Applied Mechanics and Materials Vols. 754-755

Abstract: Blending method of two or more polymer is well-established strategy to modify the physical properties without synthesizes the new polymer system. While adding magnetic filler will change the magnetic properties of the polymer as an insulator to the materials that are magnetic. The TPU/NR blends as matrix was prepared from thermoplastic polyurethane (TPU) and natural rubber (NR) in the ratio 85/15 with 1-5 wt% NiZn ferrites. The value of saturation magnetization (M_s), remanance (M_r) increased, while coercive force (H_c) decreases with increasing filler loading. For the electrical properties, resistivity decreased and conductivity increased with the increase of NiZn ferrite loading in the blends.

Abstract: Sago starch is modified with 1 wt % Poly butyl acrylate (PBA) and Poly ethylene oxide (PEO) monomer and 1 wt% of initiator, potassium persulfate (PPS) at temperature 80°C for 2 hours. Modified sago starch is cooled under room temperature for 24 hours prior to Natural Rubber Latex (NRL) compounding process. Results indicates that NRL films with PBA modified sago starch have higher mechanical properties compared to PEO modified sago starch and unmodified sago starch. Swelling test indicates that PEO gives lowest percentage of swelling and crosslink density. This is due to higher reaction probability that produce more closely packed structure with NRL matrix compared to PBA which only improved the compatibility of sago starch particle with rubber matrix. Thus, chemically modified sago starches are preferable to be used as fillers to produce better interaction between fillers and rubber matrix.

Abstract: Regenerated cellulose (RC) biocomposite films from Nypa Fruticans Fiber (NFF) and microcrystalline cellulose (MCC) were prepared by dissolving cellulose in lithium chloride (LiCl) and dimethylacetamide (DMAc). The effect of NFF content on tensile properties and X-ray diffraction were studied. The results found that the tensile strength and Young’s modulus of RC biocomposite films increased from 1 wt% to 3 wt% of NFF content and decreased at 4 wt% of NFF content. The elongation at break of RC biocomposite films decreased with increases NFF content. The crystallinity of RC biocomposite films also showed the highest crystallinity at 3 wt% of NFF content.

Abstract: The aim of the study was to compare the surface microhardness of composite resins polymerized in different mode of light unit. Three commercial composite resins: Charisma (Heraeus Kulzer Co.), Filtek Z 250 (3M ESPE Co.) and G-aenial Anterior (GC Company Co.), were used in this study. Fifteen samples of each material were obtained by placing the composite resin in plastic rings having 2 mm high and 6 mm inner diameter. All composite samples were cured using blue light-emitted diode G 0010 (SKI, China). Five samples were cured using ramp mode of the light unit, five samples were cured using single light: high intensity (constant) mode and five samples were cured using pulse mode. The samples were finished and polished and then stored in distilled water, at room temperature for 48 hours. The samples were subjected to microhardness evaluation using microhardness tester (Micro-Vickers Hardness System CV-400DM^TM, CV Instruments Namicon). A 50 g load was applied through a Vickers indenter. For each sample three indentations were made in different areas of the sample and the value of Vickers hardness was calculated as a mean result of the three recordings. Statistical Mann-Whitney U test and Kruskal-Wallis test were used to compare the values of surface hardness. Polymerization of all three composite resins using pulse mode leaded to significantly lowest mean hardness values and single light high intensity mode to the highest values. Filtek Z250 composite resin showed the highest microhardness mean values in all three polymerization mode and Charisma the lowest values. Surface microhardness of composite resins is influenced by different modes of light unit. Single light high intensity mode of polymerization leaded to the highest values of microhardness, followed in descending order by ramp and pulse mode. The best results regarding the surface microhardness was recorded for Filtek Z250composite resin, followed in descending order by G-aenial Anterior and Charisma.

Abstract: The mechanical propertiesof artificial lightweight geopolymer aggregate (ALGA) using volcano mud in concrete have been investigated at various sintering temperature. The volcano mud was mixed with alkaline activator, formed into spherical pellets, then sintered in the furnace at temperature of 500°C, 600°C, 700°C, 800°C, 900°C, 950°C, and 1000 °C. The lightweight concrete with density below than 1800 kg/m³ can be achieved at sintering temperature ALGA of 950 °C. The optimum compressive strength of 30.1 MPa was achieved at 28 days of testing. The lower water absorption of ALGA concrete was produced with 5-8 % in range.

