813 research outputs found
Dataset for publication Chougan M., Ghaffar S.H., Nematollahi B., Sikora P., Dorn T., Stephan D., Albar A., Al-Kheeta M.J. Effect of natural and calcined halloysite clay minerals as low-cost additives on the performance of 3D-printed alkali-activated materials. Materials and Design (2022) 223, 111183
No full textOpen dataset for publication Chougan M., Ghaffar S.H., Nematollahi B., Sikora P., Dorn T., Stephan D., Albar A., Al-Kheeta M.J. Effect of natural and calcined halloysite clay minerals as low-cost additives on the performance of 3D-printed alkali-activated materials. Materials and Design (2022) 223, 111183. https://doi.org/10.1016/j.matdes.2022.111183
File 1 - FTIR - data of raw and calcined material - *.opj (Origin)
File 2 - Mechanical performance print vs cast - *.opj (Origin)
File 3 - Mechanical performance - *.opj (Origin)
File 4 - TGA and XRD - data of raw and calcined material - *.opjuSeyed Hamidreza Ghaffar and Mehdi Chougan would like to acknowledge the funding received from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement ID: 101029471. Pawel Sikora acknowledges funds received from the National Science Centre, Poland, within Project No. 2020/39/D/ST8/00975 (SONATA-16)
Composite alkali-activated materials with waste tire rubber designed for additive manufacturing: an eco-sustainable and energy saving approach
No full textThere is an increasing trend in research projects and case studies to demonstrate the potential of Additive Manufacturing (AM) with concrete, better known as 3D concrete printing. Like ordinary construction, the latest upgrades on this topic are strongly focused towards improving eco-sustainability in terms of low-carbon materials. Low-carbon binders’ alternative to Portland cement and the utilisation of selected waste materials in place to virgin aggregates has high potential in fulfilling the sustainable development goals. In this paper, an experimental study was performed by incorporating ground waste tire rubber aggregates of different size gradation (0–1 mm and 1–3 mm) and replacement levels (50 v/v% and 100 v/v%) in a “greener” alkali-activated mix designed for 3D printing applications. First, the experimental program involved the optimization of mix design rheology and printing parameters to successfully integrate rubber aggregates into the printable alkali-activated mixtures. Then, a comprehensive characterization, including static mechanical testing, dynamic thermo-mechanical analysis, thermal conductivity testing, and acoustic insulation measurements was conducted. Comparison with identical Portland-based rubberized formulations designed for AM revealed better mechanical isotropy, flexural strength, thermo-mechanical behaviour, heat insulation, and high-frequency acoustic insulation for alkali-activated composites. The influence of rubber aggregate size on the fresh and hardened state behaviour of the mixes was also studied and discussed. Keeping the losses in mechanical strength restrained, the rubberized composites designed in this study have demonstrated significant thermal and acoustic insulation properties that are desired for energy-saving applications in buildings. The research verified the practicability of using waste aggregates in low-carbon binders for sustainable lightweight and thermo-acoustically effective applications, establishing an attractive starting point to address future research on material optimization for practical purposes
Graphene-engineered cementitious materials: a systematic experimental study = Materiali cementizi ingegnerizzati con grafene: uno studio sperimentale sistematico
No full textCement-based composite materials (CBCMs), including mortar and concrete, are the most common and widely used materials in construction. Ordinary Portland cement (OPC) is known as a principal constituent of CBCMs acting as a binder for the other aggregates presented in the CBCMs. The quasi-brittle behavior, low toughness, and poor tensile strength of these materials are of major concerns since they are responsible for poor durability and high maintenance costs. In the last decade, on the way of the rapidly growing interest toward nanotechnology, several researchers proposed an approach based on the interaction at the nanoscale level between the cement matrix and selected nanostructures that might result in macroscopical advantageous effects. For this purpose, graphene-based materials, including graphene nanoplatelets (GNPs), nano graphite platelets (NGPs), and graphene oxide (GO), have been proposed to offset the brittleness of the CBCMs.
