Advanced Materials Research Vol. 831

Abstract: The maturity behavior of cement mortar specimens with different concrete additives during the 28 day curing period has been examined using the AC Impedance technique. The main focus of this part of the study is to understand the impedance and capacitance behavior of the steel rebar in cement mortar using different additives during the early stages of hydration process. In this respect, two sets of specimens were prepared: One set consist of two graphite electrodes surrounded by a carbon steel rod for AC Impedance measurements. Another set consisted of two carbon steel setup that has been used for monitoring corrosion of two steel reinforcement bars embedded in cylindrical mortar specimens. The specimens are placed in a salt fog (spray) cabinet for 1,000 hrs.Galvanic current between the two coupled electrodes has been measured using zero resistance ammeter (ZRA) to monitor the extent of corrosion. The in-situ measurement was carried out in a sequential manner over a periodical basis of up to 1,000 hrs of salt fog cabinet exposure. Different mortar mixes were studied including ground granulated blast furnace slag (GGBS) and silica fume (microsilica) as additives and calcium nitrite as corrosion inhibitor and chloride as a contamination species. This data helps in understanding the corrosion activities at the rebar-concrete when interface combined with salt fog test according to (ASTM B117), which can be further correlated with the atmospheric and marine corrosion of steel rebars in concrete. The overall results have indicated the tendency of the admixture to show different hydration processes during the early stages of concrete curing. The interfacial impedance spectrums and galvanic current testing clearly identifies and documents this process for each material.

Abstract: To the flooring system of apartment buildings, resilient materials are used for reducing floor impact sound. Mainly used resilient materials are EPS or EVA. We developed cellulose resilient material and sound absorber recycled waste papers which are eco-friendly materials and evaluated performances of above materials. In addition, we developed dry double floor system which can replace the general flooring system construction in Korea. Floor impact insulation performance of developed flooring system was compared with the existing one and analyzed. Floor impact insulation performance of dry double flooring system was lower than wet type flooring system. Cellulose absorbers showed NRC 0.37, 0.53 of insulation performance, and in case of applying floor resilient material, it showed a somewhat reduced performance comparing to the existing flooring system.

Abstract: In recent years, research trend on structural condition assessments have largely shifted toward utilizing vibration based methods for structural damage detection and evaluation. On the other hand, research and applications on use of fiber reinforce polymer (FRP) on timber for strengthening or repair damaged timber members in various types of timber structures has also become increasingly popular. Although the application of FRP for repair and/or strengthening of structures has been researched for a long time, research on non-destructive assessment or evaluation of the effectiveness and reliability after FRP repairing or strengthening is yet to be carried out. In this paper, the authors made an attempt on investigation of such issue utilizing Damage Index method, which is a robust vibration-based approach for damage detection. The investigation was aiming at localizing and quantifying damage in timber beams and, more importantly evaluating the effectiveness after the damage was repaired. An experimental program was carried out on five laminated veneer lumber (LVL) beams. Various damage scenarios (i.e. severe, medium, light damage) are introduced on these beams and then repaired with carbon fiber reinforced polymer (CFRP). Experimental results indicate that the use of CFRP was effective in repairing the damaged timber beams. Utilizing Damage Index method can accurately detect the damage location. However, the investigation also shows that direct application of the Damage Index for evaluation of the effectiveness of rehabilitation of the damaged timber beam is not satisfactory. Further investigation and modification of the Damage Index method will be carried out in next stage research.

Abstract: Primarily used for domestic buildings as a sound absorber are glass wool, rock wool, etc. These absorbers as well as waste absorber created by recycling wastes, PP+PET fiber absorber made from polypropylene and polyester, wood wool board bonded with finely sliced roots of trees and foamed aluminum absorber are recyclable eco-friendly absorbers that are constantly being developed. In this study, we compared the sound absorption performance of currently used absorbers and eco-friendly building absorbers. As a result, the NRC (Noise Reduction Coefficient) was found to be 0.85 for glass wool, 0.95 for rock wool, and 0.70 for polyester, 0.65 for waste absorber, 0.75 for PET+ PP fiber absorber, 0.40 for wood wool board, and 0.75 for foamed aluminum absorber. Based on the results of these absorption coefficients, we expect the usability of the absorbers continues to increase as future eco-friendly building absorbers.

