Mercury Intrusion Porosimetry Analysis Research Articles

Study of the contact angle and roughness effects on mercury intrusion porosimetry (MIP) analysis in natural/real carbonate rocks using massive pure minerals and synthetic carbonate rocks

Studying pore networks in rocks is critical for understanding reservoir properties, with mercury intrusion porosimetry (MIP) being a key laboratory method. MIP involves capillary intrusion of mercury, with intrusion pressure (P) related to capillary diameter (d) by the Washburn equation, incorporating mercury properties like contact angle (θ) and surface tension (γ). While a constant contact angle of 140° is typically assumed for MIP, it can vary based on rock mineralogy and surface roughness. This study aims to analyze how contact angle variations and surface roughness affect MIP analysis of carbonate rocks. Initially, contact angle data was obtained for calcite, dolomite, and quartz with varying roughness levels. Synthetic rocks were then constructed using these minerals. MIP was performed using the typical 140° contact angle and a calculated contact angle from the Cassie model, which considers surface composition fraction. Natural rock MIP analysis followed, with contact angles varying due to mineral composition and roughness. The study found higher contact angles than the standard 140°, affecting pore size distributions up to 30%. Natural rock pore network curves were adjusted based on synthetic rock data analysis. These findings emphasize the need for accurate contact angle selection in MIP for precise pore distribution analysis and contribute to the further study of carbonate rocks.

Effect and mechanism of time-dependent and economical expansion materials in improving the active roof-contact for cemented paste backfill

During the backfilling process, there is often a problem of no roof-contact, and the time and state of roof-contact cannot be predicted, seriously affecting the backfilling safety and efficiency. Therefore, the expansion effect, mechanism, and time dependence of the expansion agents used to achieve roof-contact were studied through expansion ratio tests, strength tests, and microscopic analysis. The expansion ratio of the MgO-type expansion agent (MEA) can meet the requirement of backfilling, and the unconfined compressive strength (UCS) of the expansive cemented paste backfill (ECPB) was attenuated compared to that of ordinary cemented paste backfill (CPB). Through scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP) of the MgO-type ECPB, it is found that the ECB produces Mg(OH)2 crystals, which improves the compensation space inside the ECPB. MIP analysis results also show that the ECPB has higher porosity and more macropores, which is the reason for the strength attenuation of the ECPB. It is found that the expansion ratio and sedimentation ratio of fresh ECPB are time-dependent, and they both conform to logarithmic function. Afterwards, through the dynamic relationship between the sedimentation and expansion of fresh ECPB, the synthetic criterion of roof-contact based on the time-dependent model of expansion ratio and sedimentation ratio was established. The theoretical shortest roof-contact time of different experimental groups was obtained. Finally, through a comparative analysis of backfilling costs, the lowest cost and reasonable backfilling scheme were obtained. It is of great value for judging the effectiveness of roof contact, optimizing the backfilling proportion scheme, ensuring backfilling safety, and saving backfilling and mining costs.

Eco-recycled cement's effect on the microstructure and hygroscopic behaviour of compressed stabilised earth blocks

Recycled cement (RCP) retrieved from old cement waste aims to replace carbon-intensive ordinary Portland cement (OPC) in earth stabilisation, improving the mechanical performance and durability of earth construction, without significantly compromising its ecological character and thermophysical properties. This study analyses the microstructure and hygroscopic behaviour of compressed earth blocks (CEB) stabilised with RC. In addition, soil was partially replaced with construction and demolition waste (CDW) to further improve the CEB sustainability. To this end, the sorption-desorption isothermal behaviour of CEB with different soils, types and contents of stabiliser (0–10 % RCP or OPC), and varying percentage replacements of OPC with RCP (20, 50, 100 %) or soil with CDW (0, 15, 25 %) was analysed and related to their microstructure, which was characterised in terms of scanning electron microscopy, mercury intrusion porosimetry and nitrogen adsorption analysis. Unstabilised and OPC CEB were considered for comparison purposes. The microstructure of CEB was refined after RCP stabilisation, which influenced their hygroscopicity and adsorption-desorption hysteresis. Depending on the clay content of the soil, stabilisation reduced or increased the hygroscopic capacity of CEB. After stabilisation, the water adsorption decreased up to 25 % in CEB with clayey soil and increased up to 22 % in CEB with sandy soil. However, the hygroscopic behaviour was not significantly affected by the type of stabiliser. The substitution of OPC with RCP increased the volume of water adsorption up to 3 %, due to its slightly finer porosity. RCP has proven to be effective as an earth stabiliser, leading to CEB with adsorption-desorption properties similar to those of OPC CEB.

