A mechanochemical recycling strategy was proposed to mitigate the environmental impacts of magnesium slag (MS) stockpiling and to utilize MS as a lime substitute in fly ash (FA)-based autoclaved aerated concrete (AAC). Mechanical grinding and NaOH activation were employed to modify MS, enabling control over pore evolution and tobermorite crystallization in the AAC system. The results indicated that MS ground for 60 min with 0.4 % NaOH yielded AAC with a compressive strength of 3.96 MPa and a bulk density of 639.08 kg/m3. The study revealed that grinding improved foaming stability by increasing slurry viscosity, while NaOH regulated the gas release rate, achieving a dynamic balance between slurry thickening and gas evolution. Moreover, the increased active sites and lattice defects generated by mechanical grinding facilitated the dissolution of MS particles by NaOH. This synergistic effect of mechanochemical activation led to an enhanced release of soluble calcium ions from MS, promoting the formation of well-crystallized tobermorite and thereby improving AAC strength. However, excessive NaOH caused over-dissolution of Al3+, leading to the competitive crystallization of intermediate phases such as katoite, which interfered with tobermorite formation. This study provides a theoretical basis for the mechanochemical recycling of MS in AAC production.

Precast building components are commonly connected using grouted steel sleeve joints, where grout is injected to ensure effective bonding and force transfer between reinforcing bars. In pressure grouting, a single grouting operation often needs to fill multiple sleeves through narrow passages. Therefore, sleeve grout requires high flowability retention, good uniformity, and high early-age strength, while the use of coarse aggregates should be minimized. Cement-based sleeve grouts are typically modified with chemical admixtures to improve their performance. However, excessive emphasis on flowability may compromise mixture uniformity and stability. Moreover, the influence of aggregate fineness modulus on grout rheology remains insufficiently understood. In this study, the effects of chemical admixtures on particle sedimentation and apparent viscosity stratification were investigated, and the optimal admixture dosage ranges for ambienttemperature sleeve grout were determined. The effects of admixtures on flocculation development in the paste were also analyzed. Furthermore, aggregates and stone powders with different fineness moduli were used to evaluate changes in rheological and mechanical properties and to clarify the role of fineness modulus in maintaining grout uniformity. The results indicate that grout instability and apparent viscosity stratification are primarily caused by delayed flocculation development due to excessive admixture dosage. The internal distribution state of grout can be indirectly assessed using stratified apparent viscosity and the interlayer viscosity difference ratio. The optimal dosages were 0.3-0.4 wt% for polycarboxylate superplasticizer, 0.25-0.35 wt% for defoamer, and 0.10-0.15 wt% for sodium gluconate. Both the 30 min flow spread and yield stress increased with increasing fineness modulus. For grout with identical aggregate gradation, the average apparent viscosity should be adjusted according to construction requirements while maintaining a suitable interlayer viscosity difference ratio. In addition, the fineness modulus should be regulated to enhance or reduce shear-thinning behavior as required.

Although electronic fluorine-containing sludge (FS) with a high CaF2 content exhibits good mineralization effects on cement clinker calcination, its influence on the burnability of low-alkali raw meals with high Cr contents and its ability to also suppress Cr(VI) formation in clinker remain unclear. However, for cement kiln co-processing solid wastes, effectively reducing water-soluble Cr(VI) in clinker from high-Cr raw meal below the Chinese standard limit of 10 mg/kg remains challenging. Here, we prepared a low-alkali raw meal (0.33% equivalent alkali) and doped with Cr2O3 as total Cr content to 90, 140, and 190 mg/kg. Under calcination temperature of 1450 degrees C, the effects of 1.5-3.0% FS containing 25.7% CaF2 on clinker properties, Cr speciation, and water-soluble Cr(VI) were investigated. The results showed that increasing FS dosage decreased f-CaO contents, while clinker compressive strength first rose then declined. Notably, water-soluble Cr(VI) in the clinker dropped markedly with FS addition, with greater reductions observed at higher initial Cr levels. At a raw meal Cr content of 190 mg/kg, FS addition reduced water-soluble Cr(VI) from 14.28 mg/kg in FS-free clinker to 7.60 mg/kg, corresponding to a 46.8% decrease. The further analyses indicated that FS improved the clinker performance and suppressed watersoluble Cr(VI) mainly by promoting C3S development, enhancing the incorporation of Cr into silicate phases, and facilitating the formation of Cr-F-containing compounds, its facilitation of Cr incorporation into silicate phases via solid solution reaction. These findings provide an effective strategy for reducing water-soluble Cr(VI) during co-processing of high-Cr solid wastes in cement kilns.

