Aggregated understanding of characteristics of wheat straw node and internode with their interfacial bonding mechanisms

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University London.The demand for the efficient utilisation of straw biomass requires detailed analyses of its fundamental chemical structures, morphological complexity, individual cell wall components and the correlation of physicochemical to mechanical properties. The study involved two main areas: understanding the details of microstructure and characterisation/differentiation of properties of various profiled wheat straw. Comprehensive and systematic experimental programmes were therefore designed in order to thoroughly investigate the node and internode of wheat straw with quantitative appraisals and qualitative interpretations. This could contribute towards its valorisation in bio-refinery pathways. The sophisticated morphology of node and internode, inner and outer surface was investigated. It was found that the morphology across node area has a great variety when the longitudinal profile is investigated in the upwards direction to grain head. A 3D image of nodes illustrated the dense core with elliptical shaped rings organised in order to provide the echanical strength to the overall stem. The variation of cell wall composition across wheat straw node and internode showed that node yielded slightly higher Klason lignin, extractives and ash content than internode, which could be related to their morphology, precisely the higher ash and extractives content in the node are explained by thicker epidermis tissue. The physicochemical and mechanical properties of node and internode were differentiated and the effects of a combination of mild physical pre-treatment were monitored. The results indicated: i) the reduction of waxes from the outer surface, ii) significantly lower (P < 0.05) extractives and iii) the dissolution of silicon (Si weight %) on the outer surface of node and internode. The tensile strength of nodes and internodes after pre-treatments also resulted in a significant increase (P < 0.05). The accumulated characteristic data enabled the investigation of interfacial properties and bonding mechanisms of the inner and outer surface of wheat straw with thermosetting resins. Different surface functionalities and anatomical sections, altered the bonding performance, i.e. waxes and silica concentrated on the outer surface inhibited the quality of the interface. Nevertheless, the treatment improved interface (P < 0.05) between resins and the micro-porous surface of wheat straw by causing the microcellular structure of straw to expand and hence inspire the mechanical entanglement on a micro level upon resin solidification.Engineering and Physical Sciences Research (EPSRC

Enhanced Compatibility of Secondary Waste Carbon Fibers through Surface Activation via Nanoceramic Coating in Fiber-Reinforced Cement Mortars

The utilization of waste fibers in the production of reinforced concrete materials offers several advantages, including reducing environmental strain and socio-economic impacts associated with composite waste, as well as enhancing material performance. This study focuses on the development of cementitious mortars using secondary waste carbon fibers, which are by-products derived from the industrial conversion of recycled fibers into woven/non-woven fabrics. The research primarily addresses the challenge of achieving adequate dispersion of these recycled fibers within the matrix due to their agglomerate-like structure. To address this issue, a deagglomeration treatment employing nanoclay conditioning was developed. The functionalization with nanoclay aimed to promote a more uniform distribution of the reinforcement and enhance compatibility with the cementitious matrix. Various fiber weight percentages (ranging from 0.5 w/w% to 1 w/w% relative to the cement binder) were incorporated into the fiber-reinforced mix designs, both with and without nanoceramic treatment. The influence of the reinforcing fibers and the compatibility effects of nanoclay were investigated through a comprehensive experimental analysis that included mechanical characterization and microstructural investigation. The effectiveness of the nanoceramic conditioning was confirmed by a significant increase in flexural strength performance for the sample incorporating 0.75 w/w% of waste fibers, surpassing 76% compared to the control material and exceeding 100% compared to the fiber reinforced mortar incorporating unconditioned carbon fibers. Furthermore, the addition of nanoclay-conditioned carbon fibers positively impacted compression strength performance (+13% as the maximum strength increment for the mortar with 0.75 w/w% of secondary waste carbon fibers) and microstructural characteristics of the samples. However, further investigation is required to address challenges related to the engineering properties of these cementitious composites, particularly with respect to impact resistance and durability properties

Advanced Freeze-Thaw Assessment of Internally Integrated Concrete with Sodium Acetate

