Conventional Fill Materials Research Articles

Feasibility of granite processing waste as a fill material in geotechnical applications

India is the third largest granite producer worldwide, and an increasing trend in its export has been seen year by year. Granite is generally sold in dimensional and finished form. Large quarried granite blocks are processed to get a finished dimensional granite in processing industries. Processing comprises sawing, grinding and polishing operations. In processing operations, about 30 to 35 per cent of the mass of large granite blocks is left as fine Granite Processing Waste (GPW) in the form of slurry. Dumping of GPW is of major concern for the processing industries; it is often unscientifically dumped. Disposal of GPW in an unscientific manner causes adverse effects on humans and the environment. Delightful results are obtained in previous studies addressing its use in concrete, mortar building blocks and stabilization of expansive soils. GPW has the potential to serve as a fill material in geotechnical applications. However, a comprehensive characterization of GPW addressing its use as a fill material is significantly lacking. The current study intends to characterize GPW in light of its application as a non-conventional fill material in place of natural materials. Based on geotechnical and geoenvironmental tests carried out on GPW involving grain size analysis, Atterberg limits, hydraulic conductivity, swelling potential, compaction characteristics, surface morphology, chemical composition, elemental and mineralogical composition, pH and organic content analysis, it can be inferred that GPW is comparable to conventional fill materials.

Solidification/stabilization treatment of Hong Kong marine deposits slurry at high water content by ISSA and GGBS

Soft soils have been adopted as a conventional fill material in land reclamation projects, which is quite promising in Hong Kong with a huge mass of dredged marine sediments produced per year. It is proposed to use Hong Kong marine deposits (HKMD) as fill material treated by stabilisation/solidification (S/S) technology with sustainable binding material. In this work, lime, incinerated sewage sludge ash (ISSA) and ground granulated blast furnace slag (GGBS) were selected as the binding materials. The S/S performance of the binders on HKMD slurry was investigated. The results showed that the use of ISSA and GGBS as part of the binder is effective in promoting the strength of HKMD slurry with a high initial water content of 200%. The HKMD slurry treated by 30% binders (30% lime and 70% (ISSA + GGBS) with ISSA: GGBS = 3) gains strength, which became higher with increasing curing time. The results from X-ray diffraction (XRD), thermo-gravimetric (TG) analysis and scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) presented the formations of calcium (aluminium) silicate hydrate (C-(A)-S-H), Friedel’s salt, and ettringite, which are mainly responsible for the strength increase of treated HKMD with their phases filling into the pores, interlocking and reinforcing the particles in the mixture. The porosity of the treated HKMD in bulk and powder state was determined by mercury intrusion porosimetry technique (MIP) and nitrogen adsorption/desorption isotherms (NAI), it is found that the bulk porosity of treated HKMD samples reduces with curing time due to the neoformations, especially the ettringite crystal by SEM results. This work indicates the potential application of lime-activated recycling wastes (i.e., ISSA and GGBS) for S/S treatment of HKMD slurry.

A Novel Sensor for Undrained Shear Strength Measurement in Very Soft to Soft Marine Sediments Based on Optical Frequency Domain Reflectometry Technology.

Due to the short supply of conventional fill materials, such as sand, land reclamation using dredged marine deposits has recently been proposed, in which marine deposits with high water content are blow-filled into reclaiming areas. The strength development of the filled marine soils is of great importance during the sedimentation and consolidation to guide the filling process and construction of reclamation. In this study, a novel sensor based on optical frequency domain reflectometry (OFDR) technology with a simple design was developed for undrained shear strength measurement. The novel sensor consists of an optical fiber and a series of polyoxymethylene coins. Owing to the merits of OFDR technology on high resolution, fully distributed sensing, and immunity to electromagnetic interference, the novel sensor can be used to determine undrained shear strength profiles of very soft to soft marine sediments/soils with good accuracy. The sensor was calibrated in remolded marine deposits with different water contents. The good feasibility and performance of the novel sensor for undrained shear strength measurement were well validated in two physical model tests on marine deposits treated by horizontal drains with vacuum preloading.

