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In this paper, alkali-activated materials (AAMs) were prepared combining waste coral powder (CP) and blast furnace slag (BFS) as precursors, artificial seawater and deionized water as mixing water, and blends of NaOH and sodium silicate solution as alkaline activators. The effect of CP and seawater on the fluidity, mechanical properties, and hydration was discussed. The experimental results showed that a 15% CP content effectively improved the fluidity of fresh paste while having little effect on compressive strength of the samples. Compared with deionized water, the use of seawater for sample preparation resulted in a reduction of the fluidity and mechanical properties of the samples. The pore structure could be refined by CP and seawater, but gel micropores increased significantly when the CP content reached 25%. The use of CP and seawater did not cause significant changes in the type of hydration products. Although the amount of hydration products in the early stages of the samples prepared with seawater was relatively low compared with those prepared with deionized water, it gradually surpassed that in samples prepared with deionized water with increasing curing time. Increasing the CP content led to a higher reaction degree, and a CP content of 25% resulted in a reaction degree of approximately 30%–50%, which was roughly twice that of a sample containing 5% CP. These findings have important implications for the development of sustainable construction materials for utilization in marine engineering. [ABSTRACT FROM AUTHOR]

In order to realize the resource utilization of coal gasification fine ash (CGFA) in cement fields, a key is to solve the problem of low activity of CGFA. This paper studied the performance of CGFA as supplementary cementitious materials in cement. Furthermore, to enhance the activity of CGFA, targeted chemical activators were employed, with triethanolamine (TEA) and simulated high salinity wastewater (SHSW) chosen as representatives of organic and inorganic agents, respectively. It was found that CGFA had a synergistic effect with cement at a low dosage, while the inhibition effect on cement hydration was dominant at a high dosage. TEA promotes the strength development of the CGFA-cement system by promoting early hydration of cement and dissolution of active minerals in CGFA. However, the promoting effect of TEA on cement hydration will change to an inhibiting effect with the development of time, which will have an adverse effect on the development of strength. In general, the optimal dosage of TEA is 0.03 %, which can increase the 28-day activity index of CGFA from 69.1 % to 75.6 %. SHSW accelerates the strength development of the CGFA-cement system by promoting the hydration of cement and facilitating the dissolution and hydration of active minerals in CGFA. In addition, X-ray diffraction results show that a new hydration product, Friedel's salt, is formed under the excitation of SHSW. But this new hydration product will gradually dissolve as the pH decreases. The 28-day activity index of CGFA can be increased to a maximum of 83.3 % under the excitation of 2 % SHSW. [Display omitted] • The direct use of CGFA has adverse effects on the properties of cement. • Activity index of CGFA can be increased to a maximum of 83.3 % by chemical activators. • Activators promote the dissolution and hydration of active minerals in CGFA. [ABSTRACT FROM AUTHOR]

The potential application of surface modified nano‐SiO2 (NS) particles with poly (dimethyl diallyl ammonium chloride) (PDDA) has been reported in other fields, but not in civil construction. This paper aims to assess the influence of surface modified NS with PDDA on the early‐age hydration of cement paste, where cement is replaced by 0.3%, 1% and 3% of NS particle. PDDA can be introduced onto the surface of NS via long‐distance charge pairs. Calorimetric measurements of cement pastes with 0.35 w/b (water/binder) ratio show that NS particles accelerate the cement hydration, while PDDA retards it. Moreover, the cement hydration is controlled by PDDA at lower dosage of NS/PDDA particle, which delays the exothermic peaks of cement hydration, while the cement hydration is controlled by NS particle aggregates at higher dosage of NS/PDDA particle. Based on the results above, the mechanism of the adsorption of NS/PDDA particle on cement particle surfaces is proposed. [ABSTRACT FROM AUTHOR]

