• Computers and Concrete
• /
• v.12 no.3
• /
• pp.319-335
• /
• 2013

In this paper, the properties of the cement mortar modified with styrene acrylic ester copolymer were investigated. Expanded vermiculite as lightweight aggregate was used for making the polymer modified mortar test specimens. To study the effect of polymer-cement ratio and vermiculite-cement ratio on various properties, specimens were prepared by varying the polymer-cement and vermiculite-cement ratios. Tests of physical properties such as density, water absorption, thermal conductivity, three-point flexure and compressive tests were made on the specimens. Furthermore, a coupled thermal-structural finite element model of an entire corner wall was modelled in order to study the best material configuration. The wall is composed by a total of 132 bricks of $120{\times}242{\times}54$ size, joined by means of a contact-bonded model. The use of advanced numerical methods allows us to obtain the optimum material properties. Finally, comparisons of polymer-cement and vermiculite-cement ratios on physical properties are given and the most important conclusions are exposed.

• Journal of the Korean Ceramic Society
• /
• v.49 no.2
• /
• pp.161-166
• /
• 2012

The temperature-rasing sintering method was used in this study to fabricate the aggregates of uniform pore size and distribution containing reject ash occurred in the thermal power plant. The spheric green aggregates made of reject ash were put into the box furnace of 800~$1000^{\circ}C$, heated with a heating rate of 5~$15^{\circ}C$/min to 1200~$1275^{\circ}C$, sintered for 10 min and then discharged out of the furnace to the room temperature. The input temperature, heating rate and sintering temperature increased the bloating phenomenon of the specimen, and the sintering temperature among them was the most effective factor. The aggregate manufactured at $1275^{\circ}C$ had the specific gravity of about 1.0 and water absorption of 1~2%, and the pores of 500~1,000 ${\mu}m$ were uniformly distributed across the whole specimen. Especially, the aggregates fabricated using the temperature-rasing sintering method in this study showed an excellent bloating properties and uniform microstructure without black core phenomenon which is typical for the bloated ceramics synthesized by direct sintering method.

• Journal of the Korean Ceramic Society
• /
• v.55 no.1
• /
• pp.36-43
• /
• 2018

The physical and chemical analyses of mineral waste such as moisture content, water absorption, freezing-thawing resisting sexual, chemical composition and crystal structure were investigated. In the technological process of crushing, screening, molding, drying, preheating, sintering and cooling, many parameters were changed to eliminate the influence of freeze thaw stability and the ball billets were processed into slate ceramsites eventually. Adopting orthogonal experiment and range analysis, the optimal technology parameters were confirmed as preheating temperature of $300^{\circ}C$ for 25 minutes and sintering temperature of $1230^{\circ}C$ for 20 minutes. Slate wastes in Shangri-la could foam and expand without any additive. The ultra-light ceramsite could be directly used as building aggregate, since the analysis results of its leaching toxicity were eligible. Besides, effects of sintering temperature on physical property and crystal phase were also explored in this study.

• Economic and Environmental Geology
• /
• v.57 no.2
• /
• pp.185-204
• /
• 2024

This study was conducted for evaluation the geological, physical, and chemical properties of domestic sand by analyzing about 4,800 quality data of natural sand from river and land area surveyed until 2023 through the aggregate resource survey conducted by the Ministry of Land, Infrastructure and Transport. The average depth of the Quaternary unconsolidated sedimentary layer in Korea, which includes a sand layer, is about 10m (maximum depth 66m). The thickness of the sand layer within the sedimentary layer is most dominant in the range of 0.5m to 4.0m. This accounts for about 70% of the entire sand layer. In the sand layer, the ratio of sand, gravel, and clay is 60:20:10. Regardless of the provenance or geology, the sand is mainly composed of quartz, plagioclase, and K-feldspar, and the minor minerals are muscovite, biotite, chlorite, magnetite, epidote. The sand includes in 45~75% of quartz, 5~20% of plagioclase and K-feldspar, each other. And other minor minerals are included in 10%. The average grain size of sand is 0.5mm to 1.0mm, which accounts for 44% of sand samples. The water absorption rate and soundness are estimated to be suitable for aggregate quality standard in almost all sand, and the absolute dry density is suitable for 66%.

