Microstructural design of high performance natural fibre-nanoclay-cement nanocomposites

In this thesis, a novel approach has been used to provide beneficial insights for the development of new ‘environmental-friendly nanomaterials’, especially for building applications. This new approach includes the combination of thermal pre-treatment of nanoclay (i.e., producing calcined nanoclay) and chemical pre-treatment of natural fibre surfaces, to improve the microstructure, mechanical, physical and thermal properties, as well as the durability of hemp fibre-reinforced cement composites

Characteristics of nanoclay and calcined nanoclay-cement nanocomposites

The influence of nanoclay (NC) and calcined nanoclay (CNC) on the mechanical and thermal properties of cement nano-composites presented. Calcined nanoclay is prepared by heating nanoclay (Cloisite 30B) at 900 °C for 2 h. Characterisation of microstructure is investigated using Quantitative X-ray Diffraction Analysis (QXDA) and High Resolution Transmission Electron Microscopy (HRTEM). Estimation of Ca(OH)<inf>2</inf> content in the cement nanocomposite is studied by the combination of QXDA and thermogravimetry analysis (TGA) techniques. Results showed that the mechanical and thermal properties of the cement nanocomposites are improved as a result of NC and CNC addition. An optimum replacement of ordinary Portland cement with 1 wt% CNC is observed through reduced porosity and water absorption as well as increased density, compressive strength, flexural strength, fracture toughness, impact strength, hardness and thermal stability of cement nanocomposites. The microstructural analyses from QXRA and SEM indicate that the CNC acted not only as a filler to improve the microstructure, but also as the activator to support the pozzolanic reaction. Cost-benefit analysis indicates that nanoparticles are expensive but from economic point of view nanoclay is used in very small amount (i.e. 1 wt. %) in cementitious materials. As a result nanoclay does not add any significant cost but improves the mechanical properties significantly

Application of machine learning algorithms to evaluate the influence of various parameters on the flexural strength of ultra-high-performance concrete

The effect of various parameters on the flexural strength (FS) of ultra-high-performance concrete (UHPC) is an intricate mechanism due to the involvement of several inter-dependent raw ingredients. In this digital era, novel artificial intelligence (AI) approaches, especially machine learning (ML) techniques, are gaining popularity for predicting the properties of concrete composites due to their better precision than typical regression models. In addition, the developed ML models in the literature for FS of UHPC are minimal, with limited input parameters. Hence, this research aims to predict the FS of UHPC considering extensive input parameters (21) and evaluate each their effect on its strength by applying advanced ML approaches. Consequently, this paper involves the application of ML approaches, i.e., Support Vector Machine (SVM), Multi-Layer Perceptron (MLP), and Gradient Boosting (GB), to predict the FS of UHPC. The GB approach is more effective in predicting the FS of UHPC precisely than the SVM and MLP algorithms, as evident from the outcomes of the current study. The ensembled GB model determination coefficient (R2) is 0.91, higher than individual SVM with 0.75 and individual MLP with 0.71. Moreover, the precision of applied models is validated by employing the k-fold cross-validation technique. The validity of algorithms is ensured by statistical means, i.e., mean absolute error and root mean square errors. The exploration of input parameters (raw materials) impact on FS of UHPC is also made with the help of SHAP analysis. It is revealed from the SHAP analysis that the steel fiber content feature has the highest influence on the FS of UHPC

Spontaneous Rupture of Malarial Spleen: Report of Two Cases

Malaria is endemic in many tropical and subtropical regions of the world, including Saudi Arabia. The infection has serious consequences in those residing in non endemic regions on travelling to endemic areas, due to lack of immunity to the parasite. In this report, we describe the clinical course of two patients who travelled to a malaria endemic area. Both contracted the infection and presented with splenic rupture. They received splenectomy in addition to the appropriate antimalarial medications, with successful outcome

Characteristics of nanoclay and calcined nanoclay-cement nanomatrices by combination of QXDA and TGA techniques

The influence of nanoclay (NC) and calcined nanoclay (CNC) on the mechanical and thermal properties of cement nano-matrices presented. Calcined nanoclay is prepared by heating nanoclay (Cloisite 30B) at 900° C for 2h. Estimation of Ca(OH)2 content in the cement nanomatrix is studied by the combination of Quantitative X-ray Diffraction Analysis (QXDA) and thermogravimetry analysis (TGA) techniques. Results showed that the microstructure and compressive strength of the cement nano-matrices are improved as a result of NC and CNC addition. An optimum replacement of ordinary Portland cement with 1 wt% CNC is observed through decreased the porosity and increased compressive strength of cement nano-matrices. Cost-benefit analysis indicates that nanoparticles are expensive but from economic point of view nanoclay is used in very small amount (i.e. 1 wt. %) in cementitious materials. As a result nanoclay does not add any significant cost but improves the mechanical properties significantly