The fluctuating quality of industrial waste gypsum and its irrational addition into cement easily lead to the growth of secondary ettringite in the precast concrete, then easily resulting in the loss of early strength and the reduced durability of precast concrete. In this study, the components of the cement itself were optimized, the effects of Na2SO4 or Na2CO3 on the early performance of non-gypsum cement and low-gypsum cement were investigated by adjusting the content of gypsum in cement, and the mechanism of synergistic activation of cement clinker by Na2SO4 or Na2CO3 and gypsum was revealed through the analyses of setting time, mortar strength, hydration temperature, QXRD, DTG and SEM. The results showed that the samples with 2 % Na2CO3 added to cement with 0.5 wt% gypsum content obtained excellent 12-hour compressive strength more than 15 MPa and the initial setting time was more than 45 min. which suggested the possible synergistic effect of a small amount of gypsum and Na2CO3, the hydration products Monosulfoaluminate, Monocarboaluminate and Aragonite provide nucleation seeds and growth space for C-S-H, thus contributing to the intensity development of the samples over a 12-h period. However, the above hypothesis needs to be confirmed by further studies.

Autoclaved aerated concrete (AAC) is typically produced using large amounts of lime, which leads to considerable carbon emissions. Steel slag has been identified as a potential substitute for lime; however, it typically reduces foaming efficiency and increases bulk density. Due to limited research on enhancing the foaming performance of steel slag-based AAC, the effects of polyacrylamide (PAM) and hydroxypropyl methylcellulose (HPMC) as foam stabilizers were investigated in this study. The influences of PAM and HPMC on pore structure, hydration behavior, and autoclaving reactions were systematically analyzed. Under alkaline conditions (NaOH), the addition of 0.03 % PAM and HPMC significantly improved pore uniformity, and the mesopore porosity was increased by 72.9 % and 75.2 %, respectively. The resulting AAC exhibited bulk densities of 617.1 kg/m3 (PAM) and 609.2 kg/m3 (HPMC), and compressive strengths of 3.7 MPa and 3.5 MPa, respectively, meeting the GB/T 11968-2020 standards (grades B06 and A3.5). The thickening and water film formation effects of the foam stabilizers optimized the foaming performance and pore structure. The complexation and adsorption interactions between the stabilizers regulated the reaction pathways, promoting the crystallization of tobermorite. These findings demonstrate the dual function of PAM and HPMC in optimizing pore structure and regulating hydration products, offering an effective strategy to enhance the performance and resource efficiency of steel slag-fly ash based AAC.

