Science topic

Concrete Technologies - Science topic

Concrete Technologies are one of the most crucial ways to reach the sustainability and development of the world in the future is to work and research on Concrete Technology. The concerns will be to enhance structural strength and durability of the concrete. Actually, what is the boundary for concrete strength? 2000 kg/cm2, 5000 kg/cm2 or more. How long will our concrete design and implementation continue to be utilized? 50 years, 100 years or more. In this group, we strongly appreciate your new ideas to be submitted for mix designs of the concrete, QC of the concrete, implementation of the concrete and so on.
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Post everything you know about ferrock and ferrock concrete
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Dr David Stone
The History of Ferrock Ferrock was actually invented by accident in the early 2000s. Dr David Stone, the founder of Iron Shell Media Technologies and former University of Arizona PhD student, was researching ways to prevent iron from rusting and hardening when he accidentally created Ferrock.
Iron Shell, LLC
Iron Shell is a start-up material science company founded in 2012 which produces Ferrock, an environmentally friendly cement substitute utilizing waste steel dust. This technology is carbon-negative, absorbs environmental toxins, and has substantial structural advantages over traditional cement.
David Stone Founder and CTO at Iron Shell Material Technologies
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In wide RC beams, the shear reinforcement (stirrups) are distributed along the beam length and across its width. There are limits for the longitudinal spacing of stirrup legs (SL) in the current Codes of Practice. But, Do these Code have provisions for the stirrup legs spacing in the transverse direction (Sw) of these wide RC beam? Only EC2 Code deals with Sw, where it assumes that Sw = SL = 0.75d.
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has you have an answer for this question ?
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As far as FRP is concerned, there are two documents in North America for the design and detailing of RC structures, i.e., CSA S806-12 and ACI 440.1R-15. I have been trying to find any similar documents in Europe but it seems there is no unified European document so far. Any clues? 
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This is a good question.
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Some papers are giving that the ductility is directly proportional to the compressive strength of concrete. If so, what will be the relation between these two
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It is well known fact that increase in compressive strength decreases ductility of concrete. Due to which we add different types of fibers to improve its ductility.
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I have worked on structural optimization using MATLAB. Now I want to publish in an International Journal. I thought Computers and structures first. But, I would like to know which would be a suitable journal to publish such work. I have written a paper and MATLAB code as well. Thanks a ton in advance.
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I am sharing a list of good Journals which are SCI/ESCI/SCIE and Scopus Index
1. Asian Journal of Civil Engineering- Springer
2. Innovative Infrastructure Solutions- Springer
3. Frontiers of Structural Engineering- Springer
4. Canadian Journal of Civil Engineering
5. International Journal of Civil Engineering-Springer
6. Engineering Structures- Elsevier
7. Structures-Elsevier
8. Construction and Building Materials- Elsevier
9. All Journals of Techno Press dealing in Civil
10. All Journals of Emrald Publications dealing in Civil
I hope it will helps all
Regards
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I have stadium stairs made of concrete, and i need to pick an adhesive material that give a good bonding strength and can resist some environmental factors such as hot and cold weather without peeling off. ( ceramic- polymer composite).. I can،t wait to read your esteemed answers.
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I would like to recommend Silicone Rubber Compounds - RTV 2 components which perform the ability of high thermal conductivity and adhesive. Some famous brand names which you can refer ShinEtsu, Momentive, or Dow-Corning.
References:
Best regards.
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Is it possible to switch major from petroleum engineering to civil engineering? Specially related to basic concrete technology, concrete releted products and materials?
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Yes it's possible, bet definitely, it's going to cost you time, a whole new experience from process to traditional Engineering. It's worthwhile as new technologies are bound to be developed from analysis of materials.
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Fellow scientists, do you know examples of the use of nanotechnology in concrete technology?
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Nanoparticles are used in concrete for various reasons. The most important one is to increase concrete mechanical properties, such as its compressive strength.
Nano-materials like Nano-silica, Carbon Nanotubes by filling nanopores in concrete and preventing the spread of cracks, respectively, increase the strength of concrete.
There are lots of published articles in this regard.
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We know that superplasticizers' properties vary in terms of PH, Density, Mass average molecular weight, Sidechain density of carboxylic acid groups, Impeller rotational velocity, Viscosity cP, and so on.
I wonder which type of superplasticizer can disperse Nano-SiO2 in water in the best way possible to make concrete?
Furthermore, is there any test that shows how well the nanoparticles dispersed in water?
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Dear Mheran there are many chemical admixtures (superplasticizers) use to modify the properties of fresh concrete. The best approach is to perform a test using various types of superplasticizer and select the best one. An empirical selection is not always efficient.
