In water purification plants, a large area of urban land is using to store waste sludge (WS). The waste sludge from water filtration plants is aluminosilicate, which can be form a geopolymer. However, the waste sludge has low alkaline activity, so it must be used in combination with fly ash (FA) to create geopolymer products. Fly ash is a solid waste containing amorphous silica so that has high alkaline activity, suitable for treatment by geopolymer method. The geopolymerization of waste sludge from water purification plants is a relatively new method. The geopolymer is a binder formed by the chemical reaction between aluminosilicate materials and alkaline activated solutions. The alkaline activated solution used in these experiments was water glass (WG). The water glass is solution of sodium silicate (Na2O.nSiO2) dissolved in water. The research results of geopolymer materials from the mixture of fly ash, the waste sludge of Thu Duc water purification plant, Ho Chi Minh City (Vietnam), and water glass (WG) were introduced in this study. The activated Al2O3 and SiO2 oxides in the fly ash and the waste sludge can be dissolved in the water glass and polymerized into a geopolymer material. The test samples had pressed at a high pressure of 225 MPa to form cylindrical ones weighing approximately 3 grams, height about 18 mm, and 10 mm in diameter. These samples were then cured at 110 ◦C for 24 hours and at room temperature (30 +/- 5 ◦C). The methods of Fourier infrared spectroscopy (FTIR) and scanning electron microscope (SEM) had used to detect the microscopic structure and geopolymer bond formation of the samples. The compressive strength of the tested samples at 28 days old was higher than 3.5 MPa, the pH was less than 12.5, meeting the Vietnamese National Standards for unbaked materials (TCVN 6477:2016) and National Technical Regulation on environmental impact (QCVN 50:2013 / BTNMT), respectively. The results show a new approach of solidifying the waste sludge for further applications such as the manufacture of geopolymer concretes or landfill materials.

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Large scale recycling of steel slag as a cementitious additive to cement mortar and/or concrete was investigated in this paper. As the material component of steel slag is highly variable, this EAF slag is gathered from plant site of Dong Tien steelmaker in Ba Ria-Vung Tau province. Chemical compositions of slag consist almost the high content of free CaO, MgO and iron, FexOy. Lower content of cementitious mineral C3S, C2S endorses relative low hydraulic reactivity in comparing with Portland cement. After grinding slag to particle size < 90 μm (Blaine 3400 cm2/g), blended cement–steel slag with 10 to 40% by mass of slag were formulated. Both steel slag-cement Portland and steel slag-granulated blast furnace slag (GBFS)-cement Portland system were introduced to analyze early age and later age property of mortar sample. Preliminary results of resistance remark appropriate formulation of 20% of slag. By adding 20% GBFS in such product, practical application could be considered due to the typical enhancement of durability property of cement mortar in severe condition (sulfate, chlorhydric acid). Others, by considering an approach of slag treatment to improve hydraulic reactivity as the GBFS materials model present. The mineralogical composition and some cementitious properties of obtained product would be discussed for a perspective of new clinker steel slag.

Liquefied wood is one of the phenolic resin. However, unlike commercial phenolic resins that are normally synthesized by the chemical reaction between phenol and formaldehyde, liquefied wood is usually produced by reacting phenol with wood-derived materials, and catalyst at 120-180◦C. Depending on whether the catalyst is a base or a acid, the formed resin is a thermoset or a thermoplastic. In this study, wood liquefaction was prepared from a cashew nut shell waste (CNSW), phenol, and sulfuric acid catalyst. The cashew nut shell waste is taken from Binh Phuoc province - Vietnam and crushed to a size of less than 500 mm. Phenol and sulfuric acid catalyst are chemical experiments. The powder of cashew nut shell waste, phenol, and sulfuric acid were mixed and reacted at 150oC for different soaking times. An optimal soaking temperature time was determined through a cashew nut shell waste residue content in wood liquefaction products. The wood liquefaction products also were determined by a number average molecular weight (Mn) and a weight average molecular weight (Mw) by Gel permeation chromatography method (GPC); the function groups by Fourier Transform Infrared method (FT-IR). The results showed that the formed resin is thermoplastic and the optimal soaking time to prepared liquefied wood is 180 minutes. This sample has a residual cashew nut shell waste ratio of 9.44%, a number average molecular weight of 7552, and a weight average molecular weight of 10640. The liquefied wood from cashew nut shell waste can be used as a binder in the manufacture of the medium density fiberboard (MDF) or as a material to promote the sintered process in the production of woodceramic materials. In addition, the liquefied wood can also be pyrolyzed to form carbon fiber. Carbon fiber can be applied as reinforcing materials for ceramic products.