Concrete Material Technology - Science topic

I am really curious to know why we make clinker in oxidizing conditions? of course because of burning the fuel for the kiln but do the environment really affects the clinker quality.

regards

Saurabh

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.

What would be the practical range of compressive strengths of concrete of a foundation pile? 

Can it go as low as 25 MPa?

Really interested to know the lowest allowable for residential buildings

Faizal

I want to study on properties of grout admixed with pozzolans an bentonite  . but i could find any design grout mixing(without aggregate). how to choose W/S ratio??is there any code?

As per my previous concepts, the ductility of concrete in uni-axial compression decreases as the compressive strength increases.(As from the stress strain diagram, a low strength concrete fails at higher strain levels)

But when we talk about the structural elements i.e, Flexure members, Compression members numerous sources on the internet say " That the ductility of the concrete increases with the increase in the compressive strength" What could be a good justification to this? Please answer in the light of following:

1) Is it because we have improved shear strength attributed with higher strength?

2) The curvature ductility increases with the increase in compressive (Fig Attached below)

So can someone argue, that a column in pure axial state , its ductility decreases, but when we have some eccentricity ( i.e, bending) the ductility increases

Thanks in Advance!

Please help me find a brief history of Recycled Concrete Aggregate (RCA) CLASSIFICATION in the U.S. any paper or Official U.S. state DOTs' document.

Target:

To find out how many classifications of RCA we have and what is the difference?

Thank you all.

Too less or too much  alkali-activator is bad for the geopolymer,but how to determine the right amount and through what way?

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.

I want to use MTS testing machine with maximum capacity of 300 KN, but I don't know, which size of specimens is suitable to test compression and bending strength of bio composite concrete to use MTS testing Machine (E45, 300KN) ? what is your recommendation, why, and according to which standard code? #concrete #MTS_E45

Upon your experience on site and concrete on site, the phenomena of discolored of concrete might happens... how do you fix that?

To study the cementitious properties of cement substitute material should all other parameters be kept constant or should be changed?

Dear researchers,

I am looking for the following research papers:

-Carino, N.J., 1984, “The Maturity Method: Theory and Application,” Journal of Cement, Concrete, and Aggregates (ASTM), Vol. 6, No. 2, Winter, pp. 61-73.

- Knudsen, T., 1984, “The Dispersion Model for Hydration of Portland Cement: I. General Concepts,” Cement and Concrete Research, Vol. 14, pp. 622-630.

- Freiesleben Hansen, P. and Pedersen, J., 1985, “Curing of Concrete Structures,” CEB Information Bulletin 166, May, 42 p.

- Bezjaka, A., 1986, " An extension of the dispersion model for the hydration of Portland cement," Cement and Concrete Research, Vol. 16, pp. 260-264.

They are quite old papers, so really hard to find them. If anyone has these papers, could you please share them with me? Would really appreciate your help.

Kind Regards,

Minh Ho

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:

Some good models have been proposed for compression (e.g. Mander et al (1989), Scott et al (1982)). But which model to choose for tension?

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?

What are the best temperature control techniques for construction of Roller Compacted Concrete Dam

There are many confinement models for predicting the strength & stress-strain behavior of FRP confined concrete. Those are mostly two types; one is design-oriented model and another is analysis-oriented model. Is there anyone who can explain me the difference between these two types of models and how can we apply these models practically?

To all structural or geotechnical engineers, or people in the construcion materiales area, what would be your opinion of a natural concrete (with no Portland Cement) but using cohesive fine soil as cement (The water proofing problem would be solve later), now from the resistence point of view, the feasibility. Appreciate your comments

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.

I'm looking for the ratios of cement : sand : aggregates + water.

Please reply by referring valid references.

I want papers about ACV is indicating method for aggregate strength

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

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?

I have the experimental results of brick masonry prisms compressive strength and shear bond strength of brick masonry triplets. But, I cannot figure out how to find Mohr-Coulomb parameters, i.e., cohesion parameter (c) and friction coefficient (µ).? Thank you.

Thesis or Scientific article or Powerpoint presentation ...

Plenty of researches are focusing on geopolymer (e.g. alkali-activated fly ash) concretes, and review articles have claimed their advantages over OPC concrete. However, they've not been widely utilized in practice. Here comes the question, what are their disadvantages which limit their application?

What are the bacterial species used in bio-concrete and what are the chemicals used in making bio concrete?

i m modelling a 2D beam in abaqus, the model is nonlinear . i want to study the crack propagation and its mechanisms due to applied load .

in material section(in abaqus) i have used the concrete damaged plasticity, i want to know about the tension stiffening and its damaged

plz provide with some solution would b a great help

thanks

How can the Cole-Cole curve of an asphalt binder be plotted? The high and mid temperatures are from the DSR, but where to obtain the low with phase angle data? The BBR doesn't throws any result in terms of the phase angle because it is a simple flexural test.

Any references on how this can be done?

As we know water absorption of RCA is more than the natural aggregate...so how do we manage it in case of partial replacement..

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?

The surface chloride content data is missing, but the concrete was ponded with 3% NaCl solution for 30 days.

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?

i am doing my final year project so i am looking on ways to improve the strength of recycled aggregated concrete and increased the percentage of recycled aggregate used without compromising the strength of concrete.

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. 

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.

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.

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? 

What is the best size particles to be used from glass to replace the fine aggregates in self compacting concrete?

I have to interpret result of measurements of thermal properties of concrete made with use of ISOMET 2104 equipment. These results are strange: thermal conductivity is higher than expected and specific heat is lower. Is this equipment suitable for testing such a non-homogenous material as concrete?

I am in a site where I cannot economically obtain other suitable aggregates for making concrete.

please

dr

I HAVE NO GAP STILL

PLEASE my question about the size of particles and proportion and w/c

what is the best to proceed

I HAVE checked ordinary concrete

as size particles 

propotion

and type of glass

w/c ratio

Cement mortar gains strength with time due to chemical reactions involved and formation of C-S-H gel but how bond between aggregate and mortar takes place specifically.

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?!

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,

Shall we used as a cement replacemet?

i m working on self compacting mortars and i have issues about them :

1.       by which standard code I can find self-compacting mortar’s mix design?

2.       What’s the appropriate range for these proportions in self-compacting mortar? water/cement?

Cement/powder? Water/ powder?

3.       Which standard code should be used for aggregate size grading in self-compacting mortars?

i want know to calculate the bleeding rate for any mix design. 

1) with only cement =307 kg/m3 2) with cement and flyash =210+95 kg/m3 

Aggregate ratio FA/CA=0.6 and FA/ total Agg.=0.38

three cement having C3A<3% , 4-7%,and >8%

Is there any mix design following above parameters from which i can get good data to measure bleed rate evaluation for my project?

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.

high strength concrete can be obtained by using a wide variety of mix proportions if proper mix design procedures are used.

recommended mix proportions for high strength concrete?

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.

One of the most important component in hydraulic cements is calcium di and tri-silicates-based cement, which is widely used as building and construction material. There are three main compounds in the cement: dicalcium silicate (C2S), tricalcium silicate (C3S), and calcium aluminate (C3A). Highly crystalline calcium hydroxide (Ca(OH)2) and amorphous calcium-silicate-hydrate (C—S—H) are the principal phases formed in crystallinity and the hydration of calcium silicates (C2S and C3S). The paste form of hydrated cement slurry mostly consists of C—S—H and calcium hydroxide (CH). Additional phases including sulfoaluminate and secondary phases are formed. Since calcium hydroxide component (CH) is soluble in water may cause low strength. It has been reported that mechanical properties of cement are improved by reduction of CH and addition of SiO2 (S).  Biocementation is a process to produce binding biomaterials to act as cement. Such phenomena is created by a mixture of calcium-silicate-hydrate gel mixed with hydroxyapatite. In biocement composition, calcium silicate hydrate has been reinforced with co-precipitated particles of hydroxyapatite. Biocompatibility of such biomaterial is also enhanced due to absence of aluminum and magnesium in the composition of biocement. The biocement is suitable for variety of applications including dental implants, bone fixation, and bone repair. In fact, biocement is a mixture of mineral oxides once it hydrated crystals are formed. Such biomaterial are originated from living organism calcinates and silicates are as by-product of living organism or even biopolymeric materials are produced. Biocement production has extensively progressed as it is considered as green biomaterial. Environmental demand and use of biocement for stabilization of soil is in an extensive recent research growth of waste conversion to desired biomaterial.

Internally cured concrete has been shown to be effective in reducing the potential for plastic shrinkage cracking of pozzolanic concrete mixtures like Fly ash. Anybody found its significance in the case of high volume replacement by slag?

Shear critical elements experience the biaxial state of stress i.e. axial compression and transverse tension. Other than mohr-column theory, please suggest me some failure theories, which considers both states of stress. 

OM-SEM analysis on a 10-year old concrete pavement in a bus stop have shown serious damage due to AAR. It turned out that the aggregates responsible for the formation of expansive products (both amorphous gel and microcrystalline phases) and the damage are serpentinite/greenstone/greenshist. There is clear evidence for reaction between the pore solution and some mineral phases (e.g. Ca-Mg amphibole, serpentinite, etc.). The reactions, however, are not fully understood so far, especially because some of the observed mineral phases are being stabile in high pH environment. Has anybody seen serpentinite, greenstone undergo to AAR (ASR)? Thanks!

To assess the durability of concrete, permeation tests can be conducted such as air permeability, water permeability and water absorption but which permeation tests are more important in concrete? If u were to choose two out of 3, what u will choose and why? Which permeation properties are more important in concrete?

During the construction of a 200 cubic meters structural element, the cement which is used to make concrete (CPC 40) was depleted, so the company whose building the bridge changed the cement to CPC 30 which is the one available in the nearest town.

I have the mix design for F´c = 350 Kg/cm^2:

400 kg Cement CPC 40

957 kg Gravel ¾”

783 River sand

210 Lts Water

3.2 Lts Sikament 450

The las 28 day compression test for this mix gave us an F´c of 450 kg/cm^2 (which I believe is impossible with the mix design, so I asked for a calibration test of the concrete plant, i´m still waiting for the test results).

I know the mix design is not good, we have experienced severe bleeding due to the over use of the add mixture and the excessive mix water, the company who’s building the bridge won’t change the mix design because they have to pump it 64 mts, but that is another topic.

My question is does this mix design will satisfy the F´c = 350 Kg/cm^2:

410 kg Cement CPC 30

957 kg Gravel ¾”

783 River sand

210 Lts Water

3.2 Lts Sikament 450

CPC 40 means that the cement paste has a minimum compressive strength of 400 kg/cm^2 at 28 days, so CPC 30 will not achieve the same strength at 28 days, so if I the mix was designed with the ACI 211.1 how can I take the change in cement paste strength and adjust the mix.

Thank you very much

There are several characteristics that make it possible for mortars to be injected, like low setting time etc. also I want to know about these characteristics as well. Are there any codes or Standards for that?

Dear Researchers

I try to modeling the diffusion process of concrete in Abaqus. I try to use mass diffusion technique but, I failed because my lack experience. Can anyone give me advice to do this simulation step by step?

Sincerely,

Wahyuniarsih Sutrisno

i am using rice husk ash as cement in concrete,now i am using 20% of rice husk ash in concrete, whether i  can use 100% of rice husk ash in concrete ?

Hi:

I modelled this concrete reinforcement girder in Ansys Workbench with Explicit Dynamic moduler. My girder length is 27380mm, 1372mm height and 635mm width. It has got 4 bottom layers of reinforcement bars of 12mm dia. and two layers of top reinforcements of the same dia. Altogether it has about 50 bars. I gave the fixed support condition at both end face of the girder and applied only inertial load to the beam(self weight). I gave correct material properties to concrete girder and steel reinforcement. I got the error message as depicted in the screenshot attached. I doubt that I make some mistake with Analysis setting like end time, no. of cycles, time step, initial time etc. as you can see from the screen shot. Can any body please help me / suggest possible options I can try to get solve this model.

Thanks

As I know the pH value of the Geopolymer concrete is about 13 on 28 days but the alkali silica reaction and expansion on the Geopolymer concrete is very less as compare to OPC. Am I right? If I am correct then how could it happen?

Thank you in advance

Thanks.

Dear all,

I have the parameters of my Herschel-bulkley model for fresh concrete.

tau=tau0+k*gamma^n

and I want to model a valve.

In OF the tau0 and the k parameters in the transportPropertyDict should be diveded by the density while the exponent n should not be divided, correct?

Than another parameter nu0 (a viscosity) is requested. What is it's phisical meaning?

I have seen that if I put a value, let say 1e-3, in each time step the nu field is 1e-3 and not calculated according to the Herschl-Bulkley model.

Some suggestions?

Franco

Grinding agents used in the production of OPC are now very much a common practice, Can these grinding agents contribute to an accelerated setting time when blended with limestone dust?

most of the codes and service life literature provide model for chloride based degradation however i couldn't find any model for sulphate based degradation especially sulphuric acid degradation in sewage system. only reliable equation and formulae is given by pomeroy in 1974. any latest development in this field.

For different tests we get different value of characteristic compressive strength.IS456 -2000 recommand 15cm Cube strength where as ASTM Recommand the cylindrical strength.

Chemical treatments such as alkaline, saline-treatment has been experimentally proven to improve the mechanical properties of natural fibers. However, drawbacks to the treatment includes shrinkage of diameter and length. This affects the aspect-ratio of the fiber. Though the interfacial bond increases and there's a higher possibility of greater adhesion between the fiber surface and concrete matrix, the high aspect ratio will, I assume, decrease the mechanical properties of concrete? I have yet to read articles using chemically treated natural fibers in concrete mix so if anyone has any recommendation, please do drop a quick comment.

Thin cement grouts with high water cement ratio of more than 1 involve bleeding and consequence poor quality pastes. In some cases channels will form in the paste which increase its permeability and decrease its strength. I want to know that what would happened during this type of bleeding (known as Channel bleeding). 

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

I need to continue advancing my research on concrete strength.

 I need references depths of carbonation or carbanotacion constants (speed carbonation ) of concrete made with blended cements with limestone filler . any reference ?

(Xco2=kco2 (t)^(1/2))

I am modeling a post tension slab using unbonded system .. please if you have any information or any data to use them in my model specially in the contact definition

Based on the following standard ASTM C 39 and C 192, the 28 curing time does it include the time at which the concrete is inside the mold?

If yes, which means it will be cured 1 day in the mold and the remaining 27 days in moist environment?

It wasn't clear in the standard.