Aluminum Silicate Research Articles

Application of SCMs and seawater to cement-bonded calcareous sand: Macro performance, micro mechanism, and strength prediction

Cement-bonded calcareous sand (C-BCS) demonstrates promising potential for marine island construction due to its exceptional mechanical properties. However, challenges such as freshwater scarcity and the erosive effects of seawater hinder the extensive utilization of C-BCS. To address this, this study comprehensively examines the feasibility of incorporating supplementary cementitious materials (SCMs) and seawater in C-BCS, focusing on macroscopic properties, microscopic mechanisms, and strength prediction. Macroscopic tests reveal that blast furnace slag and silica fume effectively enhance the hydration process and mechanical properties of C-BCS. Moreover, the cemented specimens developed in this study partially meet the strength standards for road pavement sub-base and airport runway upper-base applications. Microscopic analyses indicate that calcareous sand serves as a plentiful source of calcium, facilitating the formation of calcium aluminate silicate hydrate (C-A-S-H) and tobermorite when combined with Al2O3 and reactive SiO2 from slag and silica fume. This enhances the mechanical properties of the samples and their resistance against seawater erosion. Additionally, a back propagation (BP) neural network model accurately predicts the unconfined compressive strength of the cemented specimens. The findings of this study support the broader implementation of SCMs and seawater in practical island engineering projects involving C-BCS.

Formation of Natural Magnesium Silica Hydrate (M-S-H) and Magnesium Alumina Silica Hydrate (M-A-S-H) Cement.

Occurrences of natural magnesium alumina silicate hydrate (M-(A)-S-H) cement are present in Feragen and Leka, in eastern and western Trøndelag Norway, respectively. Both occurrences are in the subarctic climate zone and form in glacial till and moraine material deposited on ultramafic rock during the Weichselian glaciation. Weathering of serpentinized peridotite dissolves brucite and results in an alkaline fluid with a relatively high pH which subsequently reacts with the felsic minerals of the till (quartz, plagioclase, K-feldspar) to form a cement consisting of an amorphous material or a mixture of nanocrystalline Mg-rich phyllosilicates, including illite. The presence of plagioclase in the till results in the enrichment of alumina in the cement, i.e., forms M-A-S-H instead of the M-S-H cement. Dissolution of quartz results in numerous etch pits and negative quartz crystals filled with M-A-S-H cement. Where the quartz dissolution is faster than the cement precipitation, a honeycomb-like texture is formed. Compositionally, the cemented till (tillite) contains more MgO and has a higher loss of ignition than the till, suggesting that the cement is formed by a MgO fluid that previously reacted with the peridotite. The M-(A)-S-H cemented till represents a new type of duricrust, coined magsilcrete. The study of natural Mg cement provides information on peridotites as a Mg source for Mg cement and as a feedstock for CO2 sequestration.

Flotation performance and adsorption mechanism of 2-triethylenetetramine methylene-4-nonylphenol to pyrochlore

The flotation performance and adsorption mechanism of 2-triethylenetetramine methylene-4-nonylphenol (TMNP) on pyrochlore were investigated through micro-flotation experiments, zeta-potential tests, contact angle and XPS measurements. Additionally, the frothing properties of TMNP were studied using froth volume and surface tension tests compared with DDA. The flotation results showed that TMNP exhibited strong collecting ability for pyrochlore, but showed no selectivity towards quartz or feldspar. Separation experiments showed sodium aluminium silicate was an effective depressant for the separation of pyrochlore, feldspar, quartz, and calcite. The frothing properties of both TMNP and DDA were correlated with their respective surface tensions. Contact angle experiments demonstrated contact angle increased with increasing concentrations of TMNP and DDA. Zeta potential indicated that TMNP might adsorb onto pyrochlore surfaces through electrostatic attraction and chemical adsorption while DDA only exhibited physical adsorption. XPS data provided further evidence for the chemical adsorption of TMNP onto pyrochlore surfaces.