Unraveling microstructural evolution in air-entrained mortar and paste: Insights from MIP and micro-CT tomography amid cyclic freezing-thawing damage

Understanding the microstructure evolution during the cyclic freezing-thawing process is crucial to studying the deterioration mechanisms of concrete under cyclic freezing-thawing. In this study, air voids were entrained into cement mortar and paste by AEA and polymeric microspheres. Mercury intrusion porosimetry (MIP) and micro-CT techniques were integrated to investigate the microstructure of the specimens with various freezing-thawing cycles. After subjecting the Ref. and AEA mixed mortar to 100 and 200 freezing-thaw cycles, an increase in porosity and pore entrapment was observed from the MIP results, suggesting the occurrence of damage induced by cyclic freezing-thawing. Conversely, in the microspheres mixed mortar, the presence of surface adsorbed moisture led to an initial increase in porosity and pore entrapment after 100 freezing-thaw cycles, followed by a decrease after 200 cycles, indicating a healing effect. Micro-CT analysis revealed that while the AEA mixed specimens exhibited higher air content than the microspheres mixed specimens, the latter showed a greater number of voids, which ultimately enhanced their resistance to freezing-thawing. The micro-CT results unveiled that air bubbles tended to merge in AEA mixed specimens, adversely affecting their resistance to freezing-thawing. Conversely, the microsphere-incorporated specimens displayed smooth void distribution curves, indicating a well-distributed air void system that enhances their freezing-thawing resistance. This work suggests that microspheres can be a great candidate for air-entraining materials. Combining the MIP and micro-CT analysis can better understand the microstructure change of concrete with cyclic freezing-thawing.

A microstructural insight into the compression behaviour of scaly clays

Scaly clays are intensely fissured clays with lens-shaped elements of millimetre size and they show a complex compression behaviour that poses challenges to the design and construction of geostructures (excavations, retaining diaphragms and tunnels). Scaly clays show a normal compression line (NCL) where plastic deformation accumulates, as typically observed in non-scaly clays. Yet the response observed upon unloading and subsequent reloading is very peculiar, (a) the unloading–reloading cycle is typically a closed loop with relatively large hysteresis; (b) the compressibility recorded at high overconsolidation ratio of the unloading or reloading branches is close to the NCL compressibility. This paper presents a microstructural study on an Italian scaly clay where scanning electron microscope observations are integrated with mercury intrusion porosimetry analyses and X-ray computed tomography images. The mechanism associated with the closing of inter-scale porosity and the generation of new intra-scale porosity was identified as the process responsible for the plastic deformation. Experimental observation of reconstituted clay showed a ‘quasi-reversible’ behaviour upon loading and unloading and a pore size distribution characterised only by interparticle porosity. The observation that unloading and reloading curves are parallel in natural and reconstituted clays, led to the postulation that the interparticle porosity is controlling the elastic response.

Enhanced Resistance to Desiccation Cracking of Polymer-Bentonite Mixtures: An Experimental Investigation of Underlying Mechanisms

Polymers have been shown to enhance the resistance of swelling clay soils to desiccation cracking, a critical property in engineering applications, particularly in waste containment facilities. However, the microscopic and macroscopic mechanisms driving this improvement remain poorly understood. Additionally, the influence of different mixing methods on these mechanisms is not well-established. While dry mixing is more convenient for onsite implementation, wet mixing offers intercalation between clay and polymer, resulting in potentially more durable stabilization outcomes. In this paper, key properties related to desiccation cracking of a polymer-clay mixture were measured. The mixture was synthesised by amending Na-bentonite with sodium carboxymethyl cellulose (Na-CMC) using dry and wet mixing. Soil water retention characteristics curves (SWCC), swelling and shrinkage potential, tensile strength, and pore size distribution by mercury intrusion porosimetry (MIP) were measured for both mixtures and untreated bentonite. Compared to pure bentonite, mixtures were found to have slightly reduced air-entry values, significantly lower swelling and shrinkage potentials and higher tensile strengths. In all experiments, dry mixing exhibited superior performance compared to wet mixing. MIP analysis of the amended mixtures revealed a more porous structure when compared to untreated bentonite.

