• Magazine of the Korea Concrete Institute
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• v.18 no.4 s.93
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• pp.63-67
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• 2006

• Journal of the Korea Institute of Building Construction
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• v.13 no.6
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• pp.522-529
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• 2013

As concrete forms, panel forms made of plywood used to be widely used, but recently a system form made of aluminum has been broadly adopted because of the advantages it offers in terms of constructability and economy. However, an aluminum form reacts with concrete, which is alkali, and creates hydrogen gas. As a result, air pockets occur on the concrete's surface, and its finishability deteriorates. Therefore, this research analyzed the relationship between the distribution of voids and surface roughness and the damage degree and number of uses of the aluminum form. The analysis of the distribution of voids shows that the number of voids of 0.1~1 mm, which are considered to have occurred because of chemical reaction, was 200~500 on the coating plywood, but was 1 500~2 000 on the aluminum form after 3 uses, and impossible to count after a higher number of uses. Surface roughness was $1.7{\sim}3.2{\mu}m$ on the coating plywood form, but was about $2.6{\mu}m$ after the first use and about $6.8{\mu}m$ after 10 uses, a 2.6-fold increase. Distribution of voids did not show a particular tendency depending upon the degree of damage to the concrete form, but surface roughness showed an increasing tendency as the degree of damage grows. Therefore, when using aluminum forms, surface maintenance should be carried out completely, such as prevention of damages to the form surface coating materials and spreading of separating materials on forms.

• Journal of the Korea Institute of Building Construction
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• v.13 no.5
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• pp.457-464
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• 2013

Traditionally, the material used for the form in reinforced concrete construction has been wood or steel. But recently, aluminum forms have been widely used in wall structures such as apartment buildings. Aluminum is light, easy to handle, and economically advantageous, but the hydrogen gas created due to its reaction with the alkali component in concrete gives rise to air pockets on the concrete's surface, and deteriorates the surface's finishability. In this research, to determine the influence of aluminum material on concrete, the cement paste W/C and its chemical reactivity in alkali and acid solution were analyzed. As a prevention plan, the influence of the number of applications of calcium hydroxide and various surface coating materials was analyzed. Through the analysis, it was found that the surface voids on the aluminum form are the result of the reaction of hydrogen gas with an alkali such as $Ca(OH)_2$. This can be prevented by the surface treatment of $Ca(OH)_2$, separating material and coating material. However, poor surface form and damages to the form are expected to cause quality degradation because of the aluminum-concrete interaction. Therefore, thorough surface treatment, rather than the type of separating material or coating material, is considered the most important target of management.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.4
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• pp.137-146
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• 1996

This paper presents the results of field experience from an experimental pavement construction on a low volume road using recycled concrete. The recycled concrete was prepared by replacing a half of coarse aggregate with recycled aggregate. Virgin natural sand was used as fine aggregate together a plasticizer and a fly ash (0.8% and 5% by wt. of cement, respectively). The load bearing capacity of the subbase made of recycled aggregate was acceptable. The length, thickness and width of the pavement were l00m, 20cm and 3m, respectively. From construction experience, it was found that workability and finishability of the recycled concrete mixture were relatively poor, but strengths were satisfactory. Flexural strength, compressive strength and elastic modulus at 28 days were 54Kg/$cm^2$, over 250Kg/$cm^2$, and 220,OOOKg/$cm^2$, respectively. The construction could be performed by hand without much difficulty. The surface was finished smoothly by wet fabric and only minor cracks were found on the surface.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.388-393
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• 1996

This study evaluated characteristics and performance of recycled concrete as a pavement which was constructed on a low volume road. The recycled concrete was prepared by replacing a half of coarse aggregate with recycled aggregate. Natural sand from a source was used as fine aggregate together with admixtures such as plasticizer and fly ash (0.8% and 5% by wt. of cement, respectively). The length, thickness and width of the pavement were 100mm, 20cm and 3m, respectively. From construction experience, it was found that workability and finishability of the recycled concrete mixture were relatively poor, but strengths were satisfactory. Flexural strength, compressive strength and elastic modulus at 28 days were approximately 45Kg/$\textrm{cm}^2$, 250Kg/$\textrm{cm}^2$, and 240,000 Kg/$\textrm{cm}^2$, respectively. The pavement could be constructed by hand without much difficulty. The surface was finished smoothy by wet fabric and only minor cracks were found on the surface.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.47-50
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• 2008

This study analyzed the effect of increasing the number of times using aluminum form to the surface quality of concrete through small sized test, and the result was summarized as following. At the early stage, there was no remarkable change between aluminum and coated plywood form, and the surface quality of concrete both forms slightly declined corresponding with increasing the number of times using.As void on the surface corresponding to the number of times, the voids ranged 0.1~1mm were increased corresponding to increasing the number of times using forms, and the other range voids were also increased according to increasing the number of times using forms. It was confirmed that the surface of concrete was damaged gradually. For comparison with aluminum and coated plywood form though this experimental results, there might be no difference, if release agent was used properly.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.969-972
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• 2008

This study investigated the effect of the fundamental condition such as release agent, form conditions and types to the surface of concrete with aluminum form on the various temperatures. On the observation with the naked eyes, coated plywood and aluminum form without a scratch showed similar result, and the surface quality of the concrete with aluminum form was gradually decreased corresponding to the increase of the temperature.For the surface roughness, there is no remarkable tendency according to the temperature. However, the difference in accordance with release agent occurred.As void on the surface corresponding to the various temperature, the micro voids ranged $0.1{\sim}1mm$ were increased corresponding to the increasing temperature, so it was confirmed that the chemical reaction wae accelerated. And the voids of the other range also increased. the fundamental condition such as release agent, form conditions and types

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.1
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• pp.67-75
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• 2013

Recently, the interest is increasing about the exposed concrete, accordingly, exposed concrete is expanding the use. However, concrete structures is difficult to apply the general concrete for exposed concrete, due to complex section and compact reinforcement, increasingly. Therefore, in this paper, for application of high fluidity concrete as exposed concrete, exposed high fluidity concrete using fly ash and lime stone powder was manufactured and observed quality property(fluidity properties, mechanical properties and Surface Properties) of exposed high fluidity concrete. The experiments are based on the OPC and LSP10, was evaluated Impact on the quality of concrete according to mixing ratio of FA(0, 10, 15 and 20). As a result, fluidity properties, mechanical properties and Surface Properties of exposed high fluidity concrete were satisfied to requirement conditions, fluidity and surface finishability was improved depending on mix of fly ash and limestone powder. Through this, we utilize of basic research data for development of high fluidity concrete for exposed concrete.