• Steel and Composite Structures
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• v.18 no.2
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• pp.375-394
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• 2015

This paper presents the results of four long-term experiments carried out to investigate the time-dependent behaviour of composite floor slabs with particular attention devoted to the development of non-uniform shrinkage through the slab thickness. This is produced by the presence of the steel deck which prevents moisture egress to occur from the underside of the slab. To observe the influence of different drying conditions on the development of shrinkage, the four 3.3 m long specimens consisted of two composite slabs cast on Stramit Condeck $HP^{(R)}$ steel deck and two reinforced concrete slabs, with the latter ones having both faces exposed for drying. During the long-term tests, the samples were maintained in a simply-supported configuration subjected to their own self-weight, creep and shrinkage for four months. Separate concrete samples were prepared and used to measure the development of shrinkage through the slab thickness over time for different drying conditions. A theoretical model was used to predict the time-dependent behaviour of the composite and reinforced concrete slabs. This approach was able to account for the occurrence of non-uniform shrinkage and comparisons between numerical results and experimental measurements showed good agreement. This work highlights the importance of considering the shrinkage gradient in predicting shrinkage deformations of composite slabs. Further comparisons with experimental results are required to properly validate the adequacy of the proposed approach for its use in routine design.

• Advances in concrete construction
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• v.13 no.1
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• pp.101-111
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• 2022

The rapid development of the construction industry in the world causes a rapid increase in the consumption of aggregate resources, which leads to the depletion of existing aggregate reserves. The use of recycled aggregate in the production of concrete and mortar may be a good solution to reduce the use of natural raw materials and to reduce demolition waste in the environment. In this study investigating the use of recycled aggregate in mortar production, mortar mixtures were produced by substituting 0%, 25%, 50% and 100% fine recycled aggregate (FRA) instead of natural aggregate. The effect of 20% and 40% fly ash (FA) substitutes on cement mortar performance was also investigated. Compressive and flexural strength, drying shrinkage, abrasion resistance, water absorption and capillary water absorption were investigated on the produced mortars. The increase in the use of FRA reduced the compressive and flexural strengths of mortars. While the capillarity coefficients, water absorption, rapid chloride permeability and drying shrinkage of the mortars increased with the increase in the use of FRA, the effect of the use of fly ash on the rate of increase remained lower. The increased use of FRA has improved abrasion resistance as well.

• Geomechanics and Engineering
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• v.28 no.2
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• pp.107-116
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• 2022

The steady state of unsaturated soil takes a long time to achieve. The soil seepage behaviours and hydraulic properties depend highly on the wetting/drying rate. It is observed that the soil-water characteristic curve (SWCC) is dependent on the wetting/drying rate, which is known as the dynamic effect. The dynamic effect apparently influences the scanning curves and will substantially affect the seepage behavior. However, the previous models commonly ignore the dynamic effect and cannot quantitatively describe the hysteresis scanning loops under dynamic conditions. In this study, a dynamic hysteresis model for SWCC is proposed considering the dynamic change of contact angle and the moving of the contact line. The drying contact angle under dynamic condition is smaller than that under static condition, while the wetting contact angle under dynamic condition is larger than that under static condition. The dynamic contact angle is expressed as a function of the saturation rate according to the Laplace equation. The model is given by a differential equation, in which the slope of the scanning curve is related to the slope of the boundary curve by means of contact angle. Empirical models can simulate the boundary curves. Given the two boundary curves, the scanning curve can be well predicted. In this model, only two parameters are introduced to describe the dynamic effect. They can be easily obtained from the experiment, which facilitates the calibration of the model. The proposed model is verified by the experimental data recorded in the literature and is proved to be more convenient and effective.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2004.04a
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• pp.127-139
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• 2004

The process of papermaking involves water removal on the paper machine wire, in the press section and in the dryer section. In the dryer section, liquid water in the wet web is removed mainly by evaporation. In conventional machine this is achieved by passing the web over a number of steam heated dryer rolls. A drying process of paper on a heated cylinder roll calculated based on a 1-dimensional model which concerns unsteady heat and mass transfer in the direction of paper thickness. In this study, Prediction of moisture contents average paper sheet temperature and volume fraction along a series of cylinder. Independently, developed models is compared using the same reference data. The model is implemented in CFD code, FLUENT, using user-define-function(UDFs).

• Geomechanics and Engineering
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• v.3 no.4
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• pp.267-284
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• 2011

The aim of the paper is to study the hydro-mechanical behaviour of a tuff and calcareous sand mixture. A first experimental phase was carried out in order to find the optimal mixture. This showed that the material composed of 80% tuff and 20% calcareous sand provides the maximum mechanical strength. The second experimental phase concerns the study of the drying- wetting behaviour of the optimal mixture. Triaxial shear tests in saturated and unsaturated states at constant water content were carried out on samples initially compacted at the MPO. Experimental results let to deduce the parameters necessary for the prediction of the hydro-mechanical behaviour of pavement formulated from tuff and calcareous sand mixtures, related to moisture. This optimal mixture satisfies the regulation rules and hence constitutes a good local eco-material, abundantly available, for the conception of pavements.

