• Journal of the Korea Institute of Building Construction
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• v.12 no.2
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• pp.152-160
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• 2012

The development of building must be accompanied with construction technology and performance of materials. In particular, wet processes have a high level of dependence on manpower and a low level of diversification of materials used. This study aimed to determine the applicability of various materials for wet process, mechanized construction and eco-friendly building materials through a comparison with dry premixed mortar. As a result, it was found that resin plaster and gypsum plaster's strength is lower than that of dry cement mortar, but their mechanization application, construction simplification, smoothness and bond strength are higher than that of dry cement mortar. And estimate that is valid as workability, bonding strength, eco-friendly building material in occasion of gypsum plaster.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.247-252
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• 2017

The aim of this research is the feasibility analysis of the reject ash premixed cement mortar with combined aggregate. Namely, for the combined aggregate with two different qualities of aggregates, a fundamental properties of cement mortar was evaluated depending on various replacing ratios of reject ash(Ri). According to the experimental results, the combined aggregate consisted with low-quality aggregate and sea sand did not change the flow value depending on the reject ash while the combined aggregates consisted with low quality aggregate and sea sand; and consisted exploded debris sand and sea sand the increasing reject ash increased the air content with increased replacing ratio of reject ash. In the case of compressive strength, as the replacing ratio of reject ash was increased, the compressive strength was increased. It is considered that when 5% of reject ash replacing ratio made similar quality of cement mortar with favorable quality aggregate, hence, it can be suggested that 5% replacement of reject ash for desirable fluidity and compressive strength of concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.331-335
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• 2018

The purpose of this study is to investigate the feasibility of CFBC artificial fine aggregate as a substitute for natural aggregate used in dry mortar. The basic performance of the flow, compressive strength and dry shrinkage of the dry mortar was evaluated. Four types of test dry mortar specimens using natural aggregate without expansion admixture, a specimen with modified CaO expansion admixture and natural aggregate, a specimen with modified CaO expansion admixture and CFBC artificial fine aggregate, and a specimen using CFBC artificial fine aggregate without modified CaO expansion admixture were evaluated respectively. As a result of evaluation of drying shrinkage performance at 20th day of age, the dry shrinkage performance of the specimen using modified CaO expansion admixture was found to be the highest at $250{\times}10^{-6}$. On the other hand, the specimen containing the modified CaO expansion admixture with CFBC artificial aggregate exhibited a shrinkage of $410{\times}10^{-6}$, and the drying shrinkage of specimen using natural fine aggregate without expansion admixture was $450{\times}10^{-6}$. When the modified CaO expansion material was used, and exhibited performance equal to or higher than that of the shrinkage-drying property.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.76-83
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• 2012

In this study, the research examined the effect on FC, WG, RP replacement ratio on the quality improvement of BS mortar using the RA. First of all, the flow value increased as the FC contents increased, and decreased as the WG and RP contents increased. The air contents was reduced as the FC and RP contents increased, but was increased as the WG contents went up While the compressive strength of 1 : 7 mix proportion increased with the increase of the FC and WG contents, it decreased as there was more RP contents. The compressive strength of RP could increase as the mix proportion increased, but the difference depending on the improvement material type and replacement ratio decreased gradually. The absorption deteriorated as the FC and RP contents increased in all the mix proportions, but improved a little when WG was used. Meanwhile, the absorption decreased as the compressive strength improved in all the mix proportions as a correlation, but the order was FC, RP and WG depending on the quality improvement material types. The FC and WG were most favorable in terms of quality improvement as a total analysis, and the RP and WG was most effective in terms of economical efficiency and resource recycling.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.53-59
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• 2010

Recently, NDTs (Non-Destructive Techniques) using infrared camera are widely studied for detection of damage and void in RC (reinforced concrete) structures and they are also considered as an effective techniques for maintenance of infrastructures. The temperature on concrete surface depends on material and thermal properties such as specific heat, thermal conductivity, and thermal diffusion coefficient. Different porosity on cement mortar due to different mixture proportions can show different heat behavior in cooling stage. The porosity can affect physical and durability properties like strength and chloride diffusion coefficient as well. In this paper, active thermography which uses flash for heat induction is utilized and thermal characteristics on surface are evaluated. Samples of cement mortar with W/C (water to cement ratio) of 0.55 and 0.65 are prepared and physical properties like porosity, compressive strength, and chloride diffusion coefficient are evaluated. Then infrared thermography technique is carried out in a constant room condition (temperature $20{\sim}22^{\circ}C$ and relative humidity 55-60%). The mortar samples with higher porosity shows higher residual temperature at the cooling stage and also shows reduced critical time which shows constant temperature due to back wall effect. Furthermore, simple equation for critical time of back wall effect is suggested with porosity and experimental constants. These characteristics indicate the applicability of infrared thermography as an NDT for quality assessment of cement based composite like concrete. Physical properties and thermal behavior in cement mortar with different porosity are analyzed in discussed in this paper.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.137-145
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• 2012

