Pore blocking characteristics of corrosion products formed on Aluminum coating produced by arc thermal metal spray process in 3.5wt.% NaCl solution

Lee, H.S.,Singh, J.K.,Park, J.H. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.113 No.-

Arc thermal metal spray coating is very efficient process to protect the steel from corrosion in industrial, humid and saline/coastal environments. This paper incorporates the experimental results for the performance of Aluminum coating deposited on mild steel substrate by arc thermal metal spray. Different electrochemical techniques, FE-SEM, Raman spectroscopy and XRD were used to assess the performance of deposited coating. Electrochemical studies revealed the enhanced corrosion resistance properties of coating in 3.5wt.% NaCl solution. The formation of α-Al(OH)<SUB>3</SUB> on coating substrate during exposure periods block the pores of coating and impede the penetration of corrosive species to react with substrate.

Production of price-competitive bricks using a high volume of stone powder sludge waste and blast furnace slag through cementless CaO activation

Park, H.,Jeong, Y.,Jun, Y.,Oh, J.E. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction & building materials Vol.122 No.-

Stone powder sludge is a waste by-product that is annually produced more than 7.5million tons from the manufacturing process of crushed aggregates in Korea. This study investigated the use of stone powder sludge as a substitute for fine aggregate in brick manufacturing through the CaO activation of the ground-granulated blast-furnace slag (GGBFS) system, which was found to be more suitable than portland cement for the proposed bricks that contained a large quantity of stone powder sludge. This study also discussed the characteristics of leaching, hydration products, and microstructures of hardened samples of proposed mixtures. The trial bricks had high strength, low water absorption, and low material cost. Two of the proposed trial bricks satisfied the requirements of concrete building blocks, ASTM C55, for strength and water absorption at seven days of curing, while the cement brick, with the same quantity of stone powder sludge, failed to fulfill the requirement for water absorption.

Evaluation of physical characteristics and microscopic structure of mortar containing synthetic resin

Lee, B.,Lee, J.S.,Min, J.,Lee, J.H. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction & building materials Vol.114 No.-

This study investigated the applicability of synthetic resin as neutron shielding aggregate provided by its high hydrogen content. The adopted synthetic resin was mixed using quantities of high density polyethylene (HDPE), polypropylene (PP) and ultra-high molecular weight polyethylene (UPE) replacing the fine aggregates by volume ratios of 20%, 40% and 60% converted into weight. Slump flow and tensile and compressive strength tests were conducted to evaluate the physical properties of the mortar, and image analysis, SEM and X-ray CT were performed on the fracture surface to examine the micro-structure inside the specimens. The flow of the mortar containing synthetic resin increased when using HDPE and PP but decreased in the case of UPE. Besides, the tensile and compressive strengths tended to reduce at the whole regardless of the type of resin. The image analysis showed that the strength of mortar containing HDPE and PP was influenced by the fraction of synthetic resin at the fracture surface regardless of the quantities. It seemed that the non-uniform distribution of the materials and faults with the cement matrix inside mortar provoked the loss of strength. On the other hand, larger content in powdered UPE increased the internal porosity. The loss of strength remained insignificant under a definite level but became steep beyond this level and, especially for replacement ratio higher than 60% in the present study.

Tensile behavior of naturally and artificially corroded steel bars

Ou, Y.C.,Susanto, Y.T.T.,Roh, H. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction & building materials Vol.103 No.-

The tensile behaviors of corroded steel bars are important in the capacity evaluation of corroded reinforced concrete structures. However, information on the tensile behaviors of naturally corroded steel bars is scarce. Moreover, differences in tensile behaviors between steel bars from natural and artificial corrosion are not well-understood. In this study, tensile testing was conducted on corroded steel bars from a residential building exposed to natural chloride attack, and from A706 corroded steel bars obtained from artificial corrosion using the impressed-current method. Based on the test results, reduction factors were proposed to relate the tensile behaviors with the corrosion mass loss for both the naturally and artificially corroded bars. Moreover, reduction factors from previous studies for both naturally and artificially corroded steel bars were collected. Comparison of reduction factors from this study and previous studies has shown that reductions factors for bars naturally corroded by chloride attack are generally larger than those by carbonation corrosion. Moreover, it is more appropriate to use the impressed-current method on bars embedded in concrete than on bare bars to simulate natural corrosion caused by chloride attack. On the other hand, reduction factors from the impressed-current method on bare bars are generally closer to those from natural carbonation corrosion than bars embedded in concrete.

Hydration properties of ladle furnace slag powder rapidly cooled by air

Choi, S.,Kim, J.M.,Han, D.,Kim, J.H. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction & building materials Vol.113 No.-

Present research provides a series of research to provide the hydration properties of pulverized rapidly air cooled ladle furnace slag. In aspect of sustainability, recycling slags from steel producing industry is valuable, while only blast furnace slag has been used as a construction material. Since the main obstacle of the slags to be used as a construction materials is expansion of the matrix due to the free-CaO or free-MgO. In this research, using high pressured air, the molten ladle furnace slag was cooled down rapidly, and the crystallization of these harmful components were prevented. Furthermore, because of amorphous phases and chemical composition of C<SUB>12</SUB>A<SUB>7</SUB>, and β-C<SUB>2</SUB>S, the pulverized rapidly air cooled ladle furnace slag showed rapid setting properties. Therefore, in this research scope, the rapid setting properties of rapidly air cooled ladle furnace slag was found.

