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Styrene-acrylic emulsion (SAE)-modified mortar is typically used as an impermeable cement-based material. Although high-volume SAE-modified mortar shows excellent penetration resistance performance, this property can also cause compressive strength loss. In this work, sodium oleate (SO) is used as a hydrophobic agent to enhance the antipermeability of mortar with low SAE content. The influence of the incorporation of hydrophobic agent on the mechanical properties, hydration characteristics, water absorption, and impermeable and hydrophobic properties of low content polymer emulsion-modified cement mortars was investigated. The results show that the mortar with 5% SAE and 1% SO has better impermeability, hydrophobicity, and compressive strength than a mortar with 15% SAE only, which is attributed to the physical barrier of SAE and the hydrophobicity of SO. SO works well with 5% SAE-modified mortar, and the improvements in all aspects of the performance are greater than that of the high content SAE-SO–modified mortars. However, increasing the amount of SO will not bring continuous improvement in antipermeability, as the air-entraining effects of SO increase the porosity of the matrix. [ABSTRACT FROM AUTHOR]

In this paper, the effects of citric acid (CA) and protein retarder (SC) on the properties of phosphogypsumsulfoaluminate cement composite cementitious system were investigated. The fluidity, setting time and compressive strength were tested to evaluate the workability and mechanical of composite system, and the change of conductivity, phase composition and microstructure were analyzed to clarify the influence mechanism of different retarders. The results show that the strength loss of composite cementitious system under the action of SC is smaller than that of CA when the same setting time is achieved. The addition of two retarders has a certain inhibitory effect on the dissolution of composite system during the hydration induction and the acceleration period, and CA has a greater inhibitory effect than SC at the same content. CA can cause gypsum dihydrate crystals to show a flat and coarse structure, which has a greater impact on the mechanical properties, while SC increases the overall scale of gypsum dihydrate crystals, with little change in crystal morphology, which has a smaller effect on the deterioration of the mechanical properties of composite system. [ABSTRACT FROM AUTHOR]

Alkali-activated materials (AAMs) are regarded as an alternative cementitious material for Portland cement with regards to sustainable development in construction. The purpose of this work is to investigate the properties of activated blast-furnace slag (BFS)–steel slag (SS) with sodium carbonate (NC), taking into account BFS fineness and Na2O equivalent. The hydration was investigated by rheological behavior and pH development. The hydrates were characterized by TG-DTG and XRD, and the microstructure was analyzed by SEM and MIP. Results showed that the rheology of activated BFS-SS pastes was well-fitted with the H-B model and affected by BFS fineness and NC mixture ratio. It was found that BFS fineness and NC ratio played a crucial role in the initial alkalinity of SS-BFS-based pastes. As such, lower BFS fineness and higher NC ratio can dramatically accelerate the formation of reaction products to endow higher mechanical strength of BFS-SS pastes. However, the effect of NC ratio on the microstructure development of BFS-SS based AAMs was more obvious than BFS fineness. [ABSTRACT FROM AUTHOR]

Abstract Coal gangue (CG) and coal fly ash (FA) are the main coal by-product wastes. This paper focuses on the pore structure evaluation of CG and FA blended cementing composites with various replacement levels from 3 days up to 180 days. Results indicate that negative effect of coal by-products on the compressive strength and average pore size can be reduced to a negligible level at late ages. Similar average pore size (~10 nm) and critical width (10–20 nm) are found for CG and FA composites after 90 days. Moreover, the blended composites have significantly higher gel pore fraction, and the higher the dosage the larger the gel pore fraction. Multi-fractal feature is observed with the fact that scale of micro-fractal region is found always broader than the macro-fractal region and the micro-D s is found always larger than the macro-D s. Both the micro- and macro-D s of blended composites are systematically larger than the plain pastes. Highlights • Pore structures of calcined coal gangue blended and coal fly ash blended composites are evaluated. • Pore surface multi-fractal features of various composites from 3 up to 180 days are investigated. • Correlation between pore structure and compressive strength is discussed. [ABSTRACT FROM AUTHOR]

Beta-hemihydrate phosphogypsum (β-HPG) is a low-carbon cementitious material used in construction. Nevertheless, the poor water resistance and low mechanical strength of β-HPG limit its utilization. In this study, two low-calcium fly ash (FA) slurries with median particle sizes of 1.83 μm and 1.14 μm were prepared using a wet-grinding process for the improvement of β-HPG, and the mechanical strength and softening coefficient were tested to assess the effect. The results show that wet-ground low-calcium FA can significantly enhance the mechanical strength and softening coefficient of β-HPG. Compared with specimens without wet-ground low-calcium FA, the dry compressive strength and softening coefficient of specimens with 30% wet-ground low-calcium FA (D 50 =1.14 μm) increased by 104.9% and 71.8%, respectively. It is worth noting that the 1 d compressive strength also increased by 11.9%. Specifically, wet-ground low-calcium can increase the pH value and conductivity of the FA slurry, further accelerate the hydration process of FA in β-HPG, forming more ettringite and gels to fill in the pores between dihydrate gypsum (DH) crystal, and reducing the larger pores in the hardened paste. This study can develop a high-performance cementitious material that will enable the effective use of β-HPG. • Wet-ground low-calcium FA can increase the mechanical properties of β-HPG. • As the fineness of FA increases, the heat flow will be delayed. • Wet-ground low-calcium FA improves the microstructure and pore structure. [ABSTRACT FROM AUTHOR]