Coal gasification technology is the core of clean and efficient utilization of coal, while coal gasification fine ash (CGFA) is the solid waste inevitably produced in the coal gasification process. Due to the high residual carbon content and water retention of CGFA, the solubility of its silica-aluminium-calcium-containing minerals is poor, which affects its potential cementing properties in construction materials. In this paper, the basic physicochemical properties were investigated, and it was found that small particles of CGFA (CGFA-S) had more active mineral components, lower residual carbon content (17.17%) and weaker water retention (6.91%), which facilitated the removal of impurities and water. In addition, the best effects were achieved at a heat treatment temperature of 650 °C, which exposed the minerals and increased the solution solubility, and the leaching concentrations of Si4+, Al3+, and Ca2+ increased by 21.2%, 44.6%, and 97.8%, respectively. However, when the temperature was too high (815 °C), the minerals recrystallized, leading to structural instability and dissolution difficulties, and the concentrations of the three major ions were reduced by 84.4%, 82.0%, and 42.2%, respectively, compared with the control.Finally, the optimal heat treatment temperature was 650 °C, with the highest exothermic hydration rate (11.92 mW/g) and the highest cumulative exothermic heat (199.81 J/g). The hydration products were tightly bound, and the cement mortar specimens had the highest compressive strength, with a 28d strength of 45.4 MPa. • The physicochemical properties of CGFA were analyzed based on particle size. • The extraction effect and microstructure of ash in CGFA were tested. • The hydration activity of thermally modified CGFA was investigated. [ABSTRACT FROM AUTHOR]

Highlights • The differences between natural and artificial hydraulic lime mortars were revealed. • NHL mortar have preferable fluidity compared to the artificial lime mortars. • The mechanical properties of artificial lime mortar have advantages over NHL mortar. • A part of artificial lime mortars is nearby to NHL mortar in environmental resistance. • Three kinds of lime mortars have big difference in hydration and carbonation reaction. Abstract To evaluate the differences of properties between natural and artificial hydraulic lime mortars, the macro and micro properties of natural hydraulic lime (NHL2 and NHL5) mortars, white Portland cement-aerial lime-based (CL15 and CL25) mortars and slag-aerial lime-based (SL20 and SL40) mortars were studied through the examination of their physical and mechanical properties, environmental resistance properties, hardening mechanism and microstructure of lime mortars or pastes. The results show that the NHL mortars have preferable fluidity compared to the artificial CL and SL mortars, while the mechanical properties of artificial CL and SL mortars are advantageous compared to those of NHL mortar. In terms of environmental resistance, the water resistance of SL mortar is best, closely followed by the CL mortar, and the NHL mortar is relatively weak; moreover, CL mortar shows the best sulphate resistance, and SL mortar has the best alkali resistance. The hydration reaction (or pozzolanic reaction) and carbonization reaction could occur in the three kinds of hydraulic lime pastes, and the hydration reaction of the NHL and CL pastes mainly occur in the early stage of paste hardening (before 28 days), while the pozzolanic reaction of the SL paste reach a high degree at early hardening stage (28 days) and still maintains a certain reaction rate in the later period. The carbonation reaction process of the three kinds of lime pastes continues to the later period of the hardening, and the carbonation rate of SL pastes in the later stage would be obviously enhanced; furthermore, the carbonation degree of NHL paste is obviously higher than that of the CL and SL pastes. The different hydration-hardening process and mechanism of the three lime pastes lead to differences in the morphology and pore structure among them. There are more large-size pores in NHL5 paste (the pore volume in the range of pore diameter greater than 200 nm reaches 63.13%), while the pore size of the SL paste is relatively small (the pore volume in the range of pore diameter less than 100 nm reaches 44.15%). The porosity during the 180 days curing period was as follows: SL40 (27.32%) < CL25 (29.65%) < NHL5 (33.09%). [ABSTRACT FROM AUTHOR]

This paper investigates the influence of mechanical grinding on pozzolanic characteristics of circulating fluidized bed fly ash (CFA) from the dissolution characteristics, paste strength, hydration heat and reaction degree. Further, the hydration and hardening properties of blended cement containing different ground CFA are also compared and analyzed from hydration heat, non-evaporable water content, hydration products, pore structure, setting time and mortar strength. The results show that the ground CFA has a relatively higher dissolution rate of Al2O3 and SiO2 under the alkaline environment compared with that of raw CFA, and the pozzolanic reaction activity of ground CFA is gradually improved with the increase of grinding time. At the grinding time of 60 min, the pozzolanic reaction degree of CFA paste is improved from 6.32% (raw CFA) to 13.71% at 7 days and from 13.65 to 28.44% at 28 days, respectively. The relationships of pozzolanic reaction degree and grinding time of CFA also conform to a quadratic function. For ground CFA after a long-time grinding such as 60 min, the hydration heat and non-evaporable water content of blended cement containing CFA are significantly improved. Owing to relatively smaller particle size and higher activity of ground CFA, the blended cement paste has more hydration products, narrower pore size distribution and lower porosity. For macroscopic properties, with increase in grinding time of CFA, the setting time and strength of blended cement are gradually shortened and improved, respectively. [ABSTRACT FROM AUTHOR]