The co-disposal in cement kiln is significant for waste resource utilization, energy conservation and CO2 emissions reduction. However, common practice of using multi-source wastes with varying impurities poses significant challenges to this technology. For instance, the addition of fluorine-containing sludge into raw meals can significantly alter the properties of cement clinker, it was mainly due to the co-existence of CaF2 and zinc ion as mineralization components in this sludge. The joint effects and mechanisms of these two components on the cement clinker properties have not been fully elucidated until now. To uncover the effects of zinc (ZnO) doping on the formation and hydration of CaF2-bearing C3S, various analytical methods were employed, including XRD, SEM, XPS and hydration heat flow. The results revealed that ZnO doping could activate the composite mineralizing effects of ZnO and CaF2, leading to the very low measurable f-CaO levels and the quite high immobilization rates of beyond 99.5 %. ZnO doping with CaF2 stabilized the R-type C3S polymorphism, and triggered the diffraction positions for polymorphisms move and microstructure reconstruct with many new defects. In C3S cell structure, F- possibly substitute O 2- and linked with Ca2+, Zn2+ possibly replace Ca2+ and linked with O2-. ZnO doping with CaF2 distinctly accelerated the initial hydration, shortened the duration of induction period, accelerated the hydration in the acceleration period, but severely hindered the hydration of deceleration period. In hydration solution analysis, more doping of ZnO and CaF2 preferred to affect the formation of C-S-H, but the less doping preferred to affect the formation of Ca(OH)2, while the slightly increase of F and Zn ions was related with the weak solidification /stabilization capacity of 3d's hydration products.

Ultra-High Performance Concrete (UHPC), with its excellent tensile properties, can be used as an alternative to decorative materials that are heavy in cross-section, enabling architectural decoration field to develop in the direction of light weight and changeable shape. However, the extremely low water-binder ratio of UHPC produces obvious autogenous shrinkage, which leads to the development of many micro-cracks. When the micro-cracks develop to a certain extent, they can have a very negative impact on the finishing of the architecture. This paper studies the influence of medium-burnt quicklime dosing on the hydration process and mechanical properties of UHPC cured at room temperature and elucidates the mechanism by which medium-burnt quicklime reduces autogenous shrinkage in UHPC. The results show that the crystal growth pressure generated by the hydration of f-CaO (free calcium oxide) can significantly compensate the autogenous shrinkage of UHPC. The dosage of 3% medium-burnt quicklime can make the mechanical properties and shrinkage properties of UHPC reach the relative optimum, and the autogenous shrinkage of UHPC can be reduced to 181.36 με. Although the medium-burnt quicklime reduces the hydration products by delaying the hydration of UHPC, it also can reduce the porosity and the percentage of the multi-harmful pores, and refine the pore aperture. In addition, the interfacial transition zone between the UHPC matrix and the steel fibres can be reduced due to the extrusion of Ca(OH)2 crystal growth pressure on the surrounding crystals, resulting in a tighter lapping between the crystals.

The investigate of novel cementitious system suitable for negative temperature concreting was the key way to solve the high energy consumption of traditional winter construction. In this study, the matching effects of anti-freezing agents (CaCl2, NaNO2 and Li2CO3) on the Portland cement-calcium sulphoaluminate cement blended system (PC-CSA system) based on Taguchi-Grey Relational Analysis (Taguchi-GRA method) were studied. The setting time, compressive strength and freezing point were tested, and the hydration products, pore structure and morphology were also analyzed to reveal the mechanism. The results showed that CaCl2 was the main parameter influencing the initial and final setting time. Whether at the early stage of continuous negative temperature curing, or from negative to positive temperature curing, CaCl2 had a dominant influence on the compressive strength of PC-CSA system, which promoted the increase of the early hydration products, resulting in the rapid formation of a network structure. At the later stage of continuous negative temperature curing, the influential parameter changed to NaNO2. The basic condition for hydration was provided due to the lowering of the freezing point of the liquid phase by NaNO2. The presence of Li2CO3 enhanced the promoting effect of CaCl2 on early strength. The optimal parameter combination for PC-CSA system was 1.0 % CaCl2, 2.0 % NaNO2 and 0.4 % Li2CO3 based on Taguchi-GRA method.

