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The performance of composite binders with high-volume steel slag (SS), granulated blast furnace slag (GBFS) and desulfurization gypsum (DG) were systematically investigated. The results show that the synergistic effects of high volume (40–60%) of SS with GBFS and less than 15% of DG could perform adequate setting time, higher strength, well volume stability and soundness as well as dense microstructure. The higher compressive strengths exceeding 70 MPa at 28 days and up to 80 MPa at 90 days could be obtained for composite pastes with high-volume SS, which exhibit tight relationships with [CaO]·[SO3]/[Al2O3]·[SiO2] and [CaO]·[Al2O3]/[SO3]2 molar ratios. More (15–19%) AFt and less (about 1%) portlandite produced during the hydration of composite binders. C–S–H gels and calcite crystals were formed. The composite binder possesses lower energy consumption, high carbon reduction and low cost compared with Portland cement in favor of the low-carbon cementitious material production and effective utilization of SS. [ABSTRACT FROM AUTHOR]

The present research investigated the influence of steel slag (SS) with variable particle size on the workability and mechanical properties of concrete. Different SS size ranges (0-15 μm, 15-30 μm, 30-45 μm and 45-80 μm) were obtained by sieving and then were characterised by a laser particle size analyser and a scanning electron microscope (SEM). The slump, compressive strength, pore structures and thermal analysis were used to evaluate the effect of the SS particle size on cement and concrete properties. The experimental results showed that finer SS (0-15 μm and 15-30 μm) resulted in negative effects on the workability, while 30-45 μm and 45-80 μm SS particles presented completely opposite results. Both of these effects were more apparent as the steel slag replacement ratio was increased up to 30 wt.%. Concrete samples with 0-15 μm and 45-80 μm SS particles presented comparable 7- and 28-day compressive strength to the control concrete when their replacement ratios were less than 10 wt.%. Moreover, the concrete samples with 45-80 μm SS particles at 5% dosage developed the highest compressive strengths at 7 and 28 days, which were 2% and 5% higher than the control sample, respectively. The pore structure results indicated that a composition of 5% 45-80 μm SS particles was advantageous for refining the pore structures of cement paste, further contributing to the 28-day compressive strength development of concrete.

Steel slag (SS) has been largely discharged but little utilized, causing an environmental problem in China. In this paper, SS-based composite cementitious materials with high strength were prepared by the high volume of SS (≥40%), granulated blast-furnace slag (GBFS), fly ash (FA), flue gas desulfurization gypsum (FGDG) and cement to promote the effective utilization of SS. The hydration and hardening properties were studied through setting time, compressive strength, length change, isothermal calorimetry (IC), X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS) tests. The results show that SS-based composite cementitious material exhibited a lower hydration heat release, an appropriate setting time, and volume stability. The SS cementitious material with 40% SS could obtain high strength of over 65 MPa at 28 days and 80 MPa at 90 days. The strength value of > 60 MPa is present in the binder, with 50% SS at 56 days. GBFS promotes hydration reactions and the formation of AFt and C-(A)-S-H gel, thus enhancing compressive strength. FA has a beneficial effect on later strength. The small and fine pore structures contribute to the development of strength. The main hydration products of SS composite cementitious materials are C-(A)-S-H gel, and ettringite (AFt), with less Ca(OH)2. The C-(A)-S-H gel with a lower Ca/Si ratio and a higher Al/Ca ratio in cementitious material, promotes mechanical properties. [ABSTRACT FROM AUTHOR]

Nanomaterials are widely used in cement to improve the various properties of cement-based materials. Nano-CSH is considered as an effective accelerator for the hydration of cement. This paper studied the effects of nano-CSH on the hydration behavior and compressive strength of cementitious materials with various mineral admixtures. Isothermal calorimetry test was used to study the early hydration of cement paste. Thermogravimetric and X-ray diffraction tests were used to study the evolution of hydration product and unhydrated mineral phases in the hydrated cement paste. The presentation of compressive strength can evaluate the influence of nano-CSH on the property of cement-based material at the macro level. The obtained results show that the used nano-CSH can promote the hydration of tricalcium silicate (C3S), and is more active on the hydration of tricalcium aluminate (C3A) in the samples with GGBFS. The presence of nano-CSH can definitely accelerate the secondary hydration reaction of mineral admixtures. [ABSTRACT FROM AUTHOR]