Highlights • Ultrahigh volume ultrafine BFS are prepared through wet-milling and dry-separation respectively. • The reaction degree of WS system develop at a faster rate owing to dissolution of ions. • Mixes containing WS can exhibit compressive strength of 43.9 ± 2.3 MPa after 3d of curing. Abstract The dosage of blast furnace slag (BFS) in cement is limited on account of relative low reaction rate and low early strength. Improving the early age activity of BFS is the fundamental solution for high volume BFS cementitious materials. Generally, mechanical activation is one of the main techniques to accelerate the early reaction of mineral admixtures. In this study, wet-milling and dry-separation are respectively used to prepare ultrafine BFS to improve its early reactivity. The early hydration characteristics, mechanical property, hydration products of ultrahigh volume BFS cementitious materials are analyzed to assess the efficiency of ultrafine BFS on the properties of BFS cement paste. The results show that the initial and final setting time both gradually decrease as the dry-separation BFS (GS) dosage increases, while the wet-milling BFS (WS) series present the opposite tendency. The electrical resistivity of WS specimens develops at a faster rate than that of GS specimens. Mixes containing WS, at a maximum dosage of 90%, have higher mechanical property than those with GS, resulting in an enhancement of strength. The hydration products mainly include calcium hydroxide, hydrotalcite, hydrotalcite-like phase, calcium carbonate, strätlingite, C-S-H, C-A-S-H, and akermanite. [ABSTRACT FROM AUTHOR]

• HHCW was efficiently treated into HHCWS by multiple wet-grinding. • The filling effect of HHCWS was proved in the durability of cement mortar. • The compressive strength of concrete with HHCWS of 10% was not decreased. • Utilization of HHCWS can bring significant economic and environmental benefits. To effectively eliminate waste and reduce cost, the humid hardened concrete waste (HHCW) from ready-mixed concrete production was used to produce slurry mineral admixture that was utilized in concrete by the treatment of multiple wet-grinding. The particle size distribution, morphology, liquid phase, and mineral composition of humid hardened concrete waste slurry (HHCWS) were tested. The median particle size of HHCW was reduced to 26.5 μm from bulks by initial wet-grinding and then to 1.28 μm (60 min) again by a secondary one, indicating that multiple wet-grinding was very propitious to refine HHCW. Both the electrical conductivity and pH value of the HHCWS were improved because of the increase of Ca2+ and OH- in the slurry. Three fineness (D50 = 26.5 μm, 5.71 μm, and 2.52 μm) and three dosages (5%, 10%, and 15%) of HHCWS were investigated comparatively to replace the cement in concrete or mortar. The experiment group with the HHCWS of 2.52 μm at the dosage of 10% had basically the equivalent compressive strength of the control group in C30 and C45 concrete and showed positive performance on the durability in mortar system, such as autogenous shrinkage, chloride ion permeability, and carbonization resistance. Based on benefit evaluation, multiple wet-grinding could reconcile economic feasibility with an environmental benefit and was an innovative approach to the utilization of humid hardened concrete. [ABSTRACT FROM AUTHOR]

[Display omitted] • The incorporation of ethyl alcohol was the most effective mean to refine GP. • Higher strength was exhibited in the case of specimens containing GPw and GPe. • GP showed low pozzolanic reactivity in the early age regardless of fineness. Waste glass, as a hard-to-grind material, was often grinded into powder by ball-mill in order to be used as a supplementary cementitious material in concrete. In this study, three different glass powders (GP) referred to as GPd, GPw and GPe were fabricated by different methods (i.e. dry condition, water condition and ethyl alcohol condition), and the effect of GP on the properties of cement-based materials was systematically evaluated. The results showed that the milling efficiency of GP was significantly affected by grinding condition. Ultrafine GP can be obtained as additional water or ethyl alcohol was added during the grinding process. GP showed low pozzolanic reactivity in the early age, even when the particle size was decreased to about 300 nm. GPd with large particle size and non-absorbent feature could increase effective water-to-cement ratio and thus improved the workability and early strength of specimens containing GPd, while the later strength was lower than that of reference ones due to low pozzolanic reactivity of GPd. In contrast, specimens containing GPw and GPe exhibited higher early mechanical strength than reference specimen due to the filling and acceleration effects of GP. An encouraging result indicated that GPe presented high pozzolanic reactivity at 28 d, which was seldom reported in the literature. [ABSTRACT FROM AUTHOR]

• It is possible to realize the utilization of RA as a SCM by wet-milling treatment. • Coarse RA, not disposed by ultra-fine treatment, was not suitable for cement replacement. • WA blended mixture showed almost the highest reactivity index (almost 100%) and compressive strength. • WA blended mixture showed relatively low initial and secondary sorptivity coefficients. • FA and RA groups presented higher secondary sorptivity coefficients than the other alternatives. The raw autoclaved aerated concrete waste (RA) is an important construction and demolition waste. The present work investigated the possibility of utilizing ultrafine autoclaved aerated concrete waste (WA) as a supplementary cementitious material (SCM) after wet-milling disposal. Results indicated that it is possible to realize the utilization of RA as a SCM by wet-milling treatment. The ultrafine WA blended mixture presented earlier hydration heat flow than the other alternatives. WA blended mixture showed almost the highest reactivity index (almost 100%) and compressive strength at each curing age, whereas coarse RA and SS blended systems presented the lowest values. WA blended mixture showed relatively low initial and secondary sorptivity coefficients. It was concluded that the high secondary sorptivity coefficients of FA and RA was due to the formation of connected voids by porous RA particles and partially reacted hollow FA spheres. [ABSTRACT FROM AUTHOR]