Decorative ultra-high performance concrete (UHPC) is easily contaminated with organic and inorganic pollutants owing to its hydrophilicity. Long-term pollution causes the aesthetics of UHPC to diminish gradually. The antifouling ability of decorative UHPC can be improved by adding functional coatings. However, the decorative UHPC surface is smooth and dense. An ordinary superhydrophobic coating offers a single function, and cannot adhere stably to the UHPC surface. The coating detachesis easily off after long-term use, thus causing the material to lose its self-cleaning performance. In this study, a multifunctional self-cleaning coating with a double-layered structure is designed. Polydimethylsiloxane (PDMS) is used as the bottom layer, which increases the adhesion of the coating to UHPC and provides hydrophobicity to the coating. The surface layer is a nano-SiO2/TiO2 superhydrophobic layer modified with polymethylhydrosiloxane. Nanoparticles form a regular micro/nano composite structure on the surface of the UHPC via self-assembly. The introduction of TiO2 imparts excellent photocatalytic performance to the coating. Experimental results show that the prepared multifunctional coating not only prevents the adhesion of inorganic pollutants, but also effectively decomposes organic pollutants, such as methylene blue, and significantly improves the self-cleaning performance of UHPC. When the SiO2:TiO2 ratio is 2:3 and the PDMS content is 2.5 wt%, the static contact angle of the coating surface is 157.2 degrees and the sliding angle is 2.1 degrees. The coating exhibits excellent superhydrophobic photocatalytic performance, wear resistance, water erosion resistance, acid and alkali resistance, and ultraviolet light stability. In addition, the excellent superhydrophobicity and mechanical stability of the coating are explained based on chemical characterisation and micro-area morphology analysis.

A new phase change heat storage coating is prepared in this study, which can regulate indoor temperature. The composite phase change material (D/PCM) with modified diatomite and paraffin was prepared by the porous material adsorption method. D/PCM and coatings were characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and cycle leakage ratio. The SEM results showed that diatomite modified by high -temperature expansion and acidification has a better adsorption capacity. D/PCM and C-D/PCM (heat storage coatings with D/PCM) have nearly no leakage and still show good thermal stability after 500 thermal cycles. In addition, the heat transfer process in a physical model of a reinforced concrete wall was simulated based on hourly variations in summer temperatures in Xi'an, China. The results show that C-D/PCM with a phase change temperature of 26-28 degrees C and a thickness of 5 mm provides greater heat storage capacity, good temperature regulation and energy savings within a reasonable thickness range in summer. The selected PCM coatings have a small temperature fluctuation (2.54 degrees C) and a high phase change utilization ratio (75 %), which can reduce the wall cooling load by 18.67 % in summer and save energy.

The performances and application parameters of phase change materials (PCM) are crucial for integration with construction in practice. In this paper, composite PCMs (CPCM) were prepared by paraffin/expanded graphite (EG) and applied to phase change gypsum board (PCGB). The composite PCM was characterized by SEM, DSC, leakage ratio and thermal conductivity tests to determine the optimal ratio of EG and paraffin; The thermal storage and release properties of PCGB were experimentally investigated by two building cabin models. The results showed that the CPCM obtained 12 wt% EG exhibited excellent thermal conductivity (2.32 W/mK) and latent heat (103.9 J/g). The PCGB prepared with above CPCM has excellent thermal conductivity (0.3968 W/mK) and latent heat (42.2 J/g). When the EG content exceeded 12%, the thermal properties and leakage ratio of the CPCM stabilized after 200 thermal cycles despite the increase of EG. The phase change cabin exhibited much lower heating and cooling rates than that of the pure gypsum cabin, with a 1.14 C decrease in peak internal surface temperature and a 3.4 C decrease in temperature fluctuation. In addition, the room temperature of the established reinforced concrete wall model with PCGB was simulated based on the hourly variation pattern of the winter-summer temperature in Urumqi, China. The results show that in summer, the PCGB with phase change temperature of 29-31 C and thickness of 20 mm possesses a larger heat storage capacity, with a smaller average internal surface temperature (28.63 C) and a higher average phase change utilization (61.5%), which can reduce the cooling and heating load of the wall and save energy effectively.