This paper reports the effects of welan gum on the hydration and hardening behaviors of Portland cement (PC) by using X-ray diffractometry, mercury instruction porosimetry, thermogravimetry, differential scanning calorimetry and scanning electron microscopy. Results show that welan gum has notable influence on the setting time of PC paste and the formation of calcium hydroxide (Ca(OH)2); welan gum has little impact on the total hydration heat, AFt content and/or the morphologies of hydration products even though it delays the induction period of hydration and the second reaction of the aluminate phase. Welan gum retards the early hydration of C3S and accelerates the early hydration of C4AF. The compressive strength is improved, and pore size of hardened cement paste is reduced with at the studied period when welan gum is no more than 0.05%. In this research, the cement paste with 0.05% welan gum exhibits the highest long-term (90 d) compressive strength and lowest porosity. [ABSTRACT FROM AUTHOR]

Alite-belite-ye'elimite (ABY) cement is considered to be eco-cements with adequate mechanical properties and fewer CO 2 emissions. The phase assemblage and ye'elimite content of ABY cement play a very important role in cement properties. In this study, ABY clinkers with increasing ye'elimite percentage (0.3 wt%-36.4 wt%) were prepared at 1300 °C and the phase composition was characterized by Rietveld Quantitative Phase Analysis combined with energy dispersive X-ray spectrometry. The ye'elimite formed with a calculated composition of Ca 3.92 Mg 0.02 Al 2.81 Fe 0.05 Si 0.04 S 1.16 , incorporating additional sulfur compared to the theoretical value. In addition, the hydration properties of heat evolution, hydration products and compressive strength of ABY cement are studied. The result shows that the increase of ye'elimite content leads to a more intense initial heat release and a higher cumulative heat release. The presence of ye'elimite inhibits the hydration of alite at early ages. ABY mortars with increasing ye'elimite (15.8 wt%) exhibited a higher strength (29.6 MPa) at 3 days by the contribution of ye'elimite hydration, and an increase (47.4 MPa) at 28 days. An adequate proportion of ye'elimite (<15 wt%) is favorable to the performance of ABY cement, and releases 12 % less CO 2. • ABY clinkers with a high coexistence of alite and ye'elimite were prepared. • Ye'elimite has a higher S atom and alite riches in the Zn atom in ABY clinker. • The presence of ye'elimite retards alite hydration adverse to later strength. • Adequate ye'elimite < 15 wt% favors strength development. [ABSTRACT FROM AUTHOR]

Aerogels, with ultra-low density and thermal conductivity, are key materials for the development of high-efficient thermal insulations. Yet, their low compressive strength, oxidation behavior, and poor thermal stability limit their further development. Herein, we have prepared a novel monolithic mullite aerogel using the RF/Al 2 O 3 -SiO 2 aerogel organic/inorganic hybrid as the precursor, followed by the CO 2 supercritical drying, and high-temperature mullitization. The resulting mullite aerogel displays typical "pearl-necklace" three-dimensional network, with the average pore size at around 10–20 nm, showing a large BET specific surface of 481 m2/g. The compressive strength of the mullite aerogel is as high as 15.5 MPa, much larger than those of the reported ceramic aerogels. The mullite aerogel exhibits excellent thermal insulation property, and the mass loss is only 2.5% after the butane torch evaluation with 1300 °C for 10 min under air, showing its rather excellent anti-oxidation performance, and the anti-oxidation mechanism is also proposed. • A novel monolithic mullite aerogel for high temperature thermal insulation is developed. • The aerogel shows large BET specific surface area with excellent thermal insulation property. • The aerogel displays much higher mechanical strength as compared with the reported aerogels. • The mechanism of superior anti-oxidation property for mullite aerogel is proposed in this work. [ABSTRACT FROM AUTHOR]

