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• Healing efficiency theory developed based on geometric probability. • New self-healing capsules, called engineered aggregates, are introduced. • Self-healing efficiency calculated for different cracking conditions. • Effect of size, shape and dosage of capsules on healing efficiency is evaluated. This paper presents optimal self-healing configurations in concrete using a new concept referred to herein as engineered aggregates (EA). EA are hollow particles designed to carry healing agents into the cracks in concrete. The concept of EA has been developed by the authors as a cost-effective method for self-healing in conventional concrete without having to modify the existing materials or mixing procedures. EA have an internal brittle capsule carrying the healing agents and they are covered with a cementitious coating. They are similar in size to a concrete coarse aggregate and they are added during the mixing process replacing a portion of the coarse aggregates. Similar to other self-healing materials with cast in capsules, one of the basic requirements of EA is that when concrete cracks, the cementitious coating and the embedded brittle capsule break to release the healing agents into the cavity of the crack. The goal of this study is to identify the optimal shapes and sizes of EA that can be effectively used in self-healing concrete while minimizing the volume fraction of the added healing agent (and thereby EA). The tools of geometric probability are used to determine the probability of intersection of cracks with EA and the probability of healing of cracks with different geometries: a single crack, parallel cracks, mapping cracks and multiple discrete penny-shape cracks. As such, the optimal size and shape of EA are selected based on the density and type of cracking that might occur in concrete. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the development of a hybrid model for a concrete batching and mixing plant. The model is sufficiently detailed so as to ensure that it can be used to establish the control system within an industrial monitoring and control framework. Since the concrete batching and mixing plants are hybrid systems, Global Automata were used to build the model of the physical system, since they provide greater “modeling power” being suitable for modeling of a wider variety of systems than other types of automata. Various modeling methods based on the classical hybrid systems theory are rather applied in research works with academic orientation and usually are far from the engineers of industry. A fundamental objective of this work was to adopt a development environment which will be familiar to the industrial people. The developed model entails a hierarchical structure with an automaton as supervisor and several other interactive automata describing the subsystems of the plant. The model was then used to understand the influence of various design and operating parameters on plant performance. The model was also used to establish the control strategy. Both were implemented in a SCADA (Supervisory Control and Data Acquisition) environment which monitors and controls the overall operation of the plant. This framework has been applied on a real plant of West Greece with success in all realistic tests concerning either the control operation or the model validation. [Copyright &y& Elsevier]