Recycling aluminosilicate-based solid wastes is imperative to realize the sustainable development of constructions. By using alkali activation technology, aluminosilicate-based solid wastes, such as furnace slag, fly ash, red mud, and most of the bio-ashes, can be turned into alternative binder materials to Portland cement to reduce the carbon footprint of the construction and maintenance activities of concrete structures. In this paper, the chemistry involved in the formation of alkali-activated materials (AAMs) and the influential factors of their properties are briefly reviewed. The commonly used methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG), nuclear magnetic resonance spectroscopy (NMR), and X-ray pair distribution function technology, to characterize the microstructure of AAMs are introduced. Typical characterization results of AAMs are shown and the limitations of each method are discussed. The main challenges, such as shrinkage, creep, efflorescence, carbonation, alkali–silica reaction, and chloride ingress, to conquer for a wider application of AAMs are reviewed. It is shown that several performances of AAMs under certain circumstances seem to be less satisfactory than traditional portland cement systems. Existing strategies to improve these performances are reviewed, and recommendations for future studies are given.

Supersulfated cement (SSC) is a traditional low-carbon cement, but its slow hydration and strength development has limited its practical applications. Nano silica (NS) was used to activate the hydration of SSC by taking advantage of its ability to regulate silicate and aluminate reactions. The mechanical performance of various mixes was determined, as a function of sulfation degree and NS addition, as pore structure, phase assemblage, hydration degree, and microstructure. Results showed that NS improves the hydration degree of slag, densifies the microstructure, and significantly increases both early- and late-age compressive strength. The enhancement was attributed to its effects on the hydration of slag in SSC: delaying ettringite formation, but promoting C-(A)-S-H precipitation, reducing microporosity. This study reveals the critical role of the regulation of hydration kinetics of silicate and aluminate in controlling the performance of SSC as NS does.

All kinds of sudden disasters occur frequently, causing serious impacts such as casualties, economic losses, and social disorder. Pre-disaster evacuation is the most direct and effective way to reduce casualties. Meanwhile, the distribution of relief supplies is also an important emergency measure to improve the physiological endurance of victims. To solve the problem of organizing the effective evacuation of the masses before the disaster and reasonably allocating emergency supplies, the overall optimization strategy of personnel evacuation and supplies allocation among multiple service facilities is studied. In the modeling process, the interests of the people who have not been evacuated are measured by the penalty coefficient, combined with the travel costs of the people, supplies transportation costs, and purchase costs in the network transportation system, and finally, the dynamic programming model is established with the optimization goal of minimizing the total system cost. In this paper, through GAMS platform programming, numerical experiments are carried out on the model under the 17-node road network to verify the feasibility of the model and to provide an auxiliary decision-making reference for the formulation of safe evacuation plans.

Due to the high bonding strength, Magnesium ammonium phosphate cement (MAPC) is suitable for the crack repair. However, the fast initial hydration rate, high viscosity and poor water resistance hinder its application in the crack repairing engineering. To solve the above problems, the spherical silica fume and fly ash were added into MAPC. The effects of spherical silica fume and fly ash on the rheological property, fluidity, setting time, compressive strength, water resistance and drying shrinkage of MAPC were studied. The results showed that both spherical silica fume and fly ash could reduce the plastic viscosity of MAPC and prolong the setting time. Spherical fly ash could improve the fluidity of MAPC. The late-age strength and water resistance of MAPC were increased and the drying shrinkage was reduced by adding spherical silica fume and fly ash. Therefore, it is concluded that the addition of spherical silica fume and fly ash into MAPC makes it more available to be applied in the crack repairing engineering.

