Investigation on Improvement of Flexural Behavior of Low-Density Cellular Concrete through Fiber Reinforcement for Non-Structural Applications

During the last decades, cellular lightweight concrete (CLC), or foamed concrete, has been experiencing greater interest in geotechnical, structural, and non-structural applications. The low density and high flowability makes it a favorable construction material in relation to handling, placing, and construction costs. However, the applications of low-density cellular concrete (LDCC), the category of CLC with a unit weight less than 50 pounds per cubic foot (801 kg/m3) and generally without fine aggregates, are limited mostly to backfill applications in geotechnical engineering. The main reason lies in the brittleness of the material and low to zero resistance to flexural loads. Fiber-reinforced LDCC may be a reasonable solution to improve mechanical properties and expand the application range of the material. This study investigated the effects of adding polypropylene and hybrid fibers on physical and mechanical properties of LDCC and the feasibility of expanding LDCC utilization to non-structural applications. Results showed that although there is a slight reduction of flowability and compressive strength, the flexural behavior of LDCC can be significantly improved with the incorporation of fibers. The flexural strength and flexural toughness of LDCC was found to increase from 26.8 pounds per square inch (psi) (0.18 MPa) to 217.5 psi (1.48 MPa), and from 5.67 lb-in. (0.64 kN-mm) to 292 lb-in. (33.0 kN-mm) respectively at a 1.0% addition rate of a fibrillated polypropylene fiber selected in this study, which makes it a feasible material for non-structural applications.

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Mechanical Properties and Flexural Behavior of Sustainable Bamboo Fiber-Reinforced Mortar

Applied Sciences ◽

10.3390/app10186587 ◽

2020 ◽

Vol 10 (18) ◽

pp. 6587 ◽

Cited By ~ 1

Author(s):

Marcus Maier ◽

Alireza Javadian ◽

Nazanin Saeidi ◽

Cise Unluer ◽

Hayden K. Taylor ◽

...

Keyword(s):

Mechanical Properties ◽

Fracture Toughness ◽

Construction Material ◽

High Volume ◽

Bamboo Fiber ◽

Flexural Behavior ◽

Fiber Reinforced ◽

Structural Applications ◽

Bamboo Fibers ◽

By Products

In this study, a sustainable mortar mixture is developed using renewable by-products for the enhancement of mechanical properties and fracture behavior. A high-volume of fly ash—a by-product of coal combustion—is used to replace Portland cement while waste by-products from the production of engineered bamboo composite materials are used to obtain bamboo fibers and to improve the fracture toughness of the mixture. The bamboo process waste was ground and size-fractioned by sieving. Several mixes containing different amounts of fibers were prepared for mechanical and fracture toughness assessment, evaluated via bending tests. The addition of bamboo fibers showed insignificant losses of strength, resulting in mixtures with compressive strengths of 55 MPa and above. The bamboo fibers were able to control crack propagation and showed improved crack-bridging effects with higher fiber volumes, resulting in a strain-softening behavior and mixture with higher toughness. The results of this study show that the developed bamboo fiber-reinforced mortar mixture is a promising sustainable and affordable construction material with enhanced mechanical properties and fracture toughness with the potential to be used in different structural applications, especially in developing countries.

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Effects of Uncrushed Aggregate on the Mechanical Properties of No-Fines Concrete

Engineering, Technology & Applied Science Research ◽

10.48084/etasr.1976 ◽

2018 ◽

Vol 8 (3) ◽

pp. 2882-2886 ◽

Cited By ~ 3

Author(s):

M. A. Memon ◽

M. A. Bhutto ◽

N. A. Lakho ◽

I. A. Halepoto ◽

A. N. Memon

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Coarse Aggregate ◽

Lightweight Concrete ◽

Aggregate Size ◽

Unit Weight ◽

Conventional Concrete ◽

Major Aspect ◽

Coarse Aggregates ◽

Cellular Concrete

Concrete’s self-weight is a major aspect of a structure’s overall weight. Recently, the use of lightweight concrete (no-fines, foamed and cellular concrete) has been increased. Normally no-fines concrete is produced with crushed coarse aggregate of uniform gradation. This study aims to investigate experimentally the effects of the use of uncrushed coarse aggregates on unit weight, compressive and tensile strength of the no-fines (NFC) as well as conventional concrete (CC). In addition, the effects of coarse aggregate size on the mechanical properties were also studied. Four gradations of uncrushed coarse aggregates ranging between (5.5-4.75) mm, (10-4.75) mm, (20-4.75) mm and (25-4.75) mm were used for preparing the concretes. The fixed cement-aggregate ratios of 1:6 (with w/c ratio=0.4) and 1:2:4 (with w/c ratio=0.5) were adopted for NFC and CC respectively. It was found that the gradation of uncrushed coarse aggregate has a significant effect on the mechanical properties of NFC. A maximum of 16% reduction in self-weight of the concrete without fines was obtained, as compared to that with fines. Moreover, the compressive strength of no-fines concrete significantly improved by replacing crushed with uncrushed coarse aggregate. The compressive strength increased by 16% for the batch of (25-4.75) mm.