The Performance and Reaction Mechanism of Untreated Steel Slag Used as a Microexpanding Agent in Fly Ash-Based Geopolymers

Steel slag is an industrial by-product of the steelmaking process, which is under-utilized and of low value due to its characteristics. Alkali-activated technology offers the possibility of high utilization and increased value of steel slag. A geopolymer composition was composed of steel slag, fly ash, and calcium hydroxide. Four experimental groups utilizing steel slag to substitute fly ash are established based on varying replacement levels: 35%, 40%, 45%, and 50% by mass. The final samples were characterized by compressive strength tests, and Fourier-transform infrared spectroscopy measurements, thermogravimetric measurements, scanning electron microscopy with energy dispersive spectroscopy, X-ray diffraction, and mercury intrusion porosimetry were used to investigate the chemical composition and microstructure of the final products. Higher steel slag/fly ash ratios lead to a lower bulk density and lower compressive strength. The compressive strength ranges from 3.7 MPa to 5.6 MPa, and the bulk density ranges from 0.85 g/cm3 to 1.13 g/cm3. Microstructural and energy-dispersive X-ray spectroscopy analyses show that the final geopolymer products were a type of composite consisting of both calcium aluminate silicate hydrate and sodium aluminate silicate hydrate, with the unreacted crystalline phases acting as fillers.

Combined impacts of aluminum and silica ions on RO membrane fouling in full-scale ultrapure water production facilities

In this study, a fouled reverse osmosis (RO) membrane from a full-scale ultrapure water (UPW) facility was autopsied and investigated to propose the fouling mechanism and mitigation strategies. Although the influent was introduced to the coagulation and ultrafiltration as the pre-treatment processes, thick fouling layers were found over the entire RO surface. The foulant was mainly composed of aluminum silicates due to the elevated Al concentration (up to 100 μg/L) originated from the coagulation process utilizing polyaluminum chloride, and high recovery (up to than 90%) of RO process. Lab-scale fouling tests also confirmed that the elevated Al concentration in the RO influent contributed to significant flux decline due to a bridging effect with negatively charged organic matter and the formation of aluminum silicates. The application of polydiallyldimethylammonium chloride as an alternative coagulant successfully mitigated the organic and silicate fouling. Therefore, control of the residual aluminum ions originated from the coagulation process is critical to mitigate both organic and inorganic fouling on RO membrane surfaces during the production of UPW.

Utilising Phosphogypsum and Biomass Fly Ash By-Products in Alkali-Activated Materials

Significant environmental issues are raised by the phosphogypsum (PG) waste that is being produced. In Lithuania, about 1,500,000 tons of PG waste is generated yearly, and about 300 Mt is generated yearly worldwide. A by-product of burning wood biomass in thermal power plants is biomass fly ash (BFA). By 2035, compared to 2008 levels, industrial biomass incineration for combined heat and power and, as a consequence, BFA, is expected to triple. This study revealed the possibility of using these difficult-to-utilise waste products, such as BFA and PG, in efficient alkali-activated materials (AAM). As the alkaline activator solution (AAS), less alkaline Na2CO3 solution and Na2SiO3 solution were used. The study compared the physical–mechanical properties of BFA-PG specimens mixed with water and the AAS. After 28 days of curing, the compressive strength of the BFA-PG-based, water-mixed samples increased from 3.02 to 6.38 MPa when the PG content was increased from 0 to 30 wt.%. In contrast, the compressive strength of the BFA-PG-based samples with AAS increased from 8.03 to 16.67 MPa when the PG content was increased from 0 to 30 wt.%. According to XRD analysis, gypsum crystallisation increased when the PG content in the BFA-PG-based samples with water increased. The presence of AAS in the BFA-PG-based samples significantly reduced gypsum crystallisation, but increased the crystallisation of the new phases kottenheimite and sodium aluminium silicate hydrate, which, due to the sodium ions’ participation in the reactions, created denser reaction products and improved the mechanical properties. The outcome of this investigation aids in producing sustainable AAM and applying high volume of hardly usable waste materials, such as BFA and PG.

