Influence of barite aggregate friability on mixing process and mechanical properties of concrete

• Mixing process modifies the grading curve of the barite aggregate.
• Fine dust around grains compromise the performance of interface transition zone.
• Barite microstructure is composed by adjacent layers prone to delamination.
• Strength and modulus are 30–50% lower in concrete with barite.
• Mixing time should be reduced to mitigate negative repercussions.

The main objective of this paper is to evaluate the friability of the barite aggregate during the mixing process and its influence on the fresh and hardened properties of concrete. Three types of aggregates were studied: barite (in two states, dry and wet), limestone and EAF slag. A specific test was designed in which each type of aggregate was exposed to several times of mixing to evaluate possible changes to the grading curves and in the surface of the aggregates grains. Moreover, four types of concretes were designed (two with barite, one with EAF slag aggregate and one with conventional limestone aggregate) to evaluate the repercussion of this phenomenon on the fresh and hardened state properties. The results show that the mixing process modifies the grading curve of the barite at a higher extent than in the case of the other aggregates. This also has repercussion in the properties of concrete, which shows increased workability as well as poorer compressive strength and elastic modulus. The observations from the study help to explain this behavior and provide important guidelines for the design, the production and the use of barite as an aggregate for concrete.