• The compressive strength and softening coefficient of β-HPG can be improved to 21.5 MPa and 0.66 with the content of 20% SAC. • SAC can increase the drying shrinkage and decrease the pore size of β-HPG. • Ettringite and aluminate hydroxide are formed to optimize the microstructure and improve the properties of β-HPG. Beta-hemihydrate phosphogypsum (β-HPG) as a cementitious material obtained from the dehydration of phosphogypsum (PG) can be widely used for the preparation of building materials. The main problems for its utilization are its low mechanical strength and poor waterproof properties. In this study, calcium sulphoaluminate cement (SAC) was used to improve the properties of β-HPG. The compressive strength, flexural strength, ratio of compressive to flexural strength, water absorption rate and softening coefficient were measured. The volume stability, pore structure and microstructure were characterized to evaluate the effect of SAC. The results show that SAC can improve the mechanical strength and waterproof properties of β-HPG significantly. With the addition of 20% SAC, the increase of drying shrinkage is relatively small, and the compressive strength and softening coefficient were 21.5 MPa and 0.66, increasing by 60.85% and 96.04% respectively compared to the mixture without SAC. Specifically, ettringite and aluminate hydroxide are formed and interconnected with calcium sulfate dihydrate to improve the waterproof properties of β-HPG under the effect of SAC. The crystal morphology of calcium sulfate dihydrate changes from long rods to short columns, and the pore size and total porosity of the mixture decrease, resulting in the improvement of the mechanical strength of β-HPG. The purpose of this work is to optimize the properties of β-HPG and provide a high performance cementitious material for the effective utilization of PG. [ABSTRACT FROM AUTHOR]

• Ultra-fine CS was fabricated by wet-grinding method for the first time. • The 7 and 28 d SAI of ultra-fine CS can reach 106% and 102%, respectively. • Ultra-fine CS can be used as a high-quality alternative cementitious material. The application of copper slag (CS) as a supplementary cementitious material in concrete is unsatisfactory due to the fact that CS is mainly composed of fayalite. The dissolution kinetics of fayalite determines the pozzolanic activity of CS. How to improve the dissolution of fayalite is a challenge for CS resource utilization. To address this issue, ultra-fine CS with different fineness was fabricated by wet-grinding method for the first time in this work and the performance of cement-based materials incorporating ultra-fine CS was assessed. Results revealed that an increase in CS fineness significantly promoted the decomposition of fayalite to improve the mechanical strength of mortars. The 7 d and 28 d strength activity index of ultra-fine CS can reach 106% and 102%, respectively, which has seldom been reported in the literature. Although ultra-fine CS can significantly accelerate the hydration process at the very beginning of reaction to form more hydrates, the early-age pozzolanic activity was still not ideal. The prepared ultra-fine CS exhibited good later-age pozzolanic activity, which can consume more portlandite and generate more hydrates, resulting in a denser microstructure. These results indicated that ultra-fine CS can be used as a high-quality alternative cementitious material to improve the greenness of cement and concrete products. [ABSTRACT FROM AUTHOR]

• Ultra-fine GP with d50 of 316 nm and 5.33 μm was prepared for the first time. • Ultra-fine GP significantly improved the mechanical strength of UHPC. • Ultra-fine GP is feasible to be employed to produce low cost eco-friendly UHPC. High cost and CO 2 emissions are the issues that need to be addressed in the widespread application of UHPC. The application of mineral admixtures in UHPC has become a new development direction. Ultra-fine glass powders with median diameter d50 of 316 nm (named as nGP) and 5.33 μm (named as mGP) were fabricated to replace silica fume and blast furnace slag, respectively, to prepare eco-friendly UHPC. The outcomes of the study revealed that both nGP and mGP can significantly promote the hydration of UHPC pastes. The incorporation of ultra-fine GP increased the hydration products and improved the microstructure of UHPC due to its pore filling effect, nucleation effect and pozzolanic activity. The compressive strength of UHPC containing ultra-fine glass powders was larger than the reference ones and the optimal substitution rates of silica fume by nGP and blast furnace slag by mGP were 60% and 50%, respectively. Ultra-fine GP is feasible to be employed as multi-dimensional substitute material to produce low cost eco-friendly UHPC. [ABSTRACT FROM AUTHOR]

Highlights • FA2 with D50 = 2.67 μm obtained by wet-grinding showed high pozzolanic reactivity. • 50% FA2 replacement ratio showed higher strength than that of cement at 28 d age. • Cement-FA2 system showed great environmental and economic advantages. Abstract High volume coal fly ash (FA) cementitious system (C-FA) was reported to present great economic and environmental benefits in cement and concrete industry, but the slow strength development limited its use in real engineering practice. In this study, FA was processed by wet-grinding in order to obtain super-fine particles. Three kinds of FA, namely raw FA with D50 (Median particle size) of 19.70 μm, wet-grinded FA with D50 of 2.67 μm and 7.80 μm, were used; 30%, 50%, and 70% replacement ratio in C-FA system were designed. The compressive strength, hydration, and pore structure were investigated, and the cost and CO 2 emission of the system were also considered. The results showed that FA with D50 = 2.67 μm could be obtained by 2 hours' wet-grinding; 30% replacement ratio increased the compressive strength by 16% at 1 d age and 22% at 28 d age in comparison with the reference; surprisingly, 50% replacement ratio even showed slightly higher 28 d strength than that of the reference; the main reason for the increased strength was due to the refined the pore structure, the densified hardened system, and the promoted pozzolanic reaction of FA. The system with 30% and 50% replacement ratio of wet-grinded FA (D50 = 2.67 μm) showed greater environmental and economic advantages in comparison with cement-raw FA system. Such results would be expected to offer one new way for utilization of FA and the design of low carbon cementitious materials. [ABSTRACT FROM AUTHOR]

