The mentioned “Elastic Composite, Reinforced Lightweight Concrete (ECRLC)” is a type of “Resilient Composite Systems (RCS)”.
– Resilient Composite Systems (RCS):
“Resilient Composite Systems” (RCS) are the compound materials with particular structural properties, in which, contrary to the basic geometrical assumption of flexure theory in Solid Mechanics, strain changes in beam height during bending is typically “Non-linear”. (As well, Elastic Composite, Reinforced Lightweight Concrete; ECRLC is a type of RCS with the mentioned specifics.)
Generally, Resilient Composite Systems comprise these components, as the main, necessary elements:
1) Mesh (Lattice);
2) Fibers or strands;
3) Conjoined matrix, having disseminated suitable pores and/or disseminated appropriate lightweight aggregates beads or particles. [Here, the general term of “lightweight aggregate” has a broad meaning, also including the polymeric and non-polymeric beads or particles.]
Resilient Composite Systems are made by creating disseminated suitable hollow pores and/or by distributing appropriate lightweight aggregates in the supported reinforced, fibered conjoined matrix so that “the strain changes in beam height during bending” is typically “non-linear”. Thereby, by using the mentioned method to make the said particular composite systems, we could considerably increase the modulus of resilience and bearing capacity in bending “together with” significant decrease of the weight and also possibility of beam fracture of primary compressive type. Through making these particular integrated functioning systems, for the first time, the said (paradoxical) properties have been concomitantly fulfilled in one functioning unit altogether.
Generally, in these integrated functioning units, the amount and manner of the mentioned components use in the organized system are always “so that”; the mutual (reciprocal) interactions among the components finally lead to the “typically non-linear strain changes in beam height during bending” (as the “basic functional character” of these systems with the specific testable criteria and indices) and fulfillment of the practical functional specifications of the system.
In RCS in general, the main strategy to raise the modulus of resilience in bending is “increasing the strain capability of the system in bending” within elastic limit.
Here, the main method or axial tactic to fulfill the stated strategy includes “creating suitable hollow pores and/or using appropriate lightweight aggregates, all disseminated in the matrix”, for providing more possibility of expedient internal shape changes (deformities) in the matrix, which could lead to more appropriate distribution of the stresses and strains throughout the system. Conversely, only creating hollow pores and/or using the lightweight aggregates in the matrix, “by itself”, not only won’t lead to the mentioned goals, but also will bring about weakening and fragility of the matrix! Hence, concomitantly, the matrix should be supported and strengthened. Here, this essentially strengthening and ameliorating are performed by giving attention to the internal consistency of the matrix and employing the reinforcements in “two complementary levels”: 1) Using the fibers to better distribution of the tensile stresses and strains in the matrix, and increasing the matrix’s endurance and modulus of resilience in tension and bending; 2) Using the mesh or lattice to better distribution of the tensile stresses and strains in the system and increasing the system’s endurance and modulus of resilience in tension and bending.
In these systems, the presence of the mentioned disseminated hollow pores and/or lightweight aggregates in the conjoined matrix (which has been ameliorated through forming an integrated, reticular structure) provides the possibility of “more internal deformities in the matrix” during bending. By the way, this could lead to less accumulation of the internal stresses in the certain points of the matrix during bending, better absorption and control of the stresses, and providing the possibility of more continuing the bending course, particularly within elastic limit.
Occurrence of the stated internal deformities in the system’s supported matrix during bending also includes occurrence of the deformities in the mentioned hollow pores and/or lightweight aggregates disseminated in the conjoined matrix, in two different forms. Indeed, we have the internal deformities in the fibered lightweight matrix of the system throughout the bending course, in two main different forms: A) Tendency to increasing the thickness (height) of the in-compressing layers (particularly in the upper parts of the beam) and conversion of some internal compressive stresses to the internal tensile stresses (in the axis perpendicular to the mentioned internal compressive tensions) in the in-compressing layers; B) Tendency to decreasing the thickness (height) of the in-tension layers (particularly in the lower parts of the beam) and conversion of some internal tensile stresses to the internal compressive stresses (in the axis perpendicular to the mentioned internal tensile tensions) in the in-tension layers.
In the under-bending sections of the “Resilient Composite Systems”, the established deformities in “conjoined and perpendicular to load applying direction layers” during bending are so that “the initially plane and perpendicular to beam axis sections” typically remove from “plane and vertical state” to “curve shape” during bending. Thereby, the basic geometrical assumption of flexure theory in Solid Mechanics (“linear” being of strain changes in beam height during bending) and its resulted trigonometric equations & equalities are being overshadowed in these systems.