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Additive manufacturing of ceramics: Present status and future perspectives

10.31224/osf.io/gk9n6 ◽

2021 ◽

Author(s):

Mainak Saha ◽

Manab Mallik

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

Microstructure Evolution ◽

Review Article ◽

Low Density ◽

Structure Property ◽

Future Perspectives ◽

Structural Applications ◽

Systematic Structure ◽

State Of Research

At present, fabrication of ceramics using AM-based techniques mainly suffers from two primary limitations, viz: (i) low density and (ii) poor mechanical properties of the finished components. It is worth mentioning that the present state of research in the avenue of AM-based ceramics is focussed mainly on fabricating ceramic and cermet components with enhanced densities and improved mechanical properties. However, to the best of the authors’ knowledge, not much is known about the microstructure evolution and its correlation with the mechanical properties of the finished parts. Addressing the aforementioned avenue is highly essential for understanding the utilisation of these components for structural applications. To this end, the present review article is aimed to address the future perspectives in this avenue has been provided with a special emphasis on the need to establish a systematic structure-property correlation in these materials.

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Reinforcement Efficiency of Cellulose Microfibers for the Tensile Stiffness and Strength of Rigid Low-Density Polyurethane Foams

Materials ◽

10.3390/ma13122725 ◽

2020 ◽

Vol 13 (12) ◽

pp. 2725 ◽

Cited By ~ 1

Author(s):

Jānis Andersons ◽

Mikelis Kirpluks ◽

Ugis Cabulis

Keyword(s):

Mechanical Properties ◽

Polyurethane Foams ◽

Low Density ◽

Mechanical Reinforcement ◽

Tensile Stiffness ◽

Structural Applications ◽

Cellulose Microfibers ◽

Renewable Material ◽

Reinforcement Efficiency ◽

Pu Foams

Rigid low-density closed-cell polyurethane (PU) foams are widely used in both thermal insulation and structural applications. The sustainability of PU foam production can be increased by using bio-based components and fillers that ensure both enhanced mechanical properties and higher renewable material content. Such bio-based foams were produced using polyols derived from rapeseed oil and microcrystalline cellulose (MCC) fibers as filler. The effect of MCC fiber loading of up to 10 wt % on the morphology, tensile stiffness, and strength of foams has been evaluated. For estimation of the mechanical reinforcement efficiency of foams, a model allowing for the partial alignment of filler fibers in foam struts was developed and validated against test results. It is shown that although applying MCC fibers leads to modest gains in the mechanical properties of PU foams compared with cellulose nanocrystal reinforcement, it may provide a higher content of renewable material in the foams.

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Mechanical Properties of High-Volume Fly Ash Strain Hardening Cementitious Composite (HVFA-SHCC) for Structural Application

Materials ◽

10.3390/ma12162607 ◽

2019 ◽

Vol 12 (16) ◽

pp. 2607 ◽

Cited By ~ 2

Author(s):

Chenhua Jin ◽

Chang Wu ◽

Chengcheng Feng ◽

Qingfang Zhang ◽

Ziheng Shangguan ◽

...

Keyword(s):

Mechanical Properties ◽

Fly Ash ◽

Strain Hardening ◽

Construction Material ◽

High Volume ◽

Partial Replacement ◽

Cementitious Composite ◽

Multiple Cracking ◽

High Volume Fly Ash ◽

Structural Applications

Strain-hardening cementitious composite (SHCC) is a kind of construction material that exhibits multiple cracking and strain-hardening behaviors. The partial replacement of cement with fly ash is beneficial to the formation of the tensile strain-hardening property of SHCC, the increase of environmental greenness, and the decrease of hydration heat, as well as the material cost. This study aimed to develop a sustainable construction material using a high dosage of fly ash (no less than 70% of the binder material by weight). Based on the micromechanics analysis and particle size distribution (PSD) optimization, six mixes with different fly ash to cement ratios (2.4–4.4) were designed. The mechanical properties of the developed high-volume fly ash SHCCs (HVFA-SHCCs) were investigated through tensile tests, compressive tests, and flexural tests. Test results showed that all specimens exhibited multiple cracking and strain-hardening behaviors under tension or bending, and the compressive strength of the designed mixes exceeded 30MPa at 28 days, which is suitable for structural applications. Fly ash proved to be beneficial in the improvement of tensile and flexural ductility, but an extremely high volume of fly ash can provide only limited improvement. The HVFA-SHCC mix FA3.2 (with fly ash to binder ratio of about 76% by weight) designed in this study is suggested for structural applications.