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I have seen that tensile strength of concrete is always lower than compressive strength values (generally 10-12 folds). How can we enhance the tensile strength of the concrete? Is it possible to enhance up to levels similar to compressive strength values either by addition of some SCMs, pozzolanic materials, admixtures, superplasticizers etc. or do we have to change the grade of concrete i.e. M20, M30....... M60 ....so on .., SCC, etc.?
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Dear Kunal . ,
You can use steel fibres or rubber strips and so on to increase the tensile strength of concrete.
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Obviously, it is impossible to use continuous reinforcement concrete bars; thus, several splicing methods are available to tackle the problem. Among them, overlap with tie wire, coupling, and welding methods are the common ones.
The question that has been on my mind is: What is the force transmission mechanism difference between these methods?
In the overlap splicing method, there is inherent space between the center of the bars. It means that there is a discontinuity in force transmission in this method. On the other hand, in mechanical splicing (coupling), the rebars' center is in precisely the same direction. Several tensile tests in this method have shown us that the rupture will never happen in place of the patch (beneath the coupling). While in the overlap splicing method, a fracture could occur anywhere along the rebar.
The question is that, has the force transmission mechanism taken into account for splicing rebars? Or overlap splicing method exists just to keep the rebars in their place for concreting?
Because the mentioned methods are acting quite differently in terms of the force transmission mechanism.
Thank you so much for your attention and participation.
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I think international concrete codes take these details into account. But, here we must provide an adequate running length for rebar that no debondind happen! And keeping tension force path as efficient as possible. For interaction zone, the amount of longitudinal reinforcement always doubled and no failure reported for this region in some literature That I read. Thank you that was good question.
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Please share any Example, Tutorial or any article related to CDPM. For a 3D Pushover analysis.
Thanking in anticipation!
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If you are interested in concrete model for explicit solver (VUMAT), you can use this link to download it
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I am seeking to find possible research questions on smart concrete for PhD
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We have concrete that can glow at night.
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Concrete block bricks companies are marketing that their products are eco-friendly, as they are not emitting carbon dioxide and not using soil. At that viewpoint, they are right.
But,in their manufacturing process, they are largely using cement and sand. Cement manufacturers also badly polluting environment by particulate matters and others emissions activities. Overconsumption of natural resources as well as sand extraction can cause environmental damage.
My question is, how much eco-friendly concrete block bricks is?
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Ecofriendly concrete bricks could be produced globally by using less of cement but more of pozzollanic ashes from industrial and agro activities. But most brick makers will first consider acceptance from consumers alongside the financial implications. Standards and other logistical challenges are other factors affecting it's global acceptance and adoption.
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Cement mill with spray nozzles are being used since many years. Experience suggests that it sometime helps in preventing unnecessary increase of mill temperature which in turn gives no harm to cement quality. On the other side, sometime spray nozzle does not work properly due to coating formation on it and also causes unnecessary stoppages of cement mill due to high temperature. What should be the soluton to avoid coating fornmation on spray nozzle.
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Bhautesh Mistry I am very much interested in the question you have raised. I also have a cement mill nozzle which keeps blocking especially when there is a power failure. Have you found a solution to your problem? if yes, please do share. Also is there a special type of nozzle that helps prevent this blockage? How efficient is the use of grinding aid in the nozzle in preventing this blockage and improving overall grinding efficiency? Thank you.
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Can anyone help me with finding a dataset for alkali-silica reaction(ASR) cracks? Thanks
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I am using ASTM C1579 standard mold to investigate plastic shrinkage crack in concrete. Unfortunately I cannot find any crack on the concrete surface while the contraction on the mold edges can easily be seen. So, I believe the mold is not restrained enough. I wonder if anyone else has the same experience.
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I've been using these molds for a while in my studies. It's really difficult to respond your question without considering the parameters contributing in the study. However, since the focus of my studies are in the assessment of the impact of the environmental conditions and curing practice on the cracking behaviour of this type of shrinkage, based on my experience so far, I can admit that your doubt toward these molds is justifiable and reasonable and I personally have already thought about it.
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Dear RG Community,
I intend to ask you that what are some classical examples of Geotechnical Engineering related problems, for example differential settlement in Leaning Tower of Pisa was/is considered one of the fine problem. Also if you could help me with some of the case studies which you consider will be helpful in understanding the fundamentals and core of Geotechnical Engineering.
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Mr.Muneeb,
I feel the main important one in all over the world is population increase and no space available for developing infrastructure relative to increase in population. so the construction activities have taken place as closer to an existing structure. In view of this, the stability analysis of existing structure adjacent to new construction in terms of excavation, embankment, tunneling or pile driving is a serious problem. As a geotechnical engineer we need to come out with design idea to protect the existing structure due to the effect of new construction.
Another important issue is we don't have excellent supporting ground for the new construction. So, in this case we need to develop economical ground improvement technique to support the load. Ground improvement technique alternate to conventional method is catching up among researcher . ok all the best in your research..
