Study on the influence of attached mortar content on the properties of recycled concrete aggregate

Recycled concrete aggregates mainly differ from natural aggregates in that they are composed of two different materials: natural aggregate and cement mortar attached. It is well known that cement mortar content affects other properties of recycled aggregates: absorption is higher, Los Angeles abrasion coefficient is lower, etc.. but the available data that support this statement are scattered, as they were obtained in many individual studies. There is no a general study about the quantitative influence of mortar content on other properties of the recycled aggregate. The objective of this study has been to obtain experimental relationships between the attached mortar content and other recycled aggregate properties, covering a wide range of different aggregates qualities. The interest of these general relationships is diverse: They can be used to establish the mortar content that adversely affects other important properties of the aggregate for different applications. For example, in this research it has been concluded that only recycled aggregates with mortar content under 44% could be used of structural concrete. With this criterion, aggregates with bulk specific density higher than 2160 kg/m(3), water absorption lower than 8% and Los Angeles abrasion loss under 40%, are obtained. The results can also be useful for recycling plants as they can adjust the production processes using the relationships to obtain an aggregate with pre-selected properties reducing mortar content, for example, by means of several crushing processes. This research has analyzed data from experimental works carried out in CEDEX and also from literature review. The results show that the main properties unfavourably affected by the attached mortar content are density, absorption and Los Angeles abrasion, and correlations between them and attached mortar content have been obtained and discussed in detail. (C) 2008 Elsevier Ltd. All rights reserved.