The interfacial adhesion between asphalt and steel slag aggregate is a decisive factor in the formation of an asphalt-steel slag mixture and significantly affects the quality stability of steel ...slag-asphalt mixtures. In this study, the adhesion between an asphalt and steel slag aggregate, the interfacial microstructure, the adsorption and desorption characteristics, and chemical reactions were, respectively, explored by a PosiTestAT-A adhesion puller, a scanning electron microscope, a net adsorption test, an infrared spectrometer, and a dynamic shear rheometer. The mechanism of adhesion between the asphalt and steel slag aggregate was analyzed from the perspectives of physical adsorption and chemical reactions. The results showed that different factors had different effects on the adhesion of asphalt-steel slag aggregate interface. The freeze-thaw cycle and steel slag aggregate particle size had significant effects on interfacial adhesion, while the asphalt heating temperature, water bath time, and stirring time had relatively weak effects on interfacial adhesion. Compared to a limestone aggregate, the steel slag-asphalt mixture had greater adhesion and better adhesion performance because the pits and textures on the surface of the steel slag aggregate produced a skeleton-like effect that strengthened the phase strength of the asphalt-slag aggregate interface, thereby improving the adhesion and increasing the physical adsorption between the asphalt and steel slag aggregate. In addition, due to the N-H stretching vibrations of the amines and amides, as well as SiO-H stretching vibrations, a chemical reaction occurred between the asphalt and steel slag aggregate, thus improving the adhesion performance between the asphalt and steel slag. Based on the shape of the adsorption isotherm, it was determined that the adsorption type was multi-molecular layer adsorption, indicating that the adhesion between the asphalt and steel slag mainly involved physical adsorption.
Steel slag is an industrial solid waste with the largest output in the world. It has the characteristics of wear resistance, good particle shape, large porosity, etc. At the same time, it has good ...adhesion characteristics with asphalt. If steel slag is used in asphalt pavement, it not only solves the problem of insufficient quality aggregates in asphalt concrete, but can also give full play to the high hardness and high wear resistance of steel slag to improve the performance of asphalt pavement. In this study, a steel slag aggregate was mixed with road petroleum asphalt to prepare a permeable steel slag–asphalt mixture, which was then compared with the permeable limestone–asphalt mixture. According to the Technical Regulations for Permeable Asphalt Pavement (CJJT 190-2012), the permeability, water stability, and Marshall stability of the prepared asphalt mixtures were tested and analyzed. In addition, the high-temperature stability and expansibility were analyzed according to the Experimental Regulations for Highway Engineering Asphalt and Asphalt Mixture (JTG E20-2011). The chemical composition of the steel slag was tested and analyzed by X-ray fluorescence spectrometer (XRF). The mineral composition of the steel slag was tested and analyzed by X-ray diffractometer (XRD). The asphalt was analyzed by Fourier transform infrared spectroscopy (FTIR). The results show that the steel slag asphalt permeable mixture had good permeability, water stability, and Marshall stability, as well as good high-temperature stability and a low expansion rate. The main mineral composition was ferroferric oxide, the RO phase (RO phase is a broad solid solution formed by melting FeO, MgO, and other divalent metal oxides such as MnO), dicalcium silicate, and tricalcium silicate. In the main chemical composition of steel slag, there was no chemical reaction between aluminum oxide, calcium oxide, silicon dioxide, and asphalt, while ferric oxide chemically reacted with asphalt and formed new organosilicon compounds. The main mineral composition of the steel slag (i.e., triiron tetroxide, dicalcium silicate, and tricalcium silicate) reacted chemically with the asphalt and produced new substances. There was no chemical reaction between the RO phase and asphalt.