In this way, through occurring of the stated internal deformities in the strengthened matrix, the stresses have been more “distributed” and “absorbed”, and the “rate” of increasing the internal stresses in the matrix (could lead to the plasticity and crush of the matrix) are reduced. Indeed, in these systems, the mentioned internal deformities bring about the tendency of the so-called Neutral Axis to move downward. “This tendency is opposite to the natural tendency of the neutral axis to move upward during bending.” Hence, more possibility for continuing the bending course is provided.
Indeed, due to the manner of the mentioned particular internal shape changes (in two different forms) in the system’s fibered lightweight matrix, we have “typically non-linear strain changes in beam height during bending” so that this non-linearly being is counted as the basic functional criterion (with its own indices) for Resilient Composite Systems.
– The “Elastic Composite, Reinforced Lightweight Concrete (ECRLC)” as a type of Resilient Composite Systems (RCS):
The Resilient Composite Systems (with the mentioned general structural properties and specific functional criteria), whose cement materials include the “C-S-H (Calcium Silicate hydrate) crystals”, have been named as “Elastic Composite, Reinforced Lightweight Concrete (ECRLC)”. [For instance, the composition of “Portland cement and water”, “Portland cement and water and Pozzolanic materials”, and “lime and Pozzolanic materials” all are among the cement materials that comprise C-S-H crystals.]
Regarding the special pattern of strain changes during bending in the particular Resilient Composite System called as the ECRLC, this system as an integrated functioning unit with the reticular arrangement and texture has more strain capability (particularly within the elastic limit), energy absorption and load bearing capacities in bending compared to the usual reinforced concrete beams.
Obviously, use of the said used hollow pores and/or lightweight aggregates (such as the Polystyrene beads) leads to decrease of the density. In this way, we could also get access to the so-called (thermal) insulating materials according to the case.
Thereby, through employing this applied structure, possibility of solving some of main problems of lightweight concretes application, especially deadlock of brittle and insecure being of fracture pattern in many of the usual reinforced lightweight concrete structures, is provided; reaching to bearing high capacities in bending elements (even with low dimensions & weights) is to hand, and getting access to a simple and practical opportunity for “qualitative development of capabilities of using lightweight concretes” is conceivable.
Here, it is worthy of mentioning that, if needed and “according to the case”, simultaneously using some auxiliary methods and additional, accompanying elements (such as the supplementary reinforcements, connection strips, foam pieces, reinforcing in different levels, etc) in proportion with these systems could be taken into consideration. “However, in general, these supplementary elements are not necessary for counting a system as the so-called Resilient Composite Systems (Resilient Compound Systems).”
Naturally, by more studies in the field, these structures and their applications in various fields could be developed more.
– Some Applications:
Considering the subjects and particulars mentioned for the simple, practical system named as Elastic Composite, Reinforced Lightweight Concrete (as a type of “Resilient Composite Systems”), this system could be efficiently employed as the “in-bending” and in-torsion elements and also for construction of the elements that perform the act of shielding and absorbing impacts, shocks, vibrations and dynamic loads (in bending).
As well, with respect to the properties as lightness, insulation, durability, work-ability and high forming possibility of some components used in this system (such as a special type of the lightweight concrete with high strain capability), and regarding the possibility of employing supplementary elements and auxiliary methods (according to the case), this system and some of its main components, such as the mentioned special lightweight concrete, can be employed in various cases.
Thus, they can be employed in: construction of the slabs, roofs, floors and decks, bridges, shields and pieces against blast and expulsion, road side guards, walls & partitions, kinds of the Slab Tracks and Traverses (under the rails), and various structures and objects such as multi-floor parking garages, buildings & towers, marine structures & floaters, intervening structures, lightweight facade pieces, lumbers, cabinet, counter, pips & ducts, etc.
The said particulars of the system could have high importance also in constructing high buildings & towers and in constructions in seismic areas. Lightness, high resilience and capacities of energy absorption and reserving in bending, secure fracture pattern, appropriate behavior against the disseminated high impacts and vibrations, suitable integrity, and not utilizing of the high weight & separated materials with discordant behavior are among the specifics, which are important in this regard. [As a general rule; in many cases, “Lightweight and Integrated Construction” could be counted as a crucial and practical attitude to effectively increase the resistance & safety of the constructions against earthquake and lateral forces, in the large extent. (For example, employing some lightweight and insulating, non-brittle, reinforced sandwich panels for construction could be considered in its turn… )]
In the literature about “Elastic Composite, Reinforced Lightweight Concrete (ECRLC)”, this system and some related structures & components have been presented, and some instances of the said structure with related details and the results of the replicable performed experiments have been also pointed.
Naturally, by more studies and practices on this new innovative system and the “Resilient Composite Systems” in general, these structures and their applications can be developed more.