• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2018.11a
• /
• pp.79-80
• /
• 2018

Recently, the interest in remodeling of new and old buildings is increasing worldwide. As a result, the frequency of use of architectural adhesives has increased. Currently, adhesives used in buildings are made of organic materials in most cases, and epoxy resin adhesives are most widely used. However, epoxy resin adhesives contain formaldehyde and VOCs in the room during construction, which can cause sick house syndrome. In case of building fire, it may cause damage due to carbon monoxide generated from organic materials. It is urgent to study the problem of epoxy fill adhesive made of such organic materials. Therefore, the purpose of this study is to investigate the effect of the adhesion of epoxy resin adhesive, which is a problem of epoxy resin adhesive, which is an existing organic adhesive by using inorganic materials such as magnesia and phosphate, And the inorganic adhesive which does not emit the release amount as an inorganic material.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.16 no.6
• /
• pp.163-170
• /
• 2012

With the advantage of a rapid exothermic reaction property, jet set concrete may be used as a cold weather concrete because it can reach the required strength before being damaged by cold weathers. And it can be hardened more quickly if the field temperature is properly compensated by heating. Because ordinary concrete cannot be hardened well under sub-zero temperatures, anti-freeze agents are typically added to prevent the frost damage and to ensure the proper hardening of concrete. While the addition of a large amount of anti-freeze agent is effective to prevent concrete from freezing and accelerates cement hydration resulting in shortening the setting time and enhancing the initial strength, it induces problems in long-term strength growth. Also, it is not economically feasible because most anti-freeze agents are mainly composed of chlorides. Recent studies reported that magnesia-phosphate composites can be hardened very quickly and hydrated even in low temperatures, which can be used as an alternative of cold weather concrete for cold weathers and very cold places. As a preliminary study, to obtain the material properties, mortar specimens with different mixture proportions of magnesia-phosphate composites were manufactured and series of experiments were conducted varying the curing temperature. From the experimental results, an appropriate mixture design for cold weathers and very cold places is suggested.

• Journal of the Korea Institute of Building Construction
• /
• v.17 no.2
• /
• pp.141-147
• /
• 2017

The purpose of this study is to develop an inorganic filling adhesive using MKP and borax based on Dead-burn magnesia and fly ash. First, basic experiments was conducted to derive the proper addition rate of MKP. And this experiment was carried out according to addition ratio of borax. The test items are measured for pot life, flexural strength, compressive strength, adhesive strength, tensile strength, ratio of temperature change, ratio of hardening shrinkage, radon gas and formaldehyde emission. As a result, the proper addition rate of phosphate was 35%. The pot time is about 10minutes, 15minutes and 25minutes according to addition rate of borax. The flexural strength and compressive strength were obtained at 12hours for minimum flexural strength of 8.0MPa and minimum compressive strength of 31.0MPa. The tensile strength was the least 4.1MPa, and the ratio of hardening shrinkage was maximum 2.4% and ratio of heat change was maximum - 0.3%, which satisfied all of the quality standards of 'KS F 4923' (epoxy resin for repairing concrete structures). Both Radon gas and formaldehyde emission was not detected.

• Journal of the Korea Institute of Building Construction
• /
• v.19 no.4
• /
• pp.289-297
• /
• 2019

Epoxy resin adhesives are currently used as adhesives in buildings. Epoxy resin adhesives, which are organic materials, generate harmful substances when producing adhesives, and toxic substances are high in the residential space after installation. In addition, a large amount of carbon monoxide generated from organic materials in the case of a building fire leads to personal injury. This study evaluates the feasibility of inorganic adhesives using pure inorganic materials such as magnesia, phosphate, and borax as inorganic adhesives to replace existing organic adhesives. As a result of the experiment on the selection of adequate phosphate and the characteristics of the addition rate of borax used as a retarder, the potassium phosphate monobasic was obtained as a suitable phosphate and the characteristics according to the borax addition rate were compared with the quality standard of KS F 4923 The hardening shrinkage and heat change rate satisfied the quality standards. The tensile strength was satisfactory when the borax addition rate was 4% or more, but the adhesive strength did not meet the quality standards. Further studies are needed to improve adhesion strength.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2018.11a
• /
• pp.48-49
• /
• 2018

Recently the old buildings have been increasing and increasing reconstruction. As a result, the frequency of use of architectural adhesives has increased. Adhesives are not only used for bonding but also for building materials used in various fields. However, since the adhesive is made of an organic material, it causes various skin diseases and sick house syndrome, and when a fire occurs, harmful substances are generated, and incomplete combustion may cause personal injury. Therefore, in this study, to solve the disadvantages of conventional adhesives, we tried to develop inorganic adhesives using inorganic materials.