Due to internal defects, the traditional polymer-modified cement-based coating was hard to meet the high durability requirement of construction engineering. The hydrophobic flake as a functional filler provided a new solution for improving the protection performance. However, there has been almost no application report in this system so far. In this study, we tried to obtain the optimal number and mechanism by studying the effect of hydrophobic flake on the mechanical, waterproof, and brine soaking resistance properties of the coating with calcium sulphoaluminate (CSA) cement and polyacrylate (PA) emulsion as the main components. The results showed that the unique irregular tight structure of the hydrophobic flake would not only make the internal coating rougher and denser but also cut off the transport paths of harmful molecules inside the coating. The hydrophobic flake was beneficial to the mechanical properties and the brine soaking resistance of the polymer-modified cement-based coating.

The urban heat island (UHI) effect has a significantly negative impact on the living environment in urban areas. Asphalt pavement is one of the most widely used infrastructures that absorbs solar energy, which leads to the UHI effect and premature failure. As a result, cool pavement technology has been rapidly developed in recent years to mitigate the UHI effect originating from asphalt pavement. Although several outstanding review articles have analyzed previous studies on cool pavement technologies, very few review articles have focused on how to design and expand cool pavement technology from a materials perspective. In this mini-review article, the theoretical and practical factors of the solar reflective coatings and phase-change materials, which are significantly dependent on the design of new materials, have been summarized. The main challenges and potential problem-solving ideas have been presented. In a cool pavement, the solar reflective coatings are composed of epoxy resin or acrylic polymer matrix filled with solar reflective nanoparticles, such as TiO2, SiO2, ZnO, Al2O3, or Fe2O3. The main challenges of the solar reflective coatings are the spalling of the coating polymers from the asphalt pavement surface and the dispersion of the solar reflective nanoparticle in the polymer matrix. Most importantly, it is critical to harmonize the balance between the bonding strength, aging rate, solar reflectance, curing requirements, mechanical properties, and durability of the solar reflective coating. For the nanofillers, the cost of the filler materials, the balance between UV, visible light, and near-infrared reflectance and the dispersion status of the nanofillers in the polymer matrix are the primary factors that must be concerned. For the phase-change materials (PCMs), the interaction between the asphalt and the PCMs, the decomposition of the PCMs, the toxicity of the PCMs, the distribution status of the PCMs in the asphalt matrix, and the cost are the main factors that have to be considered in constructions. This review article can not only provide basic knowledge for the development of new solar reflective pavement materials but also serve as a guide for practical applications of cool pavement in the field.

Bauxite residue (red mud) is a solid waste resulting from the aluminum production industry. Disposal or landfill of the red mud (RM) poses irreversible environmental problems; therefore, it is compelling to find practical solutions that can mitigate the negative environmental problems of RM stacking storage. In the past decades, although the recycling of RM has achieved significant progress, challenges remain from both academic and practical perspectives. Previous studies have demonstrated that all the aluminosilicate-based solid wastes have pozzolanic activity, and thus can be considered as resources to manufacture eco-friendly cementitious materials to relieve the carbon emission burden. Therefore, combining RM and other solid wastes to manufacture green cementitious materials has become a promising route to alleviate the burden of environmental pollutions. However, challenges from the fluctuation of the chemical compositions, inert activity, heavy metals stabilization, efflorescence, the side effects of the second pollutions from solid wastes, the hydration process, and mutual interaction mechanisms between the various types of solid wastes are still unclear, especially for multi-components RM-based cementitious materials. This review article summarizes the state of the art of mechanical properties, microstructure characterization methodologies, and hydration process and mechanisms of RM along with other solid wastes. The main challenges and future research trends are discussed. This article attempts to summarize the details of the RM recycling technologies that are beneficial to readers in understanding the background knowledge and research methodologies of eco-friendly cementitious materials.