• Computers and Concrete
• /
• v.21 no.3
• /
• pp.311-319
• /
• 2018

This study used a volumetric method for design. The control group used waste Liquid Crystal Displayplay (LCD) glass powder to replace cement (0%, 10%, 20%, 30%), and the PZT group used Pd-Zr-Ti piezoelectric (PZT) powder to replace 5% of the fine aggregate to make cement mortar. The engineering and the mechanical and electricity properties were tested; flow, compressive strength, ultrasonic pulse velocity (UPV), water absorption and resistivity (SSD and OD electricity at 50 V and 100 V) were determined; and the correlations were determined by linear regression. The compressive strength of the control group (29.5-31.8 MPa) was higher than that of the PZT group (25.1-29 MPa) by 2.8-4.4 MPa at the curing age of 28 days. A 20% waste LCD glass powder replacement (31.8 MPa) can fill up finer pores and accelerate hydration. The control group had a higher 50 V-SSD resistivity ($1870-3244{\Omega}.cm$), and the PZT group had a lower resistivity ($1419-3013{\Omega}.cm$), meaning that the resistivity increases with the replacement of waste LCD glass powder. This is because the waste LCD glass powder contains 62% $SiO_2$, which is a low dielectric material that is an insulator. Therefore, the resistivity increases with the $SiO_2$ content.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.3
• /
• pp.83-91
• /
• 2015

Porous concrete consists of cement, water and coarse aggregate and has been used for the purpose of decreasing the earth environmental load such as air and water permeability, sound absorption, etc. However, the physical and mechanical properties of porous concrete changes due to compaction load during construction. For such a reason, the purpose of this study is to investigate the physical and mechanical properties of porous concrete according to the kinds of binder, the ratio of water to binder and target void ratio. In particular, this study has been carried out to investigate the influence of compaction load on the void ratio, strength and coefficient of permeability. Aggregate used in this study are by-products generated during production of crushed gravel with a maximum size of 13mm. The results of this study showed that the target void ratio, the coefficient of permeability and compressive strength of porous concrete had a close relationship with the void ratio, and it will be possible that the void ratio is suggested by the mix design of porous concrete. The compressive strength of porous concrete was the highest at the content of the expansive admixture of 5% and compared to non-mixture, 10% mixture of silica fume improved compressive strength about 32%. And in the result of the study to change the compaction load, the compressive strength increased from the load of 15kN, the void ratio decreased from the load of 0.8kN, the coefficient of permeability decreased from the load 35kN, respectively.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.6 no.1
• /
• pp.128-135
• /
• 2011

In this study, in order to develop ultra rapid hardening mortar(URHM) for tunnel repairs using bottom ash of low recycle ratio and Admixture as Eco concept, fundamental properties of URHM on temperature condition of construction field were performed. Test result, URHM of three types for fluidity and setting time were as in the following : B > C > A. Those for low temperatures were later than the standard condition. Compressive, bending and bond strength were similar with three types as follow. In compressive strength, initial strength of the low were smaller than the standard but the low in the long-term were similar with the standard. On the contrary to this, bending strength were similar in initial strength but the low in the long-term were smaller than the standard. The low in bond strength was average 35% less than the standard. Length changes was as in the following : A > C > B. the low is two times much as the standard but the case using blast furnace slag particles noticeably reduced length changes. Water absorption coefficient and water vapor resistance were as in the following : C > A > B. In case of URHM added bottom ash, water absorption coefficient and water vapor resistance were increased because bottom ash is porous material.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.27 no.1
• /
• pp.46-61
• /
• 1985

