Abstract
Study was recently conducted at Kingston University to assess the suitability of using recycled concrete aggregate (RCA) and reclaimed asphalt pavement (RAP) in unbound subbase mixtures. The results showed that the use of 100% recycled aggregates increased the optimum moisture content and decreased the maximum dry density of the sub-base materials in comparison with natural aggregates. Moreover, the replacement of RCA by reclaimed asphalt pavement by 50% decreased the optimum moisture content and increased the maximum dry density in proportion to 100% RCA. The effects of physical properties on 0% air void and compaction curve were discussed for each type of subbase. The CBR values of the subbase materials prepared with 100%RCA is lower than subbase mixture with 100% natural aggregates. The CBR further decreased for replaced subbase with RAP so that 50%RCA + 50%RAP is not suitable for unbound subbase from the point of CBR view. In each mix the trend of CBR value was investigated in terms of water content. This research found some significant practical points to use in site works.
Highlights
During the last two decades, various researches were carried out to investigate the possibility of using construction and demolition waste
The compaction behavior of recycled aggregates mixed with 5% to 25% sand, cement and brick was evaluated by Melbouci (2009), who made the following observations: (1) addition of 10% by mass of cement to Recycled Concrete Aggregate (RCA), leads to the maximum dry density and a low optimum moisture content; (2) Addition to RCA of crushed brick particles having sizes lower than 0.125 mm produces higher dry density values in comparison to the case of RCA blended with sand; (3) Among all addition of 5% and10% the highest dry density is that of mixes with the cement; (4) Adding 5% brick or 10% sand or cement increases the immediate CBR values, the soaked CBR values of the mixes containing crushed brick were less than the corresponding immediate CBR values
This paper presents the result of an investigation of compaction and CBR tests for recycled concrete aggregates and reclaimed asphalt pavement as possible materials for use in unbound subbases
Summary
During the last two decades, various researches were carried out to investigate the possibility of using construction and demolition waste. 2004) and recycled concrete aggregates (RCA) (BS EN 8500-1 2006) are subjects of debate for application in bases and sub bases. These materials can give different test results depending on their sources. Chen et al (2011) investigated the potential of using fine recycled aggregates powder prepared by fine waste aggregates as filler in asphalt mixture. Comparison with the mixtures with conventional limestone powder showed that using fine recycled aggregates powder improved the water sensitivity, high-temperature properties and fatigue life of asphalt mixture
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