Ternesite-calcium sulfoaluminate (TCSA) cement exhibits excellent properties. However, it is hard for sulfoaluminate (C(4)A(3)$) and ternesite (C5S2$) to coexist in the clinker. In this study, phosphogypsum (PG) was used for producing TCSA cement clinker. The joint effects of P2O5 and F in PG as well as the CaSO4 content in raw meals on the coexistence of C(4)A(3)$ and C5S2$ were investigated. The grindability and morphology of TCSA cement clinker were characterized. By the comparison with belite-calcium sulfoaluminate (BCSA) cement, the hydration and properties of TCSA cement were investigated. Results shows that the coexistence of C(4)A(3)$ and C5S2$ is achieved under the joint effects of P2O5, F and a sufficient amount of CaSO4. TCSA cement clinker could be prepared at 1125-1200 degrees C for 15-30 min and the clinker exhibits a good grindability. Ternesite in TCSA cement clinker presents a rodlike or granular shape Compared with BCSA cement, due to higher hydration rate of C(4)A(3)$, the setting time of TCSA cement is shorter and early compressive strength is higher. Due to the hydration of C5S2$, TCSA cement exhibits a higher late age compressive strength.

An attempt at the treatment of the waste fiber (WF) from the wind turbine blade (WTB) was made through the modifier of dopamine hydrochloride and the compound modifier of dopamine hydrochloride and 2,5-dihydroxy terephthalic acid or 3,4-dihydroxy cinnamic acid or 3,4-dihydroxy benzonitrile, corresponding to obtain four modified waste fibers (MWF1, MWF2, MWF3, and MWF4). The MWFs samples’ microstructure properties were characterized using SEM, EDS, XPS, FTIR analyses, and water contact angle tests. The results revealed that all the MWF surfaces were wrapped by a distinct coating layer and had different elemental compositions and chemical groups, demonstrating the significant effect of the four modifications on the WF surfaces. The hydroxyl, amino, or nitrile groups were grafted onto the WF surfaces causing improvement of the hydrophilicity and reactivity. Furthermore, all the MWFs as the reinforced materials were incorporated into the industrial waste phosphogypsum (PG) to manufacture the phosphorous-building gypsum composites (PBGC). The effects on the micro-morphology and mechanical properties of the PBGC were evaluated. The results also show the improvement in flexural and compressive strength with the addition of MWFs into the PBGC, due to the enhancement of the compactness between the MWF and phosphogypsum matrix. In particular, the effects of three compound modifiers on the flexural and compressive strength are more significant. The highest flexural and compressive strength was contributed by the PBGC-MWF4 with 2% dosage using a compound modifier of dopamine hydrochloride and 3,4-dihydroxy benzonitrile, which were enhanced 61.04% and 25.97% compared with the PBG.

Anti-icing is a critical topic in durability assessment for pavement infrastructures, and it varies according to local policies. To provide sufficient information to winter maintenance agencies, and help compare the merits and shortcomings of each strategy, this review summarizes the widely used anti-icing strategies, including elastic surfaces or high-friction overlays, asphalt binders mixed with anti-icing additives, pavement heating technologies, deicers, and fixed automated spray technology, from academic and practical perspectives, as well as explore the impact of deicers on the durability of concrete materials. Furthermore, the costs of each method were compared to evaluate the feasibility of them. This review not only provides a summary of previous anti-icing strategies, but also sheds light on future research trends that may help address the challenges of current anti-icing strategies, and further enhance anti-icing efficiency and reduce life cycle costs.

The investigation on geopolymers has intrigued broad interests in the past decades, due to the requirements for the recycling of aluminosilicate solid wastes, such as red mud, slags, sludges and demolished concrete. Previous studies have demonstrated the feasibility of reusing this Aluminosilicate as a resource to prepare cementitious materials and indicated their promising properties at ambient temperature. However, when this material was exposed to high temperatures, especially above 1000 °C, the microstructure evolution mechanisms were not systematically investigated. In this study, the microstructural evolution process of metakaolin-based K geopolymer (molar ratio of K:Al:Si was 1:1:4) is investigated. The crystalized leucite originated from the geopolymer precursor was detected above 1000 °C. The SEM results indicate that the microstructure of the geopolymer before heating was composed of non-reacted metakaolin with a typical layered structure and reacted amorphous binder phase. As the geopolymer heated to 1000 °C, the microstructure of the geopolymer changed to a porous structure with an average pore size from 10 to 30 μm. When the heating temperature reached 1100 °C, the pores started to close along with the leucite crystallization process. As the heating temperature reached 1200 °C, most of the pores were closed. The TEM results show that the microstructure of the geopolymer, after being heated to 1400 °C, was composed of an amorphous glassy phase and crystallized leucite phase. The crystallized leucite grains originated from the nano-sized crystal nuclei, with an average size of 2–3 nm. The TEM-EDS results indicate that the chemical composition of the glassy phase was complicated. It varied from area to area because of the movement and uneven distribution of K.

