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Various problems are often encountered during the backfilling process of deep foundation pits. The development of low-cost and efficient solidified materials for the preparation of fluidized solidified soil is currently an ideal solution. This article used industrial solid waste (granulated blast furnace slag, fly ash, carbide slag, etc.) as the main raw material to study the hydration hardening properties of solidified materials and the construction feasibility of fluidized solidified soil prepared from solid waste materials. The results are as follows: Compared with cement-based materials, solid waste-based solidified materials had lower early activity. The cumulative heat release within 72 h was less than 200 J/g. Different solid wastes, such as fly ash and carbide slag, had different effects on the properties of solidified materials. Overall, they had the potential to prepare fluidized solidified soil. The prepared fluidized solidified soil had a fluidity greater than 350 mm, a 28d compressive strength greater than 3 MPa, and exhibited good workability and excellent mechanical properties. Hydration products such as C-S-H and AFt were filled in the soil structure. The 28d compressive strength well above the design requirements of general engineering projects. Meanwhile, the prepared fluidized solidified soil had good adaptability to conventional water reducers (fluidity could be increased by more than 40%) and early strength agents (1d compressive strength could be increased by more than 60%). • Use fluidized solidified soil to solve the problem of backfilling deep foundation pits. • Utilize the synergy between industrial solid waste to improve the solidification effect. • Establish the connection between solidified materials and fluidized solidified soil. • The adaptability of fluidized solidified soil to admixtures was studied. [ABSTRACT FROM AUTHOR]

As a part of by-product generated during the incineration, the municipal solid waste incineration fly ash (MFA) is a secondary pollutant. The ordinary Portland cement (OPC)-based stabilization/solidification (S/S) is a prevalent and robust technique for the treatment of MFA, which can not only effectively dispose the MFA, but also decrease the demand of OPC and reduce the greenhouse gas emissions. However, when MFA was directly utilized to partly replace the cement with a replacement ratio of 15%, the MFA-OPC based composites exhibited inferior mechanical properties. The nano silica (NS) was considered to be introduced to compensate for the strength loss caused by the MFA. In this research, the NS with varying dosages and particle sizes were integrated into the MFA-OPC composites and in total seven groups of the composites were prepared. The mechanical properties of the composites were examined and the results indicated that the composites containing 2 wt% 100 nm NS presented relatively superior mechanical properties. The incorporation of NS could increase the compressive strength of MFA-OPC composites by 37.5% at later age. Then, thermodynamic modelling and the micro-structural analysis including hydration heat, XRD, TG, MIP and SEM were coupling applied to probe into the NS modification mechanism. Experimental results indicated that the addition of NS enhanced the strength of OPC containing MFA at both early and later ages via pozzolanic reaction, hydration acceleration and micro filling effects. Overall considering the macro performance improvement and microstructure modification effect, the 2 wt% NS with particle size of 100 nm was recommended to be utilized. Therefore, this study expands the emerging application of NS and demonstrates that NS-augmented binders can ensure low-carbon and high-performance S/S of hazardous materials. • The nanoSiO 2 with varying particle sizes and dosages were utilized to compensate for the performance loss caused by the MFA. • The experimental analysis and thermodynamic modeling were coupling used to investigate the effect of nanoSiO 2 on the composites. • The optimal nanoSiO 2 particle size (100 nm) and dosage (2%) was recommended. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new nano-modified superstable foam was designed to improve the mechanical properties and pore structure of carbon fixation foam concrete. • High performance additive technology and early carbonation curing were used to improve the mechanical properties of eco-porous carbon fixation concrete. • The influence mechanism of polyvinyl alcohol on carbonation behavior of carbon fixation foamed concrete and its performance improvement mechanism were found and clarified. The introduction of carbon fixation components (calcium hydroxide) can improve the carbon fixation performance of foam concrete, however, it will reduce its mechanical properties. In order to solve the adverse effects of carbon fixation components on the mechanical properties and optimize carbon absorption properties, a specific amount of polyvinyl alcohol (PVA) is incorporated. In this study, a serial of test was employed to study the production process of nano-modified foam, and some basic properties of the foam concrete of interest. Further, the micromorphology and pore structure of the samples were analyzed by scanning electron microscope and mercury injection test. The evolution of mineral phases was examined by X-ray diffraction and thermogravimetric analysis. The results show that the carbon sequestration efficiency of foam concrete increases significantly as the amount of calcium hydroxide is increased, however, the cementitious properties of materials deteriorate, resulting in a decrease in strength. When PVA is added as a water-soluble admixture, it can enhance the mechanical properties of test blocks. It can also strengthen the bubble film of nano stabilized foam, increase bubble stability, and refine the internal pore structure of carbon fixation foam concrete. In addition, PVA can modify the calcium hydroxide morphology from a laminar structure to a smaller volume edge corrosion structure, which improves the reaction activity of calcium hydroxide with CO 2 and boosts the efficiency of carbon sequestration. [ABSTRACT FROM AUTHOR]