Highlight • TEA and TIPA noticeably hindered the formation of C-(A)S-H gel at 7 d age. • TEA accelerated the formation of hydrotalcite-like phase at 7 d age. • TEA and TIPA could expedite the dissolution of ferric phase in WGGBS. • 28 d strength of 10.0% cement-90.0% WGGBS-0.05%TEA reached 43.7 MPa. Abstract In this study, a commercially available ground granulated blast-furnace slag (GGBS) was further processed by wet grinding, and WGGBS (wet-grinded GGBS) slurry with superfine particles was obtained. To avoid self-hydration of slag and augment the grinding efficiency, one commercially available polycarboxylate superplasticizer was added. The binder, composed of 10.0% cement and 90.0% WGGBS with the addition of 0.05% triethanolamine (TEA) and 0.05% triisopropanolamine (TIPA), was designed; the cement was added to provide alkali environment and calcium ions, and organic alkali was used to promote the dissolution of GGBS. The compressive strength of mortar and hydration mechanism was investigated. The results showed that wet grinding exhibited high grinding efficiency; D(50) value of particle size distribution of WGGBS was reduced from 18 μm to 2.10 μm by wet grinding for one hour. Compressive strength of hardened WGGBS mortar was 20 MPa and 28 MPa at 7 d and 28 d, and 10% cement replacement ratio of the WGGBS increased the strength to 24.6 MP at 7 d and 32.2 MPa at 28 d. Furthermore, in C-WGGBS, 0.05% TEA increased the 7 d strength by 23%, with the value of 30.27 MPa, but 0.05%TIPA slightly reduced it to 23.5 MPa, with a decrease by 5%. Mechanism behind the increase was due to the accelerated formation of hydrotalcite-like phase, despite the retarding effect on formation of C-(A)S-H gel; the slight decline by TIPA was mainly because of the retarding effect of formation of C-(A)S-H gel as well as its air-entraining effect. Moreover, both TEA and TIPA increased the 28 d strength of cement-WGGBS system, because TEA and TIPA were able to facilitate ferric and aluminum dissolution and expedite the formation of C-(A)S-H gel as well as hydrotalcite-like phase. Additionally, it was worth noting that 0.05% TEA could make 28 d strength of the binder, composed of only 10% cement, reach 43.7 MPa, in accordance with the requirement of 42.5 grade cement. [ABSTRACT FROM AUTHOR]

Abstract In this study, the super-fine ground granulated blast furnace slag was obtained by wet grinding (i.e. WGBBS), and an attempt to activate the super-fine ground granulated blast furnace slag by sodium sulfate (SS) and sodium carbonate (SC) was made. SS/SC-activated WGGBS samples were prepared and cured at the room temperature. The compressive strength at the age of 3 d, 7 d, 28 d, and 56 d was tested. Hydration heat was assessed, and micro structure and hydrates were also characterized with XRD, TG-DTG, SEM-EDS, and NMR; the pore structure was assessed with MIP. The results showed that SS and SC efficiently activated the hydration of WGGBS with D50 = 3.87 μm at the room temperature, and such high activating efficiency of SS and SC under room temperature was seldom reported in the literature. The mechanism behind was mainly because of the super-fine particles of slag with greater amounts of hydration points, which were produced in the process of wet grinding. Difference in activating efficiency between SS and SC was mainly because the anionic groups acted as different roles in hydration process: SS could induce the formation of ettringite while SC could induce the formation of calcite. Such results were expected to provide guidance on designing weak base-activated slag system. [ABSTRACT FROM AUTHOR]

• The 1d compressive strength of the sample can reach 24.8 MPa. • The effect of compound activator is better than that of single activator. • Preparation of fly ash geopolymer with Na 2 SiO 3 /carbide slag synergistic wet-grinding. • Compound activators are expected to reduce the use of NaOH activators. • It provides an effective way for the utilization of low calcium fly ash. As the raw material of geopolymer, F-class fly ash (FFA) often needs strong alkali such as NaOH to stimulate due to its low reactivity. In this study, FFA was refined and activated by a wet grinding process, and the activation effect of calcium carbide slag (19 %) and sodium silicate (1 %, 3 % and 5 %) was evaluated when used alone or in combination. The results show that the compound activator significantly improves the hydration products and mechanical properties of the wet-grinding FFA geopolymer. Compared with the single activation system, the 28-day hydration product content of the compound activation (co-activation) system increased by 67 %, and the 1-day compressive strength reached 24.8 MPa (at least an increase of 118 %). In addition, the co-activation system significantly improved the pore structure of the geopolymer and increased the chain length and Al/Si ratio of the C-S-H gel. The results of this study showed that co-activation and mechanical activation can significantly enhance the FFA geopolymer's mechanical characteristics and microstructure, greatly encourage the ingestion of industrial solid waste, lower the application costs of high pH activators, and efficiently provide a method for the utilization of FFA. [ABSTRACT FROM AUTHOR]

