Search

The fine portion of crushed old concrete is difficult to be recycled for use in new concrete because it contains old cement paste, which generally has high porosity and low strength. Hence, in practice, the coarse portion is recycled as coarse aggregate and the fine portion is mostly not recycled. Nevertheless, attempts have been made in recent years to recycle the fine portion as waste concrete powder (WCP) by grinding before use. In this research, WCP was used to make pervious concrete. The WCP was added using the paste replacement method (PR method) of replacing an equal volume of cementitious paste. A series of pervious concrete mixes containing 100% recycled coarse aggregate and having different amounts of WCP added were produced for testing of interconnected porosity, water permeability and strength. The results showed that the addition of WCP using the PR method can improve the interconnected porosity by 9% and water permeability by 18%, greatly enhance the strength by 86%, as well as decrease the cement consumption by 10% at the same time. Therefore, the addition of WCP as paste replacement has great potential to be applied to the production of eco-friendly high-performance pervious concrete. [ABSTRACT FROM AUTHOR]

Pervious concrete needs to have many pores to achieve high water permeability, but excessive porosity may cause a serious reduction in strength. Herein, it is postulated that the interconnected porosity and open porosity, which can be separately measured, do not have the same effects on the performance of pervious concrete. To evaluate how the interconnected porosity and open porosity influence permeability and strength, a series of no-fines pervious concrete mixes with varying water/cement (w/c) ratio and paste volume were produced for testing of their interconnected porosity, open porosity, unsubmerged water permeability, submerged water permeability and compressive strength. From the test results, it was found that both the w/c ratio and paste volume have major effects on the porosity, permeability and strength. More importantly, regression analysis showed that the interconnected porosity is the governing factor determining the water permeability, whereas the open porosity and w/c ratio are together the governing factors determining the compressive strength. Lastly, the concurrent strength–permeability performance of the no-fines pervious concrete tested was evaluated. [ABSTRACT FROM AUTHOR]