Abstract: This paper investigates the influence of mechanical activation of fly ash on the toxic metals immobilization by fly ash-based geopolymers. Fly ash was firstly mechanically and then alkali-activated. Mechanical activation of fly ash was conducted in a planetary ball mill. Alkali activation of fly ash was carried out at room temperature by use of sodium silicate solution as an activator. Toxic metals (Pb and Cr) were added in the form of water soluble salts during the synthesis of geopolymers. The immobilization process was assessed via investigation of the mechanical and leaching properties of geopolymers. Structural changes of geopolymers during the toxic metals immobilization were assessed by means of gas adsorption and SEM analyses. Mechanical activation of fly ash led to a significant increase in geopolymer strength and to a reduced leaching of toxic metals from geopolymers.
Abstract: The paper deals with the experimental determination of shrinkage development of the composites based on the alkali-activated slag (AAS). The main aim of the experimental investigation was to verify the effect of the addition of shrinkage-reducing admixture (SRA) on the overall process of shrinkage properties during AAS composites ageing.
Abstract: Organic adhesive – bonded wood board materials like particleboards, plywood and others are widely used in construction, furniture, car- making, etc. However, all materials made with organic adhesives release non-reacted toxic substances, in particular formaldehyde and phenol, which produce negative effects on human health during production and use. Current trend in wood processing industry is to replace organic binders used as adhesives by inorganic ones. One of such solutions to improve indoor air quality is to replace organic adhesives by inorganic ones and the use of the alkaline aluminosilicate binders of the system R2O-Al2O3-SiO2-H2O is a highly advantageous solution and no need of preliminary treatment of wood. Among disadvantages are the low elasticity. Among disadvantages of these binders restricting their use as adhesives are low elastic properties (high modulus of elasticity, stiffness) of the resulted wood-based products. The paper covers the results of modification of the alkaline aluminosilicate binders to improve properties using specially chosen organic additives – modifiers
Abstract: It is well known, that alkali-activated materials (AAMs) are suitable for immobilization of heavy metals and other hazardous materials. This study is focused on the characterization of inhibition of three metals – Sr2+, Bi3+ and Zn2+ in alkali-activated matrices. Two type of matrices were prepared – alkali-activated blast furnace slag (BFS) and alkali-activated fly ash (FA). Sodium water glass was used as alkaline activator. The ability of these matrices to fix the metals were proved by leaching tests. Compressive strength was measured to characterize mechanical properties of the matrices. Scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) was used to examine distribution and chemical state of metals within the matrices. The observed metals mainly formed the insoluble compounds after alkali activation.
Abstract: One of the largest obstacles for the wider use of alkali-activated slag (AAS) in a building industry is its severe drying shrinkage. According to some studies shrinkage-reducing admixtures (SRAs) could be a solution of this problem, but they were also reported to have a fatal impact on AAS hydration resulting in a serious strength development slowdown. The aim of this paper was to investigate this phenomenon in a wide range of the waterglass doses (4–12% Na2O of the slag mass). Mortars without and with 2% of SRA based on hexylene glycol were prepared and their shrinkage and compressive strength development was tested. By far the highest shrinkage reduction was observed for the lowest doses of waterglass, but these were also the cases of the highest compressive strength decrease. However, it is possible to suppress the negative effect of SRA on AAS strength development through the activator dose increase with certainly decreased shrinkage reducing ability of SRA.
Abstract: This paper deals with the mechanical properties and phase study of alkali activated blast furnace slag and by-pass cement kiln dust mixture. The by-pass cement kiln dust (CKD) solves the problem with significant shrinkage of alkali activated materials which is considerably limiting their practical applications. The mechanism of action of CKD in alkali activated matrix has been investigated as well as its optimal dosage in the means of mechanical properties. The reaction products during the hydration process were characterized by X-ray powder diffraction.
Abstract: Properties of dry mixes for anchoring application (increasing of mortars strength, adhesion, volume stability etc.) based on alkali activated Portland cement (AAPC) are influenced by different factors. One of them is application of chemical admixtures with different functionality. Adhesive properties are mainly achieved by redispersible polymer powders (RPP). The main problem in choice of RPP’s type is destruction of their molecules with ester links due to alkaline hydrolysis.The purpose of work was investigation of RPP’s molecular structure influence on properties of mortar for anchoring application based on AAPC and determination of the most effective.Efficiency of RPP based on copolymer of versatile acid ester was shown. The application of this RPP provides adhesion of 1.1 MPa and consistency of 190 mm. Positive effect of copolymer of ethylene and vinyl acetate was shown despite of partial destruction of RPP’s molecule as a result of alkaline hydrolysis of vinyl acetate at early terms of hardening. Negative effect of RPP is in decreasing of mortar strength. Thus this problem solving is decreasing of powder content to values which provide necessary physical-mechanical properties (strength, adhesion).
Abstract: The consolidation via geopolymerisation is a room temperature alkaline chemical reaction of condensation between SiO2 and AlO2 monomers. Such a matrix can retain a large number of cations to compensate for the Al+3 in place of Si+4 in the tetrahedra. Arsenic-rich mine tailings from a gold mining site were activated with NaOH solution and commercial Na-Silicate (Na2O/SiO2 = 3) to produce a no-hazardous final material. Granulated blast furnace slag and metakaolin were used as co-binders to optimize the formulations. Leaching test was used to evaluate the inertization capability of the matrix after curing times of 7 and 28 days. The leaching results show that increasing curing time there is a significant decrease of As leaching due to the better consolidation of the material. Leaching of Cu, V, Ba and Zn significantly decrease, while Ni and Cr remain almost constant and Sb slightly increases.
Abstract: The paper discloses an effective way of utilization of industrial waste water treatment residues. The wide use of industrial waste water in building materials is difficult due to the presence of heavy metal. However, alkali activated cements showed high ability of immobilization of heavy metals. The compressive strength of AAC systems with water treatment residues (galvanic process waste water) is up to 40 MPa in mortars and 45 MPa in concretes. The leaching behaviour of heavy metals from the cements matrix after soaking up to 28 days was also examined with AAS.