RESUMO
Mineral wool is commonly used in construction as thermal insulation material. After the product's lifetime, it is classified as hazardous waste if no trademark of the European Certification Board for Mineral Wool Products (EUCEB) or the German Institute for Quality Assurance and Labelling (RAL) exists. Mineral Wool Waste (MWW) is typically landfilled in Europe, which is challenging due to its low bulk density and dimensional stability. This circumstance highlights the need for alternative recycling methods that increase the recycling rate of construction and demolition (C&D) waste. This article outlines the recycling opportunities of MWW and focuses on the use of thermochemical treatment of different mixtures of input materials to produce a supplementary cementitious material (SCM). The material characterisation results and investigations on the binder suitability demonstrate that the slag fractions after the thermochemical treatment are well-qualified to be used as reactive binder components. Additionally, a material flow analysis was conducted to estimate the substitution potential of MWW as SCM in the Austrian cement industry.
RESUMO
Thermal soil treatment is a well-established remediation method to remove organic contaminants from soils in waste management. The co-contamination with heavy metals raises the question if thermal soil treatment affects heavy metal mobility in soils. In this study, four contaminated soils and a reference sample were subjected to thermal treatment at 105°C, 300°C and 500°C for 7 day. Thermogravimetry and differential scanning calorimetry were used to understand the reactions, and resulting gases were identified by Fourier-transformed infrared spectroscopy. Treated and untreated samples were characterised by X-ray diffraction (XRD) and electron microprobe analysis and subjected to pH-dependent leaching tests, untreated samples additionally by X-ray-fluorescence (XRF) and inductively coupled plasma mass spectroscopy (ICP-MS). Leachates were analysed using ICP-MS and ion chromatography. Maximum available concentrations were used for hydrogeochemical modelling using LeachXS/Orchestra to predict leaching control mechanisms. Leaching experiments show that thermal treatment tends to decrease the mobility at alkaline pH of Pb, Zn, Cd, As and Cu, but to increase the mobility of Cr. In the acidic to neutral pH range, no clear trend is visible. Hydrogeochemical modelling suggests that adsorption processes play a key role in controlling leaching. It is suggested that the formation of minerals with a more negatively charged surface during thermal treatment are one reason why cations such as Pb2+, Zn2+, Cd2+ and Cu2+ are less mobile after treatment. Future research should focus on a more comprehensive mineralogical investigation of a larger number of samples, using higher resolution techniques such as nanoscale secondary ion mass spectrometry to identify surface phases formed during thermal treatment and/or leaching.
RESUMO
Landfilling of mineral wool waste in big bags at separate landfill compartments is required in Austria. This results in enormous differences in the Young's moduli between common construction and demolition (C&D) waste compartments and mineral wool compartments, which causes severe accidents in terms of overturned vehicles due to sudden subsidence of the subsurface. Conditioning of mineral wool waste might be applied to adjust its geomechanical behaviour to that of common C&D waste but has never been investigated scientifically before. In this study we compare three scenarios for the conditioning of rock wool for landfilling: (A) loosely packing, (B) cutting comminution + cement addition and (C) cutting comminution + cement-supported briquetting. The performance of the different sample bodies under landfill conditions was simulated at the lab scale by cyclic loading (1223-3112 N, up to 160 cycles) using a 'Wille Geotechnik UL 300' press. The deformation was monitored during the experiment and Young's modulus was derived graphically, whereas the test execution was piston controlled. The Young's modulus increased during the experiments from 0.2 MPa to 4.6 MPa for scenario (A), from 0.6 MPa to 20.5 MPa for scenario (B) and from 7.5 MPa to 111.0 MPa for scenario (C). These results show that a combination of comminution and cement-supported briquetting significantly increases the geotechnical performance of mineral wool waste with respect to landfilling, which is still three orders of magnitude below that of common C&D waste, which is in the range of 30,000 MPa.
