This study systematically investigates the mechanistic distinctions in how the type of nanomaterials regulates the performance of recycled aggregate concrete (RAC) under comparable particle size conditions. Three nanomaterials-nano calcium silicate hydrate (NCSH), nano titanium dioxide (NTO), and nano silica (NS) were each incorporated at 2 wt% to evaluate their effects on mechanical properties, durability, and microstructural evolution. The results reveal pronounced time-dependent efficacy among the nanomaterials. NCSH exhibited the strongest enhancement in early-age mechanical performance, increasing 1-day compressive and splitting tensile strengths by 56.9% and 41.9%, respectively. In contrast, NS demonstrated superior long-term strength development and permeability resistance, achieving a 20.1% reduction in 28-day water absorption and chloride ion penetration. Microstructural analyses indicate that NCSH primarily accelerates early hydration and structural densification through homogeneous nucleation. NS refines the pore structure and reduces calcium hydroxide content via sustained pozzolanic reactions, while NTO contributes mainly through physical filling and microstructural packing. These findings provide a mechanistic basis for the targeted selection and synergistic optimization of nanomaterials in RAC systems tailored to specific performance requirements.

The application of carbonic anhydrase-mediated biomineralization with carbon-capturing effects for concrete damage repair has garnered widespread attention. However, research on its use for concrete surface protection remains limited. This study compares carbonic anhydrase-mediated (B. mucilaginosus) biomineralized coatings, urease-mediated (S. pasteurii) biomineralized coatings, and commercial organosilane coatings in terms of surface morphology, thickness, interfacial bonding properties, wettability, composition, and microstructure. The protective performances of these coatings on mortar are evaluated through water absorption and carbonation tests, followed by an assessment of their environmental impacts. Results indicate that B. mucilaginosus coatings demonstrate superior uniformity, smoothness, and higher calcite content compared to S. pasteurii, albeit with slightly lower thickness and hydrophobicity. The bonding strength of all three coatings to mortar is similar. While the biomineralized coatings show inferior water absorption resistance compared to the organosilane coating, the B. mucilaginosus coatings exhibit exceptional carbonation resistance, with a carbonation depth of only 1.8 mm after 14 days. Notably, the environmental emissions of biomineralized coatings are merely onetenth of those of the organosilane coatings. In summary, carbonic anhydrase-mediated biomineralized coatings excel in both protective performance and environmental sustainability, showcasing promising potential for green building protection.

Tricalcium aluminate (C3A) plays an important role in the early hydration and performance development of Portland cement. However, the interaction mechanism between C3A and gypsum has not yet been fully clarified. In this study, low-field NMR (LF-NMR) was used to dynamically monitor the early hydration of the C3A–gypsum system through the evolution of 1H signal intensity, transverse relaxation time (T2), and LF-NMR-derived specific surface area (SSA). The results showed that gypsum significantly retarded C3A hydration, and a characteristic LF-NMR response at approximately 12 h was associated with the transformation from ettringite (AFt) to monosulfoaluminate (AFm) in the gypsum-limited system. These findings were corroborated by X-ray diffraction, thermal analysis, isothermal calorimetry, and scanning electron microscopy. Kinetic fitting with the JMAK model showed poor performance for pure C3A hydration but provided a reasonable fit for gypsum-containing samples. For the gypsum-limited system with a C3A: gypsum molar ratio of 1:1, the AFt-to-AFm conversion stage (7–18 h) showed an apparent kinetic regime related to crystal nucleation and growth, whereas the earlier hydration stage was mainly associated with diffusion-governed behavior.