In this paper, a permeable steel-slag–bitumen mixture (PSSBM) was first prepared according to the designed mixture ratio. Then, the interaction characteristics between steel slag and bitumen were ...studied. The chemical interaction between bitumen and steel slag was explored with a Fourier-transform infrared spectrometer (FT-IR). The influence of steel-slag chemistry, mineral composition, and bitumen reaction on phase angle, complex shear modulus (CSM), and rutting factor was explored with dynamic shear rheological (DSR) tests. The PSSBM had better properties, including high permeability, water stability, Marshall stability, high-temperature (HT) stability, and low volume-expansion rate. Bitumen-coated steel slag can prevent heavy-metal ions from leaching. In the infrared spectra of the mixture of a chemical component of steel slag (calcium oxide) and bitumen, a new absorption peak at 3645 cm−1 was ascribed to the SiO–H stretching vibration, indicating that new organic silicon compounds were produced in the chemical reaction between calcium oxide and bitumen. SiO–H had an obvious enhancement effect on the interfacial adhesion and high-temperature rheological property of the mixture. In the mineral components of steel slag, dicalcium and tricalcium silicate reacted with bitumen and generated new substances. Chemical reactions between tricalcium silicate and bitumen were significant and had obvious enhancement effects on interfacial adhesion and high-temperature rheological properties of the mixture. The results of FT-IR and DSR were basically consistent, which revealed the chemical-reaction mechanism between steel-slag microcomponents and bitumen at the interface. SEM results showed that pits and grooves on the surface of the steel-slag aggregate, and the textural characteristics provide a framework-like function, thus strengthening the strength and adhesion of the steel-slag–bitumen aggregate interface.
Alkali-activated fly ash (AAFA) can offer both significant performance benefits and environmental advantages in corrosive and high-temperature environments. However, the slow setting and limited ...early strength development of AAFA at ambient temperature strict its use to pre-cast elements that must be cured using elevated temperatures. In order to address this limitation, this experiment pursued a distinctive approach to produce a pre-polymerized suspension (PPS) using ultrafine fly ash (UFA) that was activated with NaOH, thereby generating numerous nano-scale zeolite crystals and amorphous N-A-S-H gels. PPS was used alongside UFA in conjunction to create AAFA. Combining PPS in the AAFA mixture, while cutting UFA usage by 50%, led to a 30-minute initial setting time and a 15 MPa compressive strength after 3 days, which was significantly improved compared to the nearly 3 days required by the control sample to initially set. This remarkable result was attributed to the accelerated dissolution of active Si/Al ions from UFA, as well as the nucleation template effect of nano-scale zeolite and N-A-S-H gels within the PPS that speeded up the product's polyreaction, and resulted in a dense and quickly developed hardened structure. By using PPS, the dependency on UFA and its accompanying high energy consumption was dramatically reduced. Additionally, the fast-setting and high early strength properties of the optimized AAFA paste make it ideal for in-situ construction, thereby extending the usage of fly ash resources.
Fabricated hydraulic lime (FHL), prepared by fully mixing hydrated lime and hydraulic components containing activated Si/Al, shows quicker strength development and better water resistance than that ...of hydrated lime, and has the advantage of raw material supply to replace natural hydraulic lime (NHL) for the restoration of ancient sites. As ultrafine pozzolanic powders such as nano-SiO2, silica fume, slag, fly ash and circulating fluidized bed combustion ash can not only improve the hydraulic activity, but also be beneficial for the permeability of FHL paste in the ancient sites, this study investigated the influence of the above ultrafine pozzolanic powders on the durability of FHL, and obtained an optimal FHL through orthogonal test, and its durability was compared with NHL. The results showed that nano-SiO2 had a significant improvement on the water and sulphate resistance of FHL paste as well as its early compressive strength; silica fume greatly influenced the water resistance and later compressive strength; slag is the most important factor to improve the sulphate resistance of FHL; fly ash and circulating fluidized bed combustion ash had a smaller effect on the durability of FHL. The optimum FHL is composed of 1% nano-SiO2, 2% silica fume, 10% slag, 10% fly ash, 6% circulating fluidized bed combustion ash and 69% hydrated lime, which owned much better water and sulphate resistance than NHL mortar. The superior durability of FHL pastes was mainly due to the diversification of the internal hydration products and the close connection from XRD and SEM analysis. FHL with excellent durability proposed in this paper may have a positive impact on the restoration of ancient sites. In the future, the reinforcement effect of FHL prepared in this study on cultural relics sites will be discussed.