• THEED can be used as accelerator agent to shorten the Portland cement. • THEED has the advantages of TEA and TIPA, increasing the early compressive strength and late compressive strength. • THEED can promote the transformation of AFt into AFm, and change the morphology of AFt and C-S-H. N,N,N',N'-Tetrakis-(2-hydroxyethyl)ethylenediamine (C 10 H 24 N 2 O 4 ,THEED) is a different type of alkanolamine. In this work, the physical and chemical effects of small amounts of THEED added to Portland cement were investigated. THEED can be used as an accelerator for the setting of Portland cement. The compressive strengths of standard test mortars moist-cured for 1, 3, 28 and 90 days were enhanced in some cases by the addition of THEED. THEED promoted conversion of ettringite (AFt) to monosulfoaluminate (AFm). THEED had notable effects on the morphology of AFt and C-S-H at the early age, especially on the growth direction of portlandite(Ca(OH) 2) crystals. [ABSTRACT FROM AUTHOR]

Highlights: [•] Polycarboxylate superplasticizer (PCS) was introduced to adjust the setting time of belite-rich sulfoaluminate cement. [•] Setting time was greatly relevanted to the amount of polycarboxylate superplasticizer. [•] PCS decreased the compressive strength at 1day meanwhile increased the compressive strength at 28days. [•] PCS makes the morphology of pores in the cement pastes transformed from macropores to micropores at 28days remarkably. [Copyright &y& Elsevier]

Abstract: Resorcinol–formaldehyde/alumina composite (RF/Al2O3) gels were initially prepared by using sol–gel techniques, and then dried to aerogels with supercritical fluid CO2. After thermal treatment in argon atmosphere, RF/Al2O3 aerogels were successfully converted to monolithic carbon/alumina composite (C/Al2O3) aerogels. The samples were characterized by BET, SEM, TEM and XRD, and the compressive strengths were measured. The experimental results showed that the C/Al2O3 aerogels exhibited an interpenetrating framework with high mesoporosity. The as-synthesized C/Al2O3 aerogels consisted of spherical carbon particles and alumina (fibrous or columnar), which had high BET surface area (576–831m2/g) and showed high compressive strength (5.4–9.1MPa) and Young’s modulus (286.95–476.71MPa). These novel C/Al2O3 aerogels could possibly be used as thermal isolates, catalysts and adsorbents. [Copyright &y& Elsevier]

Highlights • Hydration behaviors of the CSP-OPC binary system are investigated comprehensively. • CSP can retard the conversion of AFt to AFm. • CSP can optimize the pore structure of the hardened cement paste at long term curing period. • CSP with 5% can contribute to the early compressive strength of cement mortar. Abstract This study presents the influence of coral sand powder (CSP) on the hydration and mechanical behaviours of Portland cement paste at the curing ages from 1 day to 90 days. The early hydration kinetics of Portland cement incorporated with CSP is studied by isothermal calorimetry test. The hydrates and pore structures of cement paste are determined by X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP), respectively. Experimental results show that CSP can promote acceleration period to end in advance. XRD results imply that CSP can react with tricalcium aluminate (C 3 A) to form monocarbonate (Mc) and hemicarbonate (Hc), which can suppress the conversion of Al-phase products, viz. from AFt to AFm. From the MIP results, the addition of CSP can refine the pore structure of Portland cement paste at long-term curing age, although negative effect of CSP on the total porosity can be observed. Low replacement level of CSP (5 wt%) improves the compressive strength of cement mortar at ages from 1 day to 7 days. However, from 28 days to 90 days, the addition of CSP decreases the strength of cement mortar regardless of replacement levels. [ABSTRACT FROM AUTHOR]

Abstract In this paper, an innovative method was proposed to synthesize an alite-ye'elimite clinker by adopting a secondary heat treatment step in a different sintering atmosphere after a traditional Portland cement (PC) clinker has been heated up at 1450 °C. It was found that a pure gaseous SO 2 or mixed gas containing the gaseous SO 2 used facilitated the decomposition of C 3 S and the consumption of C 3 A in the PC clinker. Simultaneously, anhydrite (CaSO 4), ye'elimite (3CaO·3Al 2 O 3 ·CaSO 4 , C 4 A 3 $) and ternesite (4CaO·2SiO 2 ·CaSO 4 , C 5 S 2 $) coexisted in the alite-ye'elimite clinker, resulting from gas-solid reactions during sintering. The experimental results also showed that the compressive strength of the synthesized alite-ye'elimite cement was higher than that of PC. Moreover, its setting times were shorter than that of PC. [ABSTRACT FROM AUTHOR]