Feasibility of compacted attapulgite/diatomite amended clayey soils as gas barrier materials

Compacted clay liners are extensively used as barriers to control the upward diffusion of vapors of volatile or semi-volatile organic contaminants released from unsaturated contaminated soils at industry-contaminated sites. This study aimed to investigate the gas diffusion barrier performance of compacted clayey soils amended with three agents including attapulgite and diatomite individually, and attapulgite/diatomite mixture. The properties including water retention, volumetric shrinkage, gas diffusion, and unconfined compressive strength were evaluated through a series of laboratory tests of amended compacted clayey soils. The results demonstrate that the decrease in volume proportions of inter-aggregate pores leads to an increase in unconfined compressive strength (qu). Both hydrophilic groups and microstructures of attapulgite and diatomite result in an increase in water retention percent (Wt) of compacted clayey soil specimens after amendment regardless of the type of agent or initial water content (w0). Furthermore, the ratio of the gas diffusion coefficient (De) to the gas diffusion coefficient in the air (Da) was significantly reduced owing to a decrease in volume proportions of inter-aggregate pores, hydrophilic group, and microstructures of attapulgite and diatomite. Scanning electron microscope analyses revealed that rod-shaped attapulgite filled the inter-aggregate pores formed by clay particles, whereas the disc-shaped diatomite particles, characterized by micropores, failed to obstruct the inter-aggregate pores due to their larger particle size. Mercury intrusion porosimetry (MIP) analyses showed a reduction in pore volume in the inter-aggregate pores, leading to a reduction in the total pore volume for both the attapulgite and attapulgite/diatomite mixture amended clays, which is in accordance with the scanning electron microscope (SEM) results. The findings are pertinent to the practical application of compacted clay liners as gas barriers against the upward migration of volatile or semi-volatile organic contaminants at contaminated sites.

Archie's cementation factors for natural rocks: Measurements and insights from diagenetic perspectives

Archie's cementation factor, m, is a critical parameter for petrophysical studies, and the value is influenced by several factors such as the shape, type, and size of grains, degrees of diagenesis, and associated pore structure. Using integrated experimental and theoretical approaches, the goal of this study is to obtain the cementation factor of rocks (both reservoir rock and caprock) and assess the impact of diagenetic processes on the values of the cementation factor. Thirteen samples of geologically diverse rocks (six mudstones, four fossiliferous limestones, two marbles, and one sandstone) were selected to achieve these research objectives. Two approaches, the diffusion of gas tracers and the Bosanquet formula calculation using pore-throat sizes from mercury intrusion porosimetry analyses, were used to derive the cementation factors of these rock samples. These rocks were categorized into two groups based on the correlation between average pore-throat diameter and diffusivity, and an exponential-law relationship between the cementation factor and porosity was determined for these sample groups. In addition, thin-section petrography and field emission-scanning electron microscopy observations were utilized to investigate diagenetic processes, with four diagenetic patterns being established: (1) strong compaction, strong cementation, and weak dissolution-diagenesis pattern; (2) weak compaction, medium cementation, and weak dissolution-diagenesis pattern; (3) weak compaction, medium cementation, and strong dissolution-diagenesis pattern; and (4) fracture-matrix pattern. The results indicated that diagenetic processes and microfractures contribute to the variability in the cementation factors of these rock samples.