•Ultrafine pozzolanic powders added to air lime pastes, mortars.•Enhancement of mechanical property and durability achieved.•A potential repair material of restoration was prepared.
This study aims to investigate the effect of limestone filler, sulfate concentration and temperature on the thaumasite sulfate attack (TSA) in Portland cement (PC)-calcium aluminate cement ...(CAC)-gypsum ternary system. The compressive strength of mortar was tested, while X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to analyze the deteriorated products. The results indicate that the ternary system with limestone filler is susceptible to TSA. The higher the limestone content, the higher the TSA is in systems with MgSO4 solution of less than 5%. When the limestone filler content is 10% or 20%, the sulfate attack is mainly presented as gypsum sulfate attack. When the concentration of MgSO4 solution increases, the corrosion is diminished. The ternary system exposed to low concentration MgSO4 solution of 5% is prone to form thaumasite. The lower the temperature, the more vulnerable the system is to TSA. The mortar at 5 °C under 5% MgSO4 solution is rarely damaged and thaumasite could easily be detected.
The effects of redispersible polymer powders of ethylene/Vinyl acetate copolymer (EVA) and ethylene/vinyl laurate/vinyl chloride terpolymer (E/VL/VC) on the efflorescence of Portland cement-based ...decorative mortar (PCBDM) were studied. The results showed that EVA slightly prolongs the efflorescence duration of fresh PCBDM; and exacerbates efflorescence of hardened PCBDM, because it increases the content of soluble salts such as Ca super(2+), K super(+), Na super(+) ions in hardened PCBDM and promotes their migration. E/VL/VC exacerbates efflorescence of fresh PCBDM due to it easily dissolves in the surface water; but reduces efflorescence of hardened PCBDM, which is attributed to that it decreases the soluble salts content in hardened PCBDM and prohibits salts migration.Original Abstract: Straipsnyje tirta disperguojamuju polimeriniu priedu itaka drusku issikristalinimui portlandcemento pagrindu sukurtame dekoratyviniame skiedinyje (CPDM). Eksperimento metu pasirinkti etilen/vinil acetato kopolimero (EVA) ir etilen/vinil laurat/vinil chlorido terpolimero (E/VL/VC) disperguojamieji polimeriniai priedai. Tyrimu rezultatai parode, kad del EVA disperguojamojo polimero siek tiek leciau druskos issikristalizuoja skiedinyje, taciau jos labiau issikristalizuoja sukietejusiame tinke. Siuos tyrimo rezultatus patvirtina sukietejusiame tinke aptikti tirpiu drusku Ca super(2+), K super(+) ir Na super(+) jonai. (E/VL/VC) del lengvai vandens pavirsiuje tirpstanciu disperguojamuju polimenu labiau issikristalizuoja druskos skiedinyje ir leciau susidaro druskines apnasos sukietejusio tinko pavirsiuje. Sis reiskinys aiskinamas tuo, jog aptikta maziau tirpiu drusku sukietejusiame tinke. Del to mazeja drusku migracija dekoratyviniame skiedinyje.
•Using water as solvent was beneficial to the consolidation effect of hydraulic lime.•Superfine pozzolan supplied deep penetration and slight migration for FHL in matrix.•Filling and cementation of ...FHL formed a spatial network in consolidated soil-matrix.•FHL was superior in improving mechanical properties and compatibility of soil-matrix.
In this experiment, fabricated hydraulic lime (FHL) was synthesized by blended hydrated lime and superfine pozzolanic components, and the solvent for preparing lime-suspension was optimized through a static bleeding test. A systematic comparison was conducted between a commercial natural hydraulic lime (NHL) and synthesized FHL in consolidating soil-matrix. Their effects were evaluated in terms of effectiveness (penetration depth and surface hardness) and compatibility (color difference and vapor transmission). Both consolidants were proved to be compatible, while FHL-suspension outperformed NHL in effectiveness, due to the filling effect and cementation with the original loose soil particles supplied by superfine pozzolanic components, and their quicker hydration products helped the formation of a spatial network in consolidated matrixes. In addition to the known widely available raw materials supply, this experiment confirmed the properties advantages of FHL, which supplied a potentially suitable material for the anti-weathering purpose of earthen relics.