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Concrete technology
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Re-tempering with chemical admixture (need proper mixing after re-tempering, at east 70 revolutions in 2/3 minutes in transit trucks) is not harmful. It increases slump and concrete can be pumped and compacted with less efforts. Re-tempering by addition of water is always harmful as it reduces strength of concrete drastically.
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i have a master of science degree in the field of construction engineering and management and i went to continue my PHD degree in the field of concrete technology or construction materials so i need some suggestion form other researchers about research idea or title.
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High performance concrete with advanced properties like high density, low density, high water resistance, chemical resistance, weather resistance, fire resistance, radiation resistance, ductility, durability, etc customised as per project requirements
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Due to its fined microstructure, HSC possesses different mechanical properties compared to normal strength concrete. One common characteristic is its increased brittleness. Many approaches have been used to judge the material brittleness. One method is using the ratio between the tension strength to compressive strength: the lower the ratio, the more brittle. Another is the linear portion in the stress-strain curve observed in uniaxial compressive concrete. The larger the linear portion, the more brittle. In fracture mechanics, some brittleness quantifiers have been defined according to different models In fictitious crack model (FCM), a characteristic length (lch) that is defined by combining the fracture energy (Gf) with elastic modulus E and the tensile strength of material (ft). The smaller the value lch, the more brittle the material. Another common used brittleness indicator is the critical crack extension length (ac). the larger the value ac, the less brittle. When it decreases with an increase in compressive strength, we can say the brittleness increases with strength. Apart from these, what are the other approaches that can be used to define brittleness of HSC?
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Hello
I think fracture energy is the area under load disp curve, it could be one the factors in judging the brittleness of the concrete. more energy might provide less brittleness for the material. if you look at characteristic length formula, you will find other factors such as E , ft ... there.
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I tried my best to find the data in 2009, which is 25 billion tonnes [CSI,2009], see attached. Does anyone have more recent data?
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concrete technology, materials
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I am aware about autoclave, heating, using accelerator agents, Type III cements, polymer modification, and lower W/C ratios. But I am wondering if you can introduce other techniques, as well.
I am referring to achieve a compressive strength of at least 20 MPa in 1 day or less.
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In the research I conduct, I would like to compare the number of multi-family buildings erected in prefabricated concrete technology with other technologies. What did the situation look like in individual countries 20 years ago and now. In Poland, such data is collected by the Central Statistical Office. I couldn't find such statistics in the statistical offices of other countries. Does anyone know the source where they can be published?
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What do you think how important, for segregation coefficient of SCC, could be very small superplasticizer overlaps during the process of making SCC? I made some observations in my work:
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According to the previous studies [1-3], an increase in the S/C ratio within the range of 0.5 to nearly 2.25 results in a gradual increase in the compressive/flexural strength while the S/C ratio higher than 2.25 can reduce the compressive/flexural strength of the cement mortar. My mix-design consists of general-purpose cement, silica fume, superplasticizer, viscosity modifying agent, and washed high purity silica sand with a maximum particle size of 600 µm and fineness modulus of 1.29. all the proportion including the water/cement =0.35 kept constant except the S/C which changed from 0.8 to 1.0 and 17% reduction observed in compressive strength.
Moreover, the addition of Sand resulted in a lower density and all the compressive and flexural strength were measured after 28 days of curing.
Can this phenomenon be explained by the fineness modulus (particle size distribution) and/or changes in the porosity of the mixes?
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Are there any standards applying a 25mm(thickness) X 100mm(width) X 350mm(span) for concrete flexural strength test? Or maybe any possible formula could explain this?
Extra info: 3point load test, tested for a fibre reinforced lightweight foam concrete. I really need a clear explanation about this. Thank you very much in advance.
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We are investigating the mechanical properties of coir fiber reinforced concrete, and following some recommendations from previous research, we decided to reduce the alkalinity of concrete to prevent premature aging of coir fibers. We are using an OPC concrete mix with a pH of 12.5 to 13. To reduce the pH, we have incorporated into the concrete mix amounts of micro-silica and gypsum. However, no significant changes were recorded (pH of 12 to 12.2). Does anyone know an effective and practical method to reduce the pH of an OPC concrete and obtain values of 11 of less?
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Concrete strength measured using concrete cubes produce a results different than concrete cylinders.  Conservative estimates put concrete cylinders at 80% of concrete cubes, for high-strength concrete some say the percentage is near 100%.
Does anyone have experience using a cube strength in place of a cylinder's or vise-versa?  Would anyone use a "translated" cube strength specification for design?  Would anyone use a translated cube strength in place of a cylinder test for acceptance?
