This work reports and describes a novel alkali-activated metakaolin as a potential binder material for the granulation of zeolites, which are widely used as CO2 adsorbents. The alkali-activated binders are zeolite-like materials, resulting in good material compatibility with zeolite-based adsorbents. A major problem during the granulation of zeolites is that their adsorption capacities decrease by about 15–20%, because typical binder materials (for example bentonite or kaolin clay) are inactive towards CO2 adsorption. A possible pathway to solve this problem is to introduce a novel binder that is also able to sorb CO2. In such a case, a binder plays a dual role, acting both as a binding material and as a sorbent. However, it is important that, alongside the adsorptive properties, a novel binder material must fulfil mechanical and morphological requirements. Thus, in this work, physical and mechanical properties of this novel binder for zeolite granulation for CO2 adsorption are studied. Alkali-activated metakaolin was found to be efficient and competitive as a binder material, when mechanical and physical properties were concerned. The compressive strengths of most of the obtained binders reported in this work are above the compressive strength threshold of 10 MPa. The future work on this novel binder will be conducted, which includes granulation-related details and the CO2 adsorptive properties of the novel binder material. Metakaolin was used as a precursor for alkali-activated binders. Binders were synthesized using varying molarity of a NaOH solution and at varying curing conditions. The final products were characterized using density measurements, compressive strength tests, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) analysis, and scanning electron microscopy (SEM).
Cement is a widely used building material, with more than 4.4 billion metric tons produced in 2021. Unfortunately, the excessive use of cement raises several environmental issues, one of which is the massive amounts of CO2e produced as a by-product. Using recycled materials in the concrete mix is widely employed to solve this problem. A method for minimizing the use of natural cement by substituting it with secondary cementitious material that consists of wood–cement board manufacturing waste has been studied in this paper. The cement in the waste stream was reactivated by a mechanical treatment method—the use of a planetary mill, allowing it to regain its cementitious properties and be used as a binder. Physical and mineralogical analysis of the binder material was performed using X-ray diffraction (XRD), thermogravimetry/differential thermal analysis (TG/DTA) and Brunauer–Emmett–Teller analysis; granulometry and compressive strength tests were also carried out. The results show that the grinding process did not significantly change the mineralogical composition and the specific surface area; it did, however, affect the compressive strength of the samples prepared by using the reactivated binding material; also, the addition of plasticizer to the mix increased compressive strength by 2.5 times. Samples were cured in high-humidity conditions. The optimal water-to-binder (W/B) ratio was found to be 0.7 because of the wood particles that absorb water in their structure. Compressive strength increased as the grinding time increased.
Up to now, primary resources have been the main choice of raw material selection for production. Now, global market tendencies have brought significant attention to secondary resources as the price has been raised for primary materials, and there is a shortage of their delivery. This could bring an additional effort to increase the recycling level of construction and demolition waste, including expanded polystyrene (EPS). Efforts have been made to develop new efficient building materials with a high content of recycled EPS. In this paper, composite insulation material made of gypsum hemihydrate and recycled EPS beads by casting and compression methods were evaluated, and properties were compared. Thermal and sound insulation properties were characterized. Density from 48 to 793 kg/m3 was obtained and the thermal conductivity coefficient from 0.039 to 0.246 W/(m·K) was measured. Compression strength was from 18 kPa to 2.5 MPa. Composites produced with the compression method have a sound absorption coefficient α > 0.9 in the range from 600 to 700 Hz, while the samples produced by casting showed poor sound absorption with wide deviation. Compression methods had an advantage over the casting method as more homogenous and lightweight materials were produced with improved insulation properties.
A major problem in the modern world is the overuse of fossil resources. The use of such resources and of that amount contribute negatively to the environment we live in. Fossil resources should be replaced with renewable ones. That way, less impact would be done to the environment. Renewable resources would greatly contribute to a healthy sustainable future. Latvia currently ranks seventh on the number of biogas plants per 1 million per capita (27) and is searching for new ways and opportunities to switch from the production of electricity to biomethane. Thus, in this study, a mathematical approach for the calculations of biomethane potentials and emissions of different feedstocks under the anaerobic digestion principle was studied. Databases were searched for the factual numbers of livestock animals, as well as processed sludge, and average food waste. RED II and JEC Well-To-Wheels report v5 were analyzed for data on emission factors and future obligations. Out of combined biomethane potentials of different feedstocks, livestock manure’s potential share was 91%, of which 61% is dairy cow manure. The overall biomethane potential in Latvia is 2.21 to 4.28 PJ. Replacing fossil fuels with biomethane in the transport sector could lower the overall CO2-eq emissions by 12.47–23.86% or 0.4–0.8 million tonnes.
More than 4.4 billion metric tons of cement were produced in 2021 [1], making it one of the most common building materials. Unfortunately, excessive cement use brings up several environmental concerns, one being the enormous volumes of CO2e (carbon dioxide equivalent) created as a by-product. CO2e is a standard unit for measuring carbon footprint and can be calculated for all greenhouse gases using global warming potential. Reducing CO2 and other greenhouse gas emissions is crucial in modern cement manufacturing, as 0.9 kg of CO2e is produced for every kg of cement. Cement manufacturing contributed by releasing 3.96 Gt of CO2e into the atmosphere in 2021. This issue is often remedied using recycled materials in the fresh concrete mix as supplementary or pozzolanic additives. Some researchers have focused on regaining the activity of hydrated cement paste by grinding and thermally activating it [2–5], but a low-strength binder would also work for many applications. A low-strength binder recovered with as little energy as possible (only grinding, no heat treatment) could be considered a more sustainable and less energy-intensive way of recovery of the cement binder matrix. This study investigated a technique for recycling hydrated cement paste by mechanical treatment to disintegrate the hydrated cement conglomerate to reveal the unhydrated cement particles [6] that can be used as a recovered cementitious binder from processing waste from the production of wood-cement boards. Processing waste is defined as cement particles containing hydrated and unhydrated cement [7] and spruce wood fibres. The partly hydrated cement in the waste stream was mechanically processed in a planetary mill to reactivate it and restore its cementitious characteristics. The binder was characterized by density and mechanical compressive strength.
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