Strength model for blasted furnace slag mortar blended with sodium was investigated in this study. The main parameters of AAS (alkali activated slag) mortar were dosage of alkali activator, water to binder ratio (W/B), and aggregate to binder ratio (A/B). For evaluating the property related to the dosage of alkali activator, sodium carbonate ($Na_2CO_3$) of 4~8% was added to 4% dosage of sodium hydroxide (NaOH). W/B and A/B was varied 0.45~0.60 and 2.05~2.85, respectively. An alkali quality coefficient combining the amounts of main compositions of source materials and sodium oxide ($Na_2O$) in sodium hydroxide and sodium carbonate is proposed to assess the compressive strength of alkali activated mortars. Test results clearly showed that the compressive strength development of alkali-activated mortars were significantly dependent on the proposed alkali quality coefficient. Compressive strength development of AAS mortars were also estimated using the formula specified in the previous study, which was calibrated using the collected database. Predictions from the simplified equations showed good agreements with the test results.

• Journal of the Korea Institute of Building Construction
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• v.15 no.5
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• pp.451-456
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• 2015

This study aimed to evaluate of the hardened properties (mortar consistency, setting time, absorption properties, drying shrinkage, and bond strength) of the basalt powder sludge mortar recycling a basalt powder sludge occurred during the manufacture process of basalt stone as a replacing material for the sea-sand used to cement filling compound for surface preparation. The hardened mortar made of the basalt powder sludge showed an enhanced performance or similar with the properties of normal mortar used to cement filling compound for surface preparation. But, the drying shrinkage was increased more than a normal cement mortar in the hardened mortar made of the basalt powder sludge since curing 8 - 9days. And the bond strength is low in the hardened mortar used the basalt powder sludge. On the whole, properties of the hardened mortar used the basalt powder sludge correspond to the required minimum quality criterion in the KS F 4716 'cement filling compound for surface preparation'.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.445-446
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• 2009

This study investigated properties of blast furnace slag from various areas and fundamental properties and length change on the case that the blast furnace slag was applied to surface coating dry-mortar.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.100-101
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• 2016

The fineness degree of Ordinary Portland Cement (OPC henceforth) usually used in Korea's construction sites, is designated as over 2,800㎠/g. But the higher the fineness, the surface area of hydration reaction on water increases as well, resulting in large early age strength and high-intensity; so the trend is to prefer a high degree of fineness. But from a pore-space filling perspective, fine-particled cement is not always beneficial to intensity. Therefore in this study artificial modifications were given to cement fineness to analyze the effect of various fineness changes on the liquidity, air quantity and intensity of lean mixture cement mortar. As a result, the greater the degree of fineness, the better the cement was, with fine particle+OPC having the most satisfactory results due to consecutive particle distribution.

• Journal of the Korea Institute of Building Construction
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• v.19 no.5
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• pp.391-399
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• 2019

This study reviewed the possibility of recycling into exhausted aggregate resources in Korea as a means of utilizing coal gasification slag(CGS) from integrated gasification combined cycle(IGCC) while being commissioned in order to introduce the new system to Korea. In other words, in order to solve the problem of insufficient aggregate resources, CGS generated by IGCC as a residual aggregate for concrete secondary products, which is an empty mortar, was considered to replace CGS in the range of 0 to 100 % for mixed residual aggregate mixed with crushed sand A(CSa) of good quality and sea sand(SS) of deep particles, which are the most commonly used in the domestic construction industry. According to the study, replacing CGS with CSa or crushed sand B(CSb)+SS by 25 % to 50 % resulted in good results in the aspect of the granularity of the aggregate and the workability and compressive strength of cement mortar, which were found to be usable.