Applied Mechanics and Materials Vol. 525

Abstract: It is essential to eliminate heat loss through the building envelope to reduce the energy consumption in buildings. However a significant loss of heating energy caused by thermal bridge between slab and external wall in internal insulation systems which were applied in the most apartments in Korea. To improve the performance of envelope, a sandwich insulation system was proposed. This paper evaluates the thermal performance, energy performance and economic efficiency of sandwich insulation system by comparing with internal insulation system. When the sandwich insulation system was applied, heating energy consumption was reduced by 17.8% compared with internal insulation system.

Abstract: Recently, revised certification of Building Energy Efficiency Rating System has been distendedly implemented in public buildings. The Ministry of Land, Infrastructure and Transport in Korea is promoting a Green Remodeling pilot project and proceeding a variety of researches related to the method of Energy Efficiency improvement. The aim of this study was to compare the amount of building energy consumption by improving envelope systems such as curtain wall, window, and wall system of deteriorated public buildings. By improving the envelope system, heating energy consumption has been reduced about 37%.

Abstract: In this paper, the author build a new type of Kang with paraffin as its heating surface. Paraffin is a kind of phase change material ,which can stroage and release heat at a relatively constant temperature. It can make full use of the heat of the smoke in the Kang and extend the Kang heating period. We do comparison test of the the traditional Kang room and the phase change Kang room and related temperature was recorded. The tested result shows that the average temperature of the head, medium and tail of traditional Kang varies greatly,the maximum difference of the temperature is over 20°C. While the average temperatures of the head, middle and tail of the phase change thermal storage Kang are 32.59°C, 28.38°C and 26.12°C, Kang surface temperature distribution is more uniform, which improves the comfort of Kang surface. The indoor temperature with phase change thermal storage Kang shows an upward trend after the fuels burnt out until the wee hours. And the average indoor temperature is 1 °C higher than the comparision room. The phase change thermal storage Kang greatly improves the thermal comfort of its heating surface and indoor temperature.

Abstract: Void is a major disease of cement concrete pavement, and it is also the inducement of other diseases. In order to predict the void, this paper quantificational analyzes the relationship between the times of load function and the lost of materials caused by erosion based on the analysis of the shape and height of void. And then it puts forward that the volume of the lost of materials caused by erosion is equal to the void under slab and gets the prediction models of voids beneath slab corner and along longitudinal joint edge. The results suggest that when the void height is less than side length, the prediction model of void beneath slab corner is same to the along longitudinal joint edge. The development of the void only has relationships with the anti-scour performance of the base course material, the ratio of height and size of void, and the times of standard axle load.

Abstract: This study provides analytical results for heat of hydration in the mat foundation with mass concretes to investigate the effect of lift thickness in the mat foundation on the hydration heat and crack characteristics of mat foundation with mass concrete. Mass concretes were mixed with ternary cement with 1% strontium-based latent heat binder at volume fraction and Type IV low heat cement. The mat foundation has the dimension of 15m length, 20m width and 3m depth. Lift thickness of mass concrete for mat foundation was varied from 1.0m to 3.0m. A commercial software MIDAS/Gen was used to analyze the hydration heat of mass concrete foundation. The maximum adiabatic temperature rise (K), and the coefficient of temperature rise (α) for thermal analysis were drawn from adiabatic temperature rise test. Based on the results of the finite element analysis for mat foundation with different lift thickness, the highest internal temperature and thermal stress increased with increasing with lift thickness of foundation. However, for foundation constructed with premixed strontium based latent heat binder (PSLB) concrete, this phenomenon was less remarkable compared to mass concrete foundation made with low heat cement.

Abstract: The overhauling, rebuilding and enlarging of airport pavement often produce vast waste concrete. Use of these concrete as recycled aggregates, make recycled concrete. And by adopting the “double-mixed” technique with high quality fly ash and high efficiency admixture, optimizing the mix proportions design of pavement recycled concrete, research its mechanical properties and verify its application effect.

Abstract: This paper describes the experimental results on compressive and flexural behavior of alkali-activated slag (AAS) concrete reinforced with hooked end steel fiber. Two different fiber volume fractions of 0.5 and 1.0% were used for AAS concrete and Ordinary Portland cement (OPC) concretes were also mixed for comparison. Test results indicated that compressive and flexural performance of AAS concretes with water-to-binder (W/B) ratio of 0.55 are equivalent to those of OPC concrete. The addition of steel fiber to AAS concrete improves more compressive and flexural performance than those of steel fiber reinforced concrete.

Abstract: This paper provides the results of direct tensile tests for strain-hardening cement composite (SHCC) to investigate the influence of fluosilicate based shrinkage-reducing agent (SRA) on the tensile and cracking behaviors of SHCC material under direct tension. The specified compressive strength of the SHCC material is 50MPa. The adding ratio of fluosilicate based SRA for SHCC material is 2.5 and 5.0%. Two mixitures of SHCC with 2.2% polyvinyl alcohol (PVA) fibers at the volume fraction were mixed; two mixtures with SRA and one mixture of conventional SHCC material. To evaluate the tensile and cracking behaviors of SHCC materials, two dumbbell-shaped tensile specimens for each mixture were manufactured and tested in direct tension. Test results show that the addition of fluosilicate based SRA improved direct tensile and cracking behaviors of SHCC materials with rich mixture. This phenomenon is noticeable for SHCC with higher volume of SRA.

Abstract: This study is conducted to evaluate analytically the effect of casting temperature on the heat of hydration in mass concrete foundation with ternary cements and Type IV low heat cement. The mat foundation has the dimension of 15m length, 20m width and 3m depth. Casting temperatures considered for mat foundation consist of 10, 20 and 30C ̊. A commercial software MIDAS/Gen was used to analyze the hydration heat of mass concrete foundation. The maximum adiabatic temperature rise (K), and the coefficient of temperature rise˰˸α˹˰for thermal analysis were drawn from adiabatic temperature rise test. Analytical results show that blended cement PSLB_352 is the most effective to control the heat of hydration in mass concrete foundation and external temperature increases the maximum heat of hydration and crack probability of mat foundation with mass concrete.

Abstract: Alkali activated slag cement concretes are low carbon footprint building mateirals, which can meet the requirements for sustainable development. The paper covers the results of modeling a thermo-stressed state of the cast-in-situ massive alkali activated slag cement concrete structure hardened under hot environment to meet the requirements for marine engineering application. The results show that alkali activated slag cement concretes have a substantially lower heat release than that of Portland, are suitable for cast-in-situ massive alkali activated slag cement concrete structure even under hot environment.