• Geomechanics and Engineering
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• v.13 no.1
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• pp.99-117
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• 2017

Rock physics modeling of sandstone reservoir from gas fields of Krishna-Godavari basin represents the link between reservoir parameters and seismic properties. The rock physics diagnostic models such as contact cement, constant cement and friable sand are chosen to characterize reservoir sands of two wells in this basin. Cementation is affected by the grain sorting and cement coating on the surface of the grain. The models show that the reservoir sands in two wells under examination have varying cementation from 2 to more than 6%. Distinct and separate velocity-porosity and elastic moduli-porosity trends are observed for reservoir zones of two wells. A methodology is adopted for generation of Rock Physics Template (RPT) based on fluid replacement modeling for Raghavapuram Shale and Gollapalli Sandstones of Early Cretaceous. The ratio of P-wave velocity to S-wave velocity (Vp/Vs) and P-impedance template, generated for this above formations is able to detect shale, brine sand and gas sand with varying water saturation and porosity from wells in the Endamuru and Suryaraopeta gas fields having same shallow marine depositional characters. This RPT predicted detection of water and gas sands are matched well with conventional neutron-density cross plot analysis.

• Journal of Energy Engineering
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• v.27 no.4
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• pp.64-69
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• 2018

The purpose of this study is to expand the use of coal ash and coal slag in thermal power plants. In addition, controlled low strength materials was developed to prevent mine settlement. Bottom ash and KR slag are mixed at ratio of 7:3 to expand the use of industrial by-products through carbonate reaction and inhibit the exudation of heavy metals. In order to efficiently fill the abandon mine, workability and physical properties were evaluated according to flow. As a result of elution of harmful substance experiment, it was confirmed that the carbonation reaction inhibited the elution of heavy metals. It was confirmed that the difference in water ratio was the difference in specific surface area of the controlled low strength materials. It was confirmed that the working efficiency is excellent when the flowability is 300mm compared to 260mm. compressive strength measurement result was relatively high at 260mm compared to 300mm because the number of pores due to decrease of water ratio was small.

• Journal of the Korean Geophysical Society
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• v.3 no.2
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• pp.127-138
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• 2000

This study was conducted to examine the differences between dynamic and static elastic constants by use of some laboratory tests of cement mortar specimens which have different water/cement mixing ratios. Specific gravity measurement, ultrasonic velocity estimating and uniaxial compression test were adopted to acquire the dynamic and static elastic constants. Digital data acquisition and processing enhanced the accuracy of estimating the velocities of specimens drastically, Also, the method using the gradient of propagation delay time in according to increment of specimen length more enhanced the accuracy than the method using the only one specimen length over total propagation time. The correlation between density and the P and S wave velocity of specimens shows reliable positive relation and the correlation between density and the strength of uniaxial compression has the similar relationship. The dynamic Young's modulus $(E_D)$ is alway greater than the static Young's modulus $(E_S)$ and there is increasing tendency of the ratio $(E_D/E_S)$ according to the increase of density or strength of the specimens. On the other hand, there is no typical relationship between dynamic Poisson's ratio $({\nu}_D)$ and static Poisson's ratio $({\nu}_S)$ and just the ratio of ${\nu}_D/{\nu}_S$ ranges front 69 to 122 %.

• Journal of the Korea Institute of Building Construction
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• v.14 no.2
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• pp.135-142
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• 2014

The heat of hydration can be reduced through the use of retarding agents. Typical retarding agents include sugar and glucose. However, these significantly delay the setting of cement paste. For the efficient use of sugar and glucose for mass concrete construction, it is necessary to develop a technique that can provide a setting behavior equivalent to that of plain concrete. In this work, the temperature rise of cement paste was monitored with the addition of various retarders including sugar and glucose. Hydrated cement powder was made with a water to cement ratio of 5 in order to accelerate the retarded cement pastes. It was found that the addition of hydrated cement powder in retarded pastes reduced the maximum temperature of cement paste. The use of hydrated cement powder could also successfully reduce the time to reach the maximum temperature.

• International Journal of Concrete Structures and Materials
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• v.11 no.1
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• pp.59-68
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• 2017

Mercury intrusion and nitrogen sorption porosimetry were employed to investigate the pore structure of calcium sulfoaluminate ($C{\bar{S}}A$) and portland cement pastes with cement-to-water ratio (w/c) of 0.40, 0.50, and 0.60. A unimodal distribution of pore size was drawn for $C{\bar{S}}A$ cement pastes, whereas a bimodal distribution was established for the portland cement pastes through analysis of mercury intrusion porosimetry. For the experimental results generated by nitrogen sorption porosimetry, the $C{\bar{S}}A$ cement pastes have a smaller and coarser pore volume than cement paste samples under the same w/c condition. The relative dynamic modulus and percentage weight loss were used for investigation of the concrete durability in freeze-thaw condition. When coarse aggregate with good freeze-thaw durability was mixed, air entrained portland cement concrete has the same durability in terms of relative dynamic modulus as $C{\bar{S}}A$ cement concrete in a freeze-thaw environment. The $C{\bar{S}}A$ cement concrete with poor performance of durability in a freeze-thaw environment demonstrates the improved durability by 300 % over portland cement concrete. The $C{\bar{S}}A$ concrete with good performance aggregate also exhibits less surface scaling in a freeze-thaw environment, losing 11 % less mass after 297 cycles.