Microcracks significantly compromise the long-term service life of concrete structures, prompting extensive research into mitigation strategies. Embedding healing agents to impart autonomous crack repair capabilities offers a promising solution to reduce maintenance costs and enhance sustainability in the construction sector. Cementitious capillary crystalline waterproofing materials (CCCW), as inorganic rigid waterproofing agents, have garnered increasing attention owing to their excellent waterproofing performance, ease of application, environmental compatibility and cost effectiveness. Recent studies have increasingly recognised the potential of CCCW to impart self-healing functionality to concrete. This review systematically examines recent advances in CCCW-based self-healing concrete, covering the fundamental composition, mix design principles, underlying self-healing mechanisms and the efficacy of crack healing evaluated through various performance metrics and assessment methodologies. Furthermore, future research directions are proposed, providing a theoretical foundation and technical reference to facilitate the industrial application of CCCW.

Durability remains one of the key factors determining the long-term performance and service life of concrete structures. This study investigated a novel way to use waste dolomite powder (WDP) in concrete, aiming to develop a ternary aggregate system that simultaneously improves mechanical properties and durability. Experimental results showed that incorporating WDP in the concrete increased the 90-day compressive strength by up to 21.06 % and the splitting tensile strength by 10.84 %. Meanwhile, durability was significantly enhanced: compared to that of the control concrete, the reductions in drying shrinkage, water absorption and chloride migration coefficient of the concrete containing WDP were up to 17.27 %, 35.59 %, and 43.20 %, respectively. The XRD, FTIR, and TGA results verified that WDP provided a stable crystalline phase dolomite (CaMg(CO3)2) which contributes to maintaining long-term dimensional stability. Acting as a micro-aggregate, WDP effectively filled into pores and refined the interfacial transition zone (ITZ). Pore structure analysis confirmed that the cumulative pore volume decreased by up to 21.83 %, while the content of the harmless pore content (<= 20 nm) increased by 35.49 %. The SEM-EDS and Vickers hardness measurements further showed a narrower ITZ. Notably, the microhardness of the ITZ and the matrix were improved by 38.38 % and 39.62 %, respectively. In addition, the life-cycle assessment results show that incorporating WDP in concrete effectively reduced CO2 emissions, energy consumption, and economic costs. These findings demonstrate that WDP can be effectively utilized to produce more sustainable concrete with superior durability and mechanical performance.

This study proposes a sustainable strategy to valorize waste dolomite powder (WDP) through the design of a binary aggregate system in cement mortars, where WDP is utilized as an inert microaggregate. Apart from waste recycling, this approach aims to simultaneously enhance material performance and sustainability. To reveal the impact of WDP, a series of properties were evaluated, including drying shrinkage, mechanical properties, hydration products and microstructural characteristics. Experimental results demonstrate that incorporating WDP effectively improves volume stability by reducing drying shrinkage and regulating water transport behavior. Flexural and compressive strengths at 90 d enhanced by up to 14.44% and 15.32%, respectively. The XRay Diffraction, Fourier Transform Infrared Spectroscopy, and Thermogravimetry analysis suggested that WDP remained chemically stable, showing no reaction along the hydration. Microstructural analyses confirmed that WDP incorporation effectively refined the pore structure and disrupted pore connectivity. Furthermore, sustainability assessment shows that the incorporation of WDP reduces total CO2 emissions, energy consumption, and economic cost by up to 19.52%, 20.64%, and 16.58%, respectively. The findings demonstrate that binary aggregate design with WDP offers a viable pathway for developing low-carbon cementitious materials while enabling the high-value utilization of massive stone powder waste.