Corrosion behavior of laser powder bed fusion additive manufacturing produced TiNi alloy by micro-arc oxidation

To improve the corrosion resistance of TiNi alloy fabricated by laser powder bed fusion (LPBF), a porous oxidation layer was synthesized by micro-arc oxidation in a sodium aluminate and sodium silicate electrolyte. The influences of the applied voltage and the processing time on the morphology of oxidation layer were investigated, and the corrosion behavior of the oxidation layer in artificial saliva was evaluated and compared with that of the as-fabricated LPBF alloy. The results indicate that, as increasing the applied voltage and the processing time, the oxidation layer becomes uniform and integrated. The optimum parameters are with an applied voltage of 450 V and processing time of 40 min. The oxidation layer primarily contains α-Al2O3 and consists of two layers, i.e., a thin, compact and uniform inner layer and a porous outer layer. The formation of stable α-Al2O3 phase in the coating and its almost non-porous dense structure reduce the channels for corrosion ions to penetrate into the substrate through coating, thereby improving the corrosion resistance of TiNi alloy.

Performance assessment and cost-benefit analysis of low-carbon binders containing calcined sediments from Chorfa II dam as new building materials

Recently, considerable attention has been given to the valorization of dredged sediments around the world, which are considered waste. The reuse of dredged sediments has significantly contributed to Sustainable Development Goals. However, the efficiency and cost assessments of calcined sediments as a partial replacement for cement are not well understood. In this present investigation, the use of calcined sediments from dams as a green construction material on the properties of eco-pastes and mortars formulation is explored. Properties measurements, microscopic observation, eco-strength efficiency, and cost assessments were performed on fresh, hardened mortars in order to valorize calcined sediments in the cement industry. The best findings for the compressive and tensile strengths of mortars containing calcined sediments were obtained after 180 days, which was compared to the control mortar. Furthermore, microscopic analyses showed that an increase in the substitution rates of calcined sediment resulted in the increasing germination of calcium aluminate silicate hydrate gel (C-A-S-H) and calcium silicate hydrate gel (C-S-H). The control mortar showed an efficiency of 0.0902 MPa/kgCO2 eq for 28 days while the eco-strength efficiency of mortars containing 5%, 15%, and 25% of calcined sediments presented an efficiency of 0.0920 MPa/kgCO2 eq, 0.0922 MPa/kgCO2 eq, and 0.0997 MPa/kgCO2 eq, which represents an increase of 1.9%, 2.21% and 10.51%, respectively. However, the replacement of cement with calcined sediments up to a rate of 25% decreases embodied carbon. In conclusion, the cost of treatment of one (1) ton of sediments is lower than cement, which represents a reduction from 81.96% to 86%.

In Vitro and In Vivo testing of 3D-Printed Amorphous Lopinavir Printlets by SelectiveLaser Sinitering: Improved Bioavailability of a Poorly Soluble Drug.

The aim of this paper was to investigate the effects of formulation parameters on the physicochemical and pharmacokinetic (PK) behavior of amorphous printlets of lopinavir (LPV) manufactured by selective laser sintering 3D printing method (SLS). The formulation variables investigated were disintegrants (magnesium aluminum silicate at 5-10%, microcrystalline cellulose at 10-20%) and the polymer (Kollicoat® IR at 42-57%), while keeping printing parameters constant. Differential scanning calorimetry, X-ray powder diffraction, and Fourier-transform infrared analysis confirmed the transformation of the crystalline drug into an amorphous form. A direct correlation was found between the disintegrant concentration and dissolution. The dissolved drug ranged from 71.1 ± 5.7% to 99.3 ± 2.7% within 120min. A comparative PK study in rabbits showed significant differences in the rate and extent of absorption between printlets and compressed tablets. The values for Tmax, Cmax, and AUC were 4 times faster, and 2.5 and 1.7 times higher in the printlets compared to the compressed tablets, respectively. In conclusion, the SLS printing method can be used to create an amorphous delivery system through a single continuous process.