• A preparation process of clinker-free cemented iron tailings backfill material with ultra-low binder-tailing ratio. • Compressive strength of clinker-free backfill material with ultra-low binder-tailing ratio was up to 3.7 MPa. • Compressive strength of prepared clinker-free backfill material is significantly higher than previously reported work. • Hemihydrate gypsum is more efficient to improve compressive strength, settling resistance and water resistance. In order to improve the beneficiation efficiency, the ore have been ground finer or even exceed the fineness of cement. The cost of the material rises as a result of ordinary cementitious materials being unable to meet the ultra-fine backfill material needs. In this work, ground granulated blast-furnace slag (GGBS) was disposed by wet-milling process, and its median particle size (D 50) reached 1.94 μm, which effectively improved its cementing efficiency. Based on this, a clinker-free cemented iron tailings backfill material with ultra-low binder-tailing ratio (1:12) was prepared with 28 d compressive strength up to 3.7 MPa, which is significantly higher than previously reported work. HPG makes it simpler to produce backfill materials with superior compressive strength, settling ratio and water resistance than PG. At the same time, the workability, mechanical properties and ion leaching of the clinker-free backfill material reached the specification requirements. Each cubic meter of backfill material can absorb iron tailings up to 1699.92 kg/m3. [ABSTRACT FROM AUTHOR]

This research aims to explore the feasibility of using low-activity high alumina ferronickel slag (FS), carbide slag and hemihydrate phosphogypsum (HG) as main ingredients to fabricate supersulfated cement (SSC). The effect of HG dosage and FS fineness on hydration and compressive strength of SSC-FS was systematically investigated. Experimental results indicated that high mechanical strength can be achieved at ambient temperature by adjusting HG dosage and FS fineness. Increase in HG dosage postpones the initial formation of hydrates to some extent, but the amount of the final hydration products is promoted to generate higher mechanical strength. FS with smaller particle size has higher reaction activity that significantly accelerates the hydration process of SSC, leading to higher compressive strength and smaller volume expansion of SSC, and more ettringite crystals with smallish morphology formed in the pastes. If the particle size of FS is too small, however, ettringite crystals tend to precipitate at the surface of FS particles, which is unfavorable for the development of microstructure and will restrict the generation of C–S–H, thus resulting in a decrease in compressive strength and an increase in volume expansion. [ABSTRACT FROM AUTHOR]

Geopolymer is a potential substitute for high-emission cement production. Therefore, the use of fly ash with high emission as a geopolymer is an environmentally friendly and inexpensive direction. However, fly ash (FA) is a high amorphous precursor with low pozzolanic reactivity making it difficult to be activated by calcium hydroxide. In this study, the coupling of wet-milling mechanical force and calcium hydroxide was used to prepare high-performance alkaline calcium activated geopolymers. Two kinds of FA slurries with different particle sizes of D 50 = 2.96 μm and 14.2 μm were prepared, activated by calcium hydroxide (CH) with the content of 4%, 11% and 19%. Results indicated that the increase of calcium hydroxide content was beneficial to developing strength, effectively improving the chloride resistance, compacting the microstructure, but increasing the autogenous shrinkage of the geopolymers. These improvements are especially apparent in the wet-milled fly ash geopolymers (WFA) due to the pre-depolymerization implemented by wet-milled mechanical forces, and coupled with the activation effect of CH to improve the depolymerization efficiency and condensation reaction. The compressive strength of WF-CH-19 was three times higher than that of FA-CH-19, reaching 29.3 MPa at 28 d, and the compressive strength growth of WF-CH-11 even reached 591.67% at 1 d. Meanwhile, the main chain length (MCL) and Al/Si of calcium silicate hydrates were clearly improved, and pore structure was significantly refined with capillary pore increased from 29.79% to 89.23%. In addition, FA and WFA geopolymers have significant advantages over Portland cement in the environmental impact indicators such as E-energy and E-CO 2. • Low calcium FA geopolymer was prepared by coupling wet-milling mechanical force and CH activation. • Compressive strength of WFA-CH-19% reached 29.3 MPa at 28 d, three times of FA-CH-19%. • The growth rate of compressive strength is higher at low CH content. • The critical pore size is reduced from 66.92 nm to 24.59 nm in WF-CH-19%. • Significant increase in MCL and Al/Si ratio are found in WFA geopolymers. [ABSTRACT FROM AUTHOR]

• Wet grinding could be used to improve the hydration activity of GGBFS-SS binary precursor activated by sodium sulfate. • SS used as partial-substitution precursor of GGBFS decreased the setting time and improve the early strength. • Excessive SS induced micro-cracks and strength decrease in later age. • The optimum content of WSS-GS paste was 15%SS-85%GGBFS activated by sodium sulfate. Weak base Alkali-activated materials (AAM) is a potential approach to further reduce energy consumption and eco-friendly. Long setting time and low early strength limit the application in engineering. In this study, steel slag (SS) was used as a partial-substitution precursor of ground granulated blast furnace slag (GGBFS), and wet-grinded SS-GGBFS (WSS-GS) binary binders activated by sodium sulfate were designed. The results showed that the alkalinity of WSS-GS slurry was improved by the addition of SS, and the early hydration reaction and strength were promoted greatly. However, excessive SS was harmful to strength development at later age for quantity reduction of hydration products and microstructure deterioration. 15%SS-85%GGBFS activated by 3% Na 2 O-E sodium sulfate was verified with a desired performance, initial setting time was shortened by 60% and 1 d compressive strength was increased by 91% compared to GGBFS. These results provide guidance on designing of weak base-activated slag system and utilization of mass SS. [ABSTRACT FROM AUTHOR]