This study was performed to obtain the basic data which can be applied to the use of foaming mortars. The data was based on the properties of foaming mortars depending upon various mixing ratios and addings to compare those of cement mortar. The foaming agents which was used at this experiment were pre-foamed type and mix-foaming type which is being used as mortar structures. The foaming mortar, mixing ratios of cement to fine aggregate were 1:1, 1: 2, 1 : 3 and 1 : 4. The addings of foaming agents were 0.0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5% and 3.0% of cement weight. The results obtained were summarized as follows; 1. At the mixing ratio of 1 : 1, the lowest water-cement ratios were showed by foaming mortars, respectively. But it gradually was increased in poorer mixing ratio and decreased in more addition of foaming agent. The water-cement ratios were decreased up to 1. 8~22. 0% by G, 2. 2~24. 1 % by U and 0. 7~53. 1% by J foaming mortar than cement mortar. 2, At the mixing ratio of 1 : 1, the highest bulk densities were showed by foaming mortars, respectively. But, it gradually was decreased in poorer mixing ratio and more addition of foaming agent. The bulk densities were decreased up to 1. 4~20. 7% by G, 2. 3~23. 7% by U and 26. 5~56. 5% by J foaming mortar than cement mortar. Therefore, foaming mortar could be utilized to the constructions which need low strengths. 3. At the mixing ratio of 1:1, the lowest absorption rates were showed by foaming mortars, respectively. But, it gradually was increased in poorer mixing ratio and more addition of foaming agent. Specially, according to the absorption rate when immersed in 72 hours, the absorption rates were showed up to 1. 01~1. 24 times by G, 1. 03~1. 58 times by U and 1. 10~5. 91 times by J foaming mortar than cement mortar. It was significantly higher at the early stage of immersed time than cement mortar. 4. At the mixing ratio of 1:1, the lowest air contents were showed by foaming mortars, respectively. But, it gradually was increased in poorer mixing ratio and more addition of foaming agent. Air contents were contented up to 4. 0~17. 2 times by G, 5. 2~23. 2 times by U and 23. 8~74. 5 times by J foaming mortar than cement mortar. 5. At the mixing ratio of 1 : 1, the lowest decreasing rates of strengths were showed by foaming mortars, respectively. But, it gradually was increased in poorer mixing ratio and more addition of foaming agent. Specially, the strengths of 28 days were decreased 0. 4~2. 2% than those of 7 days by foaming mortar, respectively. Also, the correlations between compressive and tensile strength, compressive and ending strength, tensile and bending strength were highly significant as a straight line shaped, respectively. 6. The correlations between absorption rate, air content, compressive strength and bulk density, absorption rate, compressive strength and air content were highly significant, respectively. The multiple regression equations of water-cement ratio, bulk density, absorption ate, air content, compressive strength, tensile strength and bending strength were computed depending on a function of mixing ratio and addition of foaming agent. It was highly significant, respectively. 7. At the mixing ratio of 1 : 1, the highest strengths were showed by cement mortar and foaming mortars, by chemical reagents. But, it gradually was decreased in poorer mixing ratio. The decreasing rates of strengths were in order of H $_2$S0 $_4$, HNO$_3$ and HCI, J,U,G foaming mortar and cement mortar. Specially, at the each mixing ratio, each chemical reagent and 3.0% of foaming agent, J foaming mortar was collapsed obviously. Therefore, for the structures requiring acid resistence, adding of foaming agent should be lower than 3.0%.

• The Journal of Engineering Geology
• /
• v.33 no.1
• /
• pp.169-187
• /
• 2023

Aggregates from 84 cities and counties in Korea were tested for quality to allow analysis of the physical characteristics of aggregates from river, land, and forest environments. River and land aggregates were analyzed for 18 test items, and forest aggregates for 12 test items. They were classified according to watershed and geology, respectively. The observed physical characteristics of the river aggregates by basin were as follows: aggregates from the Geum River basin passed through 2.5, 1.2, 0.6, 0.3, 0.15, and 0.08 mm sieves; clay lumps constituted the Nakdong River basin material; aggregates from the Seomjin River basin passed through 10, 5, and 2.5 mm sieves; those from the Youngsang River basin passed through 1.2, 0.6, 0.3, 0.15, and 0.08 mm sieves; and aggregates from the Han River basin passed through 10, 5, 2.5, 1.2, 0.6, 0.3, and 0.08 mm sieves, Stability; Standard errors were analyzed for the average amount passing through 10, 0.6, and 0.08 mm silver sieves, and performance rate showed different distribution patterns from other physical characteristics. Analysis of variance found that 16 of the 18 items, excluding the absorption rate and the performance rate, had statistically significant differences in their averages by region. Considering land aggregates by basin, those from the Nakdong River basin excluding the Geum River basin had clay lumps, those from the Seomjin River basin had 10 and 5 mm sieve passage, aggregates from the Youngsang River basin had 0.08 mm sieve passage, and those from the Han River basin had 10, 0.6, and 0.08 mm sieve passage. The standard error of the mean of the quantity showed a different distribution pattern from the other physical characteristics. Analysis of variance found a statistically significant difference in the average of all 18 items by region. Analyzing forest aggregates by geology showed distributions of porosity patterns different from those of other physical characteristics in metamorphic rocks (but not igneous rocks), and distributions of wear rate and porosity were different from those of sedimentary rocks. There were statistically significant differences in the average volume mass, water absorption rate, wear rate, and Sc/Rc items by lipid.

• Journal of the Korea Concrete Institute
• /
• v.19 no.2
• /
• pp.179-188
• /
• 2007

Recently, the concern on the receipt of poor ready-mixed concrete in the construction field and the durability of concrete has been increased. Based on the such background, a large number of measuring methods of water content for fresh concrete have been developed and enforced in a developed country. In this study, to investigate practicality for quality control of ready-mixed concrete among various water content measurement techniques, microwave range method, air meter method and capacitance measurement method as measuring methods of water content were selected. Then, it was evaluated estimating performance of water content according to the change of binder types, fine aggregate types, absorption ratio, water content and water-binder ratio in series I and II. Also, it was examined influence on error occurrence of water content according to change of properties of used materials in series III. Finally, based on this study, it was proposed fundamental data to utilize measurement technique of water content to quality control of ready-mixed concrete in construction field.