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Waste carbon fibers as reinforcing elements in construction materials have recently gained increasing interest from researchers, providing outstanding strength performance and a lower environmental footprint compared to virgin fibers. Combination with cement-free binders, namely alkali-activated materials, is becoming increasingly important for sustainable development in the construction industry. This paper presents results relating to the potential use of waste carbon fibers in alkali-activated mortars. The waste carbon fiber fraction utilized in this research is difficult to integrate as reinforcement in ceramic–cementitious matrices due to its agglomerated form and chemical inertness. For this reason, a nanoceramic coating pretreatment based on nanoclay has been implemented to attempt improvements in terms of deagglomeration, dispersibility, and compatibility with alkali-activated materials. After chemical–physical and microstructural analysis on the nanoclay-plated fibers (including X-ray diffraction, IR spectroscopy, contact angle measurements, and electron microscopy) mortars were produced with four different dosages of treated and untreated waste fibers (0.25 wt.%, 0.5 wt.%, 0.75 wt.%, and 1 wt.%). Mechanical tests and fractographic investigations were then performed. The nanoclay coating interacts compatibly with the waste carbon fibers and increases their degree of hydrophilicity to improve their deagglomeration and dispersion. Compared to the samples incorporating as-received fillers, the addition of nanoclay-coated fibers improved the strength behavior of the mortars, recording a maximum increase in flexural strength of 19% for a fiber content of 0.25 wt.%. This formulation is the only one providing an improvement in mechanical behavior compared to unreinforced mortar. Indeed, as the fibrous reinforcement content increases, the effect of the nanoclay is attenuated by mitigating the improvement in mechanical performance.

Utilising recycled brick aggregate in cementitious mixtures can decrease the overdependency on limited natural resources and improve the sustainability of concrete. This paper presents a potential solution to lower the amount of waste being landfilled and increase the sustainability of 3D concrete printing technology by combining low-carbon ternary blended cement with recycled aggregates. Hence, the effect of incorporating two types of recycled brick aggregate - clay brick (CBA) and engineering brick (EBA) on the properties of 3D printable ternary blended cement were investigated. The natural aggregate in a pre-existing 3D printable blend was substituted by up to 50 wt.-% with two varieties of recycled brick aggregates available throughout Europe. The recycled brick aggregates underwent characterisation to determine their properties. The fresh property evaluation using the green strength test was used to assess the effect of aggregate replacements on the mixture's shape stability. The mechanical performance of mixtures containing CBA and EBA, both cast and 3D printable mixes, was evaluated and compared to that of the control sample. The results indicated that incorporating recycled brick aggregate enhances green strength and Young's modulus significantly. Mechanical strength performance showed significant enhancement when incorporating RBA, which reached up to 67% and 55% for both cast and 3D printing methods, respectively. The suitability of the developed mix formulations for 3D printing was assessed by printing cylindrical objects.

This paper presents the impact of incorporating carbon nanotubes (CNTs) into the 3D printing of cementitious materials, along with the effective dispersion of CNTs. Compared to the control mix, adding CNTs with superplasticizer significantly enhanced the printing quality by reducing the error in height of two-layers from 38% to 30% and an 81% enhancement in the buildability. Moreover, rheology properties revealed shear-thinning behaviour with lower viscosity, resulting in improved flowability. The progressive increase in CNT concentrations up to 0.2% yielded a noteworthy improvement in the mechanical properties. At 28 days, the incorporation of 0.2% CNTs resulted in a significant increase in the flexural strength, compressive strength, and Young's modulus by 99%, 72%, and 43%, respectively, compared to the mix containing silica fume. Microstructural investigation of the CNT-cement matrix revealed nanoscale crack bridges formed by CNTs, reinforcing the cementitious material and improving its mechanical properties.

This study explores the potential of waste brick and geo-cement aggregates as substitutes for natural sand in alkali-activated materials (AAMs) for mortar production. With a focus on achieving net-zero construction and mitigating environmental impact, the study replaces Portland Cement (OPC) and virgin aggregates with waste materials and by-products. The investigation evaluates the substitution of sand (up to 100 % by weight) in AAMs with waste brick aggregates (WBA) and waste geo-cement aggregates (WGA) obtained from demolished construction and research lab waste, respectively. The research methodology involves assessing mechanical, durability, and microstructure properties to assess the performance of the developed AAMs with waste aggregates. Notably, AAM composites containing waste brick and geo-cement aggregates surpass natural aggregate composites in terms of mechanical strength, water absorption, freeze-thaw resistance, acid ingress, and chloride attack. The 7-day 50 % waste brick mixture achieved a maximum compressive strength of 61 MPa, while a 70 % waste geo-cement mortar mixture attained a maximum flexural strength of 12 MPa. Combinations, whether comprising waste brick or geo-cement mortar aggregates, demonstrate compressive strengths well over 40 MPa, rendering them suitable for heavy load-bearing structures. The 50 % waste geo-cement mortar mixture stands out with the lowest water absorption rate of 6 % and the least compressive strength loss of 13 % after the freeze-thaw test, with reductions of 6 % and 18 %, respectively, compared to the control. Additionally, 100 % waste brick AAMs exhibit the lowest compressive strength loss after chloride and acid attack tests, with reductions of 13 % and 2.5 %, respectively. When compared to all other mixtures, the 50 % waste brick aggregates mortar mixture obtained the best overall performance. The composites developed in this study affirm their suitability for use in heavy-load structural components, showcasing favourable mechanical and durable properties. These findings underscore the need for additional exploration in this direction to advance sustainable construction practices.