In this study, untreated sewage sludge ash (SSA) was used to partially replace recycled brick fine aggregate (RBFA) or recycled concrete fine aggregate (RCFA) to prepare controlled low-strength materials (CLSM). The effects of the binder-aggregate ratio, fine aggregate type, and SSA incorporation on setting performance, compressive strength, and hydration products of CLSM were systematically evaluated, with all mixes designed for a constant slump flow. Phase composition and microstructural development of CLSM were analyzed using X-ray diffraction (XRD). Results demonstrate that in the recycled concrete fine aggregate (RCFA) – CLSM without SSA, with the increase of the binder-aggregate ratio, the setting time is shortened by approximately; However, after the addition of SSA, the opposite trend emerged, with the setting time prolonged. The recycled brick fine aggregate (RBFA) – CLSM shows a similar pattern, but the delaying effect of SSA on its setting time is weaker than that of the RCFA system. The compressive strength of all CLSM increased with the curing age and the increase of the cementitious material-aggregate ratio. When SSA is not added, the strength of RBFA-CLSM is higher than that of RCFA-CLSM, which is attributed to its lower water requirement. The incorporation of SSA significantly reduces the compressive strength of CLSM, but RBFA, due to its higher base strength, can partially offset the strength loss caused by SSA. The XRD results indicated that the main minerals of CLSM included CaCO3, SiO2, C–S–H gel and CO3-AFm phase. The gel content of C–S–H in the RCFA system is higher than that in the RBFA system. The incorporation of SSA reduced the diffraction peak intensity of CO3-AFm, and no Ca(OH)2 diffraction peak was detected, indicating that the pozzolanic reaction of the low-cementitious system and the auxiliary cementitious materials consumed all the calcium hydroxide. Finally, backfill construction was conducted with this new CLSM, and the excellent performance was confirmed.

Soda residue (SR), generated as the by-product during the production of soda ash, is an alkaline waste that contains calcium compounds. In this paper, five machine learning (ML) models, namely extreme gradient boosting (XGB), light gradient boosting (LGB), support vector regression (SVR), random forest (RF), and an ensemble ML based on artificial neural network (ANN), were presented to predict the compressive strength of SRbased alkali-activated materials (SAMs). The molar ratios of Ca/Si, Si/Al, and H2O/Na2O, along with the curing ages of specimen, and the temperature and time of the curing condition were taken as input variables. Results demonstrated that the ensemble ML model outperformed other standalone models in accurately predicting the compressive strength of SAMs, achieving R2 values of 0.99 and 0.92 for training and testing datasets, respectively. Furthermore, permutation importance analysis was conducted using the aforementioned models to determine the importance of each input variable, a nonlinear equation was then derived to establish the relationship between the input variables and the output using the Levenberg-Marquardt algorithm, contributing to a deeper understanding of the composition-structure correlations in SAMs. The ensemble ML model was used to discover relationships between input variables and output, providing a solid foundation for the effective utilization of SR.

In this work, a novel method for the disposal of ladle furnace slag (LFS) and soda residue (SR) was proposed. By applying geopolymer technology, LFS and SR were used as precursors to manufacture a geopolymer with sufficient fresh and mechanical properties that can be used in construction works, such as in non-structural components like lightweight partition walls. The effects of raw material ratios and Na2O equivalents on the fresh properties, mechanical properties, microstructure and environmental impact of LFS-SR geopolymer (LSG) were analyzed by rheology, compressive strength, XRD, TG/DTG, SEM, and calculation of embodied carbon. The results showed that the compressive strength of LSGs increased when the SR content decreased or Na2O equivalent increased, and the maximum compressive strength could reach 12.0 MPa at 28 d. The hydration products of LSG were mainly C-(A)-S-H gel, C3AH6, and AFt. Notably, the C-(A)-S-H gels formed a stable cross-linked structure, and the extremely fine granular C3AH6 further filled the pores. Furthermore, AFt was generated from the interaction between LFS and CaSO4 rich in SR during the hydration process. The carbon calculation results indicated that the embodied carbon of LSGs was significantly lower than that of traditional cement, and the LSG containing 20% SR and 12% Na2O equivalent had the highest sustainability. This study proposed strategies for mitigating the environmental hazards of alkaline solid waste and improving its resource utilization, thereby promoting sustainable development in the construction industry.