• Computers and Concrete
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• v.18 no.3
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• pp.367-388
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• 2016

In this paper, a simple practical method is introduced in which a simple weight measurement of concrete and finite element numerical analysis are used to determine the moisture transfer coefficient of concrete with a satisfactory accuracy. Six concrete mixtures with different water-to-cementitious material (w/cm) ratios and two pozzolanic materials including silica fume and zeolite were examined to validate the proposed method. The comparison between the distribution of the moisture content obtained from the model and the one from the experimental data during both the wetting and drying process properly validated the performance of the method.With the proposed method, it was also shown that the concrete moisture transfer coefficient considerably depends on the pore water saturation degree. The use of pozzolanic materials and also lowering w/cm ratio increased the moisture transfer coefficient during the initial sorption, and then, it significantly decreased with an increase in the water saturation degree.

• Journal of the East Asian Society of Dietary Life
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• v.14 no.5
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• pp.495-500
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• 2004

This study was carried out to develop a new product using Cheonggukjang (fermented soybean product) and sub-ingredients(lactic acid bacillus powder, chlorella, lactose, green tea). Fresh Cheonggukjang was dried by a infrared drying(50℃, 36hr) and powdered by a roll mill. The powder was mixed with sub-ingredients and then moulded as tablet type by a press moulder. The pH of tablet was low with the addition of lactobacillus and total sugar content was high with the addition of lactose. Disintegration, absorption capacity and textural properties of tablet were not affected by the addition of any sub-ingredient. Color of non-added tablet was yellow to red, but changed to green when chlorella was added. Sensory properties(color, taste, flavor, chewiness, hardness, acceptability) were not affected by the addition of sub-ingredients. The results indicate that functional healthy tablet could be made from Cheonggukjang powder and various sub-ingredients.

• Geomechanics and Engineering
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• v.17 no.1
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• pp.69-79
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• 2019

This work presents an experimental study of the hydromechanical behavior of a natural swelling soil taken from Boumagueur region east of Algeria. Several pathological cases due to the soil shrinkage / swelling phenomenon were detected in this area. In a first part, the hydric behavior on drying-wetting paths was made, using the osmotic technics and saturated salts solutions to control suction. In The second part, using a new osmotic oedometer, the coupled behavior as a function of applied stresses and suction was investigated. It was shown that soil compressibility parameters was influenced by suction variations that an increase in suction is followed by a decrease in the virgin compression slope. On the other hand, the unloading slope of the oedometric curves was not obviously affected by the imposed suction. The decrease in suction strongly influences the apparent preconsolidation pressure, ie during swelling of the samples after wetting.

• Computers and Concrete
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• v.26 no.6
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• pp.577-585
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• 2020

By the increasing amount of waste materials, it eventually dumped into the environment and covering a larger area of the landfill which cause several environmental pollution problems. The utilization of Palm Kernal Shell Ash (PKSA) in concrete might bring a great benefit in addressing both environmental and economic issues. This article investigates the effect of PKSA as a partial cement replacement of High Strength Concrete (HSC). Several concrete mixtures were prepared with different PKSA of 0%, 10%, 20%, and 30% replaced by the cement mass. This procedure was replicated twice for the two different target mean strengths of 40 MPa and 50 MPa. The mixtures were prepared to test different fresh and hardened properties of HSC including slump test, the compressive strength of 3, 7, 14, 28, and 90 days, flexural strength of 28-days, drying shrinkage, density measurement, and sorptivity. It was observed 10% PKSA replacement as optimum percentage which reduced the drying shrinkage, sorptivity, and density and improved the late-age compressive strength of concrete.

• Journal of Korean Society of Forest Science
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• v.60 no.1
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• pp.30-36
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• 1983

Plywood, the representative interior decorative or structural material, is so inflammable that it may cause big fires. Therefore, it is required inevitably to manufacture the "Fire retardant treated plywood", and it will be a study on the redrying of treated plywood that we ought to solve. This study was carried out to investigate the absorption of 20% $(NH_4)_2HPO_4$ solution into the soaked plywoods by hot/cold soaking for 3/3, 6/3, 9/3 and 12/3 hours and to study drying process with drying curves and drying rates by press-drying at the platen temperature of 130, 145, 160 and $175^{\circ}C$. Solution absorption of plywoods in hot/cold soaking method increased steadily with the prolonged soaking time, and water absorption is higher than DAP absorption, and then chemical retention (DAP) exceeded the minimum retention [$1.125kg/(30cm)^3$] even in the shortest soaking treatment. Drying curves of water-soaked plywoods inclined more steeply than those of DAP soaked plywoods. And the drying proceeded rapidly with the increase in platen temperature and terminated in 2.5-4 minutes at the temperature of 160 and $170^{\circ}C$. Drying rate also increased generally with the increase of platen temperature. So it was at $175^{\circ}C$ in DAP-soaking and at $160^{\circ}C$ in water-soaking when the drying rate became above 10%/min.