Byung Wan Jo

Investigations on the development of powder concrete with nano-SiO2 particles

The nano scale of particles can result in dramatically improved or different properties from conventional grain-size materials of the same chemical composition. Therefore, it is practical to add nano-silica in particle form with 99.9% of SiO2 in nano scale to improve the characteristics of cement mortar. The compressive strengths of cement mortar were evaluated at various water-cementitious ratio. Five different water-cementitious ratios were used including, 0.23, 0.25, 0.32, 0.35, and 0.48 and four contents of nano-SiO2 particles, 3%, 6%, 9%, and 12% by weight of cement. The compressive strength of cement mortar with the addition of silica fume were also evaluated at w/cm ratio of 0.48 to compare with mortar containing nano-SiO2 particles and three contents of silica fume were: 5%, 10% and 15% by weight of cement. The experimental results show that the compressive strengths of mortars with nano-SiO2 particles were all higher than those of mortars containing silica fume at 7 and 28 days. It was demonstrated that the nano-particles were more valuable in enhancing strength than silica fume. This paper also analyzed some available examinations to monitor the hydration progress continuously, such as SEM observation, residual quantity test for Ca(OH)2 and the rate of heat evolution. The results of the examinations indicate that the SiO2 in nano scale behave not only as a filler to improve the microstructure, but also as an activator to promote pozzolanic reactions.

Synthesis of a cementitious material nanocement using bottom-up nanotechnology concept: an alternative approach to avoid CO 2 emission during production of cement

The worlds increasing need is to develop smart and sustainable construction material, which will generate minimal climate changing gas during their production. The bottom-up nanotechnology has established itself as a promising alternative technique for the production of the cementitious material. The present investigation deals with the chemical synthesis of cementitious material using nanosilica, sodium aluminate, sodium hydroxide, and calcium nitrate as reacting phases. The characteristic properties of the chemically synthesized nanocement were verified by the chemical composition analysis, setting time measurement, particle size distribution, fineness analysis, and SEM and XRD analyses. Finally, the performance of the nanocement was ensured by the fabrication and characterization of the nanocement based mortar. Comparing the results with the commercially available cement product, it is demonstrated that the chemically synthesized nanocement not only shows better physical and mechanical performance, but also brings several encouraging impacts to the society, including the reduction of CO2 emission and the development of sustainable construction material. A plausible reaction scheme has been proposed to explain the synthesis and the overall performances of the nanocement.

An Experimental Study on the Characteristics of Chemically Synthesized Nano-Cement for Carbon Dioxide Reduction

Cement is becoming a principal factor in air pollution because of the creation of CO2 during its manufacturing. The exhaustion of the natural resources needed for Portland cement production is also an issue. Therefore, a substitute material for this type of cement is needed. Nano-scale materials are of great interest due to their unique optical, electrical, and magnetic properties. These properties are strongly dependent on the sizes and shapes of the particles, and, therefore, it is important to be able to develop the construction part which retains the excellent properties of the nano-sized material. The purpose of this study was to synthesize nano-powder as a substitute for cement using a chemical method. This study investigated the compressive strengths of concretes with various compositions. Specimens were tested for compressive strength three, seven, 14, and 28 days after manufacture. In the results of this study, the medium-sized (50% by weight) nano-cement particles created via chemical synthesis were less than 168 nm in size, and the compressive strength of the mortar prepared using these nanoparticles was 53.9 MPa

Wind characteristics of existing long span bridge based on measured data

This paper presents the wind characteristics of an existing long span bridge based on the measured wind data. The wind data obtained from the two measuring stations on the Seohae bridge are processed and statistically analyzed. The Weibull distribution is used to model the wind speed on the bridge. The parameters of the Weibull distribution,k andc are estimated using two methods, the that the two methods give a good fit to the distribution of the measured wind speed data on the bridge. The dominant wind directions on the FCM bridge are northwest and east. The wind rose diagram shows that strong winds usually come from the northwest. From the Weibull distribution for each direction, it can be known that the parameters ofk andc are quite different according to the wind direction.

A Fiber Bragg Grating-Based Condition Monitoring and Early Damage Detection System for the Structural Safety of Underground Coal Mines Using the Internet of Things

Accurate sensing is the key to structural health monitoring of underground coal mines while using fiber Bragg grating (FBG) sensors. However, the previously developed systems for structural monitoring of underground mines have been limited to monitoring without any capability of damage detection. Therefore, this study integrates a highly accurate FBG monitoring system and output-only data-driven approaches on an Internet of things (IoT)-based platform to develop a comprehensive mine structural safety system. This system relies on a Web 2.0 main server that runs data acquisition, data processing, and damage detection algorithms along with real-time information sharing at remote locations. This system was successfully implemented at the Hassan Kishore coal mine, situated in the Salt Range of Pakistan. Wavelength division multiplexing of the FBG strain sensors reliably captured the effects of dynamic and continuous coal excavation on the stability of mine roadway and access galleries. Principal component analysis, along with hierarchical clustering, was used to determine the damage indicator of the mine. The damage index was validated, showing the minimum value for 2% stiffness reduction. Thus, integration of FBG technology with the Internet can be effectively applied for early safety assessment of underground coal mines and information sharing in real time.

