The compressive stress of concrete is used as a design variable for reinforced concrete structures in design standards. However, as the performance-based design is being used with increasing varieties and strengths of concrete and reinforcement bars, mechanical properties other than the compressive stress of concrete are sometimes used as major design variables. In particular, the evaluation of the mechanical properties of concrete is crucial when using fiber-reinforced concrete. Studies of high volume fractions in established compressive behavior prediction equations are insufficient compared to studies of conventional fiber-reinforced concrete. Furthermore, existing prediction equations for the mechanical properties of high-performance fiber-reinforced cementitious composite and high-strength concrete have limitations in terms of the strength and characteristics of contained fibers (diameter, length, volume fraction) even though the stress-strain relationship is determined by these factors. Therefore, this study developed a high-performance slurry-infiltrated fiber-reinforced cementitious composite that could prevent the fiber ball phenomenon, a disadvantage of conventional fiber-reinforced concrete, and maximize the fiber volume fraction. Then, the behavior characteristics under compressive stress were analyzed for fiber volume fractions of 4%, 5%, and 6%.
Many researchers have studied explosion prevention and fire resistance of high-strength concrete mixed with organic fiber and steel fibers. The fire resistance of high-performance fiber reinforced cement composites is desirable in terms of physical and mechanical properties. However, the use of a polymer as an alternative to organic fiber has not been clearly studied. In this study, a slurry infiltration method was used to obtain slurry-infiltrated fiber-reinforced cementitious composites (SIFRCCs) specimens. Powder polymer was used instead of organic fibers during mixing of the slurry. The compressive and flexural strengths of the specimens after 1 hr of high temperature exposure according to the KS F 2257 (ISO 834) standard fire-temperature curve were measured. The addition of the polymer before and after high temperature (about 945 °C) exposure affected the strength of the SIFRCCs. The compressive and flexural strengths were decreased after exposure to high temperature in comparison with SIFRCCs without polymer because polymer create capillary pores due to melting and burning when exposure to high temperature. This minimizes the vapor pressure inside the concrete model and reduces the failure of the concrete model. The experimental results showed that the flexural strength at a high temperature for 1.0 % polymer content was the highest at 53.8 MPa. The flexural strength was reduced by 40~50% when compared to the flexural strength before high temperature exposure and comparing to SIFRCCs without polymer, the compressive strength in 1.5% polymer is lower, owing to voids that are created in the SIFRCCs after exposure to a high temperature.
Fire in a tunnel or an underground structure is characterized by a rise in temperature above 1000 °C in 5–10 min, which is due to the characteristics of the closed space. The Permanent International Association of Road Congresses has reported that serious damage can occur in an underground structure as a consequence of high temperatures of up to 1400 °C when a fire accident involving a tank lorry occurs in an underground space. In these circumstances, it is difficult to approach the scene and extinguish the fire, and the result is often casualties and damage to facilities. When a concrete structure is exposed to a high temperature, spalling or dehydration occurs. As a result, the cross section of the structure is lost, and the structural stability declines to a great extent. Furthermore, the mechanical and thermal properties of concrete are degraded by the temperature hysteresis that occurs at high temperatures. Consequently, interest in the fire safety of underground structures, including tunnels, has steadily increased. This study conducted a fire simulation to analyze the effects of a fire caused by dangerous-goods vehicles on the tunnel structure. In addition, a fire exposure test of reinforced-concrete members was conducted using the Richtlinien für die Ausstattung und den Betrieb von Straßentunneln (RABT) fire curve, which is used to simulate a tunnel fire.
The recent abnormal temperature phenomena such as the rise of global mean temperature and sea level due to global climate change are clear threats that can no longer be overlooked to the human beings who have pursued indiscriminate development and rapid growth. Climate change has emerged as a serious risk that threatens the survival of the entire human race from the environmental and ecological aspects, despite international efforts for several decades. The CO 2 concentration in the atmosphere has increased by approximately 39% since the industrial revolution. Even if carbon emissions are stopped right now, it is expected to take at least 50-200 years to return to the CO 2 level before the industrial revolution. Therefore, we conducted an experimental study to develop a carbon-capturing concrete that has active as well as passive carbon reduction functions using blast-furnace slag, an industrial byproduct, instead of cement. For active carbon reduction, we used calcium hydroxide and sodium silicate as carbon capture activators, and conducted tests on mechanical properties and durability characteristics. road sector, which accounts for 16% of the total GHG emissions, the need for the development of design and development technologies to absorb and reduce CO 2 to minimize CO 2 emissions is emerging [4]. Recently, the secondary environmental pollution problem is appearing due to the increase of industrial byproducts such as mining byproducts and coal incineration ashes [4]. For efficient processing of industrial byproducts, some of the industrial byproducts are mixed with existing cement or asphalt materials and these mixtures are used as construction materials [4]. Comprehensive Assessment System for Building Environmental Efficiency (CASBEE) in Japan has evaluated the GHG emissions of building materials using the CO 2 emission database of major materials since 2010 [5][6][7]. Building performance is now a major concern of professionals in the building industry and environmental building performance assessment has emerged as one of the major issues in sustainable construction [8][9][10][11]. Efforts to reduce CO 2 emission are being made through the use of procurement systems for low CO 2 emission materials and the application of high-strength concrete at construction sites. As a part of such research, there is a demand for the establishment of a quantitative assessment method of CO 2 emission from concrete production to site procurement and a proposal of a CO 2 reduction plan at construction sites [12]. However, the utilization of materials for CO 2 capture is still insufficient. The development of concrete applying CO 2 reduction technology is considered to be a leading technology for the society as a whole, as well as for the construction sector. The MIT Technology Review selected "Green Concrete", which is a CO 2 reducing concrete, one of top 10 new technologies in 2010 [4,13].Therefore, in this study, we aim to develop carbon-capturing concrete using industrial byproducts that can satisfy not only passive carb...
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