• Addition of α-HPG and PCE increased compressive strength by 162%. • α-HPG obviously increased the hydration degree of β-HPG pastes. • Adsorption amount of PCE per unit area on α-HPG was higher than β-HPG. Effect of alpha-hemihydrate phosphogypsum (α-HPG) prepared from phosphogypsum (PG) on the properties of beta-hemihydrate phosphogypsum (β-HPG) pastes was studied systematically. The results showed that α-HPG with a specific length to diameter ratio of 1:1 could improve the workability, strength and water resistance of β-HPG, and the improvement was more significant in the presence of Polycarboxylate superplasticizer (PCE). With the addition of 30% α-HPG and 0.4% PCE, the water/hemihydrate ratio for standard consistency can be reduced from 0.72 (β-HPG) to 0.41, and the compressive strength and softening coefficient can reach 29.1 MPa and 0.64, respectively. The results of X-ray diffractometer, thermoanalysis and heat of hydration showed that the introduction of α-HPG can significantly improve the hydration degree of β-HPG, and mercury intrusion porosimetry test results indicated that the pore structure was refined. These were deemed as the important reasons for the improved compressive strength and softening coefficient of β-HPG. In addition, the adsorption ability test showed that the adsorption amount per unit area of PCE in α-HPG was higher than that of β-HPG, and this explained why α-HPG could significantly improve workability of β-HPG system plasticized by PCE. These results confirmed that using α-HPG prepared from PG to improve the properties of β-HPG pastes was feasible, which would provide a new way to utilize PG. [ABSTRACT FROM AUTHOR]

• Superfine cement was obtained by wet grinding process. • Superfine cement could enhance the strength of HVFA system. • This kind of binders showed low carbon emissions and costs. The use of high-volume fly ash (HVFA) in cement-based materials can significantly reduce the CO 2 emissions. Nevertheless, slow strength development becomes the barrier for HVFA system, and the main reason is because the low alkalinity offered by Portland cement (PC) cannot efficiently activate the pozzolanic reaction of FA. In this study, wet grinding was used to process PC and obtain superfine particles, with intention to promote the hydration of PC and offer more CH for FA activation. HVFA (50% PC and 50% FA) system was designed, and 0–15% wet grinded cement (WGC) was used to replace PC. The effects of WGC on HVFA system were investigated; the CO 2 emissions and costs of WGC-HVFA system were calculated. Results showed that the superfine cement with D50 = 3.17 μm was obtained by wet grinding. The compressive strength of HVFA mortars without WGC was 14.3 MPa and 33.5 MPa at 3 d and 28 d age, while 15% WGC enhanced the compressive strength of the mortars to 22.0 MPa and 46.6 MPa, respectively. In addition, CO 2 emissions and costs of the HVFA system containing 15% WGC were 477 kg/t and 347.5 RMB/t, which were much lower than that of PC system. Such results proposed an innovative approach to enhance the compressive strength of HVFA system, with great potential in low carbon cementitious materials. [ABSTRACT FROM AUTHOR]

• Use of C 3 A as addition agent for hemihydrate gypsum (HHG) could improve the compressive strength of gypsum pastes. • Under the effect of C 3 A, HHG could achieve instant diagenesis, thereby realizing instant solidification. • The formation of AFt and the optimized pore structure could improve the water resistance of the HHG system. • NS could provide crystal nuclei to accelerate hydration process of HHG, and meanwhile playing the role of filling the pore structure. In this article, tricalcium aluminate (C 3 A) was utilized as addition agent for hemihydrate gypsum (HHG) to improve the performance of gypsum pastes, and on that basis, the optimal dosage group of C 3 A was selected for further study on the composite effect with nano-silica (NS). HHG plasters with 0–5% content of C 3 A and besides combining 3% C 3 A with 0.5% NS were made. The macroscopic properties were discussed by testing the compressive strength, setting time, consistency and softening coefficient. The hydration products were described by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and solid state nuclear magnetic resonance (NMR). The microstructure was presented by performing scanning electron microscopy (SEM). Hydration heat evolution process was studied by hydration heat analysis. The results showed that under the effect of C 3 A, HHG could achieve instant diagenesis, thereby realizing instant solidification, and its compressive strength and water resistance could also be improved to a certain extent; on the basis of C 3 A, the addition of NS could further optimize these properties. These conclusions were expected to provide reference for promoting the basic performance of HHG. [ABSTRACT FROM AUTHOR]

• Eco-friendly UHPC with high volume UGGBS (40% of the binder) was prepared. • The addition of UGGBS significantly refined the pore structure of UHPC. • The MCL and Al/Si of C-S-H gels were improved by wet-grinded UGGBS. • Compressive strength was improved by high volume wet-grinded UGGBS at early and late ages. The development of ultra-high performance (UHPC) concrete was restricted due to the large consumption and high cost of cement. In this study, eco-friendly UHPC was prepared by ultra-high content of wet-grinded ultrafine ground granulated blast furnace slag (UGGBS). And the content of mineral admixture in the cementitious system is up to 50%, of which UGGBS is as high as 40%. It was proved that the mechanical development, microstructure and hydration process of UHPC were significantly improved by UGGBS. The results showed that the compressive strength of G0UG20 was increased by 27% and 15% at 3 and 28 days compared with the reference group. Even if the cement content was reduced, the compressive strength of high volume UGGBS blended UHPC was still higher than the reference group. The addition of UGGBS significantly refined the pore structure and densified the hardened system. Meanwhile, the MCL and Al/Si of C-S-H gels were improved by UGGBS. In terms of environmental and economic benefits, the CO 2 emissions and production costs were reduced by the addition of UGGBS. [ABSTRACT FROM AUTHOR]