Pore evolution in extrusion-based 3D printed cementitious materials due to calcium leaching

Extrusion-based 3D printed cementitious materials (3DPC) require specific parameters to be met that will substantially impact printed part durability, particularly when exposed to aggressive external conditions. Due to the specificity of the spatial distribution of the pores, 3DPC are reported to exhibit performance anisotropy compared to cast materials. A fundamental understanding of the discrepancy in the pore evolution between the printing direction, lateral direction, and top direction is essential for calcium leaching from 3DPC in aggressive water. This research investigates pore structure evolution in 3DPC with the three directions in a 6 mol/L ammonium chloride solution. The leaching depths of the samples in the three directions were tested and compared. In addition, their porosity, maximum, median, and average pore diameters, pore size distribution, and pore morphology are investigated using optical microscope (OM) and mercury intrusion porosimetry (MIP) analysis. Significant differences were found between the leaching depths in the different directions of the 3DPC. Samples leached in the top direction show less leaching depth than in the other two directions, indicating the anisotropic nature of 3DPC. This was attributed to the different pore structures of the sample in the top direction compared to the other directions, as confirmed by OM and MIP analysis. Furthermore, the pore morphology is more irregular and elongated in the printing and lateral directions than in the top direction. In turn, the calcium leaching increases the porosity and coarsens the pore structure of 3DPC. The results of this study can be used as a reference for the application of 3DPC in aggressive water environments.

Evaluation of the technical properties of reactive-MgO cements produced by solar calcination of magnesite in a fluidized bed reactor

Magnesium oxide (MgO)-based cements display very interesting technical properties and environmentally-friendly features. The novel idea investigated in this study is to synthesize MgO cements, using as raw material natural magnesite calcined in fluidized bed heated by concentrated solar energy. Calcination was performed in a lab-scale system equipped with a concentrated solar simulator, operated under different process conditions. The most reactive MgO was mixed with 3% by weight of MgCO3 (nucleation agent) and four different solutions containing magnesium acetate or chloride. The binders were hydrated in air or 20% CO2 atmosphere (accelerated carbonation conditions) until 28 days. X-ray diffraction, differential-thermal and mercury intrusion porosimetry analyses, and compressive mechanical strength tests, were performed on the hydrated systems. Solar calcination produced a highly reactive MgO. The performance of the cement pastes improved at higher curing times, and when using magnesium acetate as hydration agent, as also witnessed by the application of a kinetic model. Accelerated carbonation conditions further enhanced the mechanical properties of the cements thanks to the formation of nesquehonite, allowing to reach a mechanical strength comparable to that of ordinary Portland cements class 32.5. The achieved outcomes encourage the production of low-CO2 magnesite cements from solar calcined magnesite, boosting the green aspect of the entire process.

Development and application of a 3D image analysis strategy for focused ion beam - Scanning electron microscopy tomography of porous soft materials.

In recent years, the potential of porous soft materials in various device technologies has increased in importance due to applications in fields, such as wearable electronics, medicine, and transient devices. However, understanding the 3-dimensional architecture of porous soft materials at the microscale remains a challenge. Herein, we present a method to structurally analyze soft materials using Focused Ion Beam - Scanning Electron Microscopy (FIB-SEM) tomography. Two materials, polymethyl methacrylate (PMMA) membrane and pine wood veneer were chosen as test-cases. FIB-SEM was successfully used to reconstruct the true topography of these materials in 3D. Structural and physical properties were subsequently deduced from the rendered 3D models. The methodology used segmentation, coupled with optimized thresholding, image processing, and reconstruction protocols. The 3D models generated pore size distribution, pore inter-connectivity, tortuosity, thickness, and curvature data. It was shown that FIB-SEM tomography provides both an informative and visual depiction of structure. To evaluate and validate the FIB-SEM reconstructions, porous properties were generated from the physical property analysis techniques, gas adsorption analysis using Brunauer-Emmett-Teller (BET) surface area analysis and mercury intrusion porosimetry (MIP) analysis. In general, the data obtained from the FIB-SEM reconstructions was well-matched with the physical data. RESEARCH HIGHLIGHTS: Porous specimens of both synthetic and biological nature, a poly(methyl methacrylate) membrane and a pine veneer respectively, are reconstructed via FIB-SEM tomography without resin-embedding. Different thresholding and reconstruction methods are explored whereby shadowing artifacts are present with the aid of free open-source software. Reconstruction data is compared to physical data: MIP, gas adsorption isotherms which are analyzed via BET and Barrett-Joyner-Halenda (BJH) analysis to yield a full picture of the materials.