A commercial interest in the improvement of durability is driving efforts to develop new generation of surface-treatment agents. In the previous paper, a series of nanoSiO 2 -polycarboxylate superplasticizer core-shell nanoparticles (NS@PCE) were synthesized by “grafting to” method. In this paper, we aim to explore the potential of NS@PCE to densify the surface of cementitious materials, and to study the mechanism of nanoparticles surface-treatment process by measuring water absorption ratio, dispersion stability, pozzolanic reactivity, and mercury intrusion porosimetry. Results show that NS@PCE is effective in reducing the water absorption. Various NS@PCE present different influences, it seems that NS@PCE with a moderate shell-core ratio is a more reasonable choice. A hypothesis was proposed to explain the surface-treatment effect of nanoparticles, it utilizes two properties (dispersity and pozzolanic reactivity) of nanoparticles to describe their refining-pore performance. This research indicates a new pathway for nanoSiO 2 to optimizing cementitious materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel hybrid nanoSiO 2 containing fluorinated organic (NS@TOFS) was designed. • NS@TOFS can reduce the water absorption and carbonation of coated mortar. • NS@TOFS modified surface shows less degradation after exposure to UV-rays. • A triple layered structure of NS@TOFS modified surface was found and clarified. In surface treatment technics of cement-based materials, nanoSiO 2 (NS) is effective in refining pore structure while organic water-repelling agents are often used for producing a hydrophobic surface. Due to its advantages of pore refining effect and hydrophobicity, the organic-inorganic hybrid nanoSiO 2 has attracted increasing attention. However, the UV-irradiation can result in photodegradation of organic constituents, leading to deterioration of hydrophobicity. In this study, a novel UV-resistant fluorinated hybrid nanocomposite, NS@TOFS, was synthesized and used for surface treatment on hardened cement-based materials. The water and gas permeability of the treated samples before and after UV-aging were assessed by measuring the water absorption rate, water contact angle and carbonation degree. The experimental results showed that the NS@TOFS treated samples possess enhanced water and gas impermeability after 14 days of exposure to UV rays. A morphological observation of the treated surface revealed that a synergistic effect of organic film and refined pore structure was responsible for the improved surface properties. Findings from this study well demonstrate that the developed fluorinated hybrid nanoSiO 2 holds great promise for enhancing the durability of cement-based materials under UV-irradiations. [ABSTRACT FROM AUTHOR]

NanoSiO 2 has been widely used to improve properties of cement-based composites, but effective dispersion of nanoparticles in cementitious materials remains to be a challenge for their practical applications. This paper introduces a surface modification technique that can enhance dispersion of nanoparticles in aqueous system, especially in the pore solution of cement paste. First, a series of nanoSiO 2 -polycarboxylate superplasticizer core-shell nanoparticles (nanoSiO 2 @PCE) were synthesized from silanized polycarboxylate superplasticizer and colloidal nanoSiO 2 by the “grafting to” method, the prepared nanoSiO 2 @PCE were characterized by DLS, FTIR, and TGA. Then the investigation on the interaction between nanoSiO 2 @PCE and cement shows that nanoSiO 2 @PCE exhibits higher stability in saturated calcium hydroxide solution than pristine nanoSiO 2 , and the heat development during cement hydration can be regulated by shell structure of nanoSiO 2 @PCE. The research provides a new route for nanoSiO 2 to optimizing cement-based composites. [ABSTRACT FROM AUTHOR]

• A kind of NS@GO core-shell nanoparticles was synthesized and firstly applied to reinforce cementitious materials. • The incorporation of NS@GO could more effectively enhance the mechanical property of cement composites. • A hypothesis named sandwich effect was proposed to explain the reinforcing results of NS@GO. Graphene oxide (GO) has enormous potential to improve properties of cementitious materials. Well dispersed GO in hardened cement matrix could be more effective in strengthening concrete compared to aggregated GO. While GO agglomeration is somewhat inevitable due to its fine nature, the degree of agglomeration could be tuned through particle separation. In this study, nanoSiO 2 @graphene-oxide (NS@GO) nanoparticles were synthesized using GO and colloid nanoSiO 2 (NS) by a electrostatic self-assembly method. NS, GO and the prepared NS@GO were characterized by x-ray diffraction, scanning electron microscopy, atomic force microscopy, and Fourier transmission infrared, and, the influence of NS@GO addition on the mechanical properties of cementitious composites was investigated. The results show that NS@GO can increase the flexural strength of cement composites by 49.2% at later age. A "sandwich effect" was proposed as an important reinforcing mechanism of NS@GO based on the microstructure and hydration products of NS@GO added composites. Compared with the simple NS-GO blend, NS@GO can better maintain the spatial structure of GO when mixed with cement. In addition, there would be more interactions between calcium silicate hydrates and GO during the cement hydration process, which contributes to the strength gain in NS@GO added mix. The research sheds new light on using GO and NS to optimize cementitious material design, as well as spatial coordination of different types of nanoparticles. [ABSTRACT FROM AUTHOR]