Alleviating human sufferings during and in the aftermath of disasters is one of the most important goals in humanitarian relief logistics. The lack of relief commodities, especially life-saving items, is a life-threatening loss to victims and must be considered when making emergency supply allocation and transportation decisions, even in the pre-disaster prepositioning phase. This paper proposes a scenario-based stochastic program that integrates the decisions of prepositioning facility locations, quantities of stocked emergency supplies, and service allocations in each scenario in the same modeling framework. The estimation of victims' losses for waiting for emergency supplies is measured in the typical deprivation cost function and treated as one of the main bases of decision making, besides traditional transportation costs, in determining the service allocation strategies in each scenario. Specifically, a case study with data from the hurricane threat in the Gulf Coast area of the US was conducted to demonstrate the application of this model and the significance of considering victims' welfare loss in humanitarian relief logistics. Some interesting managerial insights were also drawn from a series of numerical experiments and sensitivity analyses.

Phosphogypsum (PG) is an industrial waste from the production of phosphoric acid and phosphate fertilizer. Disposal and landfill of PG pose significant environmental problems due to its hazardous components. Although many researchers have explored the possibility of PG recycling, challenges still exist before it can be high-effectively reused. In particular, a great deal of recent attention has been attracted to explore using PG as raw material to manufacture sustainable composites. The impurities movement, recycling efficiency, and environmental impacts have to be further investigated. This review article summarized the state of the art of the purification process, application areas, and the environmental impacts of PG waste. The main challenges and potential application approaches were discussed. This article is focused on reviewing the details of the PG reusing which benefits the readers on learning the knowledge from previous efforts. The main challenges of reusing PG were discussed from the chemical, physical, and materials perspectives.

The service life of concrete products with exposure to an aggressive environment has raised great concerns in the past decades. Nanomaterials have been used as a promising approach to improve the environmental resistance of concrete products when exposed to synergistic attacks. The impacts of CaCl 2 on nano-modified concrete, especially along with freeze/thaw (F/T) and wet/dry (W/D) cycles, were barely discussed. In this study, the impacts of CaCl 2 along with F/T and W/D cycles on the nano SiO 2 and Al 2 O 3 modified concrete were investigated. The mass loss, flexural strength, compressive strength, and relative dynamic modulus of elasticity were tested to evaluate the durability of concrete products. The testing results indicate that the addition of nanoparticles has a distinctive effect on the environment resistance enhancement of concrete samples. The microstructure analysis demonstrates that with the addition of nanoparticles, high-density hydration products were formed, which is beneficial to the properties enhancement of concrete products. This study not only provides an approach to realize the nano modification on the durability of concrete products but also helps to design and fabricate environmentally resistant concrete products when exposed to a synergistic aggressive environment.

Post-disaster humanitarian relief is full of importance, complexity and difficulty, which makes people pay more attentions to various disaster relief measures and emergency management practices related to disaster preventions and reductions. The main purpose of humanitarian relief is to protect the lives of the victims in the affected areas and provide victims with the indispensable relief materials to survive from the unexpected disaster. Therefore, this paper puts its focus on some key decisions raised in the process of post-disaster humanitarian relief activities and summarizes the state-of-the-art researches in the area of critical emergency facility location, relief material allocation, emergency vehicle routing and the incorporation of the interests of the victims in the modeling framework. Specifically, through the analysis, this paper draws some key questions that can be further explored in the current research, in order to lay the foundation for the follow-up research, and can better serve the emergency rescue transportation practice under disaster conditions.