• Utilization of CP with GGBFS to replace cement partially is feasible to mitigate the strength loss of cement due to the use of CP. • After exposed to seawater to 1 year, the compressive strength of the mixture (25% CP and 25% GGBFS) still can reach 54 MPa. • The pore structure of cement paste mixed with CP and GGBFS is densified. On island, the use of discarded coral reef is a way to resolve the lack of raw material for preparing concrete. Discarded coral reef can not only be used as aggregate, but be ground to powder to replace cement. Since the cement-based material prepared with discarded coral reef is exclusively used on island, the property of the cement-based material exposed to seawater condition should be studied. In this study, discarded coral reef is ground into coral powder (CP). CP is used together with ground granulated blast furnace slag (GGBFS) to replace Portland cement (PC) partially to prepare a mixture with good performance and the minimum use of PC. The compressive strength, solid phase composition and pore structure of the cement-based material exposed to seawater condition are investigated systematically. The results show that the addition of CP decreases the fluidity of the cement mortar since it has a more rough surface than other raw materials. Although the use of CP decreases the compressive strength of cement mortar, the coupled use of GGBFS can largely mitigate the strength loss of the cement mortar by comparing 9 mixtures. When the specimens are exposed to seawater, the strength of cement mortar only decreases slightly, but the pore structure of cement paste is densified. It suggests that the use of CP and GGBFS together in the concrete can meet the construction of island; the compressive strength of the sample made with 25% CP and 25% GGBFS is around 54 MPa after exposed to seawater to 1 year. [ABSTRACT FROM AUTHOR]

This paper discusses the effect of SO 3 dopants on the M 1 polymorph formation and mechanical properties of alite containing a high content of MgO. The structure of the M 1 alite is identified by XRD, high-temperature XRD and TEM analysis. A characteristic XRD pattern of M 1 alite doped with MgO and SO 3 is determined, and TEM results show that M 1 alite has an incommensurate modulated structure feature with 2.4 times the subcell dimension along [ 2 ¯ 1 0] H ∗ and could be expressed as ha ∗  + kb ∗  + lc ∗  + m/[2.4(−2a ∗  + b ∗ )], where m = ±1. The First-Principles method is used to simulate the structure of M 1 alite, and the calculated Delta Cohesive Energy is approximately 11–12 eV between the M 1 and M 3 alite. Quantitative analysis is performed by the Rietveld method. The SO 3 /MgO (mass ratio from SO 3 to MgO) and M 1 % in alite M 1 - C 3 S % M 1 - C 3 S % + M 3 - C 3 S % × 100 % are shown to have a strong linear relationship, which can be defined as M 1 - C 3 S % M 1 - C 3 S % + M 3 - C 3 S % × 100 %  = 24.73 + 108.11 * SO 3 /MgO (%). Mechanical properties results show that appropriate SO 3 dopant can improve the compressive strength of alite containing high MgO while over dosed SO 3 will lead to a contrary effect because of the decomposition of alite. The relationship between M 1 % in the alite and the compressive strengths at different ages is also given. The optimal M 1 % in alite is approximately 68% and the best SO 3 /MgO ratio is approximately 0.43 because the compressive strength could be maximized at each age. [ABSTRACT FROM AUTHOR]

Alite-ye'elimite clinker is a high cementing clinker prepared by introducing calcium sulfoaluminate, a non-silicate mineral, into the cement clinker. The mineral composition and mechanics of tricalcium silicate-rich sulfur aluminate prepared at 1300 °C are reported. The effects of copper slag and phosphorus slag on the phase composition, heat release and compressive strength were investigated. The phase composition was analysed by X-ray powder diffraction. The results show that the copper slag and phosphorus slag can lower the burn temperature of the clinker and promote the coexistence of C 3 S and C 4 A 3 S ¯ . The quality of clinker produced at 1300 °C is satisfactory. The compressive strength of mortar curing at 28 d is higher than that of P·II 52.5. [ABSTRACT FROM AUTHOR]