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I'm working on the Fly Ash & GGBFS based geopolymer mortars in Lab. Can we consider the specifid weight of this mortars as 2000kg/m3? And when we use GGBFS instead of Fly ash, shall we reduce the content of ggbfs because of these higher specific weight?
Thank you.
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it is well known the reasons behind cracks at early age,like natural concrete shrinkage combined with outer boundary conditions restraint this volume changes. in addition changing the properties of materials with time
the standards codes and committees work to solve this issue. unfortunately this issue still not solved yet.
The question: is it this standers and committees not understand clearly this phenomenon?
or need more improvement ?
note : we talking about the through cracks not surface cracks .
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I agree with @Jessly Rajan
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Hello.
Which aggregates have a high water absorption while they have a desirable strength too?
If you can suggest me a paper contains mentioned data, it will be a great help.
thanks.
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maybe recycled aggregates
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OPC is the 2nd largest generator of CO2 after automobile industries. Researchers have claimed that geopolymer based concrete is more stronger , durable,versatile and eco friendly but unfortunately it has not been widely utilized in practice. I wanted to know its limitations and if there is any possible health hazards related to it. I have also heard that it has some sorts of toxic effects. Is it just a hoax?
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The term "geopolymer" is widely used for slag cements and alkali-activated (slag) cements, too. The production and handling of those systems (without any Ordinary Portland Cement OPC) are neither "difficult to create", have not to be "premixed only" nor "sensitive" at all. Major and fundamental research work and applications have been performed in Russia, China, Ukrania, Japan, India, Spain, Germany and Tschechia since 1990. Intense research about this very competitive product to OPC has been done and patented by P. Krivenko, F. Skvara and J. Gebauer& L. Ko{HOLCIM} and other international cement producers.
Most important is a constant quality of the components for geopolymers:
- Homogenous slags or ashes of consistent/constant quality with high glassy phases
- Proper adjustment of desired slag/ash with alkali source (Sodium or Lithium Sulfate, Sodium Silicates( "water glass"), Sodium Metasilicate, Alkali Hydroxides, Calcium Oxide and/or Hydroxide etc.
Since the constant quality of slag/ash component is necessary, geopolymer production is especially economically in those countries with/or close to a strong heavy metal industry. Geopolymers have a much improved ecological balance (less Carbon Dioxide and dust emissions compared to OPC), very good to excellent compressive strength and much better chemical resistance/durability in comparison to OPC.
The major draw-backs of geopolymers are the lack of standardisation, the strong lobby of the OPC producers....and the still lax legislation on CO2 reduction...but the time for geopolymers will come!
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I am modeling the debonding between concrete and CFRP subjected to tangential loading using ANSYS Workbench, I used (CZM/VCCT)  techniques to model the debonding. as you know with workbench you can't choose the element type directly. you have to insert commands for Solid65. or use the default solid186.
  1.  For pure tangential force applied on the plate. is it suitable to use solid65 element for concrete in this case. bearing in mind that in some failure modes in experimental there is a lump concrete attached to the plate after separation (Failure). and in others the concrete is intact (just debonding failure). 
  2. I tried different element types, but when I use the SOLID 65 command, my model lose convergence too early. If I remove cracking and crushing capability (Suppress the command), the solution runs fine without any convergence problems. (is this  due to cracking feature associated with solid65). how can I get the model to converge.
  3. in meshing,If the mid-side nodes are set to "dropped" for the default solid186 (20 nodes), will I get similar behavior as solid65 (8 nodes) (3 DOF/node for both). 
I already tried the following to get my model to converge for solid65 in workbench:
1- Refining the mesh.
2- Reducing the normal stiffness of the contact region
3- Use newton Raphson residuals.
4- Playing with steps and sub-steps (applying displacement in small intervals).
Any help or suggestions will be highly appreciated.
Thanks in advance.
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Was it to physically identify crack orientation/inclination and differentiate it between lateral, flexural, shear cracks etc? Or is it for some other function i dont know about.
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Grid provides you the pattern of cracking and directions to allow you to study the detailing of reinforcement required in the joint.
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Have you come across this error-"DURING THE CONVERSION FROM CRUSHING TO PLASTIC STRAIN Abaqus FOUND NEGATIVE AND/OR DECREASING VALUES OF PLASTIC STRAIN. VERIFY THAT THE DEGRADATION DATA UNDER *CONCRETE COMPRESSION DAMAGE IS CORRECT?"
DURING THE CONVERSION FROM CRACKING TO PLASTIC STRAIN Abaqus FOUND NEGATIVE AND/OR DECREASING VALUES OF PLASTIC STRAIN. VERIFY THAT THE DEGRADATION DATA UNDER *CONCRETE TENSION DAMAGE IS CORRECT
How to overcome this error , I was trying to replicate the problem as mentioned in the attached paper
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That error occurs when the equations to calculate the plastic strain gives a negative or a value smaller than the inelastic strain.