Evaluation of interaction properties of uniaxial geogrids with waste foundry sand

The reuse of waste materials can help alleviate problems related to placing them in landfill and can also preserve fast dwindling natural granular materials. Waste foundry sand (WFS) can be a promising candidate as a backfill material in the construction of mechanically stabilised earth (MSE) walls. In the design of such MSE structures, the interaction properties between WFS and geogrid reinforcement are important input parameters. In the present study, the interaction properties of a wide range of different polyester (PET) uniaxial geogrids with WFS in two common modes – direct shear and pullout – were evaluated using large-size interface direct shear and pullout tests. In the pullout mode, the interaction of the geogrid embedded in WFS under axial and transverse pullout was studied. The direct shear interface coefficients of four PET geogrids with WFS were found to be in the range observed in conventional fill materials. Higher axial and transverse pullout resistance factors were observed for geogrids with higher tensile strength and higher opening area ratio. Empirical equations were proposed to estimate the axial and transverse pullout resistances of geogrids at two pullout displacements. Finally, sensitivity analyses were carried out to identify the parameters significantly influencing the axial and transverse pullout resistances of geogrids in WFS.

Effects of EPS bead inclusions on stress–strain behaviour of sand

ABSTRACT: Lightweight fill solutions have been used in many civil engineering projects throughout the world. At locations with poor soil conditions, alternative lightweight construction fill materials such as expanded polystyrene (EPS) geofoam, wood chips, and tyre wastes may be used instead of conventional fill materials. These materials are used as an additive for the soil. It is known that the type, aspect ratio and content of the admixtures have an important role in the mechanical properties of the mixtures. The main objective of this study was to assess the feasibility of the potential use of EPS beads in geotechnical applications. The effect of EPS bead gradation on the stress–strain behaviour of lightweight composite materials composed of EPS bead–sand mixtures (EPS–sand) was investigated through a series of triaxial compression tests under three different confining pressures. Three different types of spherical EPS beads with different unit weights (EPS-1, EPS-2, and EPS-3) were mixed with sand with varying EPS bead content. This study has shown that the deviatoric stress of a EPS–sand mixture is not only a function of volumetric EPS bead content but it also depends on EPS bead grain size distribution (EPS bead type). Whereas volumetric EPS bead content increases when all other variables are constant (EPS bead type in EPS–sand), the initial modulus of elasticity decreases linearly. Consequently, EPS bead inclusion did not enhance the maximum deviatoric stress of EPS–sand when compared with that of the sand-only specimen. However, bead addition provides a lightweight aspect to the mixture which can be attractive to use in many geotechnical engineering projects. EPS bead content, confining pressure and EPS bead type-dependent multiple linear regression (MLR) equations were proposed to estimate the initial undrained elastic modulus of EPS–sand to reduce the cost and time involved in conventional laboratory testing of EPS–sand mixtures. Based on the stress–strain behaviour of EPS–sand, these mixtures may be utilised in geotechnical applications as a lightweight fill material.

Reuse of MSWI bottom ash mixed with natural sodium bentonite as landfill cover material

The research described in this study had the aim of evaluating the reuse of incinerator slag, mixed with sodium bentonite, for landfill capping system components. A characterization was performed on pure bottom ash (BA) samples from an incinerator in the north of Italy. The results show that the BA samples had appropriate properties as covers. The compacted dry unit weight of the studied BA (16.2 kN m(-3)) was lower than the average value that characterizes most conventional fill materials and this can be considered advantageous for landfill cover systems, since the fill has to be placed on low bearing capacity ground or where long-term settlement is possible. Moreover, direct shear tests showed a friction angle of 43°, corresponding to excellent mechanical characteristics that can be considered an advantage against failure. The hydraulic conductivity tests indicated a steady-state value of 8 × 10(-10) m s(-1) for a mixture characterized by a bentonite content by weight of 10%, which was a factor 10 better than required by Italian legislation on landfill covers. The results from a swell index test indicated that fine bentonite swelled, even when divalent cations were released by the BA. The leaching behaviour of the mixture did not show any contamination issues and was far better than obtained for the pure BA. Thus, the BA-bentonite mixture qualified as a suitable material for landfill cover in Italy. Moreover, owing to the low release of toxic compounds, the proposed cover system would have no effect on the leachate quality in the landfill.