• The effects of CF on the fresh properties and compressive strength of AAC are reviewed. • The hydration mechanism of AAC-CF system is summarized. • The effects of CF on the durability of AAC are discussed. • The environment impact of AAC-CF system is evaluated. Calcareous fillers (CF) are mineral materials with calcium carbonate as the main chemical composition, which are rich in resources and easy to handle. In recent decades, the applications of CF in alkali activated cement (AAC) to prepare low carbon emission and high performance cementitious materials have attracted extensive attention. However, the hydration behavior, performance evolution and relevant mechanism of AAC-CF system are still not fully clear. This paper provides a comprehensive review on the recent research progress of the AAC-CF system in order to fully understand the role of CF in AAC. The effects of CF on the workability, hydration, shrinkage, mechanical properties and durability of AAC are reviewed and discussed. Furthermore, crucial factors affecting the performance of the AAC-CF system are emphasized, such as content of CF, fineness of CF and concentration of activator. The action mechanism of CF in the AAC is proposed according to the review. Based on the literature review, future researches on the AAC-CF system are recommended. [ABSTRACT FROM AUTHOR]

• M1 and M3 alite along the same pseudo-hexagonal subcell direction were determined. • A new one-dimensional incommensurate modulation structure was found in M1-alite. • The relationship between SO 3 /MgO and M1 alite content in C 3 S was determined. • Compressive strength of clinker was related to the polymorph and content of alite. This paper explored the structural modulation of alite in cement clinkers doped with high content of MgO and a series amount of SO 3. The effect of alite polymorph on compressive strength had also been studied. The results showed that high content of MgO stabilized M3 type alite while the increase of doped SO 3 could gradually modulated the polymorph to M1 type. M1 type alite had an incommensurate modulation along pseudo-hexagonal subcell [ 2 - 10 ] H * direction while M3 type alite hadn't appeared this characteristic. A new incommensurate modulation was found in M1-type alite along the pseudo-hexagonal subcell [ 01 7 - ] H * direction. Quantitative analysis results showed there was a nonlinear correlation between SO 3 /MgO and alite content in clinkers which could be well fitted by the parabola curve. SO 3 /MgO and M1 alite content in C 3 S ( M1 - C 3 S M1 - C 3 S + M3 - C 3 S × 100 %) showed a linear relationship. The compressive strength of clinkers was affected by both polymorph and content of alite. The correlation between the polymorph, content of alite and compressive strength of clinkers was determined by Multiple linear regression analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Alite-ye'elimite clinker is produced at 1300 °C using copper slag and phosphorus slag. • Critical dosage of C$ can improve the early strength and reduce the clinker usage. • AFt is largely formed and morphology of C-S-H changes with C$ dosage at early age. • Insufficient dosage of C$ induces a mechanical strength loss at longer duration. Alite-calcium sulfoaluminate (ACSA) clinker containing about 45 wt% alite and 2 wt% ye'elimite was synthesized at 1300 °C using copper slag and phosphorus slag as raw materials. The effect of different dosages of gypsum on the compressive strength and hydration products at the early ages and long terms of this clinker was investigated. The compressive strength, hydration rates, hydration products evolution and the microstructures development of the pastes were studied. With the gypsum dosage of 3.4 wt% (i.e., the SO 3 /Al 2 O 3 molar ratio 1.0) in this clinker, the compressive strength was always higher than the synthesized ACSA clinker without gypsum addition and the P·Ⅱ 52.5 at all the curing ages. Especially, the 1 day compressive strength of this case was improved to be 17.7 MPa with AFt largely formed and the alite hydration accelerated. At early ages (1d and 3d), the morphology of hydrates and pore structures can be refined with appropriate dosage of gypsum. At the late ages (more than 28 days), the pore sizes of the transitional pores are slightly increased with the addition of gypsum. However, there is 5.8% of self strength loss after 90 days in this case, which is mainly attributed to the decomposition of AFt. The critical dosage of gypsum can significantly increase the early strength and decrease the usage of clinker, which will make this clinker less carbon dioxide emissions. [ABSTRACT FROM AUTHOR]

