HIGH EARLY STRENGTH CONCRETE BY MEANS OF VERY FINE PORTLAND CEMENT

DEVELOPMENTS IN CONCRETE TECHNOLOGY HAVE BROUGHT ABOUT A PROGRESSIVE INCREASE IN THE STRENGTH AT ALL AGES, BUT CONCRETE MADE WITH PORTLAND CEMENT STILL REQUIRES A CONSIDERABLE TIME TO ATTAIN ITS MAXIMUM STRENGTH. THE FINENESS OF PORTLAND CEMENT IS KNOWN TO BE AN IMPORTANT FACTOR AFFECTING THE RATE OF HARDENING, THE EFFECT OF GREATER SPECIFIC SURFACE BEING TO INCREASE THE RATE OF HYDRATION SO THAT THE EARLY STRENGTH IS HIGHER ALTHOUGH THE LATER STRENGTH MAY BE ABOUT THE SAME. A SPECIAL CEMENT HAVING A SPECIFIC SURFACE OF 7420 CM SQUARED/G WAS TESTED IN COMPARISON WITH AN ORDINARY PORTLAND CEMENT OF 2770 CM SQUARED/G AND A RAPID-HARDENING PORTLAND CEMENT OF 4900 CM SQUARED/G MATCHED IM COMPOSITION. THE INVESTIGATION WAS CONCERNED WITH HIGH STRENGTH CONCRETE AND FOR MOST TESTS AN AGGREGATE-CEMENT RATIO OF 3:1 WAS USED TO PERMIT LOW WATER-CEMENT RATIOS. /AUTHOR/