Analysis of moisture state of recycled coarse aggregate and its influence on compression strength of the concrete

Abstract

This article analyzes the impact of the moisture level of recycled coarse aggregate additions to concrete on its compression strength, with the goal of finding a logical development process that can be reproduced at an industrial level and provide acceptable results for concrete production. This study takes into account the reality in the process of the production of concrete; while many authors suggest the use of recycled coarse aggregates in a saturated state to ensure the desired ratio water to cement in the concrete, in reality, the aggregates are introduced unsaturated. The main objective of this study is to observe and analyze the behaviour of recycled coarse aggregate in concrete, so that it is not stigmatized by the extra work involved in its use. The concrete was produced using three states of the recycled coarse aggregates. In the first one, the aggregates were added in their natural state, taking into account the total water in the dosage; in the second one, aggregates were added after being submerged in water for 10 minutes and drained for 10 minutes; and in the last one, the aggregates were added in their natural state, taking into account its absorption when adding the water. In order to evaluate the recycled coarse aggregates¿ resistance to compression at 28 days, four percentages of replacement of the recycled coarse aggregates, 0%, 20%, 50% and 100% were established among the concretes studied. The study finds that to define the resistance of a concrete, the effective ratio of water to cement plays a very important role; basically, the high absorption of recycled aggregates directly affects the quality of the concrete. The results showed that the values of compressive strength increased as the replacement percentage of the recycled coarse aggregates increased when the aggregates were added in their natural state, not considering their absorption in the mixed water. The opposite result was obtained when the aggregates were added in saturated state, reflecting a significant decrease in the resistance of the concrete as the replacement percentage of recycled coarse aggregates increased.