Smart cement-based materials have the potential to monitor the health of structures. The performances of composites with various kinds of conductive fillers have been found to be sensitive and stable. However, poor dispersion of conductive fillers limits their application. This study adopted the coupling agent method to attach carbon nanotubes (CNTs) onto the surface of carbon fibers (CFs). The CNT-grafted CFs (CNT-CFs) were adopted as conductive fillers to develop a CNT-CF-incorporated cementitious composite (CNT-CF/CC). The feasibility of this approach was demonstrated through Scanning Electron Microscopy (SEM) analysis and X-ray Photoelectron Spectroscopy (XPS) analysis. The CNT-CF/CC exhibited excellent conductivity because of the introduction of CNTs compared with the CF-incorporated cementitious composite (CF/CC). The CNT-CF/CC reflected huge responses under different temperatures and moisture contents. Even under conditions of high humidity or elevated temperatures, the CNT-CF/CC demonstrated stable performance and exhibited a broad measurement range. The introduction of CNT-CFs also enhanced the mechanical properties of the composite, displaying superior piezoresistivity. The failure load for the CNT-CF/CC reached 25 kN and the maximum FCR was 24.77%. In the cyclic loading, the maximum FCR reached 20.03% when subjected to peak cyclic load at 45% of the failure load. The additional conductive pathways introduced by CNTs enhanced the conductivity and sensitivity of the composite. And the anchoring connection between CNT-CFs and the cement matrix has been identified as a primary factor enhancing the stability in performance.

The reduced properties of cementitious materials with high-volume fly ash (FA) replacement, e.g. mechanical properties in the early ages, has consistently been a major challenge for field applications. This study introduces an innovative approach in which waste dolomite powder (WDP) is utilized as a filler to enhance the properties of mortars containing high-volume FA. The incorporation of WDP effectively compensated for the reduction of early-age mechanical properties. Specifically, the flexural and compressive strengths of the mortar with 30 % FA replacement increased by 46.23 % and 98.67 % at 1 d, respectively, exceeding the control mix without FA. The corresponding results from setting time, hydration heat, and 1H low-field nuclear magnetic resonance (NMR) tests demonstrated that WDP effectively accelerated the hydration process. This enhancement is primarily attributed to the abundant nucleation sites provided by WDP, which promoted the early precipitation of hydration products. Moreover, WDP improved the packing density of the paste, thereby enhancing the continuity of the solid phase and contributing to a denser microstructure. X-ray diffraction and thermogravimetric analysis confirmed a reduction and consumption of hydration product (Ca(OH)2) with the replacement of FA and the incorporation of WDP. Microstructural analysis further demonstrated that WDP refined pore diameters, reducing total pore volumes by 40.94 % and 42.16 % compared to the control mix. Notably, the combined use of FA and WDP significantly reduced the overall CO2 emissions, energy consumption and economic cost. This study offers a promising sustainable approach to facilitate the adoption of high-volume FA cementitious materials in engineering practices.

Synthetic C-S-H/PCE nanocomposites are outstanding seeding additives to promote the early performances of Portland cement. For an extensive application of the seeding material, it is essential to understand the fundamentals of hydration, microstructure, and early strength of cement with the nanocomposites. In this study, the hydration process and microstructural evolution of cement pastes containing hydrothermal synthesized C-S-H/PCE were quantitatively analyzed by 1H low-field nuclear magnetic resonance and backscattered electron microscopy. The critical roles of the C-S-H/PCE during the dissolution of clinker, nucleation and growth of hydration products, and microstructural development of pastes were identified. Well-trained artificial neural networks (ANN) were employed to predict the early strength of pastes from synthesis parameters of C-S-H/PCE. Satisfactory predictions were obtained that the ANN modeling provides effective guidelines to tune C-S-H/PCE properties and early strength of cement.

The strength prediction of pervious concrete is hard to implement for the mix design due to the porous structure. This work studied the influence of the water-to-cement ratio on the fluidity, viscosity, and mechanical properties of cement paste. Then, the porosity, permeability, and compressive strength of the pervious concrete with various porosities were investigated, and the test results were fitted and analyzed. The result indicates that as the water-to-cement ratio increases, the viscosity of the cement paste reduces and the fluidity increases. The water-to-cement ratio has a negative linear relationship with net slurry strength. The porosity and permeability of pervious concrete fluctuate in accordance with the same rule as the water-to-cement ratio changes. The compressive strength of pervious concrete with varying design porosities increases initially, then declines as the water-to-cement ratio rises. According to the linear fitting analysis, when the water-to-cement ratio is constant, the permeability and compressive strength of pervious concrete have a positive and negative linear relationship with the design porosity, respectively. By analyzing the fitting results and combining the volume method of pervious concrete, a calculation method for mix proportion design is proposed to predict the strength of pervious concrete.