This study investigates the printability of one-part brick powder-based alkali-activated materials (AAMs) containing end-of-life brick particles as aggregate. The novel formulation showcases promise for 3D printing of small to medium-sized building blocks, reminiscent of a Lego-type system, capitalising on the rapid setting time inherent to one-part AAMs. The effect of replacing up to 50% by weight of natural aggregate with brick aggregate on the fresh properties of brick powder-based alkali-activated materials, including slump measurements, flowability, setting time, open time and green strength were investigated. In addition, the flexural and compressive strength of the 3D printed mixtures were determined and compared to those of cast specimens. The buildability and microstructure were also examined. The results showed that incorporating high porous and rough brick aggregate to replace natural aggregate is beneficial in improving the mixtures’ slump, which is essential for retaining the shape of the printed layers. However, it decreased the flowability, setting time and open time when incorporating up to 50% brick aggregate. The green, flexural and compressive strengths were increased with increasing brick aggregate content up to 50% due to enhancing interlock between the binder and brick aggregate, and the better compaction because of the absorption properties of brick aggregate. The mechanical results revealed the better performance of 3D printed specimens than the cast specimens. Moreover, the incorporation of brick aggregate enhanced the buildability of the mixtures showcasing their potential in advancing 3D printing capabilities.

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.

There 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.

This study set out to examine the unconventional use of raw oil shale (OS) as fine aggregate in concrete instead of its traditional utilisation as a pollutant energy source aiming to hinder the depletion of natural resources. Oil shale particles have been used to replace sand in concrete with 30 wt.-% and 50 wt.-% ratios. Part of the used OS particles was treated with silane prior to their addition in concrete. The fresh, mechanical, and durability properties, along with the micro-properties and surface chemistry of mixtures, were analysed by running the slump, compressive strength, permeability, scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR) tests, respectively. Five concrete mixtures consisting of 30 samples with the size of 150 mm x 150 mm x 150 mm were prepared to serve the testing programme of the study. The results revealed the formation of a well-bonded interfacial transition zone between untreated OS particles and the cementitious matrix due to the presence of pozzolanic materials in OS. However, micro cracks and enlarged capillary pores were witnessed in treated OS mixtures along with a weak interfacial transition zone between the treated OS and the cementitious matrix. Moreover, the use of 30 wt.-% untreated OS reduced the water absorption of concrete by 9% (absorption rate of 9.5%), while other mixtures experienced an increase in their water absorption with a maximum increase of 42% when using 50 wt.-% treated OS (absorption rate of 10.7%). All mixtures attained a reduction in their compressive strength compared to control sample when employing treated and untreated OS in concrete, with a minimum reduction of 13% when using 30 wt.-% untreated OS (compressive strength of 26 MPa). The strength reduction in untreated OS mixtures is due to the formation of free CaO and free SiO2, which promote concrete expansion. The interference between silane and kerogen in OS was the main reason behind the strength reduction in treated OS mixtures. However, this reduction in mixtures’ strength is considered minimal, allowing for their potential use in different construction applications like rigid pavement.

3D printing technology can be of crucial importance in the design of sustainable and energy-efficient building envelopes. With this technology, there is the potential to mechanically and thermally optimise the topology of printed walls. Additionally, the printing and infill materials used can be insulating, and thus contributing to the overall reduction of heat loss. To date, limited examples of 3D printed envelopes and information about the thermal and mechanical performance of 3D printed walls are available. This study developed a 3D printable wall element with an insulating property for application in building envelopes. Seven wall topologies are studied through simulations of mechanical and thermal performance using two mixtures: a control mixture (normal-weight) and a lightweight mixture containing expanded thermoplastic microspheres (ETM) for thermal insulation. One wall topology is selected based on the performance of the simulation and printed using both mixtures. The 3D printed envelopes were tested under compressive strength and analysed with the ARAMIS system, a digital image correlation (DIC) technology. Computer simulations and the DIC analysis identified the main causes for failure, which are the inter-filament weakness and the imperfections of the geometry of the printed envelope.

