• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.6
• /
• pp.16-23
• /
• 2018

In this study, Polydimethylsiloxane (PDMS) was applied to Strain Hardening Cement Composites (SHCC) for penetrating water repellency. The penetration depth of PDMS, strength of SHCC, and chloride ion penetration resistance of SHCC were investigated. As a result of measuring penetration depth of PDMS when applying different application method, it was confirmed that all methods satisfied the requirements of KS F 4930. Although the immersion method showed the largest penetration depth, the spray method was considered to be more appropriate considering the ease of field application. Compressive strength tests showed that the penetration depth of PDMS decreased as the compressive strength of SHCC increased. The compressive strength of M4-A and M4-B specimens with large PDMS penetration depths decreased by 9.6% and 8.0%, respectively, compared with those of M4 specimens produced without PDMS. Compressive strengths of the M1-A and M1-B specimens with small PDMS penetration depths were reduced by 4% and 2.2%, respectively, compared with the M1 specimen. As a result, it can be seen that the strength reduction rate of SHCC increases as the penetration depth of PDMS increases. The chlorine ion penetration tests showed that the chlorine ion penetration resistance increases with the penetration depth of PDMS.

• 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.1 no.1
• /
• pp.26-34
• /
• 2013

Durability performance in RC structures varies significantly with changes in cover depth and mix proportions. GGBFS (Ground Granulated Blast Furnace Slag) is very effective mineral admixture and widely used for an improved resistance to chloride attack. In this paper, characteristics such as porosity, compressive strength, and diffusion coefficient are evaluated in GGBFS concrete with 30~70% of replacement ratio and $4,000{\sim}8,000cm^2/g$ of fineness. Through the tests, more dense pore structure, higher compressive strength, and lower diffusion coefficient are obtained in GGBFS concrete, which are evaluated to be more dependent on replacement ratio than fineness. With increasing curing period from 3 to 91 days, porosity decreases to 77.47% and strength increases to 373% in GGBFS concrete. Chloride diffusion coefficient in GGBFS concrete decreases to 64.4% compared with that in OPC concrete, which shows significant improvement of durability performance.

• Journal of the Korean Geotechnical Society
• /
• v.18 no.4
• /
• pp.309-317
• /
• 2002

The mechanical characteristics of Light-Weighted Foam Soil(LWFS) are investigated in this research. LWFS is composed of the dredged soil from offshore, cement and foam to reduce the unit-weight and increase compressive strength. For this purpose, the unconfined compression tests and triaxial compression tests are carried out on the prepared specimens of LWFS with various conditions such as initial water contents, cement contents, curing conditions and confining stresses. The test results of LWFS indicated that the stress-strain relationship and the compressive strength are strongly influenced by the cement contents rather than the intial water contents of the dredged soils. On the other hand, the stress-strain relationship from triaxial compression test has shown strain-softening behavior regardless of curing conditions. The stress-strain behavior for the various confining stress exhibited remarkable change at the boundary where the confining stress approached to the unconfined compression strength of LWFS. In order to obtain the ground improvement of the compressive strength above 200kPa, the required LWFS mixing ratio is found to be 100%~160% of the initial water contents of dredged soil and 6.6% of cement contents.

• Journal of the Korean Geotechnical Society
• /
• v.22 no.11
• /
• pp.25-35
• /
• 2006

This paper investigates the mechanical characteristics of reinforced lightweight soil (RLS) using waste fishing net. RLS used in this experiment consists of dredged soil taken from construction site of Busan New Port, cement, air foam and waste fishing net. Several series of laboratory tests were performed to compare behavior characteristics between RLS and unreinforced lightweight soil, in which the reinforced effect by waste fishing net on RLS was evaluated. The experimental results of RLS indicated that the stress-strain relationship and the unconfined compressive strength are strongly influenced by the content of waste fishing net. Compressive strength of RLS Increased with the increase in curing time and generally increased by adding waste fishing net, but the amount of increase in compressive strength was not proportional to the content of waste fishing net. In this test, the maximum increase in compressive strength was obtained at 0.25% content of waste fishing net. On the other hand, water content of RLS rapidly decreased up to 7 days of curing time and converged to constant value.

• Journal of the Korea Institute of Building Construction
• /
• v.16 no.1
• /
• pp.53-58
• /
• 2016

In order to investigate the feasibility of municipal solid waste incineration ash melted slag powder as admixture, an experimental study was performed on cement mortar with municipal solid waste incineration ash melted slag powder. Fresh mortar properties and strength properties with various municipal solid waste incineration ash melted slag powder replacement ratios were estimated. There replacement ratio adopted in this study was 0, 10, 20, 30, 40, 50%. After then flow properties was considered as properties of fresh mortar. And compressive strength was determined 3, 7, 14, 28, 56 days for the hardened mortar specimens. According to the test results, the flow of mortar was increased with in replacement amount of municipal solid waste incineration ash melted slag powder. Furthermore, compressive strength at early age was decreased, whereas the compressive strength at the age of 28, 56day was increased.

