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LFNLC & ECRLC

"Lightweight Flexible Nonlinear Composite (LFNLC)" refers to a particular class of high-performance composite materials having their own structural and functional criteria such as the porous or porous-like texture and nonlinear behavior in bending. 

"Elastic Composite, Reinforced Lightweight Concrete (ECRLC)" is a cementitious LFNLC. By its use in making the beams with a substantially high strain capability, modulus of resilience and toughness in bending, we can provide a significantly higher bearing capacity in considerably less weight. Meanwhile, any possibility of a brittle, compressive failure mode, especially in ultra-lightweight and low-height beams, is eliminated. 

The ECRLC, as a lightweight resilient composite, is a versatile, comparatively inexpensive material. Likewise, these virtues are important in architecture: lightness, durability, resilience and flexibility, workability and high formability. 

Considering the strategic importance of lightweight and integrated construction in improving earthquake resistance, ECRLCs can be especially useful in seismic areas. Allowing for the behavior and resilience of this flexible system and its formability, it can also be utilized in making ultra-lightweight and insulation, Non-Brittle reinforced sandwich panels; lightweight, safe guards; some infrastructures; shock-resistant structures and blast proof (blast resistant) pieces with appropriate behavior, resilience and toughness. 

This work implies an innovative, applied method to convert a rigid solid into a flexible material with less density or to raise the elasticity of a flexible material plus reducing the density. This practical method principally involves creating a porous or porous-like texture" along with appropriately reinforcing the material and providing the essential integrity. (Creating the porous or porous-like texture is done by generating disseminated appropriate hollow pores and/or dispersing suitable lightweight aggregates throughout the reinforced conjoined matrix.) In this way, the resilience in bending increases and the density decreases. 

In the relevant papers, the main structural and functional particulars of LFNLCs, some applications, and a Reproducible, simple example of the ECRLC have been briefly presented. 

Kamyar Esmaeili (newstructure1@gmail.com, ecrlc1@gmail.com) 

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√  The last version of a relevant paper in English, titled "An Introduction to Lightweight Flexible Nonlinear Composite (LFNLC) and Elastic Composite, Reinforced Lightweight Concrete (ECRLC) as the Cementitious LFNLC", has been presented at: 

https://www.researchgate.net/publication/375463324 

• Citation: Esmaeili K. An Introduction to Lightweight Flexible Nonlinear Composite (LFNLC) and Elastic Composite, Reinforced Lightweight Concrete (ECRLC) as the Cementitious LFNLC". International Journal of Innovation in Engineering (IJIE). 2023; 3(3): 28-47. [DOI: http://dx.doi.org/10.59615/ijie.3.3.28, https://ijie.ir/index.php/ijie/article/view/112/205, https://ijie.ir/index.php/ijie/article/view/112]

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● Introduction: 

What is termed "Lightweight Flexible Nonlinear Composite (LFNLC)" or "Lightweight Resilient Nonlinear Composite (LRNLC) refers to a particular class of composite structures. The main functional criterion of LFNLCs is nonlinear behavior in bending, and the structural criteria have been presented later in this paper.

They are specifically made by "generating disseminated appropriate hollow pores and/or by dispersing suitable lightweight aggregates (such as Expanded Polystyrene Beads) throughout a methodically reinforced conjoined (well-integrated) matrix" so that the overall behavior of the system in bending is principally nonlinear. By applying this applied method to make such a lightweight nonlinear structure, it is feasible to considerably increase the modulus of resilience, the bearing capacity and the toughness in bending along with the significant decrease of the weight as well as the elimination of the possibility of failing in a brittle, compressive mode. Through making these congruently (integratively) operating systems, the stated paradoxical virtues are concurrently fulfilled in one operating unit altogether.

In view of the area under the stress–strain curve (especially till the point of elastic limit) and the curve shape, the LFNLC can be considered a flexible nonlinear structure with high capability of strain, modulus of elasticity and toughness in bending.

In general, the density of LFNLCs is less than 1920 kg/m3.

An LFNLC with a density of 800 kg/m3 or less is called "Super Lightweight Flexible Nonlinear Composite (S-LFNLC)". Here, unlike ordinary (conventional) reinforced lightweight concretes, more emphasis is placed on the flexible ultra-lightweight composites with a density of about 800 kg/m3 or less. Depending on the case, the S-LFNLC can even have more performance and merits in practice. (In addition, owing to the considerably low density, it could be considered a thermal insulation.)

Considering the texture of the conjoined matrix of any LFNLC, the terms such as "Porous-like Flexible (Resilient) Composite" and "Porous-like Nonlinear Composite" could also be taken into consideration to point out this type of lightweight flexible structure. However, these terms seem to be arguable, and the meaning of the word "porous-like" in this case should be clarified.

It is worth remarking that the term "Resilient Composite Systems (RCS)" has formerly been used, in the pertaining literature, to refer to the class of composite structures here labeled "Lightweight Flexible Nonlinear Composite (LFNLC)". Considering some important differences among the high-performance composites classified as "Lightweight Flexible Nonlinear Composite (LFNLC)" and other resilient composites, such as those called "Engineered Cementitious Composite (ECC)", here, the term "Lightweight Flexible Nonlinear Composite (LFNLC)" has been used instead of the terms "Resilient Composite Systems (RCS)" and "Lightweight Resilient Composite (LRC)". [The term "Engineered Cementitious Composite (ECC)" usually refers to a particular class of High-Performance Fiber-reinforced Cementitious Composites (HPFRCC), also entitled "Strain Hardening Cement-based Composites (SHCC)". It has also been popularly termed "Bendable Concrete (Flexible Concrete, Foldable Concrete)".

