Lightweight alkali-activated materials and ordinary Portland cement composites using recycled polyvinyl chloride and waste glass aggregates to fully replace natural sand

Data availability: Data will be made available on request.Copyright © 2023 The Authors. Polyvinyl chloride plastic (PVC) and glass waste have proven to be significant environmental concerns considering their restricted reuse and complicated recycling procedures. Glass and PVC waste materials form a substantial portion of total solid wastes that negatively influence the environment. This study aims to fully replace natural sand with recycled PVC and waste glass aggregates in alkali-activated materials (AAMs). A comprehensive testing programme was employed to investigate the effect of 100 % aggregate replacement on the composites’ mechanical performance, water absorption, impact resistance, thermal conductivity, resistance to harsh environments, and microstructural changes. Results revealed that AAMs containing recycled PVC and glass aggregates outperformed their ordinary Portland cement (OPC)-based composite counterparts in terms of mechanical properties, energy absorption, thermal conductivity, and carbon footprint estimation. Although mixtures containing recycled aggregates cannot be deemed for load-bearing applications, these composites exhibited a promising capacity to be used in insulating applications. AAMs containing 100 vol-% PVC aggregates with flexural and compressive strengths of 9 and 11 MPa, respectively, registered the highest energy absorption of about 6 J, three times higher than the AAM control sample, and the lowest thermal conductivity of about 0.5 W/mK, with about 80 % reduction of thermal conductivity compared to the AAM control sample. With the full replacement of PVC and glass aggregates, the most significant decrease in the carbon footprint is achieved for AAM (−352.25 kg CO2-eq) and OPC (−353.94 kg CO2-eq), respectively.DigiMat project, which has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement ID: 101029471

Effect of natural and calcined halloysite clay minerals as low-cost additives on the performance of 3D-printed alkali-activated materials

Crown Copyright © 2022. This study investigates the effects of natural and calcined halloysite clay minerals (“NH” and “CH”, respectively) on the performance of 3D printed alkali-activated materials (AAMs). Halloysite clay minerals are selected as they are low-cost and abundantly available. At first, different characterisation techniques were employed to characterise the NH and CH additives. Mechanical performance, extrusion window, and shape stability of several AAM formulations containing various dosages (0.5 wt% to 5 wt%) of the NH and CH additives were evaluated. The best-performing mixtures in terms of fresh and hardened properties namely, NH-1.5 and CH-1.5 mixtures (containing 1.5 wt% of NH and CH additives, respectively) were then selected for 3D printing. The results showed that the CH-1.5 mixture exhibited enhanced shape stability, buildability, and mechanical properties as compared to the control mixture. The flexural and compressive strengths of 3D printed CH-1.5 samples were 88% and 40%, respectively higher than those of the printed control samples. Using the CH-1.5 mixture, a twisted column with an intricate shape was printed to verify the suitability of the developed CH-modified AAM for the construction of complex structures. This study establishes the use of halloysite clay minerals as low-cost additives for enhancing the mechanical properties and printing performance of AAMs.European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement ID: 101029471; National Science Centre, Poland, within Project No. 2020/39/D/ST8/00975 (SONATA-16)

Durability Enhancement of Concrete with Recycled Concrete Aggregate: The Role of Nano-ZnO

The replacement of virgin aggregate with recycled concrete aggregate (RCA) in concrete mixtures offers an eco-strategy to mitigate the environmental limitations linked with traditional recycling techniques of RCA. However, the inferior properties of RCA, in contrast to virgin aggregate, present an obstacle to efficiently proceeding with this approach. Therefore, the aim of this study is to enhance the characteristics of concrete that contains RCA using nano-ZnO particles. Virgin aggregate was replaced with RCA in 30 wt.% and 50 wt.% ratios, followed by the addition of 0.5 wt.% nano-ZnO. The performance of concrete mixtures was evaluated in terms of their physical, mechanical, and durability properties. The addition of nano-ZnO particles to concrete with RCA resulted in refining its pore structure and reducing its water absorption, where the impermeability of concrete with 30 wt.% and 50 wt.% treated RCA decreased by 14.5% and 18%, respectively. Moreover, nano-ZnO treatment increased the compressive strength of mixtures with 30 wt.% and 50 wt.% RCA by 2.8% and 4%, respectively. All mixtures underwent a reduction in their 28-day compressive strength after exposure to a 5% sulphuric acid solution, where concrete with 30 wt.% and 50 wt.% RCA showed 20.2% and 22.8% strength loss, respectively. However, there was a 17.6% and 19.6% drop in the compressive strength of concrete with 30 wt.% and 50 wt.% RCA and treated with nano-ZnO

Upcycling end-of-life bricks in high-performance one-part alkali-activated materials

One-part alkali-activated materials (AAMs) can preserve natural resources and lower embodied carbon of the built environment by accommodating various wastes, industrial by-products, and end-of-life materials in their composition. This study investigates the feasibility of using end-of-life bricks in two physical states, powder and aggregate, to partially replace fly ash precursor and natural aggregate in AAMs, respectively. The mechanical characteristics, microstructure, water absorption, freeze-thaw and fire resistance of the modified AAMs were evaluated. The effect of adding different ratios of nano graphite platelets was also investigated. Results showed that brick-based one-part AAMs can achieve mechanical properties, pore structure, water absorption and freeze-thaw resistance comparable to fly ash-based AAM while having 65% better fire resistivity. Incorporating bricks as aggregate resulted in a maximum improvement of 17% and 27% in the AAMs' compressive and flexural strength levels, respectively, and a general enhancement in the freeze-thaw resistance with showing no reduction in compressive strength after exposure to elevated temperature. Incorporating 0.1 wt% nano-graphite further enhanced flexural strength by 30%, decreased water absorption by 18% and improved freeze-thaw resistance compared to the mix without nano-graphite. Moreover, adding up to 0.5% nano-graphite enhanced the fire resistivity of the composite, allowing it to exhibit 19% better strength performance than before exposure

High performance cementitious nanocomposites: the effectiveness of nano-Graphite (nG)

The reduction of CO2 emissions is one of the main challenges of 21st century. The development of new multifunctional construction materials is urgent and compulsory. The privilege mechanical, thermal and electrical behavior of Graphene-Based Materials (GBMs) was found to be potentially extremely efficacious to modify the cementitious materials from the nano- to micro-scale. Thermally and electrically conductive cement nanocomposites with superior mechanical properties and improved durability might be used for inductive wireless charging roads, high speed-train lines, under floor heating, deicing roads and high voltage transmission pipelines. However, presently, the actual effectiveness of a chosen nanocomposite formulation remains unpredictable. In this study an extensive experimental campaign has been conducted on mortars modified with nano-Graphite (nG) aimed to assess the properties of the resulting nanocomposites in terms of density, microstructure, mechanical (i.e.flexural and compressive strength) and physical properties (i.e. thermal and electrical conductivity, damping ratio), and permeability (i.e .initial surface absorption, water contact angle, volume of permeable voids and chloride ion diffusion). Premixed mortars have been modified with different dosages of commercial nG (i.e.0.01, 0.1,or 0.2% by weight of cement) dry powder. The rheological behavior of the fresh admixtures has been investigated; specimens were casted in bars and hardened in water for 7, 14 or 28 days. At 28 days all samples showed enhanced density (i.e. up to 16 %) and mechanical properties (i.e. up to 30%) combined to a remarkable decreased permeability. The lowest dosage of nG (i.e. 0.01% by weight of cement) resulted in cement nanocomposites with the highest increase in damping ratio, electrical and thermal conductivity, 68%, 30% and 55% respectively