Evaluation of shear strength parameters of sustainable utilization of scrap tires derived geo-materials for civil engineering applications

The devastation caused by the illegal dumping and burning of tires has been staggering. In civil engineering, using tires engineering properties has become a major concern. For this investigation, the research used locally sourced tire chips and sand. Using tire chips sand as an alternative backfill material requires less pressure and has more improved properties than traditional backfill. Four specimens were utilized in this experiment: pure sand and sand mixtures containing 20%, 30%, and 40% tire chips, respectively. Both the Direct Shear and Triaxial Apparatus, two of the most important geotechnical tools, were used to compare and evaluate the shear properties of soil and sand tire chips. 50, 100, and 150 kPa Confining pressure and normal stress have been utilized to maintain a consistent stress level. Direct shear apparatus had a circular shape with an area of 16.62 cm2 and Triaxial shear apparatus had a height of 7.2 cm and a diameter of 3.2 cm. The stress-strain behavior of both apparatuses under ordinary loading and deviatoric stress was reported. The angles of internal friction (Φ′) and cohesion (c′) were measured for both equipment and specimens with and without tire chips, and the failure planes for direct shear and triaxial tests were reported. In both the direct and triaxial shear tests, 30% of the tire chips sand exhibit the best results, respectively. The addition of tire chips may significantly improve the toughness of the soil

The effect of using nano agriculture wastes on microstructure and electrochemical performance of ultra-high-performance fiber reinforced self-compacting concrete under normal and acceleration conditions

This research investigates the effect of using nano agriculture waste as a partial substitute to solve increased climatic concerns in addition to producing modern ultra-high-performance fiber reinforced self-compacting concrete (UHPFC-SCC). Three types of nano materials have been incorporated, namely nano sugar cane bagasse ash (NSCBA), nano cotton stalk ash (NCSA), and nano rice straw ash (NRSA) with dosages of 1%, 2%, and 3%, respectively. Fresh concrete properties have been investigated via flow and V-funnel tests while compressive strength was evaluated up to 90 days. X-ray diffraction (XRD) analysis, Raman spectroscopy analysis and scanning electron microscopy (SEM) alongside energy dispersive spectroscopy (EDS) was performed to compliment the strength data. Finally, electrochemical measurements including linear polarization (LPR), open circuit potential (OCP) and impedance spectroscopy were investigated at normal and accelerated corrosion conditions on HSS (high strength steel Gr 60). Results demonstrate that compressive strength improved in the range of 18%− 21% between 28 and 90 days using 3% NSCBA, 3% NRSA or 1% NCSA. This is attributed to the facts that optimum dosage of nano wastes results in densification of the UHPFC-SCC matrix and strength magnitude depended on intertwining of high Ca/Si molar content in the range of 3.14–7.1 compared to 0.52 observed in the control mix (EDS analysis). Further, electrochemical measurements revealed that nano materials improved the charge transfer resistance and bulk resistance of HSS interface as well as retarded the flow of electrons between anode and cathode sites consequently limited the propagation of corrosion

A Review on Sustainable Concrete with the Partially Substitutions of Silica Fume as a Cementitious Material

Self-compacting concrete (SCC) uses a lot of natural resources, much like regular concrete, which results in unsustainable construction. Even though silica fume (SF) and other secondary cementitious materials are the subjects of a lot of studies, to determine the past, present, and future direction of research, information must first be reviewed. This paper compiles data on SSC with SF substations. Slump flow, slump T50, L-box, and V-funnel tests were used to investigate fresh SCC properties, such as filling and passing capabilities. Mechanical properties were examined using compressive, tensile, and flexure strength, while the durability characteristics of SCC were examined through water absorption, porosity, sorptivity, and chloride resistance. The internal structure of SCC, with and without SF, is reviewed through scan electronic microscopy (SEM). The results indicate that SF lacked the filling and passing ability of SCC, but is still within the limit defined by the technical specification for SCC. However, the study suggests a larger dosage of plasticizer for a higher dose of SF. Improvements in SCC’s strength and durability were also seen; however, greater doses had a negative impact on these attributes due to an absence of flowability. Researchers recommended the ideal SF dosage ranges from 10 to 15% by volume of cement. The assessment also reveals research gaps that need to be addressed