Anyhow, the LFNLC is also a high-performance flexible composite structure, which could have more flexibility and less density than the ordinary ECC.

Notwithstanding some similarities, the essential components and structural & functional criteria and specifications of the LFNLC are not the same as those of some other so-called flexible composites such as the ECC. For instance, the LFNLC density could be considerably less than the ordinary ECC density, and the appropriate pores and/or lightweight aggregates, dispersed throughout a methodically reinforced conjoined matrix, play a fundamental role in the properties and special function of the LFNLC.

However, it is also feasible to merge these technologies into one integrative system. For instance, by properly reinforcing the structure named the ECC with an appropriate lattice (such as a fitting mesh) along with generating disseminated appropriate hollow pores and/or dispersing suitable lightweight aggregates throughout the structure, we can obtain a kind of the LFNLC. The flexibility of this lighter structure, with high modulus of resilience and toughness in bending, will be greater than that of the mentioned ECC (with a higher density). In this way, the weight can be reduced, and the performance can be improved depending on the case.

In general, in LFNLCs, the virtues of lightness and significantly high capability of strain (strainability), resilience and toughness in bending are particularly prominent.

Further clarification of some discussions formerly presented in the pertaining literature, and the necessary correction, modification and improvement of some topics regarding the subject necessitated this comprehensive paper. The present paper substantially includes the essence of the former literature in an upgraded form. 

- As stated, "Elastic Composite, Reinforced Lightweight Concrete (ECRLC)" is a kind of "Lightweight Flexible Nonlinear Composite (LFNLC)" whose matrix is mainly cementitious. [Two types of cementitious materials are hydraulic cement and supplementary cementitious materials (SCMs). The cementitious materials mainly include Calcium-Silicate-Hydrate (C-S-H) crystals as the binding substance. Silica fume (micro-silica, silica dust, nano-silica), as a pozzolanic material, is an example of the SCM that can affect various aspects of concrete. (Rice husk ash, as a type of pozzolanic material, is another instance of the SCM.)]

The ECRLC can be considered a Cementitious Nonlinear Composite. In view of the particular behavior of this cement-based lightweight nonlinear composite in bending, "strain capability (especially within the elastic limit), energy absorption capacity and bearing capacity of the beams made of the ECRLC" are overall more than "those of similar ordinary reinforced concrete beams".

The ECRLC density is less than 1920 kg/m3 as well. The presence of the hollow pores and/or the lightweight aggregates decreases the density of the material in total. By employing the ECRLC, we can also easily reach a very lightweight reinforced concrete with densities of about or less than 800 kg/m3. [In general, any concrete with an oven-dry density of less than 800 kg/m3 can be classified as thermal insulation concrete (insulating, insulator, or insulative concrete).]

By utilizing the ECRLC, some substantial problems in using lightweight concrete, such as the high possibility of a brittle, compressive failure mode in the beams made of ordinary reinforced lightweight concrete (especially in those with low height and/or made of very low-density concrete as insulation concrete), can be removed. Then we can also reach the ultra-lightweight and low-height beams with a significantly high bearing capacity. 

Naturally, by more studies in the field, these structures and their applications in various fields can be developed. 

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- Previous Version in Persian:

Kamyar Esmaeili: “An Introduction to Elastic Composite, Reinforced Lightweight Concrete”. The Road & Building (Rah va Sakhteman) Magazine (Construction & Architectural Monthly Magazine, ISSN: 1728-6166); No. 50, May-Jun 2008; pp. 22-41. [Persian] (<http://www.magiran.com/magtoc.asp?mgID=3051&Number=50&Appendix=0>; also archived at <http://www.webcitation.org/69jdn3gOw>) 

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         ● NOTICE: 

On behalf of the author, there is actually "no monopoly" of the ECRLC in particular and LFNLCs in general. 

Notwithstanding the official registration of the composite material termed "Elastic Composite, Reinforced, Lightweight Concrete (ECRLC)" as an invention (in Iran) by the author and the approval of the invention by some relevant organizations (as The Iranian Research Organization for Science and Technology (IROST) through the evaluation process of The National Foundation of Elites and The Iran National Science Foundation (INSF) and despite publishing a patent application by The USPTO regarding The RCS (Resilient Composite Systems), there is no monopoly of this technology and related products in practice. All information concerning this technology has been disclosed, by the author, through open-access media for public use. [The usage of the ECRLC in construction within the relevant standards and common regulations within has also been approved and selected as a premier system by some academic and professional centers (as Tehran Construction Engineering Organization).] 

♦ توجه: 

با وجود ثبت سامانه مرکب مورد نظر (با عنوانِ "بتن سبک مسلح و مرکب ارتجاعی با تغییرات غیرخطی کرنش در ارتفاع تیر در خمش، الگوی شکست غیر ترد و مدول فنریت ویژه بالا در خمش") به عنوان اختراع (در ایران) توسط نگارنده و تایید آن از کانال مراکزِ مربوط از قبیل سازمان پژوهشهای علمی و صنعتی ایران و انتشار اطلاعات مقتضی توسط USPTO (و گذشته از برگزیده شدن طرح بهره-گیری ساده از سامانه مزبور در ساخت بنا، در چارچوب ضوابط و معیارهای جاری در صنعت ساختمان، توسط برخی مراکزِ مربوط مانند سازمان نظام مهندسی تهران)، در عمل هیچگونه انحصاری در تولید و استفاده از سامانه موسوم به بتن سبک مسلح و مرکب ارتجاعی وجود نداشته و کلیه موارد در این باره برای استفاده عموم منتشر گشته است.  

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