Abstract: This paper presents a discussion of factors affecting the performance of fly ash based geopolymer, and some recent innovations on fly ash based geopolymer. The characteristics of fly ash based geopolymer are discussed in terms of the effects of raw material selection, alkaline activators, and curing procedures. Nowadays, researchers have used geopolymer as a cementitious material to develop innovative geopolymer materials, such as porous, fibre reinforced and foam fly ash based geopolymer concrete, which are greener than the traditional cementitious material. The high-calcium fly ashes could be used to produce porous fly ash based geopolymer composites with satisfactory mechanical properties. The addition of fibres increases greatly the ductility of geopolymer. Foam can be added to the geopolymeric mixture to produce lightweight concrete. However, the manufacturing of fly ash-based geopolymer foam concrete has not been explored too much.

Abstract: Polypropylene Fibre (PF) as reinforcement has contributed to the intensity of Foamed Concrete (FC) slab when subjected to impact loading. The presence of PF in the admixture reduces the micro-porosity that generates the micro-crack of the slab. However, the fibrillation of PF in the admixture enhances the bonding mechanism system between PF and the FC matrix. The impact test conducted uses an instrumented drop-weight impact tower. Results show that FC without PF produces a distinct radial crack and clear fragments within the crater field unlike FC with PF. However, both slab materials did not generate spalling nor scabbing upon impact and the influence of porosity produces only local damage due to the mechanism of brittle crushing effect of porous walls. In this study, the energy absorption between FC with and without PF was investigated and from observation produces only minor differences. Results also verify that FC with PF did not loss its ability to absorb energy upon impact.

Abstract: An experimental investigation on the feasibility of a sustainable method for the containment of contaminated sand and its reuse for the base and surface layer of a pavement is presented in this paper. The level of contamination of contaminated sand is determined and a fly ash based compound is added for the containment. The mix proportion for the base and surface layer of the pavement is selected based on the level of contamination. A mixture of fly ash based compound and the oil contaminated sand is tested for various properties such as strength, shrinkage, chloride resistance and leachability in this preliminary investigation, and is qualified for making road foundation layers.

Abstract: Ha Tai high speed rail is a high-speed railway in cold region of China. The design criteria is very strict. There is many frozen soil over cold region. The research how to reduce the amount of subgrade frost heaving over Ha Tai high speed rail is of great significance.We use a frost heave model to simulate the subgrade frost heaving in the paper.We research how the fine power content and water content influence the frost heave amount of graded crushed stone by contrast test.The result shows that the fine power content and the water content have great influence on the frost heave amount of graded crushed stone .The frost heave ratio increases with the fine powder content and the water content.

Abstract: The point of this study was to assess the progressive collapse resisting capacity of special steel moment frame structures and the behaviour of buildings which have different height when they are losing one of their exterior columns. Two buildings were considered for this research, 7-storiy and 12-storiy buildings. Corner column as well as one of the middle columns was removed to evaluate the importance and the effect of the location of removed column in structural response. General Services Administration (GSA) and Department of Defence (DoD) guidelines are considered for choosing the method of analysis. Nonlinear dynamic analysis procedures were carried out to investigate the behavior of structures. Thus, maximum vertical displacement in the point of column removal for each structure was measured. In addition, both buildings have cover plate connections which are cosidered to be rigid in modelling.

Abstract: Vertical seismic excitation has a tremendous effect on bridges and many researchers have pointed out bridges damages occurred during the past significant earthquakes which were direct results of ignoring vertical acceleration of ground motions. Many studies have emphasized the importance of extending practical methods to reduce effects of vertical acceleration of earthquakes besides effects of horizontal accelerations; but no practical method has proposed up to now. In this article, an innovative shape memory alloy system is proposed for bridges that can simultaneously controls effects of vertical and horizontal seismic excitations on bridge and reduce them. To evaluate the effectiveness of the shape memory alloy system, a nonlinear time history analysis is conducted on a detailed three-dimensional model of a multi-span simply supported bridge using a representative ground motion. The results show that the proposed new system is very effective for reducing effects of vertical and horizontal seismic excitations on bridges.