Electrochemical realkalisation of carbonated cementitious matrix: characterization research to influence of time and current density

The depassivation of reinforcement caused by the reduction of concrete alkalinity due to the concrete carbonation process can induce the appearance of steel corrosion. The restoration of alkalinity can be done by chemical realkalinization (CRA) or electrochemical realkalinization (ERA) methods. In this context, the present work aims to evaluate the influence of the application time and the current density used in the electrochemical realkalinization process. For the development of the research, mortar samples were molded with a reinforced bar for electrical connection and remained for 24 months in a carbonation chamber. After this period, the carbonation depth that occurred was verified and then the specimens were submitted to the electrochemical realkalinization process using 3 different current values, 0.5, 1.0 and 1.5A/m2 and remained at different periods (7 , 14 and 21 days) in the recovery process. Additional tests of absorption, compressive strength, carbonation depth measurements, mercury intrusion porosimetry (MIP) and thermogravimetric analysis (TGA) were also carried out on reference, carbonated and realkalinized specimens. Based on the results of the tests, it was observed that the recovery process starts after 7 days with the lowest current density used. A better current density x application time ratio was also observed considering the results of the mercury intrusion porosimetry and thermogravimetric analysis tests in conjunction with the realkalinization process.

Anti-strength retrogression cementing materials for deep and ultra-deep wells

Recent studies have brought to light a critical issue pertaining to the conventional silica-enriched Portland cements employed in deep and ultra-deep wells. The traditional silica-enriched oil well cements were found to exhibit substantial strength retrogression during prolonged curing under high temperatures, posing a significant threat to the overall cementing quality and subsequent production safety. This study proposes a novel approach to enhance the long-term stability of traditional silica-cement systems under high temperature conditions by introducing both granulated blast furnace slag (GBFS) and fly ash to the system. Test results indicated that the addition of GBFS increased the strength stability of the traditional silica-cement system but failed to completely prevent its strength retrogression. In contrast, the combined addition of GBFS and fly ash in silica-cement system significantly enhanced its long-term strength measured after 90 d curing. The strength test results were corroborated by further evidences from permeability tests as well mercury intrusion porosimetry analyses. Detailed analysis of the set cement composition suggests that the inhibition of xonotlite phase and the promotion of tobermorite and grossular phases in hydration products are responsible for improved long-term strength stability.

Scouring erosion resistance of nano-marine concrete under the coupled effect of chloride attack and dry - wet cycles

In order to reveal the improving mechanism associated with different types of nanoparticles under the three-factor coupled effects (scour, dry-wet cycles, and Cl- attack), a laboratory investigation was undertaken to evaluate and compare the influence of nano-SiO2 and nano-Fe3O4 with different content on scouring erosion resistance properties of marine concrete. The micro-structure of the interface transition zone (ITZ) in marine-concrete, as well as the features of hydration products, were characterized using advanced techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), differential thermal gravimetric (DTG-DSC) analysis, and mercury intrusion porosimetry (MIP). The test results showed that compressive and flexural strength, as well as scouring erosion resistance of marine-concrete were enhanced with the increasing content of nano-SiO2 and nano-Fe3O4 until the threshold limit of 2%, and performance of NSC20 was better than that of NFC20. Under the three-factor coupling, the strength corrosion resistance coefficient of nano-marine concrete was negatively correlated with the scouring erosion rate and the change rate of scouring erosion area, and positively correlated with the resistivity and the Cl- diffusion coefficient with the increase of corrosion age. When the corrosion age reached 70 days, the average scouring erosion rates of NSC20 and NFC20 were decreased 19.86% and 14.43%, respectively, compared with PC. The convective depth of concrete steadily decreased while its diffusive depth increased relative to concrete without scouring. Cl- binding was increased by 28.5%, 27.2%, and 21.4% for PC, NSC20, and NFC20, respectively. The high chemical activity of nano-SiO2 and nano-Fe3O4 promoted the mechanical performance and durability of concrete through improved density and homogeneity of chlorinated products and optimized the structure of the C-S-H/C-F-H gels in ITZ, as indicated by SEM-EDS observation, XRD, and DTG-DSC analysis. The coupling effects resulted in increasing volume of air voids and micro-cracks, as well as weak ITZ due to SA, which hindered scouring resistance development, as indicated by the MIP analysis.