• Journal of Korea Foundry Society
• /
• v.5 no.2
• /
• pp.85-96
• /
• 1985

In order to investigate the effect of particle size and distribution of silica sand on the characteristics of investment, W/P ratio, setting time, temperature change during setting, setting expansion, thermal expansion and compressive strength of the investments were measured. In this experiment, magnesia clinker and mono ammonium phosphate were used as binder, and particle size and distribution of silica sand were classified for convinence into 10 categories. The main results obtained from this investigation were summerized as follows. 1. W/P ratio decreased with increase of particle size and evenness in distribution of sand grain. 2. Setting time decreased with increase of evenness in distribution of sand grain, and temperature during setting increased with evenness in distribution of sand grain. 3. Setting expansion decreased with increase of particle size, while it increased with evenness in distribution of sand grain. 4. Thermal expansion decreased with increase of particle size. 5. Compressive strength increased with increase of particle size and evenness in distribution of sand grain. From above results, G.F.N. 250 sand which contains 30% of 50-100 mesh could be recommended for investment casting.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2016.05a
• /
• pp.34-35
• /
• 2016

Most of the construction adhesive may contain harmful component to the human body with an organic adhesive. In addition, when the adhesive caused hydroquinone, alkyl benzophenone, etc, also it raises the skin diseases to workers. Therefore, the inorganic adhesive development is necessary. This study was a study to know adhesive strength properties that adhesive using a magnesium oxide according to the addition ratio of the retarder. It has experiments to two types of magnesium oxide and type and ratio of retarder differently.

• Journal of the Korea Institute of Building Construction
• /
• v.19 no.5
• /
• pp.449-456
• /
• 2019

Recent developments in architectural technologies and programs have enabled architects to think creatively and design free-form architecture. however, there are many problems in the production technology of FCP(Free-Form Concrete Panel). In particular, reduced accuracy due to lack of free-form panel production technology can lead to redesign of buildings as a result, problems such as an increase in construction cost and period. Therefore, this experiment aimed to compensate the decrease of the accuracy according to the displacement difference and to derive the proper mixing ratio for maintaining the shape during the free-form panel curing. In this study, molds were made using paraffin that is a recyclable phase change material. Concrete Panel is usually produced from Portland cement, dead burn magnesia, phosphate, borax and fine aggregate. In this study, four mixing ratios of FCP were selected after each material was blended to determine the proper blending ratio of the fluidity phase, the water absorption rate and the water content of the test piece. FCP was fabricated on the basis of the selected four compounding ratios and thickness and error rate were measured. Based on the error rate of the measured FCP, the quality standard was satisfied among the four compounding ratios.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.3
• /
• pp.103-110
• /
• 2019

Damage to the pavement system due to various causes will be required rapid repair work for reopening the vehicle traffic. The magnesium oxide phosphate composite(MPC) has a short curing time and is capable of early compressive strength development, is suitable for rapid repair materials. The aim of this study was to evaluate the hardening and compressive strength characteristics of MPC according to the water-binder (W / B) ratio and magnesium-phosphate(M / P) ratio in order to develop repair materials consisted with light burned magnesia and potassium dihydrogen phosphate. In order to ensure the workability in the field application, the difference of mechanical properties according to standard sand and ordinary sand and performance of retards were evaluated. The mix proportion with W/B ratio was about 35% and the M/P ratio was about 1.0 ~ 1.2 has a superior perfomance with strength and hardening condition. Especially, the strength of composite at only 1 day curing with W/B ratio of 0.35 and the M/P ratio of 1.2 was shown the higher than 25.0 MPa. Boric acid as a retarder was found to be suitable for ensuring the working time, and the purity of magnesium oxide was about 90 ~ 95%, which is effective for ensuring curing time and strength.

• Journal of the Korea Institute of Building Construction
• /
• v.17 no.3
• /
• pp.211-217
• /
• 2017

The objective of this study is to seek a reliable mixture proportion for magnesium potassium phosphate composite(MKPC) mortars with a near-neutral pH value (below 9.5) and a relatively good compressive strength exceeding 30MPa. The main parameter selected was the molar ratios($M_{mp}$) of $MgO-to-KH_2PO_4$ which varied from 30.4 to 3.4. The setting time of the MKPC mortars tended to shorten with a decrease in $M_{mp}$ value. With regard to the strength development ratio normalized by the 28-day strength, the ranges measured in the mortars with an $M_{mp}$ below 7.9 were 50~61% at 1 day and 60~73% at 3 days, indicating a highly rapid early-strength development. With a decrease in $M_{mp}$, the formation of struvite-K crystal identified as a primary hydration product increased, which led to the decrease of the macro-capillary pores in micro-structures. For achieving the targeted requirements for pH value and compressive strength, the $M_{mp}$ needs to be selected as below 5.1.