• C-S-H-PCE nanocomposites improve the fluidity of the PC-MK mortar. • C-S-H-PCE nanocomposites enhance the compressive strength of the PC-MK mortar. • The optimal content of C-S-H-PCE nanocomposites is 3 wt%. • C-S-H-PCE nanocomposites accelerate the hydration process of the PC-MK paste. • C-S-H-PCE nanocomposites promotes the pozzolanic reaction of MK. In this work, the effects of the synthetic calcium silicate hydrates(C-S-H)/polycarboxylate(PCE) nanocomposites (CPNs) on the hydration behaviour of Portland cement (PC) containing 20 wt% of metakaolin (MK) were evaluated. Six mixtures with different CPNs replacement levels ranging from 0 wt% to 4 wt% were designed to cast CPNs-modified pastes and mortars, respectively. The fluidity and compressive strength were tested and micro-analysis including hydration heat, hydration products, pore size distributions and microstructures for CPNs-modified pastes was also conducted to disclose the potential mechanism for modification of mortar properties due to CPNs. The current results showed that an increased CPNs content contributes to a continuously improved workability for the PC-MK binary mortars. The corresponding compressive strength development for the mortars also benefits from CPNs addition. The optimum CPNs content was determined to be 3 wt%, which contributed to the highest compressive strength obtained for all the mortars at each curing age: 36.41%, 21.37%, 14.17% and 5.66% higher compared with the control PC-MK binary mortar at 1 day, 3 days, 7 days and 28 days, respectively. It is also worth noting that mortars incorporated with 2.0 ~ 4.0 wt% of CPNs also presented higher compressive strength values than 100 wt% cement mortar at each curing age. Based on the micro-analysis results, it was speculated that CPNs not only accelerate cement hydration at the early age, but they also promote the pozzolanic reaction of MK with calcium hydraxide (CH). This synergistic effect between CPNs and MK effectively results in a much denser microstructure with a refined pore structure for the PC-MK paste, which is, thus, helpful to further improve the final compressive strength. The findings of this study provide theoretical guidelines for modifying the properties of blended cements by using nanoparticles. [ABSTRACT FROM AUTHOR]

• Hydration and mechanical properties of CSP-CSA system are studied up to 90 days. • CSP can promote the formation of AFt and inhibit the formation of AFm. • The conversion from Hc to Mc does not happen in CSP-CSA binary system. • CSP can accelerate the carbonation of AFt. • CSP can optimize the pore structure of the hardened cement paste in the long term. Recently, the studies on the application of coral reef debris to construction attracted wide attention and interest of researchers, especially in China. Coral reef debris and its powder can be used as fine aggregate and mineral admixture in concrete, respectively. The main component of coral reef debris is calcium carbonate (CaCO 3), up to 90%. In our previous research, the effects of coral sand powder on the hydration behavior and mechanical properties of Portland cement are well investigated. It is well known that calcium sulfoaluminate cement, with low production energy, reduced CO 2 emissions, fast bonding and rapid strength development, etc. has been used for decades in concrete. This paper will give a detailed fundamental research on the hydration kinetics, microstructure development and mechanical properties of the coral sand powder-calcium sulfoaluminate cement binary system up to 90 days of curing. Isothermal calorimetry test, X-ray diffraction analysis, thermogravimetric analysis, mercury intrusion porosimetry and compressive strength tests are used to evaluate the properties of the calcium sulfoaluminate cement incorporated with different contents of coral sand powder (5%, 15% and 25%). The obtained results show that coral sand powder reacts with ye'elimite to generate hemicarboaluminate. Coral sand powder optimizes the pore structure of calcium sulfoaluminate cement at long time curing. [ABSTRACT FROM AUTHOR]

• Particle size, nano-TiO 2 content, w/s ratio directly affected the compressive strength. • A small dosage of nano-TiO 2 improved the compressive strength. • Nano-TiO 2 with smaller size can better improve the compressive strength. • Nano-TiO 2 would agglomerate in the paste especially at high dosages. The effects of using different sizes of nano-TiO 2 (NT) on the hydration characteristics of Portland cement with different water to solid ratios (w/s, solid: cement + NT) were investigated in this study. Cement was partially replaced by NT with two sizes, 5 nm and 25 nm, at weight fractions of 0, 0.5%, 1.0%, 1.5% and 2.0%. The compressive strength, hydration products, hydration degree, pore structures and morphologies of the modified cement pastes were systematically evaluated. The experimental results showed that a suitable NT content effectively enhanced the compressive strength of the cement paste, and this enhancement directly depended on the NT particle size. Cement paste mixed with 5-nm NT resulted in a higher compressive strength than 25-nm NT, irrespective of the w/s ratio. The cement paste with a maximum compressive strength at all the curing ages was obtained using a 0.3 w/s ratio and 0.5 wt% of 5-nm NT (which were therefore identified as the optimal NT parameters). The compressive strength of this cement paste increased by 41.4%, 15.9%, 18.7% and 24.35% at 1, 3, 7 and 28 days, respectively, compared to a control sample. For both NT sizes, the w/s ratio and the NT content controlled the compressive strength development of the paste during the early and late ages, respectively. Compared with 25-nm NT, replacing cement by 5-nm NT within the optimum content range was more effective in accelerating cement hydration, increasing the hydration degree, decreasing the crystal size of Ca(OH) 2 , refining the pore structure and densifying the cement paste at the microscale, all of which increased the compressive strength at the macroscale. [ABSTRACT FROM AUTHOR]

