Development and Characterization of Sustainable Geomaterial Using Mining and Industrial Wastes

Abstract

The rapid growth of infrastructure needs a vast amount of natural resources to be used as an engineering material; on the other, industries and mining sectors are facing difficulty in managing their by-products. Hence, research needs in the alteration of the industrial wastes that can overcome the above challenges with minimum or no adverse effect on the geoenvironment, which especially can be termed as a sustainable material. In the present study attempts have been made to develop sustainable materials, (i) controlled low strength material (CLSM), (ii) biopolymer based cementitious material and (iii) alkali activated material (AAM) from industrial and mining wastes. The controlled low strength materials are developed using (i) less explored industrial waste ferrochrome slag (FS) and (ii) coal mine overburden with fly ash and cement as the binder for both the cases. Experimental investigations like flowability, bleeding, compressive strength, California bearing ratio (CBR), settlement, ultrasonic pulse velocity and slake durability index are made on developed CLSM. Use of optical microscope to characterise the granular material FS in terms of sphericity and workability of the material is another aspect of the present work. The developed CLSM material can be used for different structural fill works with “Low flowability, to “High flowability” with the bleeding value less than 3.5%, with water content varying from 25 to 32%. The 28 days’ density varies from 15.7 kN/m3 to 16.5 kN/m3 with ultrasonic pulse velocity values close to 2000, and the water absorption values less than 3%. The unconfined compressive strength (UCS) value upto 2.75 MPa and CBR value more than 100% was obtained.
Biopolymer-based cementitious materials are made using (i) fly ash and (ii) fine fraction of coal mine overburden for wind and water erosion control using three types of biopolymers; xanthan gum (XG), guar gum (GG) and carboxyl methyl cellulose sodium (CMC) salt. The wind erodibility of the materials are studied using water retention, surface resistance and wind tunnel test, similarly pinhole test, cylindrical dispersion tests are conducted to know the water erosion resistance. For water erosion, the CMC is more effective followed by GG and XG for both shale and fly ash. The surface strength of CMC and XG treated shale and fly ash increased with increase in concentration of solution upto 2%, but optimum percentage of GG treated samples observed at 1%. Higher surface strength of CMC and GG showed better wind erosion resistance. The surface strength of biopolymer treated cohesive material shale is more than that of non-cohesive material fly ash, with the denser microstructure of treated samples due to the bonding of particles.
The other sustainable material, alkali activated material using mine overburden and mine tailing is discussed in terms of compressive strength after 7 and 28 days of curing under ambient, alkali and sulphate solution to simulate different environmental conditions. Development of CLSM using AAM and use of slake durability index to assess the durability of developed sustainable material are some of the novelty of the present work. The AAM using mine overburdens are found to have 28 days compressive strength varying from 25.58MPa to 59.00 MPa depending upon the curing conditions and the base materials. The slake durability test indicates the developed AAM is “medium-high durable” to “high durable material”, similar to that of sandstone. The leachate analyses on the developed sustainable materials show no adverse effect on the geoenvironment.
The scanning electron microscope (SEM), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), electrical conductivity, zeta potential, etc. are also used for the characterization of basic material and the developed sustainable material to correlate with their macro properties.
The present work will help in the possible utilisation of the developed sustainable material in infrastructure. But, the future challenges are (i) development of suitable machinery and equipment for implementation of CLSM process, (ii) pilot project study on the implementation of biopolymers for erosion control at the site and (iii) identification of cost-effective activators, possibly from industrial wastes.