Preparation, Characterization of Granulated Sulfur Fertilizers and Their Effects on a Sandy Soils

There is a potential for using sulfur waste in agriculture. The main objective of this study was to design a granular fertilizer based on waste elemental sulfur. Humic acids and halloysite were used to improve the properties and their influence on soil properties. This is the first report on the use of proposed materials for fertilizer production. The following granular fertilizers were prepared (the percentage share of component weight is given in brackets): fertilizer A (waste sulfur (95%) + halloysite (5%)), fertilizer B (waste sulfur (81%) + halloysite (5%) + humic acids (14%)), fertilizer C (waste sulfur (50%) + halloysite (50%)) and fertilizer D (waste sulfur (46%) + halloysite (46%) + humic acids (8%)). Basic properties of the obtained granulates were determined. Furthermore, the effect of the addition of the prepared fertilizers on soil pH, electrolytic conductivity, and sulfate content was examined in a 90-day incubation experiment. Enrichment with humic acids and the higher amount of halloysite increased the fertilizer properties (especially the share of larger granules and bulk density). In addition, it stabilized soil pH and increased the sulfur content (extracted with 0.01 mol·L−1 CaCl2 and Mehlich 3) in the soil.

Experimental Investigation of Unconfined Compression Strength and Microstructure Characteristics of Slag and Fly Ash-Based Geopolymer Stabilized Riverside Soft Soil

To solve the issues of insufficient early strength of cement stabilized soil and high resource cost, high reduction cost, and high environmental cost induced by the application of cement, the slag and fly ash-based geopolymer was adopted as the stabilizer to treat riverside soft soil. This study mainly investigated the effects of stabilizer content, slag-to-fly ash ratio, and alkaline activator content on the strength of geopolymer stabilized soils with different curing ages. Unconfined compressive strength (UCS), scanning electron microscope (SEM), and X-ray energy spectrum analysis (EDS) tests were carried out. The results show that the stabilizer content, slag–fly ash ratio, and alkaline activator content have a decisive influence on the UCS of geopolymer-stabilized soil. The mix-proportions scheme of geopolymer stabilized riverside soft soil, with a geopolymer content of 15%, a slag–fly ash ratio of 80:20, and an alkaline activator content of 30%, is considered optimum. It is proven by SEM that the uniformly distributed gelatinous products formed in the geopolymer-stabilized soil bind the soil particles tightly. Moreover, the EDS analysis confirms that the gelatinous products are mainly composed of C-S-H gel and sodium-based aluminosilicate (N-A-S-H).

Potential of Soil Stabilization Using Ground Granulated Blast Furnace Slag (GGBFS) and Fly Ash via Geopolymerization Method: A Review

Geopolymers, or also known as alkali-activated binders, have recently emerged as a viable alternative to conventional binders (cement) for soil stabilization. Geopolymers employ alkaline activation of industrial waste to create cementitious products inside treated soils, increasing the clayey soils’ mechanical and physical qualities. This paper aims to review the utilization of fly ash and ground granulated blast furnace slag (GGBFS)-based geopolymers for soil stabilization by enhancing strength. Previous research only used one type of precursor: fly ash or GGBFS, but the strength value obtained did not meet the ASTM D 4609 (<0.8 Mpa) standard required for soil-stabilizing criteria of road construction applications. This current research focused on the combination of two types of precursors, which are fly ash and GGBFS. The findings of an unconfined compressive strength (UCS) test on stabilized soil samples were discussed. Finally, the paper concludes that GGBFS and fly-ash-based geo-polymers for soil stabilization techniques can be successfully used as a binder for soil stabilization. However, additional research is required to meet the requirement of ASTM D 4609 standard in road construction applications, particularly in subgrade layers.

Performance of cement-stabilized weak subgrade for highway embankment construction in Southeast Nigeria

Soils with poor shear strength and high compressibility underlie the wetlands of southern Nigeria. They are susceptible to intolerable settlements and account for greater than 60% of the soils in the region. While requiring embankments for any infrastructure construction, these weak soils pose significant threat to the construction and service life of highway pavements in southeastern Nigeria. Therefore, this research investigates shear strength improvement of a highway embankment’s weak subgrade soil after mass stabilization of soil with 6 and 10% Portland cement. The factor of safety against shear failure of the embankment was analyzed for un-stabilized subgrade and then cement-stabilized subgrade. The analysis was carried out for embankment heights of 4, 5, 6 and 7 m using the limit equilibrium method. Thick soft clayey silt with Cu range of 9 to 15 kPa underlay the embankment, upon improvement, the Cu of 154 and 208 kPa was obtained for 6 and 10% stabilization respectively. The FoS for the embankment on Un-stabilized soil ranged from 0.88 for a 7 m embankment to 1.2 for a 4 m embankment. The FoS after mass stabilization of 1 to 5 m soil ranged between 1.77 and 5.22 for the different embankment heights. Stability was better improved as depth of mass stabilization and cement content increased. A linear relationship was observed to exist between the cement content, strength of the improved soils, stabilization depth and the factor of safety.

Gene-Expression Programming-Based Model for Estimating the Compressive Strength of Cement-Fly Ash Stabilized Soil and Parametric Study

The study aims to develop a reliable model using gene-expression programming (GEP) technique for estimating the unconfined compressive strength (UCS) of soil stabilization by cement and fly ash. The model considered the effects of several parameters, including the fly ash characteristics such as calcium oxide (CaO) content, CaO/SiO2 ratio, and loss of ignition. The research results show that the proposed model demonstrates superior performance with a high correlation coefficient (R > 0.955) and low errors. Therefore, the model could be confidently applied in practice for a variety of fly ash qualities. Besides, the parametric study was conducted to examine the effect of fly ash characteristics on the strength of soil stabilization. The study indicates that if the fly ash contains a high amount of calcium oxide, the strength of fly ash stabilized soil is significant. In addition, fly ash could be used in combination with cement to increase the strength of the mixture. A fly ash replacement ratio is suggested from 0.19 to 0.35, corresponding to the total binder used from 10% to 30%. The research findings could help engineers in optimizing the fly ash proportion and estimating the UCS of soil stabilization by cement and fly ash.