The Study On Effect Of Transport And Carbonation For Carbon-emission Of RAC During Its Lifecycle

Building material is a major source of carbon-emission in construction industry. Its control of carbon-emission has been incorporated into energy conservation and emissions reduction. As a low-carbon concrete, Recycled aggregate concrete (RAC) not only can effectively reduce carbon-emission, but also save resources and energy. More and more attention from society would be paid to its carbon-emission with the mature of researches on RAC technology performance. Based on literature research, there is a great problem that the boundary of system is determined and its detailed scope is ambiguous during assessment. For example, the transport process is not determined and the impact of concrete carbonation is not considered. Therefore, it makes the results varied widely and unable to form unified evaluation criteria. For the problems above, the study analyzes the impact of transport and carbonation on carbon-emission of RAC during its lifecycle. The process of analysis is as follows.(1) Analyze the three main defects of past evaluations in the production process. Build a model showing the relationship between carbon-emission and recycled coarse aggregate transport distance by combining carbon-emission inventory of various raw materials during production and transport. By the model, study the relationship among recycled coarse aggregate replacement ratio, recycled coarse aggregate transport distance, and carbon-emission. In order to know about the impact of transport on carbon-emission of RAC in-depth during life cycle, analyze the image of the model.(2) Discuss the disadvantages of conventional methods with carbon-absorption and make comparative analysis of the existing prediction models for depth with carbonation. Introduce the complex model established by domestic scholars which meets practical and regional requirements. The prediction model can make up the shortages of conventional methods. Then build a new carbon-absorption model for estimating the amount of carbon-uptake under different useful life and study the effects of RAC carbonation on carbon-emission during its lifecycle.(3) Analyze and evaluate carbon-emission of two simulation cases with national and recycled concrete respectively. The results of assessment show that:1) the critical transport distance of recycled coarse aggregate is44.44km;2) focus on emission-reduction during the phase of raw materials production, especially cement, and at the same time emission-reduction should be not ignored during the transport phase;3) at the critical transport distance, the amount of carbon-absorption of two cases during50a is8.32×105kg, which makes carbon-emission reduced by30.27%.