Elastic Composite, Reinforced Lightweight Concrete (ECRLC) – A Brief

. The mentioned “Elastic Composite, Reinforced Lightweight Concrete (E.C.R.L.C.)” is a type of “Resilient Composite Systems (R.C.S.)”.

– Resilient Composite Systems (RCS):

“Resilient Composite Systems” (RCS) are the compound materials, having some particular structural properties, in which, contrary to the basic geometrical assumption of the flexure theory in Solid Mechanics, the strain changes in the beam height during bending is typically “Non-linear”. The RCS could be counted as “The Methodically Reinforced Nonlinear Porous Materials”, also having the high specific modulus of resilience in flexure. (As well, Elastic Composite, Reinforced Lightweight Concrete; ECRLC is a type of RCS with the mentioned specifics.)

Generally, the Resilient Composite Systems comprise these components as the main, necessary elements:

1) Mesh (Lattice);

2) Fibers or strands;

3) Conjoined matrix, having the disseminated suitable pores and/or the 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.]

The Resilient Composite Systems are made by creating the disseminated suitable hollow pores and/or by distributing the appropriate lightweight aggregates throughout the reinforced, fibered conjoined matrix so that; “the strain changes in the beam height during bending” is typically “non-linear”. Thereby, by applying the mentioned method to make the said particular composite systems, “considerably increasing the modulus of resilience and the bearing capacity in bending” together with “the significant decrease of the weight” and “the possibility removal of the beam fracture of primary compressive type” have been possible. Through making these particular integrated functioning systems, the stated paradoxical virtues have been concomitantly fulfilled in one functioning unit altogether.

Generally, in these integratedly functioning units, the amount and the manner of the mentioned components use in the organized system are so that; the mutual (reciprocal) interactions among the components finally lead to the “typically non-linear strain changes in the beam height during bending” (as the “basic functional character” of these systems with the specific testable criteria and indices) and the functional specifications fulfillment of the system.

In the 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 the elastic limit.

Here, the main tactic to realize the stated strategy is: “creating the suitable hollow pores and/or using the appropriate lightweight aggregates, all disseminated throughout the methodically reinforced conjoined matrix”, to provide the possibility for occurring of the expedient internal deformities in the matrix during the bending course, which could lead to the more appropriate distribution of the stresses and the strains throughout the system and the more strain capability of the beam in flexure. On the other hand, only creating the hollow pores and/or using the lightweight aggregates in the matrix, by itself, not only cannot lead to the mentioned goals, but also brings about weakening of the matrix and its fragility. Hence, concomitantly, the matrix should be well supported and strengthened. Here, this essentially ameliorating and strengthening the matrix are performed by giving attention to “the internal consistency of the matrix” and also via “employing the expedient reinforcements in two complementary levels”: 1) Using the fibers to the better distribution of the tensile stresses and strains in the matrix, and to increase the matrix endurance and the 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 to increase the system endurance and the modulus of resilience in tension and bending.

In these systems, the presence of the mentioned hollow pores and/or lightweight aggregates disseminated throughout the conjoined matrix (which has been ameliorated through making “an integrated, reticular structure”) provides the possibility for occurring of the expedient internal deformities in the matrix during the bending course. By the way, this can lead to the less accumulation of the internal stresses in the certain points of the matrix during bending, the better absorption and control of the stresses, and providing the more strain capability of the beam especially within the elastic limit.

The occurrence of the remarked internal deformities in the said methodically reinforced matrix during the bending course also means; the occurrence of the deformities in the said hollow pores and/or lightweight aggregates well disseminated throughout 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, leading to: A) The comparative increase of the thickness (height) of the in-compressing layers (particularly in the upper parts of the beam) and the conversion of some internal compressive stresses to the internal tensile stresses (on the axis perpendicular to the mentioned internal compressive tensions) in the in-compressing layers; B) The comparative decrease of the thickness (height) of the in-tension layers (particularly in the lower parts of the beam) and the conversion of some internal tensile stresses to the internal compressive stresses (on 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 deformities occurring in the “conjoined layers perpendicular to the applied load direction” during the bending course are so that; “the initially plane sections perpendicular to the beam axis” typically shift from “the plane status” to “the curve status” during the bending course. Thereby, the basic geometrical assumption of the flexure theory in Solid Mechanics (“linearly” being of the strain changes in the beam height during bending) and the respective trigonometric equations & equalities are mainly overshadowed in these systems.