Non-isothermal crystallization kinetics for CaO–SrO–B2O3–Al2O3–Bi2O3–SiO2 glass system with Ta2O5 addition

The effect of Ta2O5 at the rates of 1, 2, 3 and 4 % mol on the CaO–SrO–B2O3–Al2O3–Bi2O3–SiO2 glass system was examined by the melt-quenching at 1400 °C. Non-isothermal crystallization kinetics of the compounds were calculated using Differential Scanning Calorimetry (DSC). The kinetics study revealed activation energy values of 109.4 kJ/mol for the T1 composition, 302.14 kJ/mol for the T2 composition, 471.5 kJ/mol for the T3 composition, and 344.7 kJ/mol for the T4 composition, as determined by applying the Kissinger method. According to the average of Avrami parameters, two-dimensional crystal growth was observed in T1 glass and surface crystallization was observed in all other glass. The glass forming ability (GFA) of the glasses was investigated with the values obtained as a result of HSM analysis. In the XRD analysis performed after heat treatment at 850 °C, crystal phase development was observed in the glasses. As a result of the crystallization process, it was observed that wollastonite, strontium aluminum silicate, strontium aluminum oxide and bismuth oxide phases were formed in T1, T2 and T3 glasses.

Design and characterization of iron–calcium–aluminium–silicate–hydrate as low-temperature binder

This work aims to synthesize new cementitious materials (binders) using marble powder, rice husk ash, activated laterite and NaOH solution by applying low energy process. The binder was used to stabilize solid precursors (laterite and pozzolan). To achieve this objective, calcium–silicate–hydrate (CSH) was first synthesized at different temperatures (26, 50, 80 and 100 °C). The best physical–mechanical properties were chosen to produce iron–calcium–aluminium–silicate–hydrate [Fe–C(A)SH] at different concentrations of sodium hydroxide solution: 4, 5, 6 M. Finally, the formulated binder at 6 M of NaOH solution was used to stabilize laterite and pozzolans at the following proportions 20%, 30%, 40% and 50%. The samples were characterized after 28 days of curing at room temperature. FT-infrared spectroscopy, X-ray diffraction, and environmental scanning electron microscope ESEM-EDS permitted to confirm the formation of CSH, and Fe–C(A)SH. The mechanical test used to evaluate the performance showed that the incorporation of 10% iron-rich laterite into CSH increased the strength up to 42.93 MPa and the addition of Fe–C(A)SH in the laterite/pozzolans increased the compressive strength of the final product (15.34 and 15.8 MPa for laterite and pozzolan, respectively). The highest concentration (6 M) increases the alkalinity and reduces the efficiency of silicate polymerization affecting the final structural compound. From the results, low-energy Fe–C(A)SH-based cement and stabilized compounds appeared promising for the development of sustainable infrastructures.

The effect of nucleating temperature on the crystallization, phase formation and properties of lithium aluminum silicate (LAS) glass-ceramics

To study the influence of the nucleation mechanism in lithium aluminosilicate glass, a composition similar to commercially produced glass was used. The glass-ceramics was obtained as a result of two-stage heat treatment, differing in the nucleation temperature and coinciding in the temperature and time of crystal growth. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used to study the formed nanocrystals. It was shown that the change of nucleation temperature in the glass transition interval Tg ±15 °C significantly affects the coefficient of thermal expansion, which is due to the formation of a different number of nanocrystals of the general composition LixAlxSi1-xO2 with x = 0.33 with the size less than 50 nm.

Facile green synthesis route for new ecofriendly photo catalyst for degradation acid red 8 dye and nitrogen recovery