More active and stable catalyst is needed for degradation of organic dyes in wastewater. A new kind of polymethyl methacrylate (PMMA) microsphere hybridized with Ag and Fe3O4 was developed as catalyst. PMMA microspheres were prepared by photoinitiated dispersive polymerization, and then acrylic acid (AA) was photografted on the surface of microspheres with 365 nm UV light to prepare PMMA-AA microspheres whose carboxyl group was up to 164 x 1021 per microsphere. Under the effect of NaBH4, the Ag nanoparticles on the surface of PMMA and PMMA-AA microspheres were successfully modified with the help of carboxyl groups on the surface of PMMA and PMMA-AA microspheres. Fe3O4 particles were adsorbed onto the microsphere surface to obtain two kinds of microspheres (PMMA@Ag@Fe3O4, PMMA-AA@Ag@Fe3O4) for the catalytic reduction of methylene blue (MB) and rhodamine B (Rh-B), respectively. PMMA-AA@Ag@Fe3O4 microspheres exhibited excellently catalytic performance that the apparent rate coeffcients of MB and Rh-B were 0.045 s-1 and 0.036 s-1 respectively. The catalytic efficiency of PMMA-AA@Ag@Fe3O4 heterogeneous catalyst can reach 90% even after 8 cycles for MB. It has excellent catalytic performance, high non-selective adsorption and good reusability. Excellent catalytic performance, high non-selective adsorption and reusability even in the presence of mixed dyes.

In this article, the carbon nanotube-carbon fiber (CNT-CF)/cement-based composite served as a novel auxiliary anode in the form of overlay for the cathodic protection of reinforced concrete (RC) was proposed. The effect of CNT content and age on the conductivity of CNT-CF/cement-based composite was firstly analyzed. After applying the CNT-CF/cement-based composite, the effectiveness of cathodic protection on the reinforcement was evaluated by the corrosion potential and corrosion current, respectively, as measured by Tafel polarization and half-cell potential methods. For comparison, finite element simulation was adopted to calculate the corrosion potential and corrosion current. It showed that the resistivity of CNT-CF/cement-based composite monotonously decreased with increasing content of CNT up to 2 wt.%. When the CNT content was 0.5 wt.%, the resistivity of the composite reached the minimum value of 22.3 omega center dot cm. The resistivity for all the groups decreased with increasing age in the first 7 days. Both the experimental and simulated results showed that the CNT-CF/cement-based auxiliary anode improves the cathodic protection effectiveness for RC.

In this paper, a cement-based sensor for monitoring the performance of high-strength concrete was prepared by adding 0.5 vol%, 1.0 vol%, 1.5 vol%, and 2.0 vol% copper-coated steel fibers (CCSF) as conductive fillers. The fresh cement-based mixture was poured into a funnel-type fiber alignment device, which used its fluidity of the mixture to achieve an aligned distribution of shear-induce fiber within the cementitious matrix. The analysis results indicate that the cementbased sensor with fiber oriented distribution exhibits enhanced electrical conductivity and lower percolation threshold. In addition, the aligned CCSF in the cement matrix mitigates the impact of temperature on resistivity. The resistivity and temperature of the copper-coated steel fibers cement-based sensors (CSFCS) between 5 degrees C and 70 degrees C conform to the Arrhenius relationship. The specimens with aligned fibers demonstrate greater flexural strength compared to those with randomly distributed fibers. Additionally, they also reflect greater piezoresistive response, including higher sensitivity, better repeatability as well as less hysteresis time. Through the twodimensional cross-section analysis, the angle between CCSF and the cross-section of the fiberaligned specimen is significantly reduced, and the fiber orientation factor and fiber orientation coefficient increased considerably. The funnel device for preparing fiber-reinforced cement-based materials can effectively improve fiber orientation.