To avoid it you need to calculate the plastic strain using the equation and check that the value are always ascendant. remember that the first line of damage parameter and inelastic strain needs 0 as values, so develop the rest of the points based on the coordinates of your 0 inelastic strain point with no damage.
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Chemical structure of polycarboxylate?
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Polycarboxylates are linear polymers with a high molecular mass (Mr ≤ 100 000) and with many carboxylate groups. They are polymers of acrylic acid or copolymers of acrylic acid and maleic acid.
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I will like to model the microstructure of concrete/mortar, is there any software to model the resulting products?
Thanks
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I have used CONTACT 173 and TARGET 170 element. The shear bond strength of brick-mortar is 0.005 MPa, coefficient of friction for bed joint is 1.2 and head joint is 0.85. Does it works if i use ''bonded always'' contact pair?
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In ansys you can use CZM material with identifying the debonding parameters as an input. The contact should be bonded with pure penalty or augmented lagrange formulation.
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One of the apparatus required for freeze and thaw test according to ASTM C666 is the dynamic testing apparatus. This apparatus is used to obtain the relative dynamic modulus of elasticity and durability factor of the concrete.
However, in case where the apparatus is not available, what other apparatus or parameter can be used ?
Few studies have used UPV as an alternative, but i'm still seeking for alternative methods.
Thanks
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PVA fibers are modified with oiling agents to reduce bonding between the fiber and the cementitious matrix.
What is the best type of oiling agent and method of application is most suitable?
Also, how can PVA fiber be tested whether its coated or not
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Similar to a project I have recently seen "Nest Hilo Roof" I am going to do a Master's thesis in a CONCRETE ROOF OVER A TEXTILE MESH. I am starting to work on the literature review and it's being complicated to find other examples done before.
Thank you for your help in advance. Any literature advise would be welcome.
Regards,
Maria
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As there is no universal standards for the determination of the axial tensile stress of fiber reinforced composites, they exist various suggestions by different studies.
What is the best specimen dimension and shape (i.e. dogbone or prism) to be used in assessing the tensile stress of FRCs
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I agree with D.K. Mishra.
You can also see paper attached here.
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Within the wide use of precast concrete technology... does the precast concrete considered energy efficient?
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Dear Anil Kumar Thakur ... Thanks for answering..
So did you think that precast concrete could be considered energy efficient?
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Non destructive tests equipment for concrete are quite expensive and not readily available. Is there any non destructive test that can be improvised or built with commonly available materials to determine the strength or/and permeability properties of concrete and other cementitious composites?
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There is some developing research that utilises surface water flow to predict concrete permeability and durability characteristics. This research determines the relative covercrete skin permeability which can be standardised for various concrete parameters such as strength, porosity, and durability. You can get an idea of how it works from this link (at least through the images). http://wdnsword.iis.u-tokyo.ac.jp/research/IISopen/Kikuchi_2012.pdf
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Does it have any relevance with M50 and C50 concrete strength? In terms of designing it, will using a normal concrete design method achieving 50MPa considered a B50 grade? Thanks in advance.
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What is the effect of carbon nanotubes on concrete strength?
Please share your research results
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Cnt
1. Act as nano fibers arresting the cracks at their initial propagation.
2. Nucleation sites for the cement hydration gels helping increasing stregnth.
3. Nano fillers to the nano and microscale pores and consequently increasing the packing level of the cement matrix
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Hi everyone
I am wondering if someone can explain the positive role of superplasticizer on concrete compressive strength of constant w/c ratio?
thanks
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Hello Dear
the main purpose of adding SP is to improve the workability of concrete.. but there's a limitation of the SP mount added to the concrete mixture, otherwise that may effect in the mechanical properties of concrete such as compressive strength, tensile and flexure..
the range of SP amount used is almost 2-4 % kg/m3 of concrete.
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In a real research sense, what can be tested for in the laboratory?
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hi Rasheed Babatunde Isa
Factors affecting the strength and durability of concrete
1-Water to cement ratio
2- Wet care of concrete :
Concrete without moisture control 50% reduction in compressive strength 28 days.
Concrete with 3 days of wet care 75% resistance in conditions 28 Day of wet care.
With 28 days of wet care we will have 100% resistance.
3- Type of cement used.
4- Time factor in compressive strength :
The compressive strength of concrete should increase over time
Forecast of concrete strength growth according to ACI 209 standard As follows: f(t)=f(28)(t/4+0.85t)
5- Effect of temperature on concrete strength
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Hi dear colleagues
Do the research projects that are continuously being published by researchers to reduce the depletion of resources and to enhance the environment are applied in practice?
For example, in the field of concrete technology, there are a lot of studies have used alternatives to cement (to reduce CO2 emission during cement industry) and natural aggregates for the above-mentioned purposes. Are such studies applied practically?