• Journal of the Korean GEO-environmental Society
• /
• v.8 no.5
• /
• pp.23-29
• /
• 2007

The performance of the improved soil against liquefaction depends upon the chemical density, and it has been decided on the basis of the unconfined compressive strength of the improved soil up to date. On the other hand, several authors have proposed that the stiffness degradation could be treated as the clue for the judgment of the possibility of liquefaction. In this study, therefore, the stiffness degradation of the improved soil was estimated as the resistance against liquefaction by using the strain controlled cyclic triaxial test equipment. Based on the test results, it is concluded that the chemically treated sand can resist against the liquefaction in aspect of the reduction in effective stress and in the stiffness. Furthermore, even in the case of low chemical density, such as 2% in this study, has enough liquefaction resistance when compared with the 5~6% which often used in practical design. Considering this fact, the design of chemical density based on the unconfined strength can lead the overestimation in chemical density, and chemical density can be reduced when considering the stiffness reduction shown in this study.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.3
• /
• pp.244-250
• /
• 2023

In this paper, mortar mixed with tapioca starch was manufactured to evaluate the effect of tapioca starch on mortar, through evaluating the quality characteristics of mortar, the impact of tapioca starch on improving the performance and basic quality of mortar was examined. Tapioca starch tended to decrease flow by increasing the viscosity of the dough consistency of fresh mortar, which tended to reduce flow, and decreased by about 10 % as the tapioca starch mixing ratio increased by 0.025 %. In addition, the effect of tapioca starch on the compressive strength of mortar was at the same level regardless of the tapioca starch mixture at 28 days of age. However, at an early age of 3 days, the speed of compressive strength development was accelerated by mix ing tapioca starch. In addition, the effect of tapioca starch on the compressive strength of mortar was at the same level regardless of the tapioca starch mixture at 28 days of age. However, at an early age of 3 days, the speed of compressive strength development was accelerated by mixing tapioca starch. The speed of strength development improved by about 20 % when mixing 0.050 % tapioca starch. The adhesion strength improved by about 60 % when mixing 0.050 % tapioca starch, and the final shrinkage in length change decreased by 5 %.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.2
• /
• pp.114-121
• /
• 2017

The purpose of this study is to understand a compressive strength and propose a dry shrinkage strain equation being able to predict dry shrinkage of alkali-activated materials(AAM) mortar samples manufactured using fly-ash(FA) and ground granulated blast furnace slag(GGBFS). The main parameters investigated were the GGBFS replace ratios(30, 50, 70 and 100%) and sodium silicate modules(Ms[$SiO_2/Na_2O$] 1.0, 1.5 and 2.0). The compressive strength of AAM increased with increases GGBFS replace ratios or Ms contents. The dry shrinkage strain of AAM decreased with increases Ms contents. But, the dry shrinkage strain of AAM increased as the GGBFS replace ratio increases. Therefore, the GGBFS replace ratio seems to have very significant and important consequences for the mix design of the AAM mortar. The results indicated the R-square of single regression analysis based on each mix properties was the highest value; 0.7539~0.9786(average 0.9359). And the presumption equation of dry shrinkage strain with all variables(GGBFS, Ms and material age) has higher accuracy and its R-square was 0.8020 at initial curing temperature 23 degrees Celsius and 0.8018 at initial curuing temperature 70 degrees Celsius.

• Journal of the Korea Institute of Building Construction
• /
• v.19 no.5
• /
• pp.421-429
• /
• 2019

The changes in the resistance to chloride ingress of concrete using a ground granulated blast furnace slag (GGBFS) according to curing conditions were examined. The curing conditions were divided in air-dry curing and under-water curing. Three concrete mixures with the GGBFS replacement ratio of 0%(control), 30%, and 60% were prepared. For tests, evaluations of concrete compressive strength, and chloride ion diffusion coefficient were performed. As the GGBFS replacement ratio increased, the concrete compressive strength of the in air-dry cured specimens decreased compared to under-water cured specimens. When the chloride ion diffusion coefficient was measured, the chloride ion diffusion coefficient decreased as the GGBFS replacement ratio increased. However, the diffusion coefficient of the in air-dry cured specimen was increased up to 111% compared with the under-water cured specimen.