This study presented a comprehensive investigation of the early hydration reaction and microstructure evolution of sulfoaluminate cement (SAC) using low-field nuclear magnetic resonance (LF-NMR) and isothermal calorimetry (IC). LF-NMR, combined with total relaxation signal and transverse relaxation time (T2), was employed to characterize the evolution of evaporation water (EW) and the degree of hydration (αlf) during the initial stage of SAC hydration. The hydration process was divided into four phases. The relative content of different EW types within the paste was investigated, and the pore structure and specific surface area evolution of SAC paste were studied based on the T2. The heat release of hydration of SAC was measured using IC, and the hydration kinetics was fitted with the JMAK model. The results demonstrated that the early hydration reaction of SAC was a multidimensional controlled process influenced by various factors. Also, the crystallization nucleation rate of hydration products was inversely related to w/c. Furthermore, a successful nonlinear fitting between the weighted average of T2 and the hydration degree (αt) obtained from IC was established, providing a standard reference curve for studying hydration degree and microstructure. Finally, the hydration products and microstructure were investigated using, SEM, and TG, and the evolution of the compressive strength of SAC was also analyzed. This work gave valuable insights into SAC's early hydration behavior and microstructural development, which can contribute to a better understanding of its performance and potential applications.

We designed a new nanoprobe—NPAPF-Fe3O4 NPs (about 150 nm)—with magnetic targeting fluorescence/magnetic resonance dual-mode imaging by using the combination of an AIE dye NPAPF (bis(4-(N-(2-naphthyl)phenylamino) phenyl)-fumaronitrile) and Fe3O4 NPs. The size of the NPAPF-Fe3O4 NPs was about 150 nm. This design successfully overcame the fluorescence quenching of the organic fluorescent dyes in the presence of metallic materials, which could be used for imaging applications. Under the premise of ensuring fluorescence imaging, we introduced the magnetic resonance imaging contrast agent Fe3O4 NP with higher spatial resolution and high sensitivity, and also a magnetic field–assisted targeting effect. After the surface modification, the NPAPF-Fe3O4 NPs showed good dimensional stability, biocompatibility, and biosafety, and had a longer blood circulation time in vivo. The NPAPF-Fe3O4 NPs were used to study the in vivo and in vitro fluorescence imaging and in vitro magnetic resonance imaging. The results showed that the fluorescence intensity of NPAPF-Fe3O4 NPs was lower than that of NPAPF NPs at the same concentration in cell imaging experiments. However, due to the appropriate Fe3O4 NP doping ratio, better fluorescence imaging could be achieved by NPAPF-Fe3O4 NP both in vitro and in vivo. In addition, in vitro magnetic resonance imaging showed a linear relationship between the 1/T2 of NPAPF-Fe3O4 NPs and the concentration of Fe, which was a T2 contrast agent capable of magnetic resonance imaging.

An eco-friendly UHPC was designed by the modified Andreasen and Andersen packing model and prepared with cement partially replaced by steel slag powder (SSP) and glass powder (GP) at a fixed mass ratio of 2:1. An improved strengths and resistance to drying shrinkage was obtained with a combined replacement of SSP and GP, and the best one was achieved at the 20% replacement ratio. The leaching of Ca2+, Al(OH)4−, and SiO32− ions from SSP and GP promoted the hydration of cement. The potential cementitious activity of SSP and the pozzolanic activity of GP contributed simultaneously to the formation of extra hydration products, especially the high density C-S-H. As a result, the pore structure of the paste matrix was refined and the steel fiber/paste was enhanced. The UHPC developed with SSP and GP had lower carbon emissions and non-renewable energy consumption, which provides possibilities for its industrial application.