After long-term use, decorative UHPC may adhere to pollutants due to its hydrophilicity, which affects its aesthetics. Due to the smooth and dense exposed surface of UHPC, ordinary self-cleaning coatings have poor adhesion on its surface and are prone to peeling off due to rain wash in the environment, which cannot maintain the self-cleaning performance of UHPC for a long time. In this paper, a modified self-cleaning coating with a double layer structure was designed. The bottom layer is an epoxy resin (ER) adhesive layer to improve the adhesion performance of the coating to UHPC. The surface layer is a polymethylhydrosiloxane (PMHS) modified nano-SiO2 superhydrophobic layer, which satisfies the self-cleaning characteristics while constructing a regular rough superhydrophobic surface on the UHPC surface. The prepared superhydrophobic UHPC showed good self-cleaning performance, with a static water contact angle of 156.5 and a sliding angle of only about 2.2. The performance test results show that the double-layer structure design makes the superhydrophobic coating have good wear resistance, water erosion resistance and excellent chemical stability. The surface functional groups, micro-area morphology and roughness were characterized by Fourier transform infrared spectrometer, scanning electron microscopy, optical profiler and atomic force microscopy, respectively. The reasons for the excellent self-cleaning performance and long-term stability of the coating were explained.

Inorganic repair materials such as ordinary Portland cement-calcium aluminate cement-gypsum (OPC-CAC-G), which consist of ordinary Portland cement, aluminate cement, and gypsum, have advantages of fast hardening, high early strengths, and minimal expansion; however, they also have the disadvantages of low bond strengths and weak interface areas, which often lead to repair failure. The interfacial bonding properties of repair materials can be improved by adding highly flexible polymers. In this study, the effects of styrene-butadiene rubber (SBR) and ethylene vinyl acetate (EVA) on the interfacial bonding properties of OPC-CAC-G bonding and the mech-anism of the effect of the microstructure are examined using X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The results show that and EVA are both effective in improving the interfacial bond strength of OPC-CAC-G repair mortars. SBR is suitable for the modification of repair mortars with an optimum dose of 20%; EVA is suitable for the use as an interface agent on the surface of damaged concrete substrates with an optimum concentration of 40%.

In this paper, a parameter-based design approach for phase change wallboard is presented. Based on existing gypsum composite phase change materials, COMSOL simulation software was used to understand the influence of parameters including phase change temperature, wallboard thickness, thermal conductivity, and latent heat value on the thermal performance of phase change wallboard and analyze different indoor environments and energy-saving efficiency of various parameter schemes in practical application. The effect of those parameters for phase change wallboard that used in outer envelopes and inner partitions is also compared to determine an optimized scheme for phase change wallboard applied in the city of Xi'an. The results demonstrate the most important element that affects the inner surface temperature is the thickness of the phase change wallboard, then the phase change temperature, and last thermal conductivity. Using integrated PCM on the envelope is not only beneficial to adjust the indoor thermal environment and reduce energy consumption, but also help to achieve the best cooling and energy conservation effects by optimizing material parameters in practice. The phase transition temperature of PCM applied in walls should approach mean temperature. Furthermore, exterior walls need PCW with larger thickness and smaller thermal conductivity, and interior walls equip PCW with higher thermal conductivity and latent heat. The optimized scheme can reduce the average room maximum temperature by 1.24 degrees C and the cooling load by 953 W per square meter.

Fluorine in fluorite mineralizer and copper were easily doped together into cement clinker during cement kiln co-disposing wastes bearing Cu, yet that co-doping effects on the formation and hydration of cement clinker get few attention. The findings in this work revealed that the co-doping CaF2 (fluorine source) and CuO (copper source) into cement clinker showed a synergistic effect on the burnability, the immobilization rates of fluorine and copper in clinker phased were promoted. Compared with doping CaF2 into cement clinker, Co-doping CaF2 and CuO further enhanced the formation of alite and brownmillerite, while hindered the formation of tricalcium aluminate, and also triggered the right shift of characteristic diffraction peaks for C3S polymorphisms. It co-doping not only changed the microstructures, but also induced the visible defects on the surfaces of clinker mineral grains. In addition, most of fluorine would likely enter into the alite structure by replacing O2– of silicate phases, while most of copper would possibly enter into the brownmillerite structure by replacing Fe3+. Compared with the hydration process of cement clinker doped with CaF2, Co-doping CaF2 and CuO further accelerated the initial hydration process, obviously prolonged the induction period, but promoted the later hydration of co-doped clinker. Although the mechanisms about co-doping on the hydration process of co-doped clinker need more investigation, the above findings could extend the value-added utilization of wastes bearing Cu to reduce the large CO2 emission and energy/resource consumption in cement industry.