• Wet-grinded CS slurry with D50 of 3.0 μm was used as a lime source. • Setting times and hydration heat release were clearly promoted by the ultrafine WCS. • Both the early and late age strength was notably enhanced by appropriate WCS addition. • Carbonation resistance of high volume WFA blended composites was notably improved by WCS. Fly ash (FA) with high glassy phase content is a pozzolanic material with low activity, while carbide slag is a solid waste with portlandite crystals embedded in the impurity phases. Herein, wet-grinding method was used twice to improve the pozzolanic reactivity of FA and promote the dissolution of embedded calcium hydroxide in the CS as a lime source, respectively. Wet-grinded FA slurry (WFA) with D50 of 2.5 μm and wet-grinded CS slurry (WCS) with D50 of 3.0 μm were prepared. It was found that setting times, hydration heat release, early and late compressive strength, carbonation resistance of high volume WFA blended composites were significantly enhanced by WCS, attributed to the pre-dissolved calcium resource and alkali reserve. However, an excessive amount (12 wt%) of WCS addition causes an abnormal decrease in strength, due to the microstructure degradation by coarse portlandite crystals. Higher proportion of C-S-H might be ready for carbonation in high volume WFA blended composites, due to the promoted Al incorporation in C-S-H by wet-grinding. [ABSTRACT FROM AUTHOR]

Autoclaved aerated concrete waste (AACW) is an inorganic porous construction and demolition waste, which is possible to be environmentally used as an internal curing agent, due to its water absorption and release characteristics. In present work, fine aggregate (sand) was replaced by AACW aggregate with the same volume for internal curing purpose. The potential curing effect of AACW was also compared with a classical internal curing agent, i.e. expanded perlite (EPA), under the same particle size condition. Results indicate that the compressive strength of AACW groups after 28-day sealing curing is basically the same as that of the control group. Compared with EPA, internal curing with AACW can better improve the internal relative humidity, reduce the autogenous shrinkage, and delay the cracking time of cement mortar. At the same time, AACW effectively refines the pore structure and improves the micro-hardness of the interfacial transition zone (ITZ) through internal curing, and enhances the resistance to chloride penetration. • AACW was environmentally used to compensate the autogenous shrinkage and delay the cracking time. • The compressive strength of AACW0.054 at 28d is basically the same as that of the reference group. • AACW refines the pore structure of cement mortar and enhances the microhardness of ITZ. • This work provides new ideas for the resource utilization of AACW and brings environmental benefits. [ABSTRACT FROM AUTHOR]

• An innovative microencapsulated PCM with rigid skeleton shell was fabricated. • CA/HAP exhibits high CA absorption ratio and good physicochemical stability. • CA/HAP composite exhibits stimulation effect on cement reaction. • The maximum strength reduction is 7.9% for sample with 20% CA/HAP. This paper aims to develop a novel thermal storage cement-based material (TSCM) with good service performances using rigid phase-change microcapsules. Microcapsules were made of hollow HAP incorporated with capric acid (CA). The fabricated composite phase change material (CA/HAP) was characterized by using various techniques, such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR), thermogravimetry (TGA) and differential scanning calorimeter (DSC). The basic properties of TSCM mortars with varying amount of CA/HAP including workability, hydration heat, compressive strength and thermal regulating ability were also assessed. The test results showed that CA/HAP is small and regular in spherical shape and exhibits high absorption ratio and good physicochemical stability. The incorporation of CA/HAP in cement-based materials leads to a decrease of workability, acceleration of hydration process and significant improvement of thermal regulation property. The compressive strength of mixtures containing CA/HAP is noted to be increased when incorporating 10% of CA/HAP by volume. [ABSTRACT FROM AUTHOR]

• The nano-LS of D50 = 300 nm was prepared by wet griding. • Nano-LS could accelerate the hydration of SAC. • Providing a new way to utilize LS in SAC system. As a by-products of lithium carbonate industry, emission of lithium slag (LS) was increasingly increased due to the huge market demand of lithium salt. Therefore, LS disposal faces great challenge. In the study, a new approach to use LS in sulphoaluminate cement (SAC) system to improve the early compressive strength was proposed. Nano-lithium slag (nano-LS) was prepared via wet grinding, and the effect of nano-LS on hydration mechanism of SAC was investigated. The results indicated that nano-LS with D50 of 300 nm was prepared. In comparison with the Blank, 4.0% nano-LS promoted the 7 h compressive strength from 4.5 MPa to 24.3 MPa, with an increase by more than 4 times, and an increase by 28% at 1 d age; it also reduced the initial and final setting time to 16 min and 23 min, being reduced by 33.3% and 37.5%. This phenomenon was because nano-LS accelerated the hydration of SAC, and 4.0% dosage even made the inducing period disappear. The reason for the accelerated hydration was that the nano particles in nano-LS slurry acted as excellent nucleation seeds for speeding of the formation of hydration products. Additionally, the promoted dissolution of lithium salt during the process of wet milling also facilitated precipitation of aluminum phase to accelerate the SAC hydration. Consequently, nano-LS was expected as an excellent accelerator in SAC system. All of findings suggested an innovation new way to utilize LS in SAC system. [ABSTRACT FROM AUTHOR]