Regards
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Yes and no. Innovations are slow to transfer from the lab to the field. There are a number of reasons for this, but in my mind there are 2 primary reasons. Firstly, there is far more academic kudos in writing papers than in influencing practice. Consequently, academia is set up to support grant/journal writing far more than support for technical input. Secondly, industry is very conservative. This means that standards are often a long way behind the latest research findings (there may well be other, commercially influenced, reasons for this). The conservative nature of construction (and the low profit margins) means that industrial and academic timelines are not necessarily aligned.
I'm both sure what the solution is. But academia should encourage technology transfer while industry should put their hands in their pockets and recognise that not all research yields immediate returns.
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Can you please suggest some research topics in Concrete Technology ?
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Geopolymer Concrete
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We observed at high [temps ranging from 300'C and above] SCC cube under test explodes. Any previous study and references will be appreciated.
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Please find the attached file. This file is explaining the behavior of SCC under high temperature. I hope it can help you to find the best answer. The main reason of seeing this phenomena is transforming water to vapor and entrapping in the concrete can cause an increase in internal pressure.
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As we know water absorption of RCA is more than the natural aggregate...so how do we manage it in case of partial replacement..
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Interesting discussion!
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Hempcrete is a green material used in construction as filler material or partition wall. I wish to know the mix proportions of this concrete for beter performance.
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There are several specifications that provide equations to consider the effect of creep and shrinkage on the estimation of prestress loss. As some of the references state, creep and shrinkage equations for precast segmental concrete bridges differ from that for the other types of concrete bridges. For example, one of the references states that the creep factor for precast construction is normally around 1.6, while for in situ construction this factor would normally be between 2.0 and 2.5. Since most of the references are related to the bridges other than segmentally constructed ones, I would really appreciate it if you kindly provide me with some guidance and references related to the following points:
1. Equations for creep and shrinkage calculation in precast concrete.
2. Equations for prestress loss estimation in precast concrete bridges.
Thank you in advance.
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interested
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I have used truss element to model the tendon. But to model it as UNBONDED, should i be embedding it in concrete as the normal reinforcement is embedded.
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I have some serious issues about modelling element for pre-stressing steel tendon. 
Truss Element (T3D2) is supposed to be used for tendon (having axial stress only) but it does not have any cross-sectional shape and surface, so it is not possible to apply surface base cohesion with concrete surface and tie (with end plate) at end. 
If solid element is used, everything is fine (surface base cohesion with concrete and tie at end) but there is an unwanted flexural effect on beam from the tendon, it also acts as rio bars. You can imagine the effects when a 26 mm dia bar with 1000 MPa pre-stress exerts as a  flexural member. This results a lots of damage in surrounding concrete. 
Is there is any other suitable options? Any elements can acts in axial tension/compression only but having cross-sectional area and shape?
Thank you.
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Calculation of the confined concrete properties is necessary for non linear analysis. I am using Manders model.
Do anyone have the already built up code of excel sheet for it?
Also can anyone share the pdf file regarding information on Manders model?
Thanks in advance
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Hi Venkatesh
In attached spreadsheet, you can find Modified-Kent Park formula and Saatcioglu and Razvi formula. Hopefully, this can help you in your work.
Good luck!
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PCE superplasticizer used and a total 20s vibrating conducted.
DIN EN-196 sand also used.
//Pics attached for more detail.
I'm looking for your kind responses.
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Considering the cost of fabricating motor is low, you can try to use various content of admixture with less sand! Ensure the quality of raw materials and enough vibration, the problem is easy to be found!
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I have a problem of a test setup to do the direct tensile test in a universal testing machine. The machine jaws cannot be applied directly to grip the test specimens because of local damage and slip around the jaws. I want to  do a fabrication by attaching metal plates to the specimens and my problem is what kind of adhesive of sufficient bond strength  will I use to bond the plates to the concrete?
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Alex,
Your problem is bigger than you think. Concrete is not like metals. Not only do you have to worry about getting a grip on the sample, because concrete is such a brittle substance that gets more brittle as it gets stronger, you also have to take care not to introduce extra moments through misalignments, potentially in both x and y, that can lead to inconsistent or erroneous results. Something like the opposite of loading a compression sample through a ball is needed. I suggest this can be done through chains or cables depending on loads, attached to plates glued or bolted to your specimens. Be very careful because such attachments can fly around at failure. Even with such a system, aligning the top and bottom along the intended axis is also necessary. For this I sometimes used two lasers.
Direct tension testing of concrete is very hard. If you are looking for loading curves going from zero through the peak and back to zero, it is even harder than that. As always, the question: why do you want this value? Maybe the question is already answered. Maybe there is another test to get you the information you need, Brazilian or flexural test perhaps.
