Leaching of Heavy Metals from Contaminated Soil Stabilised by Portland Cement and Slag Bremen

2023

Construction Materials

This study aimed at evaluating the effect of blended binders on the stabilization of clayey soils intended for use as road and pavement materials in selected regions of Sweden. The stabilization potential of blended binders containing five stabilizers (cement, bio fly ash, energy fly ash, slag and lime) was investigated using laboratory tests and statistical analysis. Soil samples were compacted using Swedish Standards on UCS. The specimens were stabilized with blended mixtures containing various ratios of five binders. The effects of changed ratio of binders on soil strength was analyzed using velocities of seismic P-waves penetrating the tested soil samples on the day 14 of the experiment. The difference in the soil surface response indicated variations in strength in the evaluated specimens. We tested combination of blended binders to improve the stabilization of clayey soil. The mix of slag/lime or slag/cement accelerated soil hardening process and gave durable soil product. We noted that pure lime (burnt or quenched) is best suited for the fine-grained soils containing clay minerals. Slag used in this study had a very finely ground structure and had hydraulic properties (hardens under water) without activation. Therefore, slag has a too slow curing process for it to be practical to use in real projects on stabilization of roads. The best performance on soil stabilization was demonstrated by blended binders consisted of lime / fly ash / cement which considerably improved the geotechnical properties and workability of soil and increased its strength. We conclude that bearing capacities of soil intended for road construction can be significantly improved by stabilization using mixed binders, compared to pure binders (cement).

Section: Introductionmentioning

confidence: 60%

Section: Seismic Measurementsmentioning

confidence: 99%

Geotechnical Properties of Soil Stabilized with Blended Binders for Sustainable Road Base Applications

2023

Construction Materials

“…Existing methods of soil remediation used in environmental engineering include the evaluation of leaching potential from soil and immobilization of contaminants [39,40]. Diverse contaminants can be tested, such as toxic heavy metals, (As, Pb, Cd, Cr, Hg, Ni, and Zn) [41][42][43][44], Polycyclic Aromatic Hydrocarbon (PAH) [45], Polychlorinated biphenyl (PCB) [46], and organotin compounds Tributyltin (TBT) [47][48][49][50]. Depending on the approaches, soil leaching may be implemented with or without the renewed leachate [51], and using either dynamic or extraction tests [52].…”

Section: Introductionmentioning

confidence: 99%

“…A popular approach of the environmental engineering evaluation of soil properties includes the common leaching test [53][54][55]. Other examples use the water leach test [56,57], toxicity characteristic leaching [58], column leach test [59,60], or soil layering over the substance drainage system [61].…”

Section: Introductionmentioning

confidence: 99%

Optimized Workflow Framework in Construction Projects to Control the Environmental Properties of Soil

2023

Algorithms

To optimize the workflow of civil engineering construction in a harbour, this paper developed a framework of the contaminant leaching assessment carried out on the stabilized/solidified dredged soil material. The specimens included the sampled sediments collected from the in situ fieldwork in Arendal and Kongshavn. The background levels of the concentration of pollutants were evaluated to assess the cumulative surface leaching of substances from samples over two months. The contamination of soil was assessed using a structured workflow scheme on the following toxic substances, heavy metals—As, Pb, Cd, Cr, Hg, Ni, and Zn; organic compounds—PAH-16 and PCB; and organotin compounds—TBT. The numerical computation and data analysis were applied to the results of geochemical testing creating computerised solutions to soil quality evaluation in civil engineering. Data modelling enabled the estimation of leaching of the contaminants in one year. The estimated leaching of As is 0.9153 mg/m2, for Ni—2.8178 mg/m2, for total PAH-16 as 0.0507 mg/m2, and for TBT—0.00061 mg/m2 per year. The performance of the sediments was examined with regard to permeability through a series of the controlled experiments. The environmental engineering tests were implemented in the Swedish Geotechnical Institute (SGI) in a triplicate mode over 64 days. The results were compared for several sites and showed that the amount of As is slightly higher in Kongshavn than for Arendal, while the content of Cd, Cr, and Ni is lower. For TBT, the levels are significantly lower than for those at Arendal. The algorithm of permeability tests evaluated the safety of foundation soil for construction of embankments and structures. The optimized assessment methods were applied for monitoring coastal areas through the evaluated permeability of soil and estimated leaching rates of heavy metals, PHB, PACs, and TBT in selected test sites in harbours of southern Norway.

“…This is caused by the increased bonds between the soil's particles, which chemically reinforce its inner structure [28][29][30]. Steel slag binds soil particles effectively in contaminated soil polluted by heavy metals, and decreases leaching [31][32][33]. In turn, steel mill sludge can be used for the reinforcement of clay bricks, to decrease negative environmental consequences and to optimise its utilisation [34].…”

Section: Introductionmentioning

confidence: 99%

Simplex Lattice Design and X-ray Diffraction for Analysis of Soil Structure: A Case of Cement-Stabilised Compacted Tills Reinforced with Steel Slag and Slaked Lime

2022

Electronics

Evaluating the structure of soil prior to building construction is valuable in a large variety of geotechnical and civil engineering applications. To built an effective framework for assessing the strength of the stabilised soil, the presented workflow includes a complex approach of simplex lattice design and X-ray diffraction for the analysis of soil structure. Different from the traditional in situ measurements, we propose a statistical framework for effective decision-making on binder combination to stabilise soil collected in three localities of Southern Sweden—Bromölla Municipality (Skåne County), Petersborg (Östergötland County) and Örebro (Örebro County). A practical solution is presented that includes the evaluation of strength properties of various types of soil using ordinary Portland cement (OPC), slaked lime and steel slag as pure agents and blended binders. The specimens were collected in Southern Sweden and included sandy silty tills and clay till (clay content 6–18%). The preprocessing included the mineralogical analysis of mineral composition and soil structure by X-ray diffraction (XRD) and a sieve. The soil samples were fabricated, compacted, rammed, stabilised by six binder blends and assessed for uniaxial compressive strength (UCS). The moisture condition value (MCV) and water content tests were done for compacted soil and showed variation in the MCV values for different binders. The study determined the effects from binder blends on the UCS gain in three types of soil, measured on days 7, 28 and 90. Positive effects were noted from the steel slag/lime blends on the UCS gain in sandy silty tills. A steel slag/slaked lime mixed binder performed better compared to the pure binders. The effectiveness of the simplex lattice design was demonstrated in a series of ternary diagrams showing soil strength evaluated by adding the stabilising agents in different proportions.