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

Development of low absorption and high-resistant sodium acetate concrete for severe environmental conditions

This research presents new insight on the performance of concrete when integrated with sodium acetateand cured under extremely harsh environmental conditions: freezing temperature of 25°C and hottemperature of 60°C. Mechanical properties, water absorption, microstructural analysis and interactionmechanism of concrete and sodium acetate were evaluated by conducting the compressive strength test,Initial Surface Absorption Test (ISAT), Scanning Electron Microscope (SEM) analysis and Fourier-transform Infrared Spectroscopy (FTIR) analysis. Despite the harsh curing conditions, results showedan enhancement of 64% in compressive strength when 4% (based on the weight of cement) sodium acet-ate is incorporated within concrete with w/c ratio of 0.32 and cured under temperature of 60°C. Also,water absorption was observed to decrease by more than 79% when 2% sodium acetate is added to con-crete with w/c ratio of 0.32. SEM and FTIR analyses revealed the formation, high distribution and strongbonding of sodium acetate crystals within the concrete’s micropores

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

Microstructural, Mechanical and Physical Assessment of Portland Cement Concrete Pavement Modified by Sodium Acetate under Various Curing Conditions

Portland Cement Concrete (PCC) pavement was studied with incorporation of an environmentally friendly eco-additive, sodium acetate (C2H3NaO2). This additive was added to PCC pavement in three different percentages of 2%, 4% and 6% of binder weight. For a comprehensive elucidation of the eco-additive incorporation on the performance of PCC pavement, casted samples were cured in three different environments, namely: water, outdoors and pond water. Water absorption tests, flexural and compressive strength tests after 7 and 28 days of curing were conducted and results compared with the control samples without any addition of sodium acetate. Results demonstrated a significant improvement in the impermeability, compressive strength and flexural strength of PCC pavement when sodium acetate concrete is cured in a water bath and outdoors. However, no/little improvement in the impermeability, compressive strength and flexural strength was observed in sodium acetate samples that were cured in pond water. Microstructural analysis of treated samples by using scanning electron microscopy (SEM) illustrated the strengthening effect that sodium acetate provides to the pore structure of concrete pavement

Alkali activated materials with recycled unplasticised polyvinyl chloride aggregates for sand replacement

Incorporating recycled Unplasticised Polyvinyl Chloride (UPVC) aggregates into Alkali Activated Materials (AAMs) presents a promising approach to alleviate the environmental drawbacks associated with conventional recycling methods for UPVC. The distinctive characteristics of UPVC aggregates, as compared to natural sand, pose a challenge in the pursuit of enhancing the mechanical properties of composites. This research aims to achieve net-zero goals and promote circular economy principles by replacing traditional Portland cement (OPC) with low-carbon AAMs and natural aggregates with recycled unplasticised polyvinyl chloride (UPVC) which, accounts for 12% of global plastic production. Coarse and fine UPVC aggregates, measuring 4–6 mm and 0–2 mm, respectively, were incorporated into AAMs. An extensive array of tests was performed to assess their environmental benefits and overall performance enhancements. The results unveiled notable advantages in terms of thermal resistivity and resistance to chloride penetration in the UPVC-infused AAMs. Notably, mixtures containing 100% fine UPVC aggregates exhibited a remarkable 70% reduction in thermal conductivity (0.465 W/mk) when compared to the control. In mechanical assessments, composites containing fine UPVC aggregates surpassed those with coarse UPVC aggregates, showcasing promise for load-bearing applications. Substituting 30% of both fine and coarse UPVC aggregates with sand yielded impressive 7-day compressive strengths of 41 MPa and 35 MPa, respectively. Moreover, the utilisation of energy-dispersive X-ray spectroscopy confirmed the absence of chloride leaching after three months. The incorporation of UPVC waste aggregates led to a significant reduction in the carbon footprint of the tested AAMs. In conclusion, these composites offer an appealing and sustainable solution for both load-bearing and non-load-bearing structures

Extra-low dosage graphene oxide cementitious nanocomposites: a nano- to macroscale approach

The impact of extra-low dosage (0.01% by weight of cement) Graphene Oxide (GO) on the properties of fresh and hardened nanocomposites was assessed. The use of a minimum amount of 2-D nanofiller would minimize costs and sustainability issues, therefore encouraging the market uptake of nanoengineered cement-based materials. GO was characterized by X-ray Photoelectron Spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), and Raman spectroscopy. GO consisted of stacked sheets up to 600 nm × 800 nm wide and 2 nm thick, oxygen content 31 at%. The impact of GO on the fresh admixtures was evaluated by rheology, flowability, and workability measurements. GO-modified samples were characterized by density measurements, Scanning Electron Microscopy (SEM) analysis, and compression and bending tests. Permeability was investigated using the boiling-water saturation technique, salt ponding test, and Initial Surface Absorption Test (ISAT). At 28 days, GO-nanocomposite exhibited increased density (+14%), improved compressive and flexural strength (+29% and +13%, respectively), and decreased permeability compared to the control sample. The strengthening effect dominated over the adverse effects associated with the worsening of the fresh properties; reduced permeability was mainly attributed to the refining of the pore network induced by the presence of GO

A novel approach of introducing crystalline protection material and curing agent in fresh concrete for enhancing hydrophobicity

A new line of research to enhance the performance of concrete under adverse (harsh) and normal (air cured) curing conditions is presented. A crystallising hydrophobic admixture and curing agents were added to fresh concrete to improve its resistance against severe environmental conditions. A two-stage approach was pursued by adding the crystallising admixture to fresh concrete followed by curing agents, in a wax and liquid forms, in a separate application process, followed by exposing concrete to normal and adverse curing conditions. Results obtained suggests that protecting concrete with the crystallising admixture followed by applying wax based curing agent improves concrete strength and its resistance to water ingress than concrete cured with the liquid curing agent. When following the crystallising-wax treating system under adverse curing conditions, a more conserved strength was noticed compared to that produced by the crystallising-liquid system. Using the liquid curing agent in concrete with high water to cement ratio (w/c) has increased the cracks in the internal structure, while water permeability has decreased, either under normal curing conditions or adverse conditions. Following this protection-curing system in industry would resolve the problem of applying protection on wet surfaces and increase concrete’s resistance to deterioration. A microscopic study of the crystallising material was attained with a Scanning Electron Microscope (SEM) to check crystal growth with time