Effect of the internal curing using attapulgite aggregate on the strength of roller compacted concrete
  Basil S. Al-Shathr, Osama A. Eedan and Yasir J. Farhan
  The curing of roller compacted concrete used in road pavement with high surface area is very important especially in hot weather countries, where an incomplete curing occurs always causing shrinkage cracks and bad quality concrete. This research aims to study the effect of using lightweight manufactured attapulgite aggregate (5,10,15 and 20% partial replacement of sand volume) as internal curing material in RCC on its strength (flexural and compressive) under different curing conditions, including flan coat paint and air curing after one day of moist curing, water curing for 7 days, and permanent water curing. The results indicate that the optimum attapulgite aggregate volumetric replacement to normal sand is 5% to gain the best strength improvement, after that percentage the strength of RCC decrease. Also it was found that the best effect of attapulgite aggregate replacement (as internal curing agent) to normal sand on RCC flexural and compressive strength is when using insufficient curing by painting it with flan coat or when it is left in air after one day of moist curing, where the strength become approximately equal to RCC strength with permanent water curing until test age.