In this way, through occurring of the remarked internal deformities in the strengthened matrix during the flexure course, the stresses are more distributed and absorbed, and the rate of increasing the internal stresses in the matrix (which could lead to the matrix plasticity and crash) are reduced. Indeed, in these systems, the mentioned internal deformities in the beam during the bending course cause the tendency of the so-called Neutral Axis of the beam to move downward. (This tendency to move downward is opposite to the tendency of the neutral axis of the beams made of the usual reinforced concrete to move upward during the bending course.) Hence, the more strain capability of the beam is provided.

Indeed, due to the manner of the mentioned internal changes (in two different forms) in the reinforced and conjoined lightweight matrix during the flexure course, we have “typically non-linear strain changes in the beam height during bending” so that; this non-linearly being is counted as the basic functional criterion (with its indices) of the Resilient Composite Systems.

– The “Elastic Composite, Reinforced Lightweight Concrete (ECRLC)” as a type of Resilient Composite Systems (RCS):

The mentioned “Elastic Composite, Reinforced Lightweight Concrete (E.C.R.L.C.)” is a type of the “Resilient Composite Systems (R.C.S.)”. The RSC (with the mentioned general structural properties and specific functional criteria) whose cement materials include the “C-S-H (Calcium Silicate hydrate) crystals” have been termed 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 which comprise the C-S-H crystals.]

In view of the special pattern of the strain changes during the bending course in the particular Resilient Composite System called ECRLC, this system, as an integratedly functioning unit with the reticular arrangement and texture, has more strain capability (especially within the elastic limit), energy absorption capacity and bearing capacity in bending compared to the usual reinforced concrete beams.

Obviously, employing the said hollow pores and/or lightweight aggregates (such as the Polystyrene beads) in the matrix leads to the density decrease. [In this way, we can also get access to the so-called thermal insulation, lightweight materials according to the case.]

Thereby, through utilizing this applied structure, the possibility of solving some of the main problems in the lightweight concretes application, especially the strategic deadlock of brittlely and insecurely being of the fracture pattern in many of the usual reinforced lightweight concrete structures, is provided; reaching to the high bearing capacities in the bending elements (even with the low dimensions & weights) is to hand, and getting access to a simple and practical opportunity for “the qualitative development of the capabilities for using the lightweight concretes” is conceivable.

Here, it is worthy of mentioning that, if needed and “according to the case”, concomitantly using some auxiliary methods and accompanying elements (such as the supplementary reinforcements, connection strips, foam pieces, additionally reinforcing in different levels, etc) in proportion with these systems could be taken into consideration. However, in general, these supplementary elements are not necessary to count a system as the so-called Resilient Composite System (Resilient Compound System).

– Some Applications:

Considering the subjects and particulars mentioned for the RCS and the ECRLC (as a simple and practical technology), these systems can be efficiently employed as the “in-bending” and in-torsion elements, and also for making the elements that perform the act of shielding by absorbing the impacts, shocks, vibrations, and dynamic loads (in bending).

As well, in consideration of the properties as lightness, insulation, durability, work-ability and the high forming possibility of some components used in these systems (such as a special type of the lightweight concrete with the high strain capability), and regarding the possibility of employing the supplementary elements and auxiliary methods (according to the case), these systems and some of the used components, such as the mentioned special lightweight concrete, can be utilized in various cases.

For instance, they can be employed in: the 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, cabinets, counters, pips & ducts, etc.

The said particulars of the RCS & ECRLC have the high importance also in constructing the high buildings & towers and especially in construction in the “seismic areas”. Lightness, the high modulus of resilience and capacities of energy absorption and reserving in bending, the secure fracture pattern, the appropriate behavior against the high impacts and vibrations, the suitable integrity, not benefitting from the high weight and separated materials with the discordant behavior, etc are among the specifics which are important in this regard.

In general, in many cases, “Lightweightly and Integratedly Constructing” can be counted as the pivotal and practical tactic 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 or 3D-panels, “with the high modulus of resilience and appropriate behavior against the bending loads and impacts”, for construction could be considered in its turn… [It is worth remarking that; contrary to the ECRLC, the usual reinforced lightweight concretes, especially in the very low densities, are dramatically brittle; they do not have the appropriate behavior and resistance against the high bending loads and impacts.]

In the literature about the RCS & ECRLC, these systems and some related structures and components have been discussed, and some instances of the structure termed ECRLC with the related details and the results of some performed experiments have been presented.

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.

[“Updated in Dec 2016”]