND OTHER PROPERTIES OF CONCRETES PRODUCED WITH THESE NATURAL SANDS WITH AND WITHOUT THE ADDITION OF AIR-ENTRAINING AGENTS ARE TO BE TESTED. EFFORTS ARE BEING MADE TO DEFINE THE NATURAL AIR VOIDS CONTAINED IN THE FINEST SANDS BY MEANS OF A SIMPLE METHOD SO THAT, BEFORE THE SANDS ARE USED TO MANUFACTURE CONCRETE, AN ESTIMATE CAN BE MADE OF WHETHER THE FRESH CONCRETE PRODUCED WITH THE SANDS WILL HAVE THE OBSERVED SPRING EFFECT OR NOT. BY TIMELY ELIMINATION OF UNSUITABLE FINE SAND CONSTITUENTS THE SPRINGING BACK OF THE NATURAL AND ARTIFICIAL AIR VOIDS SHOULD BE REDUCED IN SUCH AS WAY THAT THE SURFACE CONDITION OF THE ROAD CONCRETE IS NO LONGER IMPAIRED.