•Composite SPs gave a significant improvement on fluidity and strength of AAFAs.•The effect of composite SP stems from the synergism of melamine and naphthalene.•Composite SPs maintained structural ...stability in NaOH solution within 60 min.•Steric resistance cannot be ignored in the dispersion mechanism of composite SPs.
Workability could be a serious drawback for fresh alkali activated fly ash (AAFA) due to its high viscosity caused by alkaline activators. However, the reported optimum superplasticizers (SPs) only produced a slight improvement of fluidity while brought ambivalent effect on the strength in final NaOH-activated AAFA products. To obtain AAFAs with high fluidity and strength, 8M NaOH-AAFAs with low w/b at 0.24 were synthesized, and the effect of composite SPs consisted of naphthalene and melamine on fluidity and strength was investigated. Compared with naphthalene and melamine used separately, the composite SPs gave a maximum reduction in plastic viscosity, corresponding to the largest mini-slump and the lowest fluidity collapse. The workability improvement caused by composite SP was provided from the synergism of melamine and naphthalene, as the significant improvement of melamine on initial fluidity and the excellent fluidity retention supplied by naphthalene. Moreover, the application of composite SPs at lower dosage (1%) could give a significant improvement on the compressive strength of AAFAs. Further, the stability and water reduction mechanism of composite SP were also assessed, and results revealed that the decomposition of sulfonate in naphthalene and triazine ring in melamine was delayed; indicating naphthalene and melamine could maintain their structural stability within 60 minutes when adopted together. In addition, the steric resistance effect cannot be ignored in the dispersion mechanism of composite SPs, while the electrostatic repulsion played a dominant role when naphthalene and melamine used separately. The outcome of this study will be supportive to the ongoing research related to the construction performance of AAFAs in the aim of promoting their in-situ applications
•Ultrafine AAM heated with microwave exhibited faster and more serious efflorescence.•The impact of microwave is even worse for precursors with more amorphous phase.•Weak crystallization of reaction ...products improved the instability of sodium ions.•A less compact structure dominated by fine capillaries promoted ions transmission.
Using coal combustion ashes to synthetize alkali-activated cements (AACs) has significant advantages in the sustainable development of coal industry and exploiting cementitious materials for special occasions. Microwave heating and ultrafine precursors have been reported to improve the reaction extent that would greatly influence the strength development at the early ages of AACs, however, few researches focused on their influence on efflorescence, which is caused by the excessive unreacted alkaline in AACs diffusing to its surface, and reacting with CO2 in the air to form white carbonate deposits on the surface, and efflorescence may lead powder and peel on the AAC surface and gradually lose strength from the outside to the inside. In order to investigate the influence of microwave heating and ultrafine precursors on efflorescence, AAC samples adopting normal and ultrafine coal combustion ashes, and heated with steam and microwave respectively were synthetized. Additionally, the properties including geo-polymerization products, pore structure and moisture transport process which directly affect efflorescence were also compared. The results revealed that AACs heated with microwave exhibited faster and more serious efflorescence, especially for precursors with more amorphous phase and higher geo-polymerization reactivity, which can be attributed to the weak crystallization of reaction products improving the instability of sodium ions, and a less compact microstructure dominated absolutely by capillaries that promotes moisture movement, and also the transmission of sodium ions. Faster efflorescence tendency also revealed on AACs synthetized with ultrafine coal combustion ashes, however, their damage was significantly lower than that of microwave heating, and the increased moisture transport rate caused by the unitary capillaries distribution concentrated at 30 nm–100 nm may be the key reason. These results enrich the research on the application of coal combustion ashes and the influencing factors of AAC efflorescence.
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