Laboratory Study on Mixture Design of Grouted Macadam
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Date
2017-04
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Addis Ababa University
Abstract
Grouted macadam is a composite material which consists of porous asphalt concrete with 25–35% air voids, in which a designed cementitious grout is filled. This research tried to design grouted macadam mixtures from local materials and evaluate the contribution of cementitious grout in the resultant grouted macadam. The study utilized laboratory-based experimentation program with three phases.
The cementitious grout mixture involving ordinary Portland cement, silica sand, bagasse ash, megaflow SP1, and water is designed using the Taguchi approach. Based on the results of the first phase of the study, a water to binder ratio of 0.76, silica sand content of 10% replacement by weight of cement, and bagasse ash content of 10% replacement by weight of cement, and megaflow SP1 1.5% by weight of the binder is proposed for use in the grouted macadam.
Using penetration grade 60/70 bitumen, the porous asphalt concrete is designed to have a target air voids content of 30%. The grout mixture that was proposed above is prepared and applied to the 65mm thick porous asphalt concrete specimens that were prepared with bitumen contents of 3.1% and 3.6%. It is observed that all these specimens are fully penetrated by the grout. Marshal stability and indirect tensile strength (ITS) tests are conducted on the grouted macadam and maternal porous asphalt specimens. At the 3rd day of air-curing, the Marshal stability result of grouted macadam is found to be 91.5% higher than that of maternal porous specimens. At the 28th day of air-curing, the tensile strength result of grouted macadam is found to be 81.75% and 84.85% higher than that of maternal porous specimens, at 25 ºC and 40 ºC respectively. Cementitious grout is the cause for these improvements.
The research concludes that the grout mix proportion proposed in this study, has good grouting ability and its contribution in the grouted macadam material is high. The Marshal stability and ITS tests indicated that the grouted macadam mixtures have promising performances.
Keywords
GROUTED MACADAM, CEMENTITIOUS GROUT, TAGUCHI APPROACH
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Keywords
Grouted Macadam; Cementitious Grout Taguchi Approach