Abstract: Lightweight concrete is generally used particularly at high-rise buildings in order to reduce the risk of earthquake. It is common that lightweight concrete is made with less Portland Cement associated with pozzolanic material as a binder. In this paper, calcined-Sidoarjo mud was identified as pozzolanic material as cement substitution. The mud contains SiO_2, Al₂O₃ and Fe₂O₃ and to be expected it has properties as a potential pozzolanic material. Paste and mortar as specimens made from mixtures of calcined-Sidoarjo mud, fly ash, lime, portland cement and natural sand. The specimens were then mixed with a commercial chemical foaming agent and Aluminum powder as aerating agents. The results showed that test paste specimens using chemical foam showed higher compressive strength and density than those of using aluminum powder. Lightweight paste made with chemical foam has compressive strength of 10.7 Mpa with density of 1133kg/m³. Moreover, the specimens of lightweight mortar had the compressive strength of 4.8 MPa, and the density of 1154.7kg/m³. Lightweight paste specimens using aluminum powder had a compressive strength of 2.8 Mpa with density of 1013kg/m³, while lightweight mortar specimens showed compressive strength of 2.4 MPa, and the density was 966kg/m³.

Abstract: This study was conducted to compare the mechanical properties of fly ash artificial geopolymer aggregates with natural aggregate (rock) in term of its impact strength, specific gravity and water absorption.The raw materials used were fly ash, sodium hydroxide, sodium silicate and natural aggregate. After the artificial geopolymer aggregate has been produced, its water absorption, specific gravity and aggregate impact test has been done. All results obtained were compared to natural aggregate. The result shows that the fly ash geopolymer aggregate are lighter than natural aggregate in term of its specific gravity. The impact value for fly ash artificial geopolymer aggregate slightly high compared to natural aggregate while it has high water absorption value compared to natural aggregate. As conclusion, the fly ash artificial geopolymer aggregate can be used as one of the construction materials in concrete as an alternative for coarse aggregate besides natural aggregate with more lightweight properties.

Abstract: Steel slag waste is a by-product of steel mining industry. Effort to utilize the steel slag in concrete production has been failed due to its high contents of MgO which causes volumetric instability of the hardened concrete. Researchers also have failed to utilize the steel slag in the sub-base of road construction due to its low compaction ratio. Geopolymer concrete is a new sustainable material made of mainly two materials which are alkali liquid and source material. The source material usually has to be pozzolanic. However, the chemical composition of the steel slag has shown that the steel slag is not considered as a pozzolanic in accordance to the requirement of the ASTM. Therefore, a special modification has been carried on and a geopolymer steel slag brick has been developed. The new developed geopolymer steel slag brick has compressive strength of about 10 MPa which is made the brick suitable for construction of a load bearing walls.

Abstract: Energy saving in building technology is among the most critical problems in the world. Thus it is a need to develop sustainable alternatives to conventional concrete utilizing more environmental friendly materials. One of the possibilities to work out is the massive usage of industrial wastes like ground granulated blast furnace slag (GGBS) to turn them to useful environmental friendly and technologically advantageous cementitious materials. In this study, ground granulated blast furnace slag (GGBS) is used to produce of alkali activated slag (AAS) mortar with the effect of alkaline activator concentration. Alkali activated slag (AAS) mortar is accelerated using alkaline solution of sodium silicate mixed with sodium hydroxide. The fixed ratio of sodium silicate to sodium hydroxide is 1.7 and the concentration of sodium hydroxide is varied from 6M to 12M. Concentration of 10M NaOH promotes the best properties of mortar by achieving the greatest compressive strength. Substitution of mineral admixture also influences strength performance of AAS mortars. The mortar with 20% calcium carbonate demonstrates the maximum compressive strength. The used of alkaline activation system is the best method to prepare industrial byproduct concrete. Moreover, alkali activated product itself gains superior properties which lead to the system become the most interesting method to produce sustainable concrete.

Abstract: The characteristics of mortars made from ordinary Portland cement with various composition of ground granulated blast furnace slag (GGBS) were investigated in this research. Ground granulated blast furnace slag (GGBS) was chose as an alternative binder to partially replace high energy consuming Portland cement in concrete according to the composition of the slag itself. GGBS were blended with Portland cement from 20 to 80 weight percent. The samples were mechanically tested for water absorption and compressive strength after 7, 14 and 28 days. From research, the most suitable proportion is 60% OPC + 40% GGBS which gain the highest compressive strength and the lowest water absorption among OPC blended mortars. These mortars used water to hydrate and solidify with ratio water to binders 0.7 equally.