The synergistic action mechanisms of ternary industrial waste stabilized lead ion contaminated soil

In this study, ternary industrial waste comprising red mud, carbide slag and phosphogypsum was combined with cement to act as a curing agent for the remediation of Pb2+-contaminated soil. The mixing proportions of the four materials were determined based on the resulting mechanical and permeability properties as well as the pH and leached Pb2+ concentration of the solidified soil. Furthermore, variations in the compressive strength, pH of leachate, permeability coefficient and leached Pb2+ concentration with the curing age were studied. Additionally, scanning electron microscopy, X-ray diffraction, sequential extraction and mercury intrusion porosimetry analyses were performed to characterize the mineral constituents and microstructures of the solidified soil. The experimental results reveal that when cement, red mud, carbide slag, and phosphogypsum were added at mass percentages of 10 %, 2.5 %, 1.25 % and 1.25 %, respectively, the strength of the solidified soil increased and the permeability coefficient reached 10−7 cm/s. In this case, the pH value was 11.91, and the leached Pb2+ concentration was 0.403 mg/L, which comply with the environmental safety standards. Moreover, with increasing curing age, the strength increased, the permeability coefficient decreased, pH slightly increased and leached Pb2+ concentration decreased. The results revealed that the stabilization mechanism of the Pb2+-contaminated soil depends on the adsorption and physical encapsulation of the hydration products as well as the formation of a small amount of lead compounds, thus converting Pb2+ from a highly soluble state to a less reactive state.

Application of electro-injection method in improving cement mortar durability

An electrochemical method for improving the durability of cement mortar by injection of nanoparticles (alumina (Al2O3)-coated silica (SiO2)) is presented. In this method, nanoparticles are injected into cement mortar pores under an external electrical field, refining the pore structure of cement mortar. The efficiency of electro-injection nanoparticle treatment with different applied electric fields was evaluated by monitoring the evolution of cement mortar resistivity. The improvement of cement mortar durability after electro-injection of nanoparticles was assessed by examining the resistance to water absorption, carbonation, sulfate attack and chloride diffusion. The microstructure of cement mortar after the electro-injection treatment was analysed using scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), X-ray diffraction (XRD) and differential thermo-gravimetric analysis (DTG). The results show that cement mortar durability can be improved by the injection of nanoparticles under external electric field. The efficiency of electro-injection nanoparticle treatment increased with the increase of applied electric field. The resistance to water absorption, carbonation, sulfate attack and chloride diffusion were significantly improved by using the electro-injection method. The improvement in cement mortar durability can be attributed to the filling effect of nanoparticles.

Improving dispersion of recycled GFRP fiber in cement mortar with sodium hexametaphosphate

The dispersion of recycled glass fiber reinforced plastic (rGFRP) fibers in cement mortars has a significant impact on both the workability and mechanical properties of the composites. In this study, the dispersity of three types of rGFRP fibers was improved in two methods: Method 1: the dispersant (Sodium Hexametaphosphate, SHMP) was directly added into the mortar, and Method 2: the rGFRP fibers were pre-dispersed by the SHMP solution and then added into the mortar. The effect of the two fiber-dispersion methods on workability, mechanical properties, and microstructure of the rGFRP fiber reinforced mortars were investigated by Zeta potential test, mechanical tests, Mercury intrusion porosimetry and X-ray micro-CT analysis. The results showed that Method 2 had more significant improvement in mechanical strength than Method 1 for all types of rGFRP fiber reinforced mortar. The flexural strength of the mortars increased by 58.3%, 43.2% and 105.4% with 7.5 wt% GF1, GF2 and GF3 treated by Method 2, respectively, compared to their untreated counterparts. The pre-dispersion of the fibers with SHMP facilitated better dispersion of the large rGFRP fiber clusters in the mortar by increasing the surface charge of the fibers and enhancing repulsion between them, thus improving the mechanical performance of the mortar. The results of this study will promote the utilization of rGFRP fiber in construction materials.

Preparation a High-Performance of Gangue-Based Geopolymer Backfill Material: Recipes Optimization Using the Taguchi Method.