Antifungal performance of BFS mortar with various natural antifungal substances and their physical properties

So, H.s.,Jang, H.s.,Lee, B.r.,So, S.y. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.108 No.-

This study discusses the basic physical properties, as well as the durability and antifungal performance of blast furnace slag (BFS) mortar with various natural antifungal substances. As a series of basic experiments, the antifungal performances of various natural antifungal substances extracted from Marjoram, Phytoncide, Thyme, Ginkgo leaves, and Chitosan were investigated on five types of mold: Chaetomium globosum, Aspergillus niger, Aureobasidium pullulans, Gliocladium virens, and Penicillium pinophilum. Marjoram and phytoncide extracts, which showed excellent antifungal performance in the basic experiment, were selected and applied to the antifungal mortars. The physical properties in addition to the durability and antifungal performance of the antifungal mortars were investigated. The results clearly showed that the antifungal mortars with the marjoram extract had excellent antifungal performance compared with other antifungal mortars with natural antifungal substances. Their antifungal performance was at an equivalent level to that of the mortars with organic chemical antifungal agents. It was also shown that the optimum addition rate of marjoram extract in the mortar was 3% by mass of binder, considering antifungal performance and durability. The adverse effect of marjoram and phytoncide extract on the consistency and strength of antifungal mortars was insignificant.

Theoretical and experimental study on mechanical properties and flexural strength of fly ash-geopolymer concrete

Nguyen, K.T.,Ahn, N.,Le, T.A.,Lee, K. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.106 No.-

In this paper, evaluation of the mechanical properties of heat-cured low-calcium fly-ash geopolymer concrete and the behavior of geopolymer concrete beams are reported in detail. The mechanical properties are evaluated using the modulus elasticity, Poisson's ratio, stress-strain relation, and indirect tensile strength. Behavior of the geopolymer beam is determined using a flexural test with four-point bending, elastic theory, and a finite element model (FEM). The measured modulus elasticity values of geopolymer concrete are lower than those calculated using current standards for normal concrete. The Poisson's ratio is from 0.16 to 0.21, which is similar to the values of conventional concrete. The stress-strain relation in compression matches well with the formulation designed for Portland cement concrete. The indirect tensile strength is a fraction of the compressive strength but it is higher than the calculated value using an expression designed for normal concrete. The deflections at mid-span, and the crack patterns of the geopolymer concrete beam determined from FEM, are better matched with the experimental results than with the elastic theory results.

Effects of cold joint and loading conditions on chloride diffusion in concrete containing GGBFS

Yoo, S.W.,Kwon, S.J. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction & building materials Vol.115 No.-

RC (Reinforced Concrete) structures undergo deterioration and the initiated corrosion in the steel is considered as one of the most critical problems. For efficient construction of structures, construction joint should be installed, however cold joint occurs reluctantly due to delayed concrete placing and poor condition of the old concrete surface. The chloride ingress in cold joint concrete is more rapid than that in sound concrete, and it is also affected by loading conditions. This paper presents a quantitative evaluation on chloride diffusion coefficient considering the effects of cold joint and loading conditions. For the work, concrete samples with 0.6 of w/b (water to binder) ratio are prepared. Compressive and tensile stresses are induced with 30% and 60% of ultimate strength, respectively. The chloride diffusion coefficients in accelerated condition are measured under loading, and the effects of cold joint and loading levels are evaluated. In order to investigate an effect of GGBFS (Ground Granulated Blast Furnace Slag) on chloride diffusion, 40% of GGBFS replacement ratio is considered for OPC (Ordinary Portland Cement) and the GGBFS effect is evaluated considering cold joint and loading levels. The effects of stress level, pore structure improvement through GGBFS, and cold joint on chloride diffusion coefficient are quantitatively investigated.

Internal-curing efficiency of cold-bonded coal bottom ash aggregate for high-strength mortar

Kim, H.K.,Ha, K.A.,Lee, H.K. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction & building materials Vol.126 No.-

Herein is reported the results of a study on the internal-curing efficiency of cold-bonded bottom ash aggregates (CBBA) used in high-strength mortar. The flow and compressive strength of high-strength mortar with CBBA were measured. To evaluate the internal curing efficiency of CBBA, the autogenous deformation and internal relative humidity of mortar with pre-wetted CBBA were observed at an early age. In addition, the degree of hydration was measured, and then differential thermal and thermogravimetric analyses (DTA/TGA) were carried out to understand the hydration kinetics of the mortar. The experimental results of mortar with CBBA were compared with those of mortar with raw bottom ash, and with artificial lightweight aggregates. Compared with raw bottom ash, CBBA showed greater mitigation of autogenous shrinkage, meaning that a lower volume proportion of CBBA was sufficient to eliminate autogenous shrinkage in the high-strength mortar.

Effects of anisotropic voids on thermal properties of insulating media investigated using 3D printed samples

Chung, S.Y.,Stephan, D.,Elrahman, M.A.,Han, T.S. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.111 No.-

An insulating medium is a material designed for reducing heat conduction through entrained voids in the material. A specimen of insulating media contains numerous voids, the spatial distribution of which strongly affects the physical properties of the material, such as thermal conductivity and strength. The thermal performance of the material improves as the void ratio increases while the strength of the material decreases. Therefore, an appropriate method for examining the void distribution in the materials is necessary for better understanding of the material behavior. In this study, the effect of anisotropic voids on the material properties of insulating media is investigated. A 3D printer is utilized to generate a series of insulating media with different anisotropic voids. The void distributions of the specimens are characterized using probabilistic functions, and the thermal and mechanical properties of the specimens are also evaluated by means of real and numerical experiments. The results demonstrate an effect of anisotropic voids on the material properties that appropriately arranged anisotropic voids strongly affect the reduction of thermal conductivity for a specific direction, and that anisotropic voids can be utilized as a promising approach to develop high-performance insulating materials.