Aqueous-based carbon dioxide sequestration

Abstract The worlds prime need demands the reduction of the increasing amount of anthropogenic greenhouse gases in the atmosphere, especially carbon dioxide (CO2), being the leading component of the global warming. Amongst the various technologies adopted for CO2 sequestration, the aqueous-based mineral sequestration route is a promising approach in which CO2 can be chemically stored in the thermodynamically stable solid carbonate residue permanently and safely. Although the mineral CO2 sequestration method possesses the adequate fundamental advantages, such as the high sequestration capacity because of the large availability of the feedstock (rock) worldwide, the sequestration occurred spontaneously in nature because of the exothermic process and CO2 stored permanently and safely because of the formation of the thermodynamically stable product. However, the mineral carbonation reaction rate at the atmospheric condition is very slow that, in turn, limits the technology to be implemented industrially. Therefore, the attention of researchers focuses on influencing the rate of the mineral CO2 sequestration process. Mineral carbon sequestration is a lengthy option as compared with that of other sequestration routes, but its fundamental advantages justify the necessity for further research. In this chapter, prime issues, such as chemistry, processing conditions, engineering aspects, environmental impact, and life cycle of the aqueous-based mineral CO2 sequestration method, have been discussed appreciably to enable the process to be implemented practically.

Strength and Durability Assessment of Portland Cement Mortars Formulated from Hydrogen-Rich Water

We investigated the effects of hydrogen-rich water (HRW) on the strength and durability of Portland cement mortars. We comparatively assessed the performances of HRW-based mortars (HWMs) with respect to cement mortars fabricated from control water (CWM). The results indicate that the use of HRW significantly improves the compressive, flexural, and splitting tensile strength of mortars at both the early and later ages of curing. Durability was assessed in terms of capillary absorption, ultrasonic pulse velocity (UPV), dynamic elastic modulus (DEM), and electrical resistivity (ER). We attribute the generally improved mechanical and durability properties of HWMs to the formation of more cement hydrates with fewer voids in the hydrogen-rich environment. Based on X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM) analyses, we deduce that the use of HRW in Portland cement mortars produces a more compact, dense, and durable microstructure with fewer voids due to a higher degree of hydration.

Prediction of the curing time to achieve maturity of the nano-cement based concrete using the Weibull distribution model: A complementary data set

This data article provides a comparison data for nano-cement based concrete (NCC) and ordinary Portland cement based concrete (OPCC). Concrete samples (OPCC) were fabricated using ten different mix design and their characterization data is provided here. Optimization of curing time using the Weibull distribution model was done by analyzing the rate of change of compressive strength of the OPCC. Initially, the compressive strength of the OPCC samples was measured after completion of four desired curing times. Thereafter, the required curing time to achieve a particular rate of change of the compressive strength has been predicted utilizing the equation derived from the variation of the rate of change of compressive strength with the curing time, prior to the optimization of the curing time (at the 99.99% confidence level) using the Weibull distribution model. This data article complements the research article entitled “Prediction of the curing time to achieve maturity of the nano-cement based concrete using the Weibull distribution model” [1].

An Experimental Study of the Characteristics of Environment-Friendly Construction Materials by Recycling Sewage Sludge Ash

As a basic stage for developing new construction material utilizing sewage sludge ash, this study is identified by specific material characteristics through XRD, SEM, uniaxial compressive strength, porosity, and the drying shrinkage by manufacturing mortar with sewage sludge ash. The average drying shrinkage of sewage sludge ash mortar aged 7 days showed 88% of the strain of the one aged 28 days. The porosity of sewage sludge ash mortar was about 7~10%. The more quick lime and blast furnace slag were added, the less porosity appeared.

Finite Element Analysis for Setting Shrinkage Stress of Recycled-PET Polymer Concrete

Results from experimental and analytical investigation on the setting stress of recycled-PET polymer concrete are presented. Setting shrinkage test on polymer concrete was, carried out and the fractal dimension of the crack patterns detected on microsco pe images was measured. Numerical simulations of the tests were performed by means of a lattice model and non integer dimensions were measured on the predicted lattice damage patterns. The setting shrinkage cracks that are obtained with lattice are is good agreement with the experimental results.