• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.1
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• pp.159-169
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• 2002

This study is intended to discuss the application of expansive additives for concrete to improve the durability of precast concrete box culvert by inducing the chemical prestress. The precast concrete box culvert using expansive cement are tested to verify the effect of expansive additives. The results show that the initial cracking load and yielding load of the expansive cement numbers are increased when they are compared with those of the normal concrete. In the prototype precast concrete box culvert experiment, initial crack control effect and strength of joint are increased, but the deflection is decreased by expansive cement. Brides, reinforcement ratio is decreased about 14.6 percent in compering with the case of using normal cement. If can be the concluded that the use of expansive additives to induce the chemical prestress was improve the durability in concrete box culvert.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.77-80
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• 2009

The purpose of the study was to examine engineering characteristics due to fine particle cement and gypsum contents to improve early strength of concrete substituted blast furnace slag powder. The results were as follows. Above all, For fluidity, generally all mixtures had lower fluidity than Plain mixture and was not satisfied target scope, but for mixture substituted the gypsum showed a little increasing trend. For air content, generally all mixtures compared to Plain mixture had decreasing tendency. However, all mixtures were satisfied target scope. For compressive strength, long-term strength was better than early strength according to ternary blast furnace slag contents was increased. For complex mixture was better than individual use of gypsum and fine particle cement.

• International Journal of Highway Engineering
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• v.15 no.5
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• pp.101-110
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• 2013

PURPOSES : The purpose of this study is to evaluate the durability of ternary blended concrete mixtures adding ultra fine admixture. METHODS : From the literature review, crack was considered as the main distress failure criterion on concrete bridge deck pavement. To reduce the initial crack development due to drying shrinkage, CSA expansion agent and shrink reduction agent were used to ternary blended concrete mixtures as a admixture. Laboratory tests including chloride ion penetration test, surface scaling test, rapid freeze & thaw resistance test, non restrained drying shrinkage and restrained drying shrinkage test were conducted to verify the durability of ternary blended concrete mixtures. RESULTS : Based on the test results, proposed mixtures were verified as high qualified durable materials. Expecially initial drying shrinkage crack was not occurred in ternary blended concrete mixtures with CSA expansion agent. CONCLUSIONS : It is concluded that the durability of proposed ternary blend concrete mixture was acceptable to apply for the concrete bridge deck pavement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.68-69
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• 2019

Integrating 3D printing into architecture is gaining attention because it allows construction of construction structures without formwork. Among them, 3D printing construction materials must have high flow performance and at the same time ensure the performance that does not collapse during lamination. Therefore, in this study, we tried to determine the fluidity and lamination properties of mortar formulations, and set the thickener incorporation ratio as the formulation parameters. As a result of this experiment, it was confirmed that the lamination performance was secured from the thickening agent mixing rate of 1.5%.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.158-159
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• 2022

This study analyzed the temperature stress through mixtures mass concrete hydration heat analysis according to the replacement rates of FAC and CGS. As a result of the analysis, it was possible to confirm the effect of reducing hydration heat when CGS is substituted for the low heat mixture of mass concrete. However, the stress of the FAC+CGS combination exceeded the tensile stress. It is believed that it is necessary to apply the insulating sheet of the surface part and reduce the unit weight of cement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.118-119
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• 2021

In this study, we confirmed the basic characteristics of paste and mortar 1:1, 1:2, 1:3 composition using concrete sludge solid content for the purpose of developing a resource-recycling cement secondary products. The 1:2 mortar formulation showed the best compressive strength. The steam curing strength is superior in the order of C20, BS40, BS20 and Control. it is judged that the FA combination is not suitable.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.30-31
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• 2021

This study aims to build a deep learning model that can predict the value of concrete mixing properties according to a given concrete strength value. A model was created for a total of 1,291 concrete data, including 8 characteristics related to concrete mixing elements and environment, and the compressive strength of concrete. As the deep learning model, DNN-3L-256N, which showed the best performance on the prior study, was used. The average value for each characteristic of the data set was used as the initial input value. In results, in the case of 'curing temperature', which had a narrow range of values in the existing data set, showed the lowest error rate with less than 1% error based on MAE. The highest error rate with an error of 12 to 14% for fly and bfs.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.34-35
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• 2021

In this study, we compared and analyzed hydration heat of the Concrete(NC) and non-fired Hwangto Concrete(HT). The Concrete(NC) was based on the mix that showed 30, 45 MPa on compressive strength on 28th and Only cement was used to make it. and We substituted 30% of weight of unit cement to non-fired Hwangto to create non-fired Hwangto Concrete(HT).

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.331-338
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• 2006

This paper presents the experimental results on volumetric changes in ordinary portland cement concrete made with various water-to-cement ratios(W/C's) ranging from 0.32 to 0.50 and cured in low different conditions. Curing regimes employed in this work were designed to exhibit autogenous and drying shrinkage as well as swelling of concrete. The concrete avoided any moist evaporation(Regime f showed only autogenous shrinkage and the lower the W/C, the feater the autogenous shrinkage. The concrete exposed to air drying conditions at $20{\pm}1^{\circ}C$ and $60{\pm}3%$ RH after 6-day water curing at $20{\pm}1^{\circ}C$(Regime II) swelled and then started to shrink. The maximum swelling value of concrete developed in water curing was between 15 and $40{\pm}10^{-6}$, and the greatest total shrinkage(autogenous+drying shrinkage) was obtained for the mixture made with W/C of 0.32. The concrete let to air drying conditions(Regime III) showed greater total shrinkage compared to the concrete cured in Regime II. The concrete exposed to air drying condition after 6-day sealed curing(Regime IV) exhibited slightly smaller total shrinkage than that of the concrete cured in Regime III. Net drying shrinkage that can be derived from the results of Regime I, III, and IV increased as the W/C increased despite of similar total shrinkage. This result indicated that drying shrinkage governs total shrinkage of high-W/C concretes. In other words, a portion of autogenous shrinkage in total shrinkage increased in low-W/C concretes. Therefore, it should be controlled in terms of cracking potential. Finally, total shrinkage of high-strength and high-performance concrete made with low W/C can be effectively reduced by appropriate early moisture curing.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.4
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• pp.329-336
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• 2008

Efficient traffic network is required in urban area for good living condition. However, dense traffic network creates traffic jam and gives bad influences to the ground environment. Therefore, advanced use of underground and tunnel is required. But, in the last 20 years many tunnel fire accidents have occurred all over the world. Increase of tunnels and increase of traffics result in increase of tunnel fire. Tunnel fire creates damage to people and to the tunnel structure. Also, tunnel fire creates a big economical loss. In a mountain tunnel, the stability of the tunnel will not be disturbed by fire although the tunnel lining will get a severe damage. However, in a shield tunnel or immersed tube tunnel, cut and cover tunnel, there is a high possibility that tunnel itself will collapse by fire because their tunnel concrete lining is designed as a structural member. The aim of this experimental research is to verify the fire protection performance of newly developed cementitious material compared with the broadly used existing products in Europe and Japan. For the experiments, the general NATM tunnel concrete linings with the newly developed material were tested using fire loading curve of RABT (Maximum peak temperature is $1,200^{\circ}C$) and RWS (Maximum peak temperature is $1,350^{\circ}C$). From the test results, the newly developed fire protection material applied with 30 mm thickness showed good fire-proofing performance under RABT fire loading.