3D printing is a developing technology that has the ability to use different materials to produce concrete elements with complex shapes. The utilization of geopolymers or alkali-activated materials (AAMs) in 3D printing is receiving significant interest due to the environmental benefits of replacing ordinary Portland cement (OPC). The use of solid activators to produce a one-part geopolymer can help the broader use of geopolymers at large scales, as the corrosive, viscous, and hazardous liquid activators used in two-part geopolymers do not present a feasible large-scale solution for this technology. This paper reviews the 3D printable one-part geopolymers, their compositions, and the effect of different precursor compositions, activator content, and different admixtures on the fresh and hardened properties of the mixtures. The environmental impact and cost assessment of one-part geopolymers produced by conventional and 3D printing methods are also discussed and compared to OPC and two-part geopolymers. This review concluded that one-part geopolymers are easier to mix and use than two-part geopolymers and have a lower carbon footprint than two-part geopolymers and OPC concrete. However, one-part geopolymers may not be as strong as two-part geopolymers, but they are still better than OPC.

The rapid development in 3D printing applications requires exploring a sustainable printable mixture to decrease the environmental impact induced by the existing Ordinary Portland Cement (OPC) mixtures and enable 3D printing technology to reach its peak efficiency. The high-volume substitution of OPC with supplementary cementitious materials (SCMs) is of significant interest as a promising solution for developing low-carbon feedstock for 3D printing. Yet, those materials share the problem of limited availability. The combination of limestone and calcined clay could be a promising alternative, offering various benefits, including replacing OPC in high ratios. This paper reviews 3D printable limestone calcined clay cement (LC3) mixtures, compositions, and chemical behaviour. The effect of different sand-to-binder ratios, additives content, OPC replacement levels, clay grade and calcination, and admixtures on the fresh, hardened and printing properties of the 3D printed mixtures are critically discussed. The environmental impact and production cost of the LC3 system compared to OPC and other systems are also critically evaluated along with the applications, future directions and research gaps in this field. The findings of this review show that 3D printed LC3 has a similar hardened performance and better microstructure than OPC system. Moreover, cast LC3 system has 30–50% lower environmental impacts depending on the replacement level and better economic feasibility than OPC. Therefore, making it a suitable feedstock for the innovative manufacturing technology of 3D printing.

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.

Construction projects in Kuwait’s Ministry of Public Works (MPW) involve numerous resources and stakeholders, necessitating effective communication and data sharing to avoid errors, conflicts, and resource wastage. Integrating Building Information Modelling (BIM) into the traditional procurement management approach has the potential to revolutionise the construction industry, enabling remote access to information and waste prevention, particularly for megaprojects. Despite its benefits, BIM adoption has been slow in MPW projects. This study investigates the reasons behind this reluctance and proposes a framework to integrate BIM into MPW projects. A qualitative research method of narrative analysis on semi-structured open interviews with key stakeholders in MPW was conducted to identify the benefits and barriers of BIM implementation. The study found that while tangible barriers were absent, challenges included a lack of senior management support, an inadequate BIM-skilled workforce, adherence to traditional processes, and limited awareness of BIM’s importance in circularity and sustainability. Nevertheless, a pilot project demonstrated improvements in collaboration, visualisation, budget estimation, and information sharing through BIM. This study proposes a framework for incorporating BIM into the MPW tendering process to address these issues, validated through interviews with tender managers. This framework aligns with Kuwait’s Vision 2035 for sustainable buildings and the Sustainable Development Goals (SDGs) of the United Nations by encouraging the implementation of BIM. Since BIM has the potential to be an effective instrument in reaching these global goals, Kuwait’s construction industry should embrace and deploy BIM.

An in-depth investigation of the incorporation of silane-treated and untreated glass waste in concrete is presented in this research. Coarse and fine aggregates were replaced with glass waste in 30 wt.-% and 50 wt.-% ratios, while glass powder was employed as an additive to concrete with 2 wt.-% and 5 wt.-% ratios. Physical, mechanical, microstructural and surface chemical properties of the produced concrete samples were studied by conducting water absorption test, compressive and splitting tensile strength tests, Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) analyses, respectively. The results showed that the combined influence of glass waste and silane coupling agent enhanced the impermeability of concrete by 87% when replacing sand with 50 wt.-% glass. In addition, all modified mixtures showed a reduction in their 28 days’ compressive strength compared to the control, except mixtures where untreated glass powder was used as an additive, which led to an increase in their compressive strength by 1%. Moreover, replacing sand with 50 wt.-% glass enhanced the splitting tensile strength of concrete by 25%. Microstructural analysis revealed a delaminated interface between glass and cement paste when using silane-treated coarse glass and the formation of Ettringite at later ages.