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The surface chloride content data is missing, but the concrete was ponded with 3% NaCl solution for 30 days.
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Petr Konečný, Can you provide an example of the whole process? An excel sheet maybe?
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I want to show the particle binding between the sand particles. which technique is effective ?(ex. SEM, CT scan)
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I think X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Brunner−Emmet−Teller (BET) may be helpful for you. XRD and XPS can clarify the particle binding type (crystal or amorphous; valence state) .  And BET can present porosity and specific surface area.
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Type III cement is generally preferred for High strength development, and are usually finer than the OPC/Type I cement. In India, which type of cement is classified under Type III?! Whether OPC 53 grade belong to this category?
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The ASTM has designated five types of portland cement, designated Types I-V.  Physically and chemically, these cement types differ primarily in their content of C3A and in their fineness.  In terms of performance, they differ primarily in the rate of early hydration and in their ability to resist sulfate attack.  
pl. follow the link to compare the properties
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There is commonly some missing information in the scientific studies researching some properties of the special concretes such as lightweight, heavyweight, self-consolidating, pre-placed aggregate, pervious etc. Are the concretes more tend to segregate (also including bleeding) than ordinary workable concrete becuase of their complex nature?  
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Concrete is not a homogeneous material even at macroscopic level, thus, it is not easy to define a definite border for the segregated concrete and accepteble concrete. This is why the data on the segregation or degree of homogeneity of concrete is very limited. Obviously the lack of proper test method(s) to evalute segragation plays a important role in this subject.   
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Although modified VSI test with 0.5 increment rate was used in several studies, there is no any accessible document to evaluate visual segregation of SCC. 
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Thank you Sina Dadsetan for your answer. I cannot access that standard from my university. I have ASTM C 1611. My question is related with increment rate of VSI not cone orientation. I think the standards refer the same VSI rating values (0, 1, 2 and 3). But I want to express the values with 0.5 increment rate as 0.0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0. I cannot find any materials (article, report etc.) for the rating. 
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Although VSI test is commonly known as static segregation evaluation method for self-compacting concrete, it is rarely expressed as dynamic segregation method in some studies. Can the both phenomenons (static and dynamic assessments) express  with the test method.
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You may be interested to hear that I investigated an example of severe static segregation where, in the worst case, coarse aggregate had sunk over 5m from the top of a 55m deep pile (not true self-compacting concrete but high flow concrete that consolidates under its own weight with no vibration). The site records showed no evidence of dynamic segregation problems through VSI in any of approx. 300 batches.
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I have a mix design of cement flyash blend. After doing rietveld refinement I have found that the ettringite percentage that was 1.57% at 7 days reduced to 0.85% at 28days. The gypsum content that was 0.67% at 7 days increased to 2.52% at 28days. Not sure, if I have identified the peak of gypsum correctly. Based on the past literature, ettringite normally converts into AFm phase but not back to gypsum.
I am quantifying the samples using external standard method and value of factor "G" which i'm using is 1890.29. The formula, which i'm using for the calculation of phases is (S * ρ * V2 * µ)/G. Where S=scale factor; ρ = density of a particular phase; V2= square of the volume of unit cell of the same phase; µ = absorption coefficient of the mix.
The scale factors were:
Ettringite @ 7day =  0.00000632                Gypsum @ 7day = 0.00004583
Ettringite @ 28day = 0.00000341               Gypsum @ 28day = 0.00014414 
Ettringite density = 1.79 g/cm3 and unit cell volume = 2306.04 pm3
Gypsum density = 2.32 g/cm3 and unit cell volume = 493.34 pm3
µ = absorption coefficient of the mix = 49.29 cm2/g
The data was collected at Brukers D4 Endevor with the following settings:Cu ka Anode, Stepsize 0.013 deg, time per step 1 sec, 40 Kv and 40 mA
I have attached the jpeg images of the refined samples for both 7 and 28days and have also attached .raw files. I would highly appreciate if someone could have a look and suggest if the identification is correct or there is something wrong in that.
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I think that the issue is mainly a phase misID. Since you have calcite in your system, its quite likely that the peak that you're assigning to Gypsum at latter ages corresponds to hemicarboaluminte or monocarboaluminate (both are AFm phases), both have their main peak around this position. In fact, the main peak of Mc matches perfectly your data, as you can see in the attached image (you've not only one Mc peak, but all of them, always remember that a good phase ID require the presence of all the main peaks of the candidate phase, unless you suspect strong texture). Hope this would be helpful for you :)
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There are some commercial softwares to model the SCC in fresh state in point of segregation with coupled restrainments (aggregate and reinforcing bar) . e.g. Flow3D, Fluent, etc. What are their advantages and disadvantages relative to each other in terms of convenience, inputs, outputs, assessment etc.   