Nanomaterials have been applied for the modification of cement-based materials with a low-dosage addition in recent years. Graphene oxide (GO) has been studied in many papers for use in cement-based materials with properties of a two-dimensional sheet-like structure, its extraordinary mechanical properties, high aspect ratio and hydrophilicity. To study the effects of graphene oxide on the hydration of tricalcium silicate, the hydration heat, hydration products and micro-structure of a C3S-GO hydration system were studied in this paper. The results showed that GO increases the hydration heat by promoting the hydration rate of C3S, though the (K) could not react with the C3S hydration products (such as the calcium hydroxide and C-S-H gel produced by the C3S hydration). It was found that the addition of GO changes the crystallite size of the hydration products through observing the SEM image. The GO modified the morphology of the C3S hydration products and led to a more compacter structure.

Lightweight aggregate concrete manufactured by solid waste or recycled by-products is a burgeoning topic in construction and building materials. It has significant merits in mitigating the negative impact on the environment during the manufacturing of Portland cement and reduces the consumption of natural resources. In this review article, the agricultural and industrial wastes and by-products, which were used as cementitious materials and artificial lightweight aggregate concrete, are summarized. Besides, the mechanical properties, durability, and a few advanced microstructure characterization methods were reviewed as well. This review also provides a look to the future research trends that may help address the challenges or further enhance the environmental benefits of lightweight aggregate concrete manufactured with solid waste and recycled by-products.

This study describes the preparation and characterisation of MIL-53(Fe) and its effect on the performance of forward osmosis (FO) membranes. The cellulose acetate (CA)/MIL-53(Fe) hybrid membranes were fabricated using the method of phase inversion by dispersing MIL-53(Fe) in a CA casting solution. To improve the selectivity and permeability performance of FO membranes, the effects of MIL-53(Fe) content, casting solution temperature, coagulation bath temperature, and annealing temperature were studied. Results from scanning electron microscopy, membrane porosity, atomic force microscopy, and water contact angle tests of all the membranes show that the structural properties of the CA/MIL-53(Fe) hybrid membranes were optimised. The results of the FO performance tests, including the values of water flux and reverse salt flux, indicate improvement in the selectivity and permeability properties of the CA/MIL-53(Fe) hybrid membranes. Under the conditions of deionised water as the feed solution and 1 M NaCl solution as the draw solution, the water flux and reverse salt flux of the CA/MIL-53(Fe) hybrid membranes reached 34.9 L/(m(2).h) and 2.02 g/(m(2).11), respectively, in comparison with CA membranes. This study demonstrates that MIL-53(Fe) can improve the desalination performance and structural properties of FO membranes.

With the growing reliance on chloride-based deicers in winter roadway maintenance operations, the concerns over their adverse impacts have been highlighted in recent years, especially the direct stress that applied chemicals bring to the receiving roadside soil, water bodies, aquatic biota, and vegetation through snowmelt runoff, infiltration and wind blow. This work started from synthesizing current knowledge on the negative/toxicological effect of chloride-based snow and ice control products to the natural ecosystem, and then put an emphasis on the examination of typical methods used to assess the toxicity of chloride-based deicers on the water quality and aquatic biota in the laboratory and field tests. The summary focused on the species to test, calculation process, and influential factors in the laboratory test, followed by the field sample collection options, timing of sampling, key variables and bio-assessments in the field test to quantify toxicological effects of chloride-based chemicals. Finally, efforts on current theoretical research and the need for further work (e.g., field monitoring and bio-assessments or bio-monitoring over time, the effective correlation between laboratory toxicity data with field data, and the relationship among key variables and resulting toxicity index) were discussed.