This study novelty is that new photo catalyst prepared from sustainability low cost precursors. Dark red color hydrogel composites have been easily prepared from gelatin biopolymer using a simple sol–gel method. Gelatin doped by cobalt chloride, and silver nanoparticles (SNPs) in the presence of traces amount of sodium dodecyl sulfate surfactant and calcium chloride. Water-insoluble Gelatin composites are thermally stable photocatalysts for the degradation of toxic anionic acid red 8 dye. Promising photodynamic activity confirmed by fluorescence emission at λmax 650 nm. Optical absorption in Vis. light enhanced photo catalytic activity. Silver nanoparticles enhanced crystallinity, and improved optical properties and porosity. Dopants by CoCl2 and silver nanoparticles increased band gap of gelatin composites from (1.82 to 1.95) indicating interfacial charge separation. Low band gaps improved photo catalytic activity. Optical band gaps (Eg) lower than 2.0 eV indicates high catalytic activity in the photo degradation acid red 8 dye using Vis. light, wavelength 650 nm. Percent removal efficiency (%Re) of the dye at 500 ppm initial concentration, pH 1, contact time 30 min., and 0.20 g L−1 dose photo catalyst reached 95%. pH not affects removal efficiency. So, gelatin composites removed AR8 dye by photodegradation mechanism rather than adsorption due to photodynamic activity. Kinetics of photodegradation followed pseudo first order kinetic with rate constant k1 5.13 × 10−2 min.−1 Good electrical conductivity and magnetic properties (effective magnetic moment (µeff 4.11 B.M) improved dye degradation into simple inorganic species. Nutrients NH4+, and NO3− degradation products recovered by using alumina silicate clay via a cation exchange mechanism.

Selective and efficient extraction of lithium from spodumene via nitric acid pressure leaching

The thriving electric vehicle market has fueled a remarkable surge in the demand for lithium. Consequently, a heightened emphasis has emerged on the extraction of lithium from spodumene deposits. However, the sustainable growth of the lithium industry encounters challenges. The traditional process has the disadvantages of high acid consumption, high extraction rate of impurities and difficult purification of leach liquor. To address these challenges, this study proposes a process for the selective and efficient extraction of lithium from spodumene via nitric acid pressure leaching. In an autoclave at 200 °C, initial nitric acid concentration of 1 mol/L, liquid-to-solid ratio of 2.5 mL/g, and holding time of 30 min, 95 % Li was extracted, with low extraction rate of impurity elements. During pressure leaching, the aluminum–silicate cage structure of β-spodumene remains intact, while H+ freely exchanges with Li+ within the structure, resulting in the formation of HAlSi2O6. Subsequently, the leach liquor underwent thermal decomposition at 250 °C to achieve lithium-aluminum separation. It's noteworthy that nitric acid can be recycled in the process, resulting in low acid consumption. The proposed process has the potential to contribute significantly to the lithium industry by facilitating the adoption of environmentally friendly and sustainable practices.

Distribution of Groundwater Hydrochemistry and Quality Assessment in Hutuo River Drinking Water Source Area of Shijiazhuang (North China Plain)

The Hutuo River Drinking Water Source Area is an important water source of Shijiazhuang (North China Plain). Knowing the characteristics of groundwater chemistry/quality is essential for the protection and management of water resources. However, there are few studies focused on the groundwater chemistry evolution over the drinking water area. In this study, total of 160 groundwater samples were collected in November 2021, and the spatial distribution of groundwater chemistry and related controlling factors were analyzed using hydrological and multivariate analysis. The entropy-weighted water quality index (EWQI) was introduced to assess the groundwater quality. The results show that the hydrogeochemical types of groundwater are Ca-HCO3 (78.1%), mixed Ca-Mg-Cl (20%), and Ca-Cl (1.9%) in the area. Graphical and binary diagrams indicate that groundwater hydrochemistry is mainly controlled by water–rock interaction (i.e., rock weathering, mineral dissolution, and ion exchange). Five principal components separated from the principal component analysis represent the rock–water interaction and agricultural return, redox environment, geogenic sources, the utilization of agricultural fertilizer, the weathering of aluminum silicates, and dissolution of carbonates, respectively. More than 70% of the samples are not recommended for irrigation due to the presence of high salt content in groundwater. EWQI assessment demonstrates that the quality of the groundwater is good. The outcomes of this study are significant for understanding the geochemical status of the groundwater in the Hutuo River Drinking Water Source Area, and helping policymakers to protect and manage the groundwater.

Evaluation of microstructure evolution and mechanical properties of Al-10Zn-1.63Si/Irvingia gabonensis particulates alloy composites.