The main objective of this PhD research work is to develop graphene-based cementitious composites (GBCCs) using low cost and commercially available graphene nanoplatelets (GNPs), nano graphite platelets (NGPs), and graphene oxide (GO). The project further investigated the effect of these nanomaterials on the rheology, microstructure, mechanical, and physical properties of a commercial premixed mortar at both early (7 and 14 days) and later ages (28 days). A full set of graphene engineered cementitious composites has been prepared using EN-998-2 premixed mortar as matrices, two GNPs water pastes, one NGPs powder, and two GO (one water suspension and one powder). The actual impact of the different GBMs and their dosage (i.e.0.01, 0.1, or 0.2% by weight of cement) was assessed in terms of rheology of fresh admixtures along with density, microstructural features, permeability (i.e .initial surface absorption, water contact angle, volume of permeable voids and chloride ion diffusion), physical properties (i.e. thermal and electrical conductivity, damping ratio) and mechanical properties (i.e. flexural and compressive strength) of the hardened nanocomposites.
It is concluded through various characterization and experimental campaigns that all GBMs regulated the microstructure of the cementitious composites along with the densification and influenced the permeability, physical, and mechanical properties of GBCCs uniquely. A significant improvement in the permeability, physical, and mechanical properties of newly developed GBCCs has been achieved, and that could be due to the generation of distinctive microstructure generated by the pozzolanic behavior of these nanofillers. Based on the observations of test results and comprehensive characterization, the possible mechanisms of permeability barriers, conductive pathways, and microstructure developments of GBCCs have been established
Enhanced Compatibility of Secondary Waste Carbon Fibers through Surface Activation via Nanoceramic Coating in Fiber-Reinforced Cement Mortars
No full textThe 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.</p
Eco-sustainable approach for cementitious mix construction materials: A preliminary comparison between geopolymer and cement based matrices incorporating Tire recycled rubber
No full textSustainability concept in the cement and concrete industry involves various environmental and
socio-economic aspects such as, low energy consumption, CO2 emission reduction, natural resources preservation, and recyclability [1]. “Green” concrete technology, has the potential for
eco-friendly development, where industrial waste or low-carbon binders can reduce consumption
of Portland cement and natural resource, leading to less environment pollutions [2]. This work
presents an experimental study for the comparison between geopolymer matrix and a traditional cementitious matrix (i.e. Portland cement) filled with rubber particles, deriving from end-of-life tires,
as replacement of raw mineral aggregates. Rubberized geopolymers can be attractive solutions to
reduce dangerous emissions and promote the clean disposal of waste tires [3]. Rubber-modification
could confer to the material specific performances in terms of lightweight, durability, deformability,
and thermo-acoustic insulation properties [4]. To explore the potential of rubber-geopolymer
compounds for the construction sector, an experimental comparative study with rubber-Portland
mortars (Figure) was performed. Preliminary investigations were conducted on rubber-cement
samples obtained by varying the binder, the sand-rubber replacement ratio, and the rubber particle
size
Mechanical and physical characteristics of alkali- activated mortars incorporated with recycled polyvinyl chloride and rubber aggregates
No full textOne 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
Application of Analog Adaptive Filters for Dynamic Sensor Compensation
No full textThis paper investigates the application of analog adaptive techniques to the area of dynamic sensor compensation, of which there is little reported work in the literature. The case is illustrated by showing how the response of a load cell can be improved to speed up the process of measurement. The load cell is a sensor with an oscillatory output in which the measurand contributes to the response parameters. Thus, a compensation filter needs to track variation in measurand whereas a simple, fixed filter is only valid at one specific load value. To facilitate this investigation, computer models for the load cell and the adaptive compensation filter have been developed. To allow a practical implementation of the adaptive techniques, a novel piecewise linearization technique is proposed in order to vary a floating voltage-controlled resistor in a linear manner over a wide range. Simulation and practical results are presented, thus demonstrating the effectiveness of the proposed techniques
The influence of nano-additives in strengthening mechanical performance of 3D printed multi-binder geopolymer composites
No full textThe weak mechanical properties the 3D printed parts can limit the competence of this technology when compared to conventionally cast-in-mold cementitious composites structures. However, experimental results in this study showed that the incorporation of nano additives could improve the mechanical property of printed structures. Six geopolymeric mixtures were designed and tested for their flow-ability, shape stability, buildability and mechanical performance. Different dosage of nano graphite platelets (NGPs) ranging from 0.1% to 1%, by the weight of geopolymer, were incorporated to the best performing geopolymer. The 3D printed geopolymer with 1% of NGPs increased the flexural strength by 89% and 46% compared to the same 3D printed and casted geopolymer without any NGPs, respectively. The same increase for compressive strength was 28% and 12%. Moreover, the geopolymer mix containing 1% of NGPs demonstrated the best shape retention and buildability
Digital fabrication and integration of Material reuse for environmentally friendly cementitious composites building blocks
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