A new line of research is presented in this study where sodium acetate is used as a protective material for concrete. A newly developed freeze-thaw method that depends on the alteration of temperature and humidity is introduced in this research to investigate the efficacy of integrating sodium acetate with concrete with different water to cement ratios (w/c). Results from the introduced freeze-thaw method were compared with the outcomes of a standard freeze-thaw testing method. The distressed concrete was tested for water absorption and compressive strength after finishing six months of freeze-thaw testing. Results demonstrated the effectiveness of sodium acetate in protecting concret

Processes and materials used for direct writing technologies:A review

Direct Writing (DW), also known as Robocasting, is an extrusion-based layer-by-layer manufacturing technique suitable for manufacturing complex geometries. Different types of materials such as metals, composites, ceramics, biomaterials, and shape memory alloys can be used for DW. The simplicity and cost-efficiency of DW makes it convenient for different applications, from biomedical to optics. Recent studies on DW show a tendency towards the development of new materials and applications. This represents the necessity of a deep understanding of the principles and parameters of each technique, material, and process challenge. This review highlights the principles of many DW techniques, the recent advancements in material development, applications, process parameters, and challenges in each DW process. Since the quality of the printed parts by DW highly depend on the material extrusion, the focus of this review is mainly on the ceramic extrusion process and its challenges from rheological and material development point of view. This review delivers an insight into DW processes and the challenges to overcome for development of new materials and applications. The main objective of the review is to deliver necessary information for non-specialist and interdisciplinary researchers

Comprehensive Investigation of the Long-term Performance of Internally Integrated Concrete Pavement with Sodium Acetate

The research carried out in this study presents the effectiveness of using sodium acetate as a protective material for concrete pavement. A newly developed freeze-thaw method that depends on the alteration of temperature and humidity is introduced in this research to investigate the efficacy of integrating sodium acetate with concrete with different water to cement ratios (w/c). Results from the introduced freeze-thaw method were compared with the outcomes of a standard freeze-thaw testing method. The distressed concrete was tested for water absorption and compressive strength after finishing six months of freeze-thaw testing. Additionally, the morphology of sodium acetate and its interaction with concrete were investigated by using Scanning Electron Microscope (SEM). Results demonstrated the effectiveness of sodium acetate in protecting concrete

Mechanical and physical characteristics of alkali- activated mortars incorporated with recycled polyvinyl chloride and rubber aggregates

One of the ways to achieving net-zero concept in the construction industry is to use alternatives to Portland cement (OPC) and virgin aggregates for concrete manufacturing. Recycled rubber and polyvinyl chloride (PVC) aggregates in conjunction with low-carbon binders can be potentially utilised to substitute natural sand and reduce the negative environmental impacts of OPC. A replacement of natural sand (up to 70% by volume) in alkali-activated materials (AAMs) with recycled rubber and PVC particles derived from tyre waste and insulation coating of electric wires, respectively, was investigated in this study. The performance of developed AAMs was evaluated using a comprehensive testing program including mechanical, physical and microstructure assessments. AAM composites with PVC and rubber particles outperformed natural aggregate composites in terms of thermal resistivity, water absorption, volume permeability voids (VPV), and high-frequency sound insulation. Results showed that 70% PVC mixture achieved the lowest water absorption rate and thermal conductivity with a reduction of 73% and 20%, respectively, compared to the control mixture. A maximum reduction of 34% in VPV was observed in the 70% rubber mixture when compared to the control mixture. In terms of mechanical properties of waste stream aggregates, PVC outperformed rubber. The results showed that 30% replacement of PVC and rubber would produce composites with 7-day compressive strengths of 35 MPa and 25 MPa, respectively, which can be used to produce high-load bearing structures. The Energy-dispersive X-ray Spectroscopy (EDX) was performed to detect chloride leaching from PVC aggregates, where results indicated that no leaching had occurred after more than 90 days of casting. Regarding the carbon emission, the carbon footprint of AAM composites is decreased by using the polymeric fractions in place of sand. The developed composites of this study can be used safely in non-load bearing structural elements with promising physical and mechanical performance