This study demonstrates the feasibility of using Irvingia gabonensis shell particulates (IGSp) as alternative reinforcing materials in the development of aluminium-based composites. In this experimental study, the microstructure, phase composition, and mechanical behaviour of Al-10Zn-1.63Si/xIGSp (wt%, x = 1, 3, 5 and 7) composites were investigated. The Al-10Zn-1.63Si based composites were fabricated using the stir-casting technique. Different weight percentages (1, 3, 5 and 7) of IGSp were added to the Al-10Zn-1.63Si matrix. The chemical constituents of the IGSp were determined using X-ray fluorescence (XRF). The grain characteristics and phase(s) compositions were determined using Scanning Electron Microscopy (SEM) and X-ray diffractometer (XRD). The ultimate tensile strength, hardness, and impact strength of the developed composites were also determined. The SEM and XRD results revealed the presence of different phases: aluminium phosphate (Al16P16O64), gahnite (ZnAl2O4), andalusite (Al2SiO5), Quartz (SiO2) and aluminium silicate (Al2O3.5.SiO2). Results show that addition of IGSp led to an increase in ultimate tensile strength, with the highest value (128 MPa) obtained at 3 wt% IGSp. The hardness of the composites increased with increasing concentrations of IGSp, reaching a maximum value of 285 HV after adding 7 wt% IGSp. The impact strength improved with the addition of IGSp, with the highest value (30 J) obtained at 1 wt% IGSp. The improvements in mechanical properties were attributed to the dispersion of three major phases: aluminium silicate (Al2O3.54.SiO2), Al16P16O64 and Al2O3.54.SiO2. These phases contributed to the enhanced strength and hardness of the composites. The study noted a sudden decrease in ultimate tensile strength with higher concentrations of IGSp due to the increase in the intensities of Al16P16O64 and precipitation of hard but brittle new phase; Al2Si60.6O126.33. The study concludes that IGSp has the potential to serve as an alternative reinforcing material for aluminium-based composites.

Characterization of Acid Activation of Bentonite Clay of Hadar, Afar, Ethiopia

The applications of various clay minerals are related to their structural, physical, and chemical characteristics. These properties of the clay minerals dictate their utilization in the industries and beneficiation required before usage. The study aimed at establishing the potentiality of acid‐activated clay mineral from Hadar, Afar, Ethiopia. XRD, SEM, energy‐dispersive X‐ray fluorescence (EDXRF), and FT‐IR spectroscopies were employed to characterize the chemical compositions and interaction in the bentonite samples. The XRD results revealed that the native and activated bentonite clay contains similar minerals, such as montmorillonite (MMT) ([Ca, Na]0.33 [Al, Mg]2[Si4O10][OH]2.nH2O), quartz (SiO2), albite (NaAl2SiO6), zeolite (CaAl2O3.SiO2.nH2O), and aluminum silicate. Thus, attributes of the bentonite clay was composed of SiO2 and Al2O3 indicating that it is an aluminosilicate mineral, and the morphology of bentonite was supported by SEM. The chemical analysis by EDXRF revealed that the native bentonite (NB) consisting of 58.18 wt% (SiO2), 14.28 wt% (Al2O3), and Na2O > CaO are the major constituents of the clay with other oxides present in low amount. There was an increase in the SiO2 content in activated bentonites, and the Al2O3, Fe2O3, and MgO contents have decreased by 48.56%, 66.36%, and 84.42%, respectively. The FT‐IR spectra bands at 1627 cm−1 and 1027 cm−1 were attributed to Al–Mg–OH, Al–Al–OH, and Al–OH–O–Si stretching vibration, and the reduction of the content of the octahedral cations is accompanied by a decrease of both OH bending vibrations at 1627 and 3401 cm−1. The FT‐IR result is in clear agreement with the SEM, XRD, and EDXRF studies which indicate sequential degradation of the clay sheet upon acid treatment. Hence, rendering the activated bentonite clay of Hadar has accounted for their demand for different industrial applications such as its use as detoxifier, sealant, binder, fillers for paper, pharmaceutical products, absorbent, adsorbent, catalyst, and nanoclays.

