Influence of different sources of coal gangue used as aluminosilicate powder on the mechanical properties and microstructure of alkali-activated cement

Abstract

Coal mining wastes are associated with serious environmental problems; they have potential as building materials, including alkali-activated cement. In this study, the effect of different coal mining wastes on the mechanical properties and microstructural development of alkali-activated materials (AAMs) was evaluated through XRD, SEM and FTIR spectroscopy. Different alkali-activated compounds were produced; the alkaline solution was composed of NaOH+Na2SiO3. The results obtained using the calcined coal sludge showed excellent mechanical performance, with compressive strength higher than 60 MPa. However, addition of metakaolin and ordinary Portland cement was necessary to increase the mechanical performance of calcined coal gangue materials. The formation of N-A-S-H gel and the incorporation of iron ions into the cementitious matrix were evidenced. Ultrasonic pulse velocity indicated the early polymerization during the reaction processes. The study verified that the different characteristics of the wastes influence the performance of alkali-activated materials.

Porous alkali‐activated material from hypergolic coal gangue by microwave foaming for methylene blue removal

“…Sharp diffraction peaks representing quartz (SiO 2 , PDF 00‐046‐1045) and hematite (Fe 2 O 3 , PDF 00‐033‐0664), accompanied by a weak peak of muscovite (KAl 3 Si 3 O 10 (OH) 2 , PDF 01‐075‐0948) and cristobalite (SiO 2 , PDF 01‐082‐0512), were observed in HCG, with a particularly sharp quartz peak at a 2 θ value of ∼26.6°. The broad halo between 20° and 35° in the X‐ray pattern of the AAM indicates the formation of an amorphous sodium aluminosilicate gel (N–A–S–H) during the synthesis of the material 71,72 . As shown in Figure 2A, the main crystalline phases of the HCG and pure AAM powders are essentially identical, with quartz and hematite being the most abundant phases.…”

“…The characteristic absorption bands at 1091, 797, 778, and 695 cm −1 are ascribed to quartz 79–81 . The broad peak at 3441 cm −1 is the characteristic of O–H asymmetric stretching (3000–3700 cm −1 ), which is associated with the formation of hydrated compounds 72,82,83 . The bending vibration of O–H is observed at ∼1626 cm −1 , indicating the presence of water molecules 84–86 .…”

“…The broad halo between 20 • and 35 • in the X-ray pattern of the AAM indicates the formation of an amorphous sodium aluminosilicate gel (N-A-S-H) during the synthesis of the material. 71,72 As shown in Figure 2A, the main crystalline phases of the HCG and pure AAM powders are essentially identical, with quartz and hematite being the most abundant phases. The density of the peak at ∼21.8 • is attenuated, possibly due to the synergistic effect of alkali activation and microwave activation as the sodium silicate glass forms.…”

Mullite-Based Ceramics from Mining Waste: A Review

“…In recent years, an increased demand for the appropriate and efficient use of coal gangue has been observed in different sectors. Thus, several studies can be found in the literature aimed at the use of this waste in geotechnical applications [116], alkaline-activated materials [117,118], as zinc and manganese ion adsorbent [119,120] or in agricultural applications [121]. Commonly, coal gangue is composed of a mixture of sandstone, shale and carbonaceous slate, with SiO 2 and Al 2 O 3 as its main chemical constituents.…”

Experimental Study of the Mechanical and Microstructure Characteristics of Coal Gangue Road Stabilization Materials Based on Alkali Slag Cementation

“…Moreover, the production of cement is a process involving high pollution and energy consumption, which is contrary to the theme of green building materials. The identification of inorganic industrial by-products that can replace Portland cement, and the use of industrial by-products [18][19][20][21] to reduce pollution and the environmental burden, have become research hotspots in environmental protection. The alkali-activated gel material is a mixture of aluminosilicate and alkali metal hydroxide or alkali metal silicate solution [22,23], which is an inorganic polymer.…”