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Behavior of Foam Particles Lightweight Concrete with Time

International Journal of Current Engineering and Technology ◽

10.14741/ijcet/v.8.4.13 ◽

2018 ◽

Vol 8 (04) ◽

Author(s):

Sohila A. El-Khouly ◽

Amr H. Zaher ◽

Ehab F. Sadek ◽

Khalid M. Hilal

Keyword(s):

Lightweight Concrete ◽

Load Level ◽

Experimental Results ◽

Time Dependent ◽

Flexural Behavior ◽

Unit Weight ◽

Experimental Program ◽

Sustained Load ◽

Polystyrene Foam ◽

Loading Test

Lightweight Concrete with polystyrene foam particles (LWC) was obtained through the use of polystyrene foam as a partial aggregate’s replacement to reduce the concrete dry unit weight from 23 KN/m3 to 18.50 KN/m3. This research presents an experimental and theoretical investigation in the long-term behavior of LWC in compression and flexure. Two experimental programs were conducted; namely, creep and shrinkage of LWC under compressive loading test, and the time-dependent flexural behavior of reinforced LWC beams. The main variable in the first experimental program was the percentage of sustained load, while the main variables in the second experimental program were the percentage of sustained load and the percentage of compression reinforcement. Experimental results showed that LWC exhibits a significantly higher time-dependent strain (shrinkage plus creep) than normal weight concrete (NWC) under sustained compressive load and at the same compressive strength, with an increasing percentage about 9%. The creep strains of LWC seemed to be proportional to the stress to strength ratio. The timedependent deflections of the LWC beams were higher than those of NWC beams with increasing percentage about 25%. Addition of compression steel reinforcement (As`) to LWC beams reduced time-dependent deflections. Sustained load level and LWC time-dependent deflection were directly proportional. Finally, models and equations proposed by different codes were used to evaluate the obtained experimental results. From the theoretical study, it was found that Bazant-Baweja B3 Model gave superior shrinkage strains prediction for LWC. The ACI 209R-92 presented preferable predictions of creep strain and time-dependent deflection of LWC.

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Properties and Microstructure Distribution of High-Performance Thermal Insulation Concrete

Materials ◽

10.3390/ma13092091 ◽

2020 ◽

Vol 13 (9) ◽

pp. 2091 ◽

Cited By ~ 2

Author(s):

Malek Mohammad ◽

Eyad Masad ◽

Thomas Seers ◽

Sami G. Al-Ghamdi

Keyword(s):

Thermal Conductivity ◽

Compressive Strength ◽

Thermal Insulation ◽

High Performance ◽

Lightweight Concrete ◽

Concrete Mixture ◽

Unit Weight ◽

Expanded Perlite ◽

Micro Computed Tomography ◽

Structural Applications

The aim of this experimental study is to develop high strength and lightweight concrete mixture suitable for structural applications. This work investigates the effect of replacing normal aggregate either partially or totally with expanded perlite aggregate. This material allows for better thermal insulation properties, thus decreasing the energy usage within the life cycle of the concrete structure. Expanded perlite aggregate was used in concrete by 20%, 40%, 60%, 80%, and 100% in replacement of the natural aggregate. Material characterization tests of compressive strength, flexural strength, and thermal conductivity were carried out for six concrete mixtures. In addition, microstructure analysis was performed with the aid of a micro-computed tomography system to investigate the effects and relation of microstructure quantities on material properties. The proposed concrete mixture, which has 100% of expanded perlite aggregate, has a unit weight of 1703 kg/m3 and achieved reduction percentage of thermal conductivity around 62% (1.81 to 0.69 W·m−1·K−1) and a compressive strength of 42 MPa at 28 days; and thus is ideal for structural applications with enhanced properties.