Thermodynamic Simulation of Alkali-activated Processes of Tuff-Based Geopolymer

The quantity of tuff powder is more than that of tuff mechanized sand in the dry process, which belongs to solid waste. In this paper, tuff from Gansu, Yunnan, Jiangxi, Sichuan, and Tibet was selected as the research object, and the composition of tuff in different areas was defined. Temperature and NaOH concentration were used as variables to conduct thermodynamic simulation, so as to explore the influence of both on the products after alkali-activated. The results show that the main products of alkali-activated tuff geopolymer are sodium silicate aluminate hydrate/calcium silicate aluminate hydrate (CNASH), magnesium silicate hydrate (MSH), Gibbsite, Goethite, and Quartz, except in the Jiangxi area. The amount of CNASH increases gradually with the increase of NaOH concentration, while the amount of Quartz decreases gradually with the increase of NaOH concentration. In the range of 20°C to 100°C, temperature has a significant effect on the production of CNASH and Quartz. The production of CNASH increases first and then decreases with the increase of temperature, and reaches the maximum at about 60°C. The production of Quartz increases with increasing temperature. The conclusion of this paper is helpful in understanding the alkali-activated mechanism of tuff powder.

Improving the strength of metakaolin-lime based binder

Pozzolanic reaction of low-calcium metakaolin (MK) with calcium hydroxide (CH) at ambient temperature in the presence of water forms a series of hydrated phases such as tetracalcium aluminate hydrate (C4AH13), calcium silicate hydrate (C-S-H) and calcium aluminum silicate hydrate (stratlingite - C2ASH8). Stratlingite is the main crystalline phase and is responsible for the strength of the binder. Tetracalcium aluminate hydrate (C4AH13) is carbonated upon contact with air or converted to hemicarboaluminate and/or monocarboaluminate if the system contains excess carbonate phases (calcite or calcareous aggregates). However, the calcium aluminate hydrates formed after the reaction of MK with lime lose their strength over time due to their instability. Especially in a high humidity environment where there is no carbonation, the presence of both stratlingite and (CH) in the binder creates weak phases called katoite (Ca3Al2(SiO4)(OH)8) and can reduce the mechanical strength and durability. On the other hand, it has been determined that using chemical activators to increase the pozzolanic reactivity is the most feasible method, although it increases the cost of the material. In this study, it is aimed to eliminate the phases that cause katoite formation and improve the performance of the binder by using alkaline hydroxide solution in a mixture of metakaolin and slaked lime, similar to the pore solution caused by hydrated cement. For this aim, the effect of sodium carbonate (N-Na2CO3), quicklime (C-CaO) and calcite (CC-CaCO3) on the (CH-Ca(OH)2) activated metakaolin system is investigated through the experimental campaign. The preparation of the mixtures is done by the novel one-part mixing method.

Inflation in Real Estate Development: A Time Series Analysis of Incidental Variables on Construction Costs in Chile

Soil is the basic material for the manufacture of compressed earth bricks, working the soil without any type of stabilization the physical and mechanical properties are minimal. This research aims to evaluate the physical and mechanical characteristics of compressed earth bricks stabilized with different dosages 5, 8, 12, 12, 15 and 18 % of cement, the tests that were performed were: absorption, compressive strength and flexural strength per unit of masonry, compressive strength of piles, diagonal compressive strength of walls and the X-ray diffraction test of the bricks; the results obtained from the different tests determine that with 18% cement the optimum strengths are obtained, the samples subjected to the absorption test have a 12. 63%, as for their compressive strength increased by 53. 95%, flexural strength in 43%, resistance to compression of piles in 36.6%, diagonal compression strength of walls in 41.24%, taking as a reference base the standard sample of 0% cement, in the X-ray diffraction test of the compressed brick stabilized with 18% cement where predominates the 32. 4% of calcium silicate, 23.8% of aluminum silicate, 17.4 % of hydrated calcium, 14.2 % of illite, 6.86 % of calcium oxide, 3.34 % of quartz, 1.2 % of kaolinite and goethite 0.8 % ; it is concluded that the bricks of compressed earth stabilized with cement (BCESC) is a sustainable construction alternative that improves the mechanical properties of the soil