[Display omitted] • SCMs pastes by CO 2 and coupled CO 2 -standard curing were exposed to high temperature. • Coupled CO 2 -standard curing yielded the highest compressive strength at 600 ℃. • Coupled CO 2 -standard curing of SCMs pastes induced a denser pore structure at 600 ℃. • Glass powder barely showed pozzolanic reaction or carbonation promotion but was inert in cement blocks. This study seeks to understand the influence of CO 2 curing on the high-temperature performance of cement paste incorporated with different types of common supplementary cementitious materials (SCMs). The results showed that due to the simultaneous generation of CaCO 3 and hydration products, the samples carbonated for 2 days and then standard cured for 26 days (CS curing) had the best high-temperature resistance, which was reflected by higher compressive strength, lower water absorption and decreased water sorptivity. Interestingly, the porosity of the CS cured ground granulated blast furnace slag (GGBS)-incorporated cement block decreased by 26.80% after exposure to 600 ℃ due to the transformation of large loose pores into more compact small pores. Glass powder (GP) was inert in the paste matrix with no obvious pozzolanic reaction and negligible improvement of carbonation degree, leading to the lowest elevated-temperature performance; whereas, GGBS and fly ash (FA) increased the generation of CaCO 3 by 19.05% and 15.08%, respectively. Overall, findings from the present study demonstrate that the employment of CS curing of SCMs blended cement blocks has great potential to reduce carbon footprint and improve performance under elevated temperatures. [ABSTRACT FROM AUTHOR]

Highlights • DIP was applied to analysis the microstructure. • The relationship between pore size and pore shape was established. • The forming mechanisms of capillary pores was studied. Abstract Pore structure is a significant microstructural characteristic in cement-based materials and dominates the mechanical and transport properties of the materials. In this study, sectional plane analysis based on backscattered electron scanning electron microscope (SEM-BSE) images was used to provide insights into the nature of the pore structure. The effects of the w/c ratio on the total porosity and heterogeneity of the local porosity were analyzed. By coupling using Digital Image Processing (DIP) method, each single pore displayed on SEM-BSE images was captured, and the equivalent circular diameter, hydraulic radius, and roundness of each single pore were calculated to describe its size and shape characteristics. The relationship between the pore size and pore shape was also established by comparing the pore size distribution and the shape parameter distributions. Results indicates that pores become less spherical with increasing pore sizes. Status oriented model was further introduced to simulate the hydration process and investigate the forming mechanisms of capillary pores. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mass ratio of CA-SA to MMT is 35:65 which can prevent the leakage of PCM. • CA-SA/MMT/GR has suitable phase change temperature and high latent heat. • CA-SA/MMT/GR can keep the thermal property after 300 thermal cycles. • The thermal conductivity of CA-SA/MMT/2 wt%GR increases by 156.4%. • CA-SA/MMT/GR significantly enhances the heat storage capacity of mortar. A novel composite phase change material (PCM) of capric-stearic acid/montmorillonite (CA-SA/MMT) with thermal conductivity enhanced by graphene (GR) was prepared. It was characterized by FT-IR, XRD, SEM, DSC and thermal conductivity tests. The temperature response of CA-SA/MMT/GR was evaluated by heating and freezing the composite PCMs in tinfoil cups. The phase change mortar containing CA-SA/MMT/2 wt%GR was also prepared, and its mechanical strength and thermal behavior were tested. The adsorption rate experiment results show that the mass ratio of CA-SA to MMT is 35:65, which can effectively prevent the leakage of PCM. The FT-IR, XRD and SEM results demonstrate that the prepared CA-SA/MMT/GR has good chemical compatibility and stability. The DSC results reveal that the CA-SA/MMT/GR has suitable phase change temperature and high latent heat, and it can retain the phase change behavior after 300 thermal cycles. The thermal conductivity of CA-SA/MMT/2 wt%GR increases by 156.4% compared with CA-SA/MMT. The heat transfer efficiency of CA-SA/MMT gradually increases with the increase of GR. The mechanical strength and thermal behavior results of phase change mortar demonstrate that the flexural strength and compressive strength decrease and the heat storage capacity increases with increasing the percentage of CA-SA/MMT/2 wt%GR. [ABSTRACT FROM AUTHOR]