• The hydration superposition effect of SSCP was clarified. • The microstructure of SSCP hydration products was analyzed. • The hydration mechanism of SSCP was revealed. Steel slag has great potential as a supplementary cementitious material, and often shows good effects when used in combination with granulated blast furnace slag (GBFS). In order to reveal the interaction law of steel slag and GBFS, the hydration superposition effect and mechanism were studied in this paper in terms of ion dissolution, hydration heat, hydration products, hydration degree, microstructure and mechanical properties. The results show that steel slag and GBFS have a significant hydration superposition effect, and the strength of the paste when the two are used in combination is much higher. The mechanical properties at the early and later ages are the best (16.5 MPa at 7 days and 31 MPa at 28 days) when the steel slag-to-GBFS ratio is 1:1 and 2:3, respectively. Steel slag-slag composite powder (SSCP) has three exothermic peaks, which are the dissolution peak, hydration peak of steel slag and pozzolanic ash reaction peak of GBFS (after 85 h), respectively. The fibrous and amorphous C-S-H gels and plate Ca(OH) 2 appear in the SSCP pastes at 3 days. Furthermore, the microstructure of hydration products consists of a number of fiber-like and particle-like C-S-H gels with widths ranging from 15 nm to 20 nm and lengths ranging from 50 nm to hundreds of nanometers. The C-S-H gels wrap the unhydrated mineral phase (UMP) to form a nucleus(UMP) - membrane (C-S-H) structure. The early hydration of steel slag would increase the pH and conductivity of the pore solution, promoting the dissolution of aluminosilicate glass in GBFS and pozzolanic ash reaction, at the same time, the consumption of Ca(OH) 2 by the pozzolanic ash reaction would promote the further hydration of steel slag. The synergistic hydration effect of SSCP would promote hydration and generate more hydration products to fill the pore structure, resulting in good hardening properties. [ABSTRACT FROM AUTHOR]

This paper investigates the viability of industrial crude glycerol (C-GLY) as grinding aids of the granulated blast furnace slag (GBFS). The effects of C-GLY on the particle characteristics and hydration activity of GBFS are studied. The results show that C-GLY can effectively optimize the particle characteristics of ground GBFS. Both the sieve residue and angle of repose of GBFS powder with 0.08 wt% C-GLY are obviously reduced and the specific surface area is improved. The particle size distribution of GBFS powder with C-GLY becomes narrow and particle content of less than 32 μm is obviously increased. In the initial grinding period, the uniformity coefficient of GBFS powder is reduced by C-GLY, while the uniformity coefficient is increased in the latter grinding period. Additionally, 7d and 28d hydration degree of ground GBFS (50 min grinding time) paste with C-GLY are improved by 4.9% and 5.8%, respectively. For the different grinding time, all the activity indexes of different ground GBFS powder are effectively improved by C-GLY. And the uniformity and compactness of hydration products of blended cement paste containing ground GBFS with C-GLY are also improved. By contrast, the action effects of C-GLY on the grinding performance and hydration activity of GBFS are close to that of TEA and better than that of glycerol. Due to the huge cost advantage of C-GLY, its comprehensive performance is better than that of other grinding aids, selecting C-GLY as GBFS grinding aids is feasible. [ABSTRACT FROM AUTHOR]

This paper presents the ultrafine grinding performance of fly ash with grinding aids (GA) and effect of GA on the particle characteristics, pozzolanic reaction degree of ultrafine fly ash (UFFA) and properties of blended cement containing UFFA. The experimental results indicate that GA can improve the particle characteristics of ground fly ash. The specific surface area of UFFA with 0.05 wt% GA is higher by 104 m 2 /kg than control sample. The particle size distribution of UFFA with GA becomes narrow and particle content of less than 16 μm is obviously increased. Additionally, the fluidity and loose bulk density of UFFA have also been improved. For pozzolanic reaction degree, 3-day, 7-day and 28-day hydration degree of UFFA with GA is increased by 1.2%, 2.3% and 4.6%, respectively; and 3-day, 7-day and 28-day activity index of UFFA with GA is also increased by 6%, 8% and 9%, respectively. For properties of blended cement containing UFFA, enhancement effect of UFFA with GA on the strength of blended cement containing 20 wt%, 30 wt% and 40 wt% fly ash are significant, and 3-day strength is increased by 12.6%, 6.6% and 6.6%, respectively, 28-day strength is increased by 6.5%, 9.3% and 10.5%, respectively. In this study, the hydration degree and microstructure of blended cement containing UFFA paste are also analyzed by SEM, XRD, IR and TG-DTA. The studies show that improvements such as hydration degree, products quantity, uniformity and compactness of products structure of blended cement containing UFFA are attributed to finer particle size and better particle size distribution caused by the addition of GA. [ABSTRACT FROM AUTHOR]