This investigation aims to study the performance of different hybrid binders as environmentally-friendly cementitious soil stabilizers as well as Nanosilica as a reactive powder. Mechanical properties and microstructural analysis in addition to the molecular and mineralogical specifications were investigated to evaluate the performance of stabilized soil samples. For this purpose, a series of experimental tests including scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) are considered as well as mechanical tests to investigate the various aspects of the material. The results showed that the incorporation of Nanosilica not only improved the unconfined compressive strength (UCS) of the stabilized samples, but also the elastic modulus which is indicative of Nanosilica's tendency to increase the ductility of samples. In Portland cement (PC) and phosphorus slag blended cement (SBC)-based samples, the results confirmed that samples containing Nanosilica possess an intensified C–S–H phase compared to other samples. It appeared that the supplied reactive Nanosilica to the matrix showed better participation reaction of Ca2+ of Portlandite for formation of extra C–S–H phase due to the observed phase change of needle-like crystals of Portlandite in lower amount with smaller particles. Moreover, the microstructure results revealed that the presence of Nanosilica leads to more densified binder matrix with more coverage of soil particles. The incorporation of Nanosilica in SBC exhibited a more densified matrix with higher UCS values compared to PC samples. The presence of 2 wt% of Nanosilica in the alkali-activated phosphorus slag cement (AAC)-based samples resulted in lengthening the aluminosilicate chain with more substituted Al with reactive Si. In AAC-based samples, with incorporated Nanosilica a compact interfacial bond of matrix and soil particles was observed.

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.

Due to global environmental concerns related to climate change, the need to improve the service life of structures and infrastructures is imminently urgent. Structural elements typically suffer service life reductions, leading to poor environmental sustainability and high maintenance costs. Graphene oxide nanosheets (GONSs) effectively dispersed in a cement matrix can promote hydration, refine the microstructure and improve interfacial bonding, leading to enhanced building materials’ performance, including mechanical strength and transport properties. Cement-based nanocomposites engineered with GONSs were obtained using two commercial nanofillers, a GO water suspension and a free-flowing GO nanopowder, characterized by fully comparable morphology, size and aspect ratio and different oxidation degrees (i.e., oxygen-to-carbon molar ratio), 0.55 and 0.45, respectively. The dosage of the 2D-nanofiller ranged between 0.01% and 0.2% by weight of cement. The electrical and thermal properties were assessed through electrochemical impedance spectroscopy (EIS) and a heat flow meter, respectively. The results were discussed and linked to micrometric porosity investigated by micro-computed tomography (μ-CT) and transport properties as determined by initial surface absorption test (ISAT), boil-water saturation method (BWS) and chloride ion penetration test. Extra-low dosage mortars, especially those loaded with a lower oxidation degree (i.e., 0.45GO), showed decreased permeability and improved barrier to chloride ion transport combined with enhanced thermal and electrical conductivity with respect to that of the control samples.

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.

This study investigates the addition of Poly-vinyl Alcohol (PVA) fibres and attapulgite nanoclay to alkali-activated materials (AAMs) with the aim of enhancing the mechanical performance and optimizing the printability and buildability of AAMs. The fresh properties of six mix formulations, including flowability, slump values, rheology, shape retention, and extrusion window, were evaluated. The best performing mixes, that exhibited optimal fresh properties, were 3D printed, and their mechanical performance, microstructure, and buildability were investigated. The addition of 1 wt.-% attapulgite nanoclay (i.e. A-1) showed the desirable fresh properties required for 3D printing, as well as providing sufficient mechanical reinforcement to the samples. The 3D printed A-1 samples showed an improved flexural and compressive strength by 43% and 20%, respectively, compared to both the casted and printed control mixes. Moreover, microstructure analysis, including SEM, Rapidair measurement, and micro-CT, provided evidence of the compatibility by showing the lowest pores anisotropy and mixture homogeneity, between attapulgite and AAMs.

The widespread popularity of additive manufacturing in most industries ranging from biomedical to aerospace suggests a transformation in manufacturing, which has recently also emerged in the construction sector. This paper presents an active system for the extrusion-based 3D printing of cementitious materials. The system can be extended to other materials and scaled up with slight hardware modifications. The proposed system uses an unconventional yet simplistic approach to generate a consistent output of material throughout the printing process. The effectiveness of the extruder is demonstrated through an extensive printing and testing of various cementitious-based materials. The printing and material parameters, which are essential for high mechanical strength printed object were investigated and optimized through a logical iterative loop of trials. The results showed the shape retention of 3D printed objects using the proposed design of extrusion-based system in conjunction with optimized rheology of cementitious-based materials was encouraging for larger scale 3D printing.

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. Keywords: Fresh concrete, Concrete pavement, Microstructure, Freezing and thawing, Sodium acetate, Concrete protection

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.

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.