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COMPRESSIVE STRENGTH EVALUATION OF LIGHTWEIGHT CONCRETE WITH EXPANDED GLASS AGGREGATE BY ULTRASONIC PULSE VELOCITY METHOD

Proceedings of International Structural Engineering and Construction ◽

10.14455/isec.res.2020.7(1).mat-10 ◽

2020 ◽

Vol 7 (1) ◽

Author(s):

Christopher Collins ◽

Saman Hedjazi

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Lightweight Concrete ◽

Lightweight Aggregate ◽

Ultrasonic Pulse Velocity ◽

Ultrasonic Pulse ◽

Pulse Velocity ◽

Normal Weight ◽

Unit Weight ◽

Normal Weight Concrete

In the present study, a non-destructive testing method was utilized to assess the mechanical properties of lightweight and normal-weight concrete specimens. The experiment program consisted of more than a hundred concrete specimens with the unit weight ranging from around 850 to 2250 kg/m3. Compressive strength tests were performed at the age of seven and twenty eight days. Ultrasonic Pulse Velocity (UPV) was the NDT that was implemented in this study to investigate the significance of the correlation between UPV and compressive strength of lightweight concrete specimens. Water to cement ratio (w/c), mix designs, aggregate volume, and the amount of normal weight coarse and fine aggregates replaced with lightweight aggregate, are the variables in this work. The lightweight aggregate used in this study, Poraver®, is a product of recycled glass materials. Furthermore, the validity of the current prediction methods in the literature was investigated including comparison between this study and an available expression in the literature on similar materials, for calculation of mechanical properties of lightweight concrete based on pulse velocity. It was observed that the recently developed empirical equation would better predict the compressive strength of lightweight concrete specimens in terms of the pulse velocity.

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Microstructural and Mechanical Properties Changes of Silicon Nitride Based Ceramic Using Post-Sintering Heat Treatment

Materials Science Forum ◽

10.4028/www.scientific.net/msf.727-728.1085 ◽

2012 ◽

Vol 727-728 ◽

pp. 1085-1091

Author(s):

José Vitor C. Souza ◽

O.M.M. Silva ◽

E.A. Raymundo ◽

João Paulo Barros Machado

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Fracture Toughness ◽

Grain Size ◽

Wear Resistance ◽

High Hardness ◽

Gas Pressure ◽

Low Density ◽

Nitrogen Gas ◽

Structural Applications

Si3N4based ceramics are widely researched because of their low density, high hardness, toughness and wear resistance. Post-sintering heat treatments can enhance their properties. Thus, the objective of the present paper was the development of a Si3N4based ceramic, suitable for structural applications, by sintering in nitrogen gas pressure, using AlN, Al2O3, and Y2O3as additives and post-sintering heat treatment. The green bodies were fabricated by uniaxial pressing at 80 MPa with subsequent isostatic pressing at 300 MPa. The samples were sintered at 1900°C for 1 h under N2gas pressure of 0.1 MPa. Post-sintering heat treatment was performed at 1500°C for 48 h under N2gas pressure of 1.0 MPa. From the results, it was observed that after post-sintering heat treatment there was a reduction of α-SiAlON phase and increase of β-Si3N4phase, with consequent changing in grain size, decrease of fracture toughness and increase of the Vickers hardness.

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FLEXURAL BEHAVIOR OF REINFORCED LIGHTWEIGHT CONCRETE BEAMS MADE WITH ATTAPULGITE AND ALUMINUM WASTE

Journal of Engineering and Sustainable Development ◽

10.31272/jeasd.25.2.4 ◽

2021 ◽

Vol 25 (02) ◽

pp. 24-35

Author(s):

Zahraa A. Mirza ◽

◽

Nibras N. Khalid ◽

Keyword(s):

Mechanical Properties ◽

Failure Mode ◽

Ultimate Load ◽

Lightweight Concrete ◽

Concrete Beams ◽

Lightweight Aggregate ◽

Reinforced Concrete Beams ◽

Flexural Behavior ◽

Lightweight Aggregate Concrete ◽

Flexural Ductility

Lightweight concrete reduces the total dead load of structural elements and seismic loads significantly. This paper presents the production Attapulgite Lightweight aggregate concrete (ALWAC) and its effect on the flexural behavior of reinforced concrete beams. Attapulgite was treated with sodium hypochlorite of 6% concentration for 24 hours. The variable considered was the aluminum waste (AW), used as a fiber, of fraction (0, 0.5 and 1%) by concrete volume. Behavior was investigated in terms of cracking and ultimate load, load-deflection relationship, failure mode, crack patterns and flexural ductility. The mechanical properties of the ALWAC were studied. It was observed that, Attapulgite improves the mechanical properties of concrete when comparing the experimental value with theoretical ones for the reference mixture. AW has a disparate effect on the mechanical properties of ALWAC. The increase in the proportions of AW showed an increase in the cracking load and decrease in the ultimate load by 37.14% and 22.45 %, respectively, at AW of 1%. Experimental value of ultimate load in all beams was higher than the theoretical value (ACI simplified method). AW increases the deflection at the same magnitude of applied load, and reduces the number and propagation of the flexural cracks in beams. All beams exhibited a typical tension failure mode and failed in ductile manner.

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