Strength and mechanical behavior of short polypropylene fiber reinforced and cement stabilized clayey soil

A new type of geopolymer composite was synthesized from two industrial wastes, red mud (RM) and rice husk ash (RHA), at varying mixing ratios of raw materials and the resulting products characterized by mechanical compression testing, X-ray diffraction, and scanning electron microscopy to assess their mechanical properties, microstructure, and geopolymerization reactions. Prolonged curing significantly increases the compressive strength and Young’s modulus, but reduces the ductility. Higher RHA/RM ratios generally lead to higher strength, stiffness, and ductility, but excessive RHA may cause the opposite effect. The compressive strength ranges from 3.2 to 20.5 MPa for the synthesized geopolymers with nominal Si/Al ratios of 1.68–3.35. Microstructural and compositional analyses showed that the final products are mainly composed of amorphous geopolymer binder with both inherited and neoformed crystalline phases as fillers, rendering the composites very complex composition and highly variable mechanical properties. Uncertainties in the composition, microstructure, the extent of RHA dissolution, and side reactions may be potential barriers for the practical application of the RM–RHA based geopolymers as a construction material.

Synthesis and characterization of red mud and rice husk ash-based geopolymer composites

Biomineralization is a naturally occurring process in living organisms. In this review, we discuss microbially induced calcium carbonate precipitation (MICP) in detail. In the MICP process, urease plays a major role in urea hydrolysis by a wide variety of microorganisms capable of producing high levels of urease. We also elaborate on the different polymorphs and the role of calcium in the formation of calcite crystal structures using various calcium sources. Additionally, the environmental factors affecting the production of urease and carbonate precipitation are discussed. This MICP is a promising, eco-friendly alternative approach to conventional and current remediation technologies to solve environmental problems in multidisciplinary fields. Multiple applications of MICP such as removal of heavy metals and radionuclides, improve the quality of construction materials and sequestration of atmospheric CO2 are discussed. In addition, we discuss other applications such as removal of calcium ions, PCBs and use of filler in rubber and plastics and fluorescent particles in stationary ink and stationary markers. MICP technology has become an efficient aspect of multidisciplinary fields. This report not only highlights the major strengths of MICP, but also discusses the limitations to application of this technology on a commercial scale.

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Formations of calcium carbonate minerals by bacteria and its multiple applications.

Production of rice husk ash for use in concrete as a supplementary cementitious material

Soil stabilization is a technique to improve the engineering and geotechnical properties of soils such as mechanical strength, permeability, compressibility, durability and plasticity. Much has been learned about soil stabilization techniques and additives over the past century. The state of the practice in stabilization techniques and challenges is presented with a discussion. Moreover, available studies regarding the effects of various types of stabilizing agents on the engineering and geotechnical properties of stabilized soils are reviewed here. These stabilizing agents include both calcium-based and non-calcium-based additives. Eco-friendly additives as alternative materials to conventional stabilizing agents are also discussed in this paper. In addition, the problems associated with the presence of disruptive salts and sulfate as well as the techniques to overcome these problems in soil stabilization projects are reviewed.

Soil and clay stabilization with calcium- and non-calcium-based additives: A state-of-the-art review of challenges, approaches and techniques

Stabilization of residual soil with rice husk ash and cement

The chemical stabilisation of soils was studied by using cement and rice husk ash. Three types of soils, residual soils, kaolinite and bentonite, were used in the study. The experimental study included the evaluation of the main index properties of the soil and compaction, along with a characterisation of the materials through X-Ray diffraction. Test results show that both cement and rice husk ash reduces the plasticity of soils. In term of compactability, addition of rice husk ash and cement decreases the maximum dry density and increases the optimum moisture content. From the viewpoint of plasticity, compaction characteristics, and economy, addition of 6 - 8 percent cement and 10 - 15 percent rice husk ash are recommended as an optimum amount.

E.A. Basha

Papers

Stabilization of residual soil with rice husk ash and cement

Effect of the cement-rice husk ash on the plasticity and compaction of soil