Co-Doped Magnesium Oxychloride Composites with Unique Flexural Strength for Construction Use

In this study, the combined effect of graphene oxide (GO) and oxidized multi-walled carbon nanotubes (OMWCNTs) on material properties of the magnesium oxychloride (MOC) phase 5 was analyzed. The selected carbon-based nanoadditives were used in small content in order to obtain higher values of mechanical parameters and higher water resistance while maintaining acceptable price of the final composites. Two sets of samples containing either 0.1 wt. % or 0.2 wt. % of both nanoadditives were prepared, in addition to a set of reference samples without additives. Samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and energy dispersive spectroscopy, which were used to obtain the basic information on the phase and chemical composition, as well as the microstructure and morphology. Basic macro- and micro-structural parameters were studied in order to determine the effect of the nanoadditives on the open porosity, bulk and specific density. In addition, the mechanical, hygric and thermal parameters of the prepared nano-doped composites were acquired and compared to the reference sample. An enhancement of all the mentioned types of parameters was observed. This can be assigned to the drop in porosity when GO and OMWCNTs were used. This research shows a pathway of increasing the water resistance of MOC-based composites, which is an important step in the development of the new generation of construction materials.

Physical-Chemical Studies of the Process of Condensation of a Clinker-Free Binder

The possibility of using a clinker-free binder as an alternative to expensive and energy-intensive Portland cement is being considered. The pozzolanizing effect of volcanic rocks is presented, where along with the binding of calcium hydroxide by silica to hydrosilicates, the binding of calcium hydroxide by “free” alumina to hydroaluminates also takes place. In the process of hardening of the clinker-free binder, the phase mineralogical composition of the formed new formations differs from the new formations that are synthesized during hardening of traditional Portland cement, which explains the difference in their properties. The new formations that are formed during the hardening process of clinker-free cements are mainly low-basic hydrosilicates, and alkaline aluminosilicates give the cast-in-place stone water resistance, frost resistance, waterproofing, etc., in a word, durability. Physical and chemical studies of the hardening process of clinker-free lime-igneous cements have been carried out, which indicates the possibility of replacing the energy-intensive Portland cement with cheaper clinker-free cement.

Processing of polymer wood composite material from pine cone and the binder of phenol formaldehyde/PVAc/molasses and improvement of its properties

This paper deals with the processing of polymer wood composite material from pine cone and the binder of phenol formaldehyde/PVAc/molasses and improvement of its properties. The production of pine cone based polymer binding and molasses added composite material, and the development of the non-flammability, insect attack and water resistance properties of this material has been studied in the research. To this end, pine cone, polyvinyl acetate (PVAc), phenol-formaldehyde, molasses, hemp fiber and waste colemanite have been used in the production of composite materials. It is aimed to produce a cheaper composite material less harmful to human health using plant based waste materials. According to the results of the flexural strength test conducted in the laboratory, the most suitable composite material producing parameters were detected as 0.25 filler/binder (f/b) ratio, 35% molasses ratio, 100°C molding pressure temperature, 49 kg/cm2 molding pressure, 240 µm mean particle size, 20 minutes for molding pressure time, 20% PF ratio and 0.5% hemp fiber ratio. It was determined that molasses could be used at a ratio of 35% for producing composite materials and, PF resin and hemp fiber samples provide the necessary water resistance. It was observed that the colemanite waste used in the mixture adds the nonflammability property to the composite material and decreases flexural strength and screw withdrawal strength.