• Journal of the Society of Disaster Information
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• v.8 no.3
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• pp.204-212
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• 2012

Lightweight soils are very economical and environment friendly materials that are valuable in field without wasting construction materials, dredged soils and clay/ silty soils during construction. Recently, the research of lightweight soils mixed with recycled material (recycled tire powder, rice husks) have been investigated. In this study the mix design factors (i.e., weight of soil, water content, foaming agent and added water) were analyzed and optimized mix design was suggested using cement content for revealing strength. For the analysis the stress-strain behavior, strength with respect to time, and experimental strength for the component of recycled material were analyzed. Finally, target strength was determined to calculate reasonable and economical mix ratio and the optimized cement content was suggested.

• Journal of the Korea Concrete Institute
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• v.17 no.2 s.86
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• pp.303-309
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• 2005

This study aims the evaluation of the corrosion of steel bar embedded in antiwashout underwater concrete, which has rather been neglected to date. To that goal, accelerated steel bar corrosion tests have been performed on three series of steel bar-reinforced antiwashout underwater concrete specimens manufactured with different admixtures. The three series of antiwashout underwater concrete were: concrete constituted exclusively with ordinary portland cement (OPC), concrete composed of ordinary portland cement mixed with fly-ash in $20\%$ ratio (FA20), and concrete with ground granulated blast furnace slag mixed in $50\%$ ratio (BFS50). The environment of manufacture was in artificial seawater. Measurement results using half-cell potential surveyor showed that, among all the specimens, steel bar in OPC was the first one that exceeded the threshold value proposed by ASTM C 876 with a potential value below -350mv after 14 cycles. And, the corresponding corrosion current density and concentration of water soluble chloride were measured as $30{\mu}A/mm^2$ and $0.258\%$. On the other hand, for the other specimens that are FA20 and BFS50, potential values below -350mV were observed later at 18 and 20 cycles, respectively. Results confirmed the hypothesis that mineral admixtures may be more effective on delay the development of steel bar corrosion in antiwashout underwater concrete.

• Magazine of the Korea Concrete Institute
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• v.7 no.3
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• pp.149-155
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• 1995

An experimental study was carried out to investigate the strength implovlng effect of stone dust in no fines concrete. The cement aggregate ratios of 1:6, 1:8 and 1:10 and several water-cemment ratios between 30% and 56% were chosen for the mix design of no-fines concrete. For the no-fines concrete with stone dust, the weight ratio of cement to stone dust 1:1 was adopted and super plasticizer, 1.5% of cement in weight, was used to obtain proper and workable state of concrete. The compressive and tensile strength test were performed and the results for the different mix designs were compared with each other. The results show that the compressive strength of no-fines concrete can be improved by 38% and the tensile strength by 17%~72% for the same w/c, when the same weight of stone dust as cement is mixed together.

• KIEAE Journal
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• v.7 no.4
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• pp.113-118
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• 2007

From the construction material the cement and the concrete which will reach to 90% are used to construction. But the cement occurrence (from the whole industry 4.4% of carbon dioxide exhaust quantity) makes the carbon dioxide of manufacture hour and anti- the recognition which is an environment industry. The cement absorbs the carbon dioxide during life period of the life time. It calls carbonation. In this study in order to evaluate the carbon dioxide absorption of the cement test produced the mortar specimens which it follows in the W/C. And carbonatable material of mortar specimens (calcium hydroxide) the quantitly it measured, reference study it led and absorption of carbon dioxide quantity it produced. Finally two result comparisons leads and it is a fundamental study which does the test evaluation possibility and a propriety investigation of carbon dioxide absorption quantity in objective.

• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.457-466
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• 2002

An artificial neural network was applied to predict compressive strength, slump value and mix proportion of a concrete. Standard mixed tables were trained and estimated, and the results were compared with those of the experiments. To consider variabilities of material properties, the standard mixed fables from two companies of Ready Mixed Concrete were used. And they were trained with the neural network. In this paper, standard back propagation network was used. The mix proportion factors such as water cement ratio, sand aggregate ratio, unit water, unit cement, unit weight of sand, unit weight of crushed sand, unit coarse aggregate and air entraining admixture were used. For the arrangement on the approval of prediction of mix proportion factor, the standard compressive strength of $180kgf/cm^2{\sim}300kgf/cm^2$, and target slump value of 8 cm, 15 cm were used. For the arrangement on the approval of prediction of compressive strength and slump value, the standard compressive strength of $210kgf/cm^2{\sim}240kgf/cm^2$, and target slump value of 12 cm and 15 cm wore used because these ranges are most frequently used. In results, in the prediction of mix proportion factor, for all of the water cement ratio, sand aggregate ratio, unit water, unit cement, unit weight of sand, unit weight of crushed sand, unit coarse aggregate, air entraining admixture, the predicted values and the values of standard mixed tables were almost the same within the target error of 0.10 and 0.05, regardless of two companies. And in the prediction of compressive strength and slump value, the predicted values were converged well to the values of standard mixed fables within the target error of 0.10, 0.05, 0.001. Finally artificial neural network is successfully applied to the prediction of concrete mixture and compressive strength.