Utilisation of recycled concrete aggregate in asphalt mixture

• Main Author: Leo, Yong Huan.
• Other Authors: Wong Yiik Diew
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Civil engineering::Construction technology
• Online Access: http://hdl.handle.net/10356/49028
• Institution: Nanyang Technological University

The objective is to investigate the feasibility of full replacement of granite aggregates with recycled concrete aggregates (RCAs), for making a porous asphaltic concrete wearing course for lightweight load applications such as pedestrian or cycling paths. Three mixes, each incorporating a different type of filler, were designed according to LTA’s specification for porous asphaltic mixes. LTA-PA-1, LTA-PA-2 and LTA-PA-3 are the 3 mixes which use RCA, hydrated lime and kaolin as fillers respectively. Pen 60/70 is used as binder with a binder content of 5.5% for all 3 mixes. Two types of specimens were fabricated, namely small cylindrical specimens and rectangular slab specimens. Water permeability test was conducted on the small cylindrical specimens to check on their porosity and the amount and connectivity of the voids. LTA-PA-1 had the highest porosity followed by LTA-PA-3 while LTA-PA-2 had the lowest porosity. Durability aspects of the 3 mixes were evaluated via moisture susceptibility tests and weathering tests which involved comparing the skid resistance and rutting resistance of the specimens before and after weathering. LTA-PA-1 and LTA-PA-2 were found to have higher moisture resistance while LTA-PA-3 was highly moisture susceptible. Skid resistance of all specimens met LTA’s criteria for acceptance of open-graded pavements. LTA-PA-2 was able to retain 100% of its skid resistance after weathering while LTA-PA-1 had the lowest strength to resist rutting due to the high porosity. From the results, LTA-PA-2 was the best mix as it showed consistently good results in the tests conducted due to the good anti-stripping characteristic of the hydrated lime filler used. It is feasible to fully replace granite aggregates with RCAs except that hydrophilic fillers such as kaolin should not be incorporated as it would greatly diminish the moisture damage resistance of the mixes.