Fluorine (F) from fluorite mineralizer and copper (Cu) would be introduced together into raw meals during cement kiln co-processing hazardous wastes containing Cu, unfortunately the cooperation effects of fluorine and copper on the properties of cement clinker are still vague, it directly restricts the resource utilization of these wastes in the cement industry. Therefore, the cooperation effects of fluorine (CaF2) and copper (CuO) on the formation and properties of tricalcium silicate (C3S) were unveiled. The results indicated that a small cooperation addition of CuO could reduce distinctly f-CaO content of C3S doped with CaF2, and its burnability would be promoted notably, the immobilization of fluorine and copper in doped C3S also were promoted. Compared with C3S doped with CaF2, a cooperation addition of CuO and CaF2 further improved the formation of C3S grains and increased the structural symmetry of C3S crystal. The cooperation effects triggered the diffraction peaks for C3S polymorphisms to shift right, and induced the visible defects on the surface of C3S grains. In the current incorporation amounts of CaF2 and CuO into C3S, F- and Cu2+ would dissolve in its structure possibly by the replacement of O2- and Ca(2+ )respectively. CaF2 addition accelerated the initial hydration, but postponed the later hydration of C3S. The initial hydration was further accelerated by a cooperation addition of CuO, and its effects would be quite different if changing cooperation amounts of CaF2, accelerating or decelerating the hydration process of doped C3S relied on the cooperation amounts of CaF2 and CuO. The findings in this work would be expected to provide a promising solution to reduce the large energy consumption and CO2 emission in cement industry.

Flue gas desulfurization gypsum blocks were prepared using polymethylhydrosiloxane as a waterproofing and antiefflorescence agent, flue gas desulfurization gypsum as the matrix, and fly ash as the mineral admixture. The mechanical properties, water absorption, softening coefficient, surface contact angle, phase composition, and microstructure of the flue gas desulfurization gypsum blocks were determined with a universal testing machine, contact angle tester, X-ray diffractometer, Fourier-transform infrared spectrometer, and scanning electron microscopy. The salt crystallization phenomenon on the block surfaces was also observed to evaluate antiefflorescence performance. Results showed that flue gas desulfurization gypsum blocks containing 0.4 wt% polymethylhydrosiloxane had optimal overall properties. The compressive and flexural strength values were 16.03 and 6.80 MPa, respectively; the water absorption rate was 3.25%; the softening coefficient was 0.83; and the contact angle with water was 121.75?. The introduction of polymethylhydrosiloxane improved water resistance for flue gas desulfurization gypsum blocks, which also discharged water from the blocks and removed soluble salt, effectively prevented efflorescence.