[Display omitted] • Combined use of waste glass and RHA greatly alleviates wastes disposal at landfills. • Use of RHA improved mechanical and durability of cement mortar. • Addition of RHA suppressed RG-induced ASR expansion. • RHA holds great promise as eco-friendly pozzolanic materials. Using recycled glass (RG) to replace river sand in the production of cement-based materials saves the increasingly depleting natural sand resources. Previous studies have shown that the smooth surface and reactive silica of RG adversely affected its bonding with the cement paste and thereby caused a potential alkali-silica-reaction (ASR). This study used rice husk ash (RHA) as an eco-friendly mineral admixture to ameliorate the properties of the RG incorporated mortar. A fixed replacement of 50% RG was used to replace sand, while varying proportions (10%, 20% and 30%) of RHA were adopted to replace cement. For comparison, a mixture containing only sand and cement was used as the reference sample. The flexural and compressive strength, water absorption, ASR expansion, and rapid chloride mitigation (RCM) of the hardened samples were evaluated. In addition, SEM, XRD, and TG analysis were employed to analyze the microstructures and chemical compositions of different samples. The results showed that incorporating RG as a river sand replacement in cement mortar reduced flexural and compressive strength and increased water absorption and chloride ion penetration. Moreover, the ASR expansion value (0.34%) was beyond the permissible limit (0.1) indicated by the ASTM C1260. The addition of RHA improved the mechanical properties and durability of the cement mortar at a later curing age as a result of the RHA-induced pozzolanic reaction and micro-filler effect. By converting portlandite (CH) derived from cement hydration into secondary C-S-H, the use of RHA greatly reduced the porosity (augmenting the compressive and flexural strength) and concurrently suppressed the RG-induced ASR expansion. The results of XRD, SEM and TG analysis corresponded well with the macro-property analysis and helped to elucidate the underlying mechanisms of the RHA-induced beneficial effects. Findings from this study provide new insights into the potential use of eco-friendly RHA in addressing the mechanical and durability problems associated with the use of RG as aggregate in cementitious materials. [ABSTRACT FROM AUTHOR]

• The effect of polyacrylamide on the corrosion inhibition performance of steel was studied. • Polyacrylamide improves the corrosion inhibition performance of steel. • PAM participates in the formation of adsorption film on the steel surface. The research examined the effect of polyacrylamide (PAM) on corrosion inhibition performance for steel in the simulated concrete pore solution. Linear polarization resistance, electrochemical impedance spectroscopy, potentiodynamic polarization, X-ray Photoelectron Spectroscopy and molecular dynamics simulations are performed to investigate the inhibitive effect and mechanism of PAM for steel corrosion. Results reveal that PAM improves the inhibition performance of steel corrosion and the inhibition efficiency increases with PAM content increasing. The maximum inhibition efficiency (about 99%) is achieved when the concentration of PAM is 0.15%. The improvement of corrosion inhibitive performance by PAM is due to the generation of adsorption film on steel, and the adsorption of PAM is following the Langmuir adsorption isotherm. In addition, the inhibition mechanism by PAM on steel corrosion is determined using molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

• The effect of fine aggregate size on the ITZ's microstructure was studied via SEM-BSE technique. • A numerical method was proposed to calculate the spacing factor between adjacent sand particle. • ITZ volume fraction was determined via nearest surface function and inflection distance for ITZ overlapping was derived. • ITZ thickness was compared with inflection point and average spacing factor to illustrate the percolation effect. The interfacial transition zone (ITZ), existing between the cement matrix and aggregates, is commonly viewed as a weak link for its highly porous microstructure. Enormous research has been conducted experimentally, analytically, and numerically on ITZ from the aspects of its forming mechanisms and influencing factors. In this paper, the effect of fine aggregate size on the formation of ITZ was investigated as well as the overlapping of ITZ between adjacent aggregate particles. Four mortar mixes were prepared with varying fine aggregate sizes. Via quantitative analysis on the backscattered electron image (BSE), the porosity and thickness of the ITZ was experimentally determined. Nearest surface function was further introduced to calculate the volume fraction of the ITZ based on the obtained thickness. Also, the inflection point for overlapping was roughly estimated from the differential volume fraction distribution curve of ITZ. The spacing factor between adjacent aggregate particles was defined and numerically calculated, which was further compared with value of ITZ thickness and inflection point for overlapping to understand the role of aggregate size on the overlapping phenomenon of ITZ. [ABSTRACT FROM AUTHOR]