WEATHER RESISTANCE OF CONCRETE COMPARED WITH NATURAL ROCKS

WITTERUNGSBESTAENDIGKEIT VON BETON IM VERGLEICH MIT NATURSTEINEN

A SIGNIFICANT PART OF THE STUDY CONSISTED IN THE EXAMINATION OF CONCRETE SLABS WHICH HAD BEEN EXPOSED TO WEATHERING FOR SEVERAL YEARS. COMPARATIVE STUDIES WERE MADE ON SLABS OF NATURAL STONE USED IN BUILDINGS. THE SLABS TESTED HAD BEEN SUBJECTED TO OPEN-AIR WEATHERING FOR APPROXIMATELY 30 YEARS AND HAD BEEN STANDING IN WATER ABOUT 35 CM DEEP, AND WERE MADE OF 17 DIFFERENT CONCRETE MIXES. THE COMPRESSIVE STRENGTH OF THE CONCRETE, DEGREE OF CARBONATION AND THE CONDITION OF THE REINFORCING BARS WERE ESTABLISHED. CONCRETES WITH CEMENT CONTENTS OF 200 AND 300 KG PER CUBIC METRE HAD WATER CEMENT VALUES OF 1.29 TO 0.50. IN SLABS MADE OF LOWER QUALITY CONCRETE ONLY THE CEMENT SKIN OR THE FINE MORTAR TO A DEPTH OF 3 MM AT THE MOST HAD BEEN WORN AWAY BY WEATHERING. ORIGINAL COMPRESSIVE STRENGTHS WHICH WERE BETWEEN 73 AND 498 KP PER CUBIC CM HAD ALWAYS RISEN CONSIDERABLY - THEY WERE BETWEEN 267 AND 849 KP PER CUBIC CM. NO CORROSION WAS FOUND AND, WITH A FEW EXCEPTIONS, CARBONATION WAS ONLY A FEW MM DEEP.