• The hydration process of ferroaluminate cement is tested and analyzed. • Gas permeability and chloride diffusion coefficient of FAC is much lower than OPC. • Pores with size of 10–100 nm have dominant effect on permeability and diffusivity. This study investigated the hydration process and durability properties of ferroaluminate cement (FAC). Hydration heat, hydration products, compressive strength, gas permeability and chloride diffusion coefficient were investigated experimentally for FAC mortar samples with different water-to-cement ratio (0.5, 0.45 and 0.4) and were compared with OPC mortar samples with the same mixing proportion. The mechanism of the difference in the durability of two cements was revealed from the perspective of pore size distribution and hydration products. The results show that FAC has a relatively fast hydration rate and the compressive strength at early age is larger than OPC. The gas permeability and chloride diffusion coefficient of FAC mortar samples are approximately 3–4 times lower than that of OPC mortar samples. The permeability and diffusivity of both FAC and OPC decrease significantly when the w/c decreases from 0.5 to 0.4. The main hydration products of FAC are ettringite, ferric hydroxide and aluminum hydroxide gel, large amounts of ettringite make FAC to form a dense structure, the proportion of the pores with pore size of 10–100 nm in FAC sample decreases greatly with compare to the OPC sample, which endows FAC superior impermeability properties. [ABSTRACT FROM AUTHOR]

The ferrite aluminate cement (FAC) could rapidly lose fluidity or workability due to its excessive hydration rate, and greatly reduce the construction performance. Chemical admixtures are commonly used to provide the workability of cement-based materials. In this study, to ensure required fluidity of FAC, chemically different water reducing agents are incorporated into the FAC pastes. The experiments are performed with aliphatic water reducing agent (AP), polycarboxylic acid water reducing agent (PC) and melamine water reducing agent (MA), respectively. Influence of the water reducing agents on fluidity, setting time, hydration process, hydration product and zeta potential of the fresh cement pastes is investigated. The results show that PC has a better dispersion capacity compared to AP and MA. Besides decreasing water dosage, PC also acts as a retarder, significantly increasing the setting times, delaying the hydration rate and leading to less ettringite in the hydration process of FAC particles. The water reducing agents molecules are adsorbed on the surface of positively charged minerals and hydration products, however, for PC, steric hindrance from the long side chain of PC plays a critical role in dispersing cement particles, whereas AP and MA acting through an electrostatic repulsion force. [ABSTRACT FROM AUTHOR]

• Ladle furnace slag contains a large amount of C 12 A 7 with early hydration activity. • Ladle furnace slag significantly shortens cement setting time. • Cement hydration heat release is significantly affected by ladle furnace slag. • A proper amount of ladle furnace slag has a slight expansion effect on cement. Ladle furnace slag (LFS) is a potential new resource for the preparation of cementitious materials with early hydration activities. To evaluate the application performance of LFS as a supplementary cementitious material, the effects of LFS on the hydration and hardening performance of cement were studied from the aspects of the hydration process, the physical and mechanical properties, the microstructure of the hardened paste, and the volume stability. The results showed that LFS has a significant setting acceleration effect and micro-expansion effect on cement. The blended cement containing LFS and ordinary Portland cement (LFS-OPC) had a better hydration product structure, mechanical strength, and volume stability at a low dosage (≤10%) of LFS. LFS with a high content (10%–30%) had a significant acceleration setting effect on the cement system, and the C 3 AH 6 and AFm contents were high in the ultra-early stage (1 d), which were the main source of the ultra-early mechanical strength of the cement system. However, the strength and volume stability of the LFS-OPC with a high content of LFS were poor in the middle and late stages. It was also found that the hydration process of the LFS-OPC system could be divided into two distinct stages: the early hydration of aluminate minerals, such as C 12 A 7 and C 3 A, and the later hydration of silicate minerals, such as C 3 S. With the increase in the LFS content, the hydration heat release rate of first stage of the blended cement increased significantly, indicating that LFS has the hydration characteristics of aluminate minerals. As a supplementary cementitious material, LFS has an excellent early hydration reaction activity. [ABSTRACT FROM AUTHOR]