• Journal of the Korea Concrete Institute
• /
• v.18 no.2 s.92
• /
• pp.205-211
• /
• 2006

The objective of this study was to evaluate the durability of low shrinkage high performance concrete(LSHPC), which was combined with expansive additives and shrinkage reducing admixtures. We tested for not only LSHPC but also high performance concrete(HPC) and normal concrete(NC) to be compared with the durability of LSHPC. HPC was made in the same water-binder ratio of LSHPC without expansive additives and shrinkage reducing admixture. As a result, it was found that LSHPC had higher compressive and tensile strength than that of HPC. LSHPC showed more excellent performance than HPC and NC in the case of resistance to chloride ion penetration and resistance to carbonation and also showed nearly 100 durability factor in the freeze-thawing test with 500 cycles. From the examination about the watertightness and the pore distribution, it was found that the durability of LSHPC was improved because its hardened cement paste is organized closer. So we can conclude that when LSHPC is applied to structures in field, it is possible to reduce the shrinkage and crack in concrete and improve the durability.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.5
• /
• pp.23-29
• /
• 2023

The goal of this study is to evaluate the bursting characteristics and fire resistance performance of mixed cement concrete containing fibers at very high temperatures. For this purpose, FA-based, Slag-based, and each mix according to the amount of fiber mixed were heated to room temperature, 150℃, 300℃, 600℃, and 900℃, and then the burst shape, compressive strength, and elastic modulus were measured and evaluated. As a result of the experiment, it was found that relatively more surface damage occurred in FA-based specimens when heated at ultra-high temperatures than in slag-based specimens, and there was a difference between the mix without fibers and the mix with fibers when heated at ultra-high temperatures, that is, at 900℃. In the mix without fibers, a decrease in strength of more than 5% occurred. In addition, the elastic modulus also showed the same phenomenon as the compressive strength, and in particular, the decrease in elastic modulus was found to be greater than the amount of decrease in compressive strength. Meanwhile, estimation equations for compressive strength and elastic modulus according to heating temperature were statistically proposed.

• Computers and Concrete
• /
• v.10 no.5
• /
• pp.523-539
• /
• 2012

Silica fume has long been used as a mineral admixture to improve the durability and produce high strength and high performance concrete. And in marine and coastal environments, penetration of chloride ions is one of the main mechanisms causing concrete reinforcement corrosion. In this paper, we proposed a numerical procedure to predict the chloride diffusion in a hydrating silica fume blended concrete. This numerical procedure includes two parts: a hydration model and a chloride diffusion model. The hydration model starts with mix proportions of silica fume blended concrete and considers Portland cement hydration and silica fume reaction respectively. By using the hydration model, the evolution of properties of silica fume blended concrete is predicted as a function of curing age and these properties are adopted as input parameters for the chloride penetration model. Furthermore, based on the modeling of physicochemical processes of diffusion of chloride ion into concrete, the chloride distribution in silica fume blended concrete is evaluated. The prediction results agree well with experiment results of chloride ion concentrations in the hydrating concrete incorporating silica fume.

• Computers and Concrete
• /
• v.10 no.2
• /
• pp.197-217
• /
• 2012

This research deals with the prediction of compressive strength of normal and high strength concrete using neural networks. The compressive strength was modeled as a function of eight variables: quantities of cement, fine aggregate, coarse aggregate, micro-silica, water and super-plasticizer, maximum size of coarse aggregate, fineness modulus of fine aggregate. Two networks, one using raw variables and another using grouped dimensionless variables were constructed, trained and tested using available experimental data, covering a large range of concrete compressive strengths. The neural network models were compared with regression models. The neural networks based model gave high prediction accuracy and the results demonstrated that the use of neural networks in assessing compressive strength of concrete is both practical and beneficial. The performance of model using the grouped dimensionless variables is better than the prediction using raw variables.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.03a
• /
• pp.338-350
• /
• 2010

As existing materials for ground reinforcement, chemical grout material using cementitous materials and waterglass was used. But many problems in terms of ground reinforcement effects were implicated. In this study, for development and applicability verification of new materials, viscosity, fluidity, permeability, Self-Leveling, keeping of drilled hole, antiwashout underwater, resistance of water (groundwater dilution and minimize material eluting) and the early strength and long-term strength characteristics of developed materials was confirmed, and material standards, and establishing construction standards for the various model tests were conducted. As a result, high viscosity, flowability, permeability and keeping of drilled hole characteristics are excellent, in addition to the early strength properties, dilution does nat occur to groundwater, including groundwater is available for dealing with environmental issues. Application of basic and reinforcement method by Filler function in addition to structure can also or development of a new concept can be expected. In addition, middle and large-diameter drilled shaft, micropile, ground anchors, soil-nailing, steel pipes multi-grouting reinforcement for cement injection process could be used enough to even be considered.