• Utilization of high volume fly ash in steam-cured cement mortars was investigated. • Both the early and late compressive strength of steam-cured mortars were enhanced by UFA. • Pore structure of steam-cured high volume FA blended composites was effectively refined by UFA. • The amount of CH after steam curing was generally lower than that with standard curing. • The MCL and Al/Si of C-S-H gels under steam curing were improved by UFA. Utilization of high volume fly ash is generally limited in steam-cured concrete products due to the delayed strength development. In present work, ultrafine fly ash (UFA) with a median particle size of 2.3 μm was prepared with wet-grinding technology. The influence of different FA fineness, UFA content (30–70%) and curing regimes on the compressive strength and microstructure of steam-cured high volume fly ash cement composites were studied. Both the early and late compressive strength of steam-cured FA blended composites were enhanced by wet-milled UFA with replacement level as high as 50%, and the strength was even higher than that of pure cement group. Pore structure of steam-cured high volume FA blended composites was effectively refined by UFA. The amount of CH after steam curing was generally lower than that with standard curing. Furthermore, the main chain length and Al/Si of C-S-H gels under steam curing were improved by UFA. Compared with prolonging the curing duration, increasing the curing temperature seems more efficient for the incorporation of aluminum from fly ash into the calcium silicate hydrates. [ABSTRACT FROM AUTHOR]

• Nano-carbide slag seed was prepared with wet-grinding method. • The initial and final setting time was greatly shortened by 61.4% and 51.7%. • The early-age hydration kinetic of cement was notably accelerated by nano-CS seed. • The 8-hour compressive strength was greatly enhanced by the nano-CS seed by 3350%. In present work, a novel nano-CS seed was prepared by wet-grinding method and added to cement to accelerate the early hydration. With 5% nano-CS seed, the initial and final setting time was clearly shortened by 61.4% and 51.7% respectively; the dormant period and the main hydration peak was notably advanced by 52.9% and 43.5% respectively. Early compressive strength, especially the 8-hour strength, was greatly promoted by the nano-CS seed by 3350%, with 5% nano-CS seed. It was speculated that the early-hydration and early-strength was accelerated by weakening the electrical double layer shielded around the silicate phase, thus shortening the dormant period. Results highlighted that the prepared nano-CS seed in present work is expected to be practically used as a new type accelerator. [ABSTRACT FROM AUTHOR]

Industrial wastes consumed by the preparation of building materials is a potential method to ensure the sustainable development. In this study, lithium slag (LS), as the by-product of lithium salts production, was treated by wet grinding process to prepare micro particles and used to expedite the early hydration of Portland cement (PC). The physical-chemical properties of micro-lithium slag (micro-LS) was characterized comprehensively. Binary system of PC and micro-LS was designed and its compressive strength at 16 h, 1day, and 28 days was measured. The hydration process was observed by hydration heat. Hydrates trait was investigated by XRD, TG-DTG, and NMR; pores structure was estimated by MIP and SEM. Results showed that the micro-LS with D50 = 300 nm was obtained by wet grinding, in which the crystalline was far lower than the amorphous phases. More importantly, micro-LS could significantly promote the early strength of PC. 4.0% dosage increased the strength by almost 3 times at 16 h and by more than 50% at 1 day; 28 days strength was also increased by 28%, indicating that micro-LS expected to be used as an excellent accelerator for PC. The great improvement was mainly contributed to the nucleation inducing effect on hydration, the refined pore structure, and the high pozzolanic reactivity of micro-LS. The research suggested an innovation method for the utilization of LS. • Lithium slag with D50 = 300 nm could be prepared via wet-grinding. • The micro-LS could act as an excellent accelerator for PC hydration. • A novel way to dispose lithium slag was suggested. [ABSTRACT FROM AUTHOR]

• D50 of raw materials decreased to around 3 μm by wet grinding. • Strength of WGGBS increased clearly by the use of wet grinded waste gypsum. • Increased strength was attributed to the evolution of hydrates and porosity. Replacement of Portland cement by industrial wastes has been accepted as a potential way to reduce carbon emissions. Ground granulated blast furnace slag (GGBS), desulphurization gypsum (DG), and phosphogypsum (PG), known as the common industrial wastes, were used in this study. Binders comprised of GGBS and waste gypsum were designed to develop a novel low carbon material; in order to promote the reactivity raw materials were processed by wet grinding. Compressive strength was examined and hydration process was researched by XRD, TG, NMR, SEM, and MIP. Results showed that wet grinded PG (WGPG) and wet grinded DG (WGDG) were able to greatly augment compressive strength of wet grinded GGBS (WGS) system. The reasons were attributed to the accelerated formation of ettringite and the reduced porosity. On the one hand, the presence of ettringite could construct the crystal skeleton resulted in the hardening of system accelerated. On the other hand, the constantly produced C-S-H gel densified the microstructure and decreased the porosity significantly. Moreover, in comparison with WGDG-WGS system, the early strength of WGPG-WGS system was lower caused by the retardation effect of phosphorus in PG. Results was expected to be used for the design of low carbon materials. [ABSTRACT FROM AUTHOR]