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Sulfate attack is recognized as a significant threat to many concrete structures, and often takes place in soil or marine environments. However, the understanding of the behavior of alkali-activated and geopolymer materials in sulfate-rich environments is limited. Therefore, the aim of this study is to investigate the performance of alkali silicate-activated fly ash/slag geopolymer binders subjected to different forms of sulfate exposure, specifically, immersion in 5 wt% magnesium sulfate or 5 wt% sodium sulfate solutions, for 3 months. Extensive physical deterioration of the pastes is observed during immersion in MgSO 4 solution, but not in Na 2 SO 4 solution. Calcium sulfate dihydrate (gypsum) forms in pastes immersed in MgSO 4 , and its expansive effects are identified as being particularly damaging to the material, but it is not observed in Na 2 SO 4 environments. A lower water/binder (w/b) ratio leads to a greatly enhanced resistance to degradation by sulfate attack. Infrared spectroscopy shows some significant changes in the silicate gel bonding environment of geopolymers immersed in MgSO 4 , attributed mostly to decalcification processes, but less changes upon exposure to sodium sulfate. It appears that the process of 'sulfate attack' on geopolymer binders is strongly dependent on the cation accompanying the sulfate, and it is suggested that a distinction should be drawn between 'magnesium sulfate attack' (where both Mg 2? and SO 4 2-are capable of inducing damage in the structure), and general processes related to the presence of sulfate accompanied by other, non-damaging cations. The alkali-activated fly ash/slag binders tested here are susceptible to the first of these modes of attack, but not the second.

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Drying of cement paste, mortar or concrete specimens is usually required as a preconditioning step prior to the determination of permeability-related properties according to standard testing methods. The reaction process, and consequently the structure, of an alkaliactivated slag or slag-fly ash blend geopolymer binder differs from that of Portland cement, and therefore there is little understanding of the effects of conventional drying methods (as applied to Portland cements) on the structure of the geopolymer binders. Here, oven drying (60°C), acetone treatment and desiccator/vacuum drying are applied to sodium silicateactivated slag and slag/fly ash geopolymer pastes after 40 days of curing. Structural characterization via X-ray diffraction, infrared spectroscopy, thermogravimetry and nitrogen sorption shows that the acetone treatment best preserves the microstructure of the samples, while oven drying modifies the structure of the binding gels, especially in alkali-activated slag paste where it notably changes the pore structure of the binder. This suggests that preconditioning drying of alkali activated based materials strongly affects their microstructural properties, providing potentially misleading permeability and durability parameters for these materials when pre-conditioned specimens are used during standardized testing.

The dominant emerging materials from more than 30 years ago are plastics, ceramics, and composite materials. Composite materials have steady growth in the volume and number of its applications as it enviably penetrates existing markets while creating new ones. Contemporary composite materials are well established in today's market of specialty and everyday products with its proven worth as weight-saving materials. There is a current challenge of cost-effectiveness and environmental friendliness, thus leading to the search for low-cost polymeric-reinforced composites using entirely biodegradable fibers. Bamboo fibers have provided some response in the production of materials that are recyclable, biodegradable, and sustainable. The natural fibers yield composites with high strength-to-weight ratios as a function of the best properties of each component. Researchers have found sustainable high-end quality industrial products that can be generated from raw materials like bamboo fibers. Due to its high strength-weight ratio, bamboo fibers are often used to replace natural glass fiber. Thus, the much attention has been given to its composites with different matrix materials. This article gives a review of recent developments of bamboo fiber-based reinforced composites, its processing methodology, and applications.

The catalytic potential of calcium oxide synthesized from mud clam shell as a heterogeneous catalyst for biodiesel production was studied. The mud clam shell calcium oxide was characterized using particle size analyzer, Fourier transform infrared spectroscopy, scanning electron microscopy, and BET gas sorption analyzer. The catalyst performance of mud clam shell calcium oxide was studied in the transesterification of castor oil as biodiesel. Catalyst characterization and transesterification study results of synthesized catalyst proved the efficiency of the natural derived catalyst for biodiesel production. A highest biodiesel yield of 96.7% was obtained at optimal parameters such as 1 : 14 oil-to-methanol molar ratio, 3% w/w catalyst concentration, 60°C reaction temperature, and 2-hour reaction time. Catalyst reusability test shows that the synthesized calcium oxide from mud clam shell is reusable up to 5 times.