Application of coal waste and lime in recycled mixtures with bitumen emulsion

The technical, environmental and economic advantages of pavement cold recycling technology are well known as an efficient method for asphalt concrete pavements rehabilitation. Nowadays, additives are used for improving the implementation situation and upgrading the performance of cold recycled mixtures. The increasing costs of preparing the common additives such as cement and lime and also the pollutants that result from their production processes were among the most important reasons for widely using waste additives like fly ash. In this study cold waste powder in its natural and ash forms was used as an additive in the cold recycled mixture with bitumen emulsion. In addition, lime powder was separately and as a compound used in the cold recycled mixtures. The performance of the studied mixtures was assessed by Marshall, indirect tensile strength, moisture sensitivity and resilience modulus tests. The test results showed that using coal waste and its ash improved the mechanical features of the mixtures in such a way that marshal stability, tensile strength and resilience modulus were increased too. As a matter of fact, the effects of using coal waste ash on the mechanical features of the mixtures was obviously related to the existence of more pozzolanic materials in its chemical compounds. Further, the application of coal waste ash reduced the moisture sensitivity of the mixture, while using coal waste caused an increase in the mixture's moisture sensitivity. Moreover, the results showed that adding 3% of lime to the recycled mix significantly caused a decrease in the moisture sensitivity. Also lime could be used as a complement for coal waste and its ash because the results showed improvement of the mechanical features and the durability of the mixture due to the occurrence of cementitious reactions specifically in the long-term.