The strip filling method in underground reservoir needs high strength to achieve the requirements of water storage. In order to address the challenges associated with costly and weak filling materials, this study aimed to develop an economically efficient and high-strength gangue-based geopolymer backfill material (GBGBM). To achieve this, the Taguchi method was employed to design a series of 25 experiments, each consisting of four factors and five levels. This study focused on investigating the effects of different gangue gradation levels, sand ratios, water binder ratios (w/b), and aggregate binder ratios (a/b) on the working characteristics and unconfined compressive strength (UCS) of the GBGBM. The optimal combination of the GBGBM was determined by employing a signal-to-noise ratio (S/N)-based extreme difference and variance analysis. The results revealed that the w/b ratio exerted the most substantial influence on both the slump and UCS. Specifically, when employing a gradation of 50%, a sand ratio of 55%, an a/b ratio of 2.5, and a w/b ratio of 0.64, the slump measured 251.2 mm, the UCS at 3d reached 5.27 MPa, and the UCS at 28d amounted to 17.65 MPa. These findings indicated a remarkable improvement in early UCS by 131.14% and the late UCS by 49.45% compared to gangue-based cement backfill material (GBCBM). Additionally, this study examined the hydration products and microstructures of both GBGBM and GBCBM using X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) analyses. Significantly, the GBGBM exhibited notable advantages over the GBCBM, including a 78.16% reduction in CO2 emissions, a 73.45% decrease in energy consumption, and a 24.82% reduction in cost. These findings underscore the potential of GBGBM as a sustainable and cost-effective alternative to GBCBM.

A bio-inspired mineral precipitation method to improve the freeze-thaw resistance of cement concrete pavement

Mineral precipitation has been proven to be an effective surface treatment for reducing the porosity of Portland cement concrete (PCC), leading to significant improvement in its freeze-thaw (F-T) resistance. Inspired by human teeth, this study proposes to produce a protective surface layer for PCC through in-situ precipitating hydroxyapatite (HAP), the same mineral found in the tooth enamel, on the concrete surface to improve its freeze-thaw resistance. This protective layer was generated by simply treating the mortar surface with a diammonium hydrogen phosphate (DAP) solution. Experimental results reveal that the F-T resistance is significantly improved, with the DAP-treated specimens surviving three times as many cycles as the control group. The proposed treatment also enhances the compressive strength of the mortar specimens by 35% and reduces saturated water absorption by up to 50%. Analysis of mineralogy suggests that DAP reacts with calcium ions from hydrated cement, leading to HAP precipitation and calcium phosphate on the cement mortars' surface. Particularly, the nanoindentation results indicate that the mineral phase with a lower density tends to react more readily with DAP, leading to its conversion into minerals with significantly higher packing density. Quantitative backscattered scanning electrons (BSE) images and mercury intrusion porosimetry (MIP) analysis verify that the microstructure of the cement mortar surface was densified by the formation of HAP and calcium phosphate induced by the proposed treatment. The proposed method exhibits great potential in enhancing the longevity of PCC pavements in cold regions.

Effect of various powder content on the properties of sustainable self-compacting concrete

This research goal is to evaluate the characteristics of glass powder (GP), quartz powder (QP), and limestone powder (LP) as Supplementary Cementitious Materials (SCMs) to replace cement content in terms of fresh and hardened properties of Self-Compacting Concrete (SCC) for sustainable building construction. Moreover, the obtained results were modeled using a soft computing approach. This investigation created ten mixtures incorporating varying percentages of GP, QP, and LP by replacing cement at about 0 %, 10 %, 20 %, and 30 %, respectively. The slump flow and J-ring tests were done to observe how SCMs affected the properties in fresh condition. In addition, the mechanical properties and pore structure configuration of the specimens were investigated. It was observed that GP and LP positively affected the fresh properties, increasing the mixes flowability by up to 8 %. Moreover, 20 % GP was able to enhance the compressive strength by 7 % by improving the pore structure of the cement matrix, which was confirmed by the mercury intrusion porosimetry analysis. Finally, the built machine learning models indicated good accord with test outcomes for Artificial Neural Network (R2 = 0.95) and could be applied to calculate the compressive strength of concrete containing GP, QP and LP for construction housing sector.