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Thank you professor for your suggestion. I dowloaded the software. The program is seen very useful for structural members in hardened state. I' m researching the concrete in fresh state as a liquid. I want to dynamically model the segregation of aggregates by depending on reinforcing bar blocking and aggregates amount/size etc. in flowing of the concrete . 
regards
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Like Bogue's equation for compound composition (C3S, C2S, C3A and C4AF) estimation of Portland cement based concrete, Is there any method/equation available for the estimation of the same for fly ash? 
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Dear Lincy,
There is no need to estimate quantities of "C3S, C2S, C3A, C4AF" in fly ash because there are no such minerals in fly ash. Fly ash consists of mostly amorphous phases. Ideally, the major component is amorphous silica (in class F fly ash). Usually, some content of lime (CaO), which in class C fly ash can be high. Maybe some alumina, sulfate, and alkali. You may have some minor contaminating compounds too. As crystalline phases in fly ash, you may have mullite and quartz in relatively small amounts (depending on the source of fly ash), but most phases are amorphous (that is why you will not be able to identify them by XRD). The most important components from the viewpoint of cement reactivity are amorphous silica, lime, and alumina. I hope this will help you.
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In an FTIR analysis of cementitious materials (Fly ash and cement combination) from 3 hours to 28 days of hydration, the peaks were identified only at upsilon (2&3) vibrations of H2O. No other peaks were observed at any other region (for eg. corresponding to Ca(OH)2). What could be the possible reasons?! or only two peaks should be expected for such a study?! 
What do the bandwidth shift and increase in peak intensity of an FTIR spectrum of cementitious materials indicate?!
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But they were recorded using an ATR?
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I have just finished casting 36 geopolymer mortar mix designs. Several variables were set in my work. Nanosilica replacement dosage (0, 2, 4% of slag weight), microsilica replacement dosage (0, 5, 7.5 and 10% of slag weight), chemical activator type (2 types), solution to base material ratio (2 levels).
I am asking about the best approaches to determine optimized mix designs for further tests.
In the first stage the compressive strength and flowability of mortars were evaluated.
best,
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Once you have made trial mixes and tested the required responses such as compressive test and other tests of interest ,you can then apply surface response methodology to optimize the mixes otherwise you will be forced to conduct several tests to come up with an"optimized mix"
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I am doing a project on pre and post yielding behaviour of normal, standard and high strength concrete, we did tests on aggregate and sand  according to IS codes and we are in the stage of casting the concrete  but i am confused as to what literature do I refer for the project? I have been referring only the code books till now. Can anyone help me?
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really interesting answer Fernando
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While carring on the mix design by means of doing Marshall method,  the binder was prepared at specified mixing temperature in the heating instrument. However, the binder was aged with heating time increasing.  Anyone knows what the best way to estimate the aged  degree of the binder during mixing process to avoid binder aged phenomenon.
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you can check it ..either by traditional method like bitumen retained penetration after 5 hrs thin film oven test or by more scientific approach  viscosity test (AR). regards
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Analysis of punching shear in flat slab, to the action of 1 m/s.
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How can I Create a Model of Bow and arrow and Associated Frequencies
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concrete mix are of many types ,generally for domestic construction we use M20 grade of concrete where 'M' is the mix
of ingredients such as cement, agrregates(fine and coarse) and water and '20'refers to compressive strength of concrete for 28 days of curing with water.
steps invovlved in concrete mix are
1)collecting raw materials such as cement (43 grade or 53 grade),fine agrregate(sand)and coarse aggregate(gravel or stone)
2)batching:-weighing of all the raw materials the ratio of M20 grade of concrete should be (1:1.5:3) which means 1 part of cement,one and half part of sand and three parts of gravel with water by water cement ratio.
3)the water cement ratio should be 0.45 of all mix
4)mix the all ingredients such as cement ,affregates and water.
5)after mixing the freshly mixed concrete should be used for its application .the initial setting time of concrete is 30 mins and final setting time sholud be less than 10 hrs.
so this was about the mix design for M20 concrete.
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Thank you very much for replying Dhirendra Singhal . This information of yours is really helpful. Also, thank you very much for your inputs.
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In the calculation of the water/cement ratio and of mix proportions in general, the volume of the liquid superplasticizer must be taken into account.
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Thank you very much for replying Saad Sarsam. This information of yours is really helpful. Also, thank you very much for your inputs.
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Thanks 
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Dear Nadim,
I agree with Rytis and I would like to add the following; In case you want to identify failure mechanisms (matrix cracking, fibre breakage etc) in composites you may need to use resonant sensors in order to amplify your resolution in a specific narrow band frequency.
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analysis by ansys
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In our software ATENA (http://www.cervenka.cz/products/atena) this can be accomplished easily by assigning special parameters along with bond properties to our reinforcement model.
See for instance: