| 1. |
- Hatem, Mohammed, et al.
(författare)
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Design of concrete mixes by systematic steps and ANN
- 2012
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Ingår i: Journal of Advanced Science and Engineering Research. - 2231-8844. ; 2:4, s. 232-251
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Tidskriftsartikel (refereegranskat)abstract
- The current research caters for the possibility of arriving at a system for designing concrete mixeseasily using available materials locally by specified wide ranges of pre-requisites of three mainprescribed properties to cover a good variety of practical mixes, which are water, water-cement ratioand total aggregate-cement ratio. Using these three properties, a tri-linear form was constructed bygraphical technique manner based on absolute volume approach. This approach defines as asummation of absolute volume for each of these three materials individually water, cement andaggregate should be equal to the absolute volume of whole concrete mixture based on thesealtogether. A quad-form area which includes a wide range of mixes can be formed from thisrepresentation. This area should achieve all the prescribed properties aforementioned. Artificial neuralnetwork concept used in this study also to build easily and quickly system which can be translatedinto Excel sheet. This system predict proportions of concrete mixture and the compressive strengthusing the results designed by the quad-form area method in addition to the data from literature around500 mixes based on local materials used in Iraq. Six input parameters (water to cement ratio, theslump, % of fine to total aggregate content, maximum aggregate size, fineness modulus of fineaggregate and the compressive strength) were used in this system to get the outputs. In addition, nineinput parameters ((water, cement, sand and gravel contents) and the properties of the mix (Finenessmodulus, W/C ratio, the slump, % of fine to total aggregate and the M.A.S)) were used as basis ofcompressive strength model. The algorithm of this system aimed to reduce the high number of trailmixes error as well as saving the labors, cost and time. Results indicated that the concrete mix designand the compressive strength model can be predicted accurately by using graphical perspective andthe ANN approach.
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| 2. |
- Hatem, Mohammed, et al.
(författare)
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Enhancement of Workability of Cement-Poor Concrete by Optimizing Paste Content
- 2014
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Ingår i: Engineering. - : Scientific Research Publishing, Inc.. - 1947-3931 .- 1947-394X. ; 6:13, s. 869-876
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Tidskriftsartikel (refereegranskat)abstract
- This study describes the performance of concrete in fresh state, intended for sealing deep boreholes in the host rock of radioactive repositories. Set of different paste volumes, combinations of water-to-powder ratios and fine aggregate contents have been performed within the frame of this study. The main objective was to search for tendencies, logical connections and phenomena that occur for different combination of materials regarding the fluidity and segregation and mainly the effect from the (paste) or fine aggregate content. It shall be pointed out that this investigation is a suggestion on how concrete can be optimized using two simple test methods based on changing the paste content. The results highlighted the importance of having sufficient amounts of filler and cement paste for separate and carry larger particles, which gives the concrete good workability and fluidity at casting. It was concluded that the slump behaviors can be optimized based on the adjustments of the superplastisizer dosage.
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| 3. |
- Hatem, Mohammed, et al.
(författare)
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Optimization of concrete by minimizing void volume in aggregate mixture system
- 2012
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Ingår i: Journal of Advanced Science and Engineering Research. - 2231-8844. ; 2:3, s. 208-222
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Tidskriftsartikel (refereegranskat)abstract
- The behavior of concrete is affected by the size, distribution of the voids, the porosity and of the granulometry of the aggregate mixture. As a consequence it necessary for engineers to consider in detail particle packing concepts and their influence on the physical performance of concrete. The present study included determination of the fineness modulus, cement paste volume based on slump test and the properties of fresh and hardened concrete. It also comprised a study of the applicability of two theoretical models Toufar’s and 4C-packing program for selecting suitable relative amounts of the concrete constituents, for obtaining a minimum void ratio. Comparison of the results was made from using these theoretical models literature-derived experimental data. The models gave similar results and suggest similar combinations of materials to give minimum void ratio. Optimization of the composition of the aggregate material in concrete is beneficial with respect to economy (low cement content), strength and durability. It was noted that minimizing the void ratio (V) tends to raise the stiffness and that the compressive strength (푓푐′) is closely related also to their molding (R) and fineness modules (FM). It was found that the compressive strength can be predicted by applying the formula;푓푐′=−2.1−63.8 푉+0.150 푅+10.4 퐹푀; R2=0.94, and two other relationships related to slump data and cement content.
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| 4. |
- Hatem, Mohammed, et al.
(författare)
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Proportioning of cement-based grout for sealing fractured rock-use of packing models
- 2013
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Ingår i: Engineering. - : Scientific Research Publishing, Inc.. - 1947-3931 .- 1947-394X. ; 5:10, s. 765-774
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Tidskriftsartikel (refereegranskat)abstract
- Fractured, very permeable rock hosting repositories for radioactive waste will require grouting. New grout types of possible use where long-term performance is needed should have a small amount of cement for minimizing the increase in porosity that will follow from the ultimate dissolution and erosion of this component. They have to be low-viscous and gain strength early after injection and packing theory can assist designers in selecting suitable proportions of various grout components. Optimum particle packing means that the porosity is at minimum and that the amount of cement paste needed to fill the voids between aggregate particles is very small. Low porosity and microstructural stability must be guaranteed for long periods of time. Organic additives for reaching high fluidity cannot be used since they can give off colloids that carry released radionuclides and talc can be an alternative superplasticizer. Low-pH cement reacts with talc to give high strength with time while Portland cement gives early but limited strengthening. The clay mineral palygorskite can be used for early gelation because of its thixotropic properties. Once forced into the rock fractures or channels in soil it stiffens and serves as a filter that prevents fine particles to migrate through it be lost. However, its hydrophilic potential is too high to give the grout a high density and high strength. According to the experiments carried out most of the investigated grouts are injectable in fractures with apertures down to 100 μm.
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| 5. |
- Hatem, Mohammed, et al.
(författare)
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Rheological properties of low pH cement-palygorskite injection grout
- 2013
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Ingår i: Journal of Advanced Science and Engineering Research. - 2231-8844. ; 3:3, s. 167-192
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Tidskriftsartikel (refereegranskat)abstract
- The rheological properties of cementitious materials containing fine particles, such as mineral admixture were investigated using a Viso Star-L rheometer with cylindrical spindles. Selected features of the behavior of these materials are evaluated from a rheological perspective through literatures results for the past 30 years. One of the important factors that governs the ability of grout to penetrate fractures, channels and porous material is the rheology. The mineral admixture was clay palygorskite which can be used for early gelation because of its thixotropic properties as well as the powder quartz used as aggregate. The cementitious materials were designed and three recipes (MPG1, MPG2 and MPG3) were examined in this research by changing the mix proportions of the mineral admixture palygorskite and water content. For ensuring the accuracy of rheological measurement for the candidate’s grouts, necessary verification was been evaluated such as, influence of mixing time, stability and “time effect” to the accuracy of viscosity measurement, and yield stress as well as the physical properties at 3, 7 and 28 days. The results showed that grouts recipes with quartzite aggregate of different granulometry, are chemically compatible and fulfill the requirement of containing no organic matter. Candidate’s grouts found to satisfy the stable sedimentation criteria with sedimentation rates less than 5% after 2 hours. Furthermore, it was found that the grout recipe 3 followed by 1 showed lower yield stress and plastic viscosity which are (0.1 Pa and 0.269 Pas) and (0.288 Pa and 0.531 Pas) respectively.
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| 6. |
- Hatem, Mohammed, et al.
(författare)
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Talc-based concrete for sealing borehole optimized by using particle packing theory
- 2013
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Ingår i: Journal of Civil Engineering and Architecture. - : David Publishing Company. - 1934-7359 .- 1934-7367. ; 7:4, s. 440-455
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Tidskriftsartikel (refereegranskat)abstract
- The paper describes assessment of the performance of cement-poor concreteson the basis of packing theory. The concretes are intended for sealing segments of deep boreholes and have a small amount of cement for minimizing the mutual chemical impact on the contacting clay seals. The composition is examined by application of packing theory with respect to the cement/aggregate ratio and the gradation of the aggregate material which is crushed quartzite for providing high internal friction after maturation, as well as to talc added for fluidity and to the small amount of cement. Low porosity and micro-structural stability must be guaranteed for very long periods of time. The study exemplifies how packing theory assist designers in selecting optimal proportions of the various components. Optimum particle packing implies minimizing the porosity and thereby reducing the amount of cement paste needed to fill the voids between the aggregate particles. The use of talc as inorganic super-plasticizer since ordinary organic additives for reaching high fluidity at casting are undesirable, and since talc reacts with cement and provides high strength in along-term perspective.
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| 7. |
- Latif, Sarmad Dashti, et al.
(författare)
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Development of prediction model for phosphate in reservoir water system based machine learning algorithms
- 2022
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Ingår i: Ain Shams Engineering Journal. - : Elsevier. - 2090-4479 .- 2090-4495. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Phosphate (PO4) is a major component of most fertilizers, and when erosion and runoff occur, large amounts of it enter the water bodies, causing several problems such as eutrophication. Feitsui reservoir, the primary source of water supply to Taipei, reported half of the reservoir's pollutants from nonpoint-source pollution. The value of the PO4 in the water body fluctuates in highly nonlinear and stochastic patterns. However, conventional modeling techniques are no longer sufficiently effective in predicting accurately such stochastic patterns in the concentrations of PO4 in water. Therefore, this study proposes different machine learning algorithms: the artificial neural network (ANN), support vector machine (SVM), random forest (RF), and boosted trees (BT) to predict the concentration of PO4. Monthly measured data between 1986 and 2014 were used to train and test the accuracy of these models. The performances of these models were examined using different statistical indices. Hyperparameters optimization such as cross-validation was performed to enhance the precision of the models. Five water quality parameters were used as input to the proposed models. Different input combinations were explored to optimize the precision. The findings revealed that ANN outperformed the other three models to capture the changes in the concentrations of PO4 with high precision where RMSE is equal to 1.199, MAE is equal to 0.858, and R2 is equal to 0.979, MSE is equal to 1.439, and finally, CC is equal to 0.9909. The developed model could be used as a reliable means for managing eutrophication problems.
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