• Cement hydration and hardening properties is negatively with the [Na 2 O eq ·[C 3 A]/[SO 3 2. • The [Na 2 O eq ·[C 3 A]/[SO 3 2 molar ratio is better <0.5 for good properties. • The reduction of 28-day compressive strength is not correlated with the reaction degree of C 3 A. [ABSTRACT FROM AUTHOR]

• Ultrafine nanograins are introduced in the Zr 59 Ti 6 Cu 17.5 Fe 10 Al 7.5 BMG by annealing. • Mechanical performance of the Zr 59 Ti 6 Cu 17.5 Fe 10 Al 7.5 BMG is significantly enhanced. • High compressive fracture strength of 1910 MPa and plasticity of 12.1% are obtained. • Good corrosion resistance of the as-cast Zr 59 Ti 6 Cu 17.5 Fe 10 Al 7.5 BMG was maintained after annealing. Ni-free Zr-Ti-Cu-Fe-Al bulk metallic glass (BMG) is regarded as a prospective candidate for practical applications. However, a high Ti content in the BMG causes a sharp deterioration of mechanical performance. Herein, the effects of isothermal annealing on the structure, mechanical performance, and corrosion resistance of the Zr 59 Ti 6 Cu 17.5 Fe 10 Al 7.5 BMG are investigated. The alloy after a short-time annealing at 573 K shows admirable compressive strength and plasticity of 1910 MPa and 12.1%, respectively, which are much higher than 1733 MPa and 4.3% of the pristine BMG. This enhancement was ascribed to precipitation of ultrafine Al 3 Zr 2 nanograins from the BMG matrix. However, the prolonged annealing induces propagation of nanocrystals and decreases free volume in the alloys, leading to the deterioration of mechanical performance. The electrochemical study demonstrates that the BMG maintains good corrosion resistance after the annealing. This work offers an avenue for designing high-performance Ni-free BMG-based alloys. [ABSTRACT FROM AUTHOR]

• TiO 2 @SiO 2 nanoparticles can better improve compressive strength of cement than nano-TiO 2 did. • Nano-TiO 2 particles formed microscale agglomerates in the hardened cement matrix. • TiO 2 @SiO 2 can limit the agglomeration of TiO 2 nanoparticles in cement matrix. • TiO 2 @SiO 2 nanoparticles resulted in a considerable improvement in the microstructure of cement matrix. This paper presented the contribution of core/shell TiO 2 @SiO 2 nanoparticles to the hydration properties of Portland cement and the contribution was compared with that of nano-TiO 2. Both nanoparticles were used to partially replace cement at 1 wt%. The mechanical property and microstructure of the cement pastes were experimentally characterized using compressive strength and scanning electron microscope (SEM), respectively. Specially, thermodynamic modeling was also applied to predict the phase assemblages and calculate the corresponding volumes. The results showed that the paste with 1 wt% TiO 2 @SiO 2 developed a much higher compressive strength than the paste with or without nano-TiO 2 added at each curing age. Both SEM and mapping analyses showed that obvious agglomeration of nano-TiO 2 could be observed in nano-TiO 2 modified cement paste, which decreased its efficiency in the cement paste. However, nano-TiO 2 was well distributed when TiO 2 @SiO 2 was added because of its limiting effect on the agglomeration of nano-TiO 2 , further densifying the microstructure. The calculated hydrates volumes by thermodynamic modeling also indicated that TiO 2 @SiO 2 would result in producing most hydrates of all the pastes, thus contributing to a denser microstructure and a much higher compressive strength development. [ABSTRACT FROM AUTHOR]