Performance of industrial by-products in controlled low-strength materials (CLSM)

As the construction industry continues to recognise the importance of sustainable development, technologies such as controlled low-strength material (CLSM) have come to the forefront as viable means of safely and efficiently using by-product and waste materials in infrastructure applications. CLSM, also known as flowable fill, can be defined as an engineered backfill material containing fine aggregates, Portland cement, water and a by-product material. CLSM can provide an economically and technically feasible alternative to conventional fill materials because of potential cost savings related to its unique and often superior technical properties. In this present experimental study, three industrial by-products, namely fly ash (FA), rice husk ash (RHA) and quarry dust (QD), were used as constituent materials in CLSM. Mixture proportions were developed for CLSM containing these industrial by-products and were tested in the laboratory for various properties, such as flowability, unconfined compressive strength (UCS), stress-strain behaviour, density, water absorption and volume changes. Comparison between the two pozzolanic materials, namely FA and RHA, for their potential to produce an effective CLSM has been made. It can be observed from the results that by-product materials such as FA, RHA and QD can be successfully used in CLSM. This successful utilization of by-product materials is important to sustainable development and is the focus of this research.

Assessment of the use of spent copper slag for land reclamation

The shortage of waste landfill space for waste disposal and the high demand for fill materials for land reclamation projects in Singapore have prompted a study on the feasibility of using spent copper slag as fill material in land reclamation. The physical and geotechnical properties of the spent copper slag were first assessed by laboratory tests, including hydraulic conductivity and shear strength tests. The physical and geotechnical properties were compared with those of conventional fill materials such as sands. The potential environmental impacts associated with the use of the spent copper slag for land reclamation were also evaluated by conducting laboratory tests including pH and Eh measurements, batch-leaching tests, acid neutralization capacity determination, and monitoring of long-term dissolution of the material. The spent copper slag was slightly alkaline, with pH 8.4 at a solid : water ratio of 1 : 1. The batch-leaching test results show that the concentrations of the regulated heavy metals leached from the material at pH 5.0 were significantly lower than the maximum concentrations for their toxicity limits referred by US EPA's Toxicity Characteristic Leaching Procedure (TCLP). It was also found that the material is unlikely to cause significant change in the redox condition of the subsurface environment over a long-term period. In terms of physical and geotechnical properties, the spent copper slag is a good fill material. In general, the spent copper slag is suitable to be used as a fill material for land reclamation.

Material Properties of High Volume Fly Ash Cement Paste Structural Fill

Fly ash can be effectively used as compacted or flowable fill material in the construction of structural fills for building foundations, embankments, base and subbase courses for highways and railroads, dikes, levees, bridge abutments, and landfill cover in lieu of conventional earth materials. In this study, high volume fly ash cement paste composite formed of various combinations of fly ash, cement, lime, silica fume, and chemical admixtures has been examined in terms of its physical (dry unit weight, void ratio, apparent specific gravity, linear shrinkage), mechanical (unconfined compressive strength, flexural strength), and durability properties (hydraulic conductivity, soundness by use of sodium sulphate) at 0, 100, and 200mm slump values. The results indicate that the cement paste, providing certain advantages over conventional fill materials with its lower unit weight, higher strength, and higher volume stability can be designed for any required engineering performance for use in the construction of compacted to self-compacting structural fills and promises high volume fly ash utilization with low technology requirements avoiding scarce use of raw resources.

ENVIRONMENTAL IMPACTS OF PHOSPHOGYPSUM VS. BORROW PITS IN ROADFILL CONSTRUCTION

A comparison was performed of the environmental impacts of using phosphogypsum versus conventional fill materials (e.g., from borrow pits) for road construction. The study compared a hypothetical roadway with an actual roadway in Florida; the two facilities differed only in that phosphogypsum was employed as fill material instead of conventional materials. The effect of the two construction approaches on the plant and animal communities was considered, as was the impact on the surface and ground water. A summary was made of the comparative impacts, and a comparison matrix was constructed using integral numbers to depict impacts ranging from – 5 (most impact) to 0 (none) to + 5, showing most benefit of the part of the project on a given resource. Values were subjective, based upon investigators' experience. Four categories (plant and animal communities, water quality, water resources, and air quality) were considered. The cumulative total was +12 for phosphogypsum and – 6 for conventional fill material.

Field Study of Shredded-Tire Embankment

Interim data from the ongoing field study of an experimental shreddedtire embankment constructed near Williamsburg, Virginia, are presented. Approximately 1.7 million shredded tires, mixed with a conventional fill material, were used. The results to date indicate that the settlements are somewhat larger than usual in the embankment, but there are no problems with stability. Groundwater monitoring showed no abnormal concentrations. Infrared scans reveal no signs of a potential exothermic reaction in the embankment core.