• International Journal of Concrete Structures and Materials
• /
• v.2 no.2
• /
• pp.145-152
• /
• 2008

So far, there has been no study of the concrete to strengthen in the lining of the tunnels, except for the study of the stability of subgrade and the tunnel construction technologies. In the existing concrete work for tunnel lining, lots of problems happen due to the partial compaction and the material segregation after casting concrete. Accordingly, the aim of this study is to improve economic efficiency and secure durability through the improvement of the construction performance and quality of the concrete for the tunnel lining among the civil structures. Therefore, the compactability and strength properties of the High Flowing Self-Compacting Lining Concrete (HSLC) are evaluated to develop the mixing proportion for design construction technology of HSLC that can overcome the inner cavity due to the reduced flowability and unfilled packing, which has been reported as the problem in the existing lining concrete. The result of the evaluation shows that the ternary mix meets the regulations better than the binary mix. Consequently, it has been judged applicable to the cement for tunnel lining.

• International Journal of Concrete Structures and Materials
• /
• v.8 no.3
• /
• pp.229-238
• /
• 2014

Typical high-performance concrete (HPC) mixtures are characterized by low water-cementitious material ratios, high cement contents, and the incorporation of admixtures. In spite of its superior properties in the hardened state, HPC suffers from many practical difficulties such as its sensitivity to early-age cracking (which is associated with self-desiccation and autogenous shrinkage). In this context, conventional curing procedures are not sufficiently effective to address these limitations. In order to overcome this issue, two strategies,which are based on the use of internal reservoirs of water, have been recently developed.One of these strategies is based on the use of lightweight aggregates (LWA), while the other is based on the use of superabsorbent polymers (SAP). This paper studies and compares the efficiency of the LWA and SAP approaches.Moreover, some of the theoretical aspects that should be taken into account to optimize their application for internal curing of HPC are also discussed. Two fine LWA's and one SAP are studied in terms of autogenous deformation and compressive strength. Increasing the amounts of LWAor SAP can lead to a reduction of the autogenous deformation and compressive strength (especially when adding large amounts). By selecting appropriate materials and controlling their amount, size, and porosity, highly efficient internal water curing can be ensured.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.1105-1108
• /
• 2008

This paper investigated measures of spalling prevention and mechanism to secure stability of subjected to a fire circumstance. The results were summarized as following. 1) There were 4 kinds of methods for spalling prevention, such as declining percentage of water content and cement water ratio, isolating from high temperature with fire proof covering, giving lateral resistance stress, and discharging vapor pressure using fibers. 2) It was confirmed that methods using fibers to a new construction and fire proof covering to a existing construction on the basis of investigation for the spalling mechanism through the existing theory of spalling and a new theory of WPB.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2019.05a
• /
• pp.34-35
• /
• 2019

In recent years, the construction industry has also applied the dry method that can be assembled in the field by industrialization and factory production, which is free from climatic effects and can reduce the cost due to mass production and simplify the work in the field. Among the building materials used in this dry method, ALC products are made by mixing calcium oxide, gypsum, cement, and water in silica and putting them in an autoclave to create voids in the interior through steam curing at high temperature and pressure. But it requires curing cycle conditions of warming, isothermal, and temperature curing. It depends on the performance of the product depending on the curing conditions, the economical efficiency due to high oil prices, the emission of greenhouse gases by the use of fossil fuels. Experiments were conducted to select an appropriate animal protein foam for lightweight foamed concrete block which was cured by applying a prefilling method to replace existing ALC products. As a result of investigating the characteristics of lightweight foamed concrete by type of animal protein foam, it is considered that FP3 is most suitable for manufacturing lightweight foamed concrete block.

• Advances in materials Research
• /
• v.11 no.4
• /
• pp.251-277
• /
• 2022

Disposal of industrial waste in cities where municipal authorities permitting higher floor area ratio coupled with increasing living standards, a lot of demolition waste is being generated. Its disposal is a challenge particularly in megacities where no landfills are available. The ever-increasing cost of building construction materials also necessitates consuming demolition wastes in a useful manner to save fresh natural raw materials. In the present work, the crushed waste glass is used in high-strength concrete as a partial replacement of fine aggregate. The control concrete of grade M60 was proportioned following BIS 10262-2009. The crushed waste glass has been used as a partial replacement with varying percentages of 10, 20, 30, and 40% by weight of fine aggregate. Experimental tests were carried on the fresh and hardened state of the concrete. The effect of crushed waste glass on the workability of the concrete has been investigated. Non-destructive tests, acid attack tests, compressive strength, split tensile strength, and X-ray diffraction analysis was carried out for the control concrete and concrete containing crushed waste glass after 7, 28, and 270 days of normal curing. The results show that for the same w/c ratio, the workability of concrete increases with increasing replaced crushed waste glass content. However, the decrease in compressive strength of the concrete after 28 days of normal curing and further after 28 days of acid attacks, up to 30% replacement level of fine aggregate by the crushed waste glass is insignificant.