Brain-computer interfaces (BCIs) are currently integrated into traditional rehabilitation interventions after stroke. Although BCIs bring many benefits to the rehabilitation process, their effects are limited since many patients cannot concentrate during training. Despite this outcome post-stroke motor-attention dual-task training using BCIs has remained mostly unexplored. This study was a randomized placebo-controlled blinded-endpoint clinical trial to investigate the effects of a BCI-controlled pedaling training system (BCI-PT) on the motor and cognitive function of stroke patients during rehabilitation. A total of 30 early subacute ischemic stroke patients with hemiplegia and cognitive impairment were randomly assigned to the BCI-PT or traditional pedaling training. We used single-channel Fp1 to collect electroencephalography data and analyze the attention index. The BCI-PT system timely provided visual, auditory, and somatosensory feedback to enhance the patient’s participation to pedaling based on the real-time attention index. After 24 training sessions, the attention index of the experimental group was significantly higher than that of the control group. The lower limbs motor function (FMA-L) increased by an average of 4.5 points in the BCI-PT group and 2.1 points in the control group (P = 0.022) after treatments. The difference was still significant after adjusting for the baseline indicators ( $\beta =2.41$ , 95%CI: 0.48–4.34, P = 0.024). We found that BCI-PT significantly improved the patient’s lower limb motor function by increasing the patient’s participation. (clinicaltrials.gov: NCT04612426)

The titanium-containing pickling sludge (TS sludge) was regarded as one hazardous waste due its Cu, Zn and Ni leaching pollution, and there were hardly any effective treatments on the TS sludge. The feasibility of utilizing TS sludge to prepare raw meal was discussed by a series of experiments. The results revealed that 1.0% addition of the TS sludge effectively improved the burnability of the calcined clinker, and forwarded the formation of alite with more amounts and smaller size, while 5.0% addition of the TS sludge led to more formation of interstitial phases, and further hindered the formation of alite and belite. The optimal workability of produced cement at different calcination temperatures was acquired as the addition reached 1.0%, and the highest unconfined compressive strength of produced mortars was attained as 49.37 MPa (28 days) when 1.0% addition of the TS sludge was incorporated at 1450 degrees C. Fluorine in TS sludge mainly distributed in the silicate phases, and mostly accumulated on the boundary of alite and belite phases. The preferential distribution of titanium was detected in the interstitial phases, but the distribution of Cu, Ni and Zn was stochastic. This had a positive effect on the prevention of corrosion of steel, by free fluorine ions, when used in reinforced concrete, and it provides a feasible direction for the comprehensive utilization of titanium-containing pickling sludge with limited proportions in cement raw materials. The immobilization ratios of F, Cu, Zn and Ni were higher than 99.50%, and the hazardous elements leaching under different leaching environments incorporating 5.0% addition of the TS sludge would not provoke the second leaching pollution. (C) 2020 Elsevier Ltd. All rights reserved.

The comprehensive utilization of wasted pickling sludge in the cement kiln would be a promising practice, but the calcination process of cement clinker became complicated due to the simultaneous introduction of titanium and fluorine. In this paper, the formation and hydration of tricalcium silicate (C3S) doped with CaF2 and TiO2 were discerned by XRD, FT-IR, XPS and isothermal calorimetry. The results revealed that the addition of CaF2 more than 1.5% would promote the appearance of CaTiO3 as the indicator of the solution limit of TiO2, and the formation of CaTiO3 and beta-C2S was a concomitant process as the solution limit of TiO2 reached. The addition of 0.5% TiO2 and some addition of CaF2 (<= 1.5%) would reduce the polymorph symmetry of C3S, while more addition of CaF2 and TiO2 would actualize the higher polymorph symmetry from Ml to R form. The IR spectra for the polymorphs (T3, M3, R + M3, R) became broader with the increase of the polymorph symmetry of C3S. The replacement of O-2 by F would not be interfered by the simultaneous introduction of titanium, a Ti2p 1/2 peak at 463.39 eV reflected the solution of titanium in the structure of C3S, and the defect reactions of the doped C3S with CaF2 and TiO2 were proposed. The doped C3S had a higher heat flow than the undoped C3S in the initial period, the more addition of CaF2 inhibited the initial hydration activity of C3S, while the addition of TiO2 improved the effect. The incorporation of TiO2 into the doped C3S aggravated the retardation effect caused by CaF2 on the hydration in the acceleration period. The dopant types displayed a more distinct effect than the types of C 3 S polymorphs on the hydration activity of C3S. (C) 2020 Elsevier Ltd. All rights reserved.