Cement Samples Research Articles

Assessing Durability and Stability of Calcium Sulfoaluminate Cement-Stabilized Soils Under Cyclic Wet–Dry Conditions

Periodic wet–dry processes are a significant weathering mechanism that can quickly alter a soil’s mechanical characteristics, reducing its resilience and durability. This study investigates the physical and microstructural characterization of stabilized soils through experimental analysis. While the conventional approach to ground improvement involves the application of ordinary Portland cement (OPC) and lime for treating unstable soil, this research explores calcium sulfoaluminate (CSA) cement as an eco-friendly alternative with comparable efficacy and fewer adverse environmental effects. The primary objective is to evaluate the impact of cyclic wet–dry (W–D) events on the durability and stability of CSA cement-treated sand using comprehensive laboratory testing. Various samples were prepared with cement contents of 3%, 5%, 7%, and 10%, corresponding to the optimum moisture content. Stabilized soil specimens underwent testing for unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) after curing for 3, 7, 14, and 28 days. Subsequently, these specimens were exposed to zero, one, three, five, and seven W–D cycles. The outcomes show a decrease in the strength and durability index of the soil with a rising number of W–D cycles. However, the decline in the strength and durability of CSA-treated soil samples is significantly mitigated as the CSA content increases from 3% to 10%. The findings indicate that after seven W–D cycles, the UCS value of 10% cemented samples dropped by 14% after 28 days of curing, whereas 3% specimens experienced a 28% loss in strength. Similarly, UCS values for 5% and 7% cement content reduced from 666 kPa to 509 kPa and from 1587 kPa to 1331 kPa, respectively, indicating improved resilience with higher CSA content. The durability index was less affected during the first three cycles, but showed a more pronounced decline after five and seven cycles. For 3% cemented soil, the durability index dropped from 0.95 to 0.71, whereas for 10% cemented soil, it decreased from 0.97 to 0.82 after seven W–D cycles. The scanning electron microscope (SEM) also determines the cement–soil interaction before and after W–D, and it was noted that the pores and cracks increased after each cycle. Based on the findings, it is established that subgrade materials treated with CSA cement demonstrate durability, environmental sustainability, and suitability for integration into road construction projects.

Methodological Impact on Curing Kinetics of Bone Cement Based on Poly (Styrene-co-Methyl Methacrylate)-2D Nanofiller Nanocomposites.

Herein, we report the methodological impact on the curing kinetics of bone cement based on polymer nanocomposites prepared using different methods. Poly (styrene-co-methylmethacrylate)-2D nanofiller nanocomposites (P(S-MMA)-2D Nanofiller) were prepared using bulk and suspension polymerization methods to study the effect of the different methods. The prepared nanocomposites were well-characterized for chemical, thermal, mechanical, and structural characteristics using Fourier Transform Infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), nano-indentation, and scanning electron microscopy (SEM) techniques, respectively. The FT-IR results confirmed the successful formation of the polymer nanocomposites. The DSC results showed that the prepared nanocomposites have higher thermal stabilities than their copolymer counterparts. The nano-indentation results revealed that the elastic modulus of the copolymer nanocomposites (bulk polymerization) was as high as 7.89 GPa, and the hardness was 0.219 GPa. Incorporating the 2D nanofiller in the copolymer matrix synergistically enhances the thermo-mechanical properties of the bone cement samples. The polymer nanocomposites prepared using the suspension polymerization method exhibit faster-curing kinetics (15 min) than those prepared using the bulk polymerization (120-240 min) method.

Effects of aggregate size distribution and carbon nanotubes on the mechanical properties of cemented gangue backfill samples under true triaxial compression

Effects of aggregate size distribution and carbon nanotubes on the mechanical properties of cemented gangue backfill samples under true triaxial compression

Carbon sequestration and environmental impacts in ternary blended cements using dyeing sludge and papermaking sludge

AbstractThis research delves into the hydration processes and ecological repercussions of cement blended with papermaking sludge (PS) and dyeing sludge ash (DS). It targets the alleviation of detrimental environmental impacts from solid waste, alongside evaluating their prospective utilization in cement product fabrication. Low-temperature roasting DS is rich in phosphates, which impose a hindering effect on the initial hydration of cement clinker, and displays superior pozzolanic activity when juxtaposed with PS. Meanwhile, the incorporation of PS heightens the malleability of the cement paste blend, consequently modulating the pore size distribution within the cement matrix, resulting in amplified compressive resilience of the amalgamated cement samples. Additionally, the inclusion of DS and PS presents an augmented surface area, promoting the nucleation of hydration by-products. The infusion of a greater quantity of hydration by-products within the mixed cement matrix fosters pore refinement and advances strength development. Furthermore, the blended cement proficiently constrains heavy metals inherent in the sludge and curtails ecological implications during cement product fabrication. Furthermore, compared with conventional Portland cement, the ternary blended cement employs un-calcined PS and low-temperature activation DS. This approach facilitates enhanced carbonation and CO2 sequestration from industrial waste streams, thereby achieving carbon reduction at the source.

The Recycling Use of Concrete Waste as Aggregate to Produce Different Types of Concrete

The present study depends on two types of concrete: the first and second samples belong to Portland cement with a high strength of 52.5 R, and ordinary Portland cement with a normal strength of 42.5 N, respectively. The physical tests for these two samples according to Iraqi Standard Specification No. 5 of 2019 were conducted. Whereas the third and fourth samples of concrete waste were taken from Mosul City and Al-Anbar Governorate. The concrete waste samples were broken into different-size particles as a fine and coarse aggregate using a mechanical crusher (Los Angeles). According to the Iraqi Standard Specification No. 45 (1984, the Physical and chemical tests for both fine and coarse natural aggregate and recycled concrete waste were conducted. The physical and mechanical results of the recycled aggregate testing samples were found to be within the limits of specifications, in which a reference concrete was made from the standard cement samples with natural aggregate for comparison. The natural aggregate was replaced with 100% recycled aggregate, and its behavior was studied through mechanical properties tests, including compressive strength, flexural resistance, and direct tensile resistance within 7 and 28 days. The results show a decrease in the compressive, flexural, and direct tensile strength in the subjected samples compared to the reference specimens. The study concluded that a 100% replacement ratio of coarse and fine recycled aggregate can be used successfully with different types of cement to obtain a new type of concrete that can be used in several engineering fields. The mechanical properties of the new concrete depend mainly on the type, class and quality of the natural cement even on the properties of the recycled aggregate.

Comprehensive Comparative Review of the Cement Experimental Testing Under CO2 Conditions

Global warming is presently one of the most pressing issues the planet faces, with the emission of greenhouse gasses being a primary concern. Among these gasses, CO2 is the most detrimental because, among all the greenhouse gasses resulting from anthropogenic sources, CO2 currently contributes the largest share to global warming. Therefore, to reduce the adverse effects of climate change, many countries have signed the Paris Agreement, according to which net zero emissions of CO2 will be achieved by 2050. In this respect, Carbon Capture and Sequestration (CCS) is a critical technology that will play a vital role in achieving the net zero goal. It allows CO2 from emission sources to be injected into suitable subsurface geological formations, aiming to confine CO2 underground for hundreds of years. Therefore, the confinement of CO2 is crucial, and the success of CCS projects depends on it. One of the main components on which the confinement of the CO2 relies is the integrity of the cement. As it acts as the barrier that restricts the movement of the sequestrated CO2 to the surface. However, in a CO2-rich environment, cement reacts with CO2, leading to the deterioration of its physical, chemical, transfer, morphological, and mechanical properties. This degradation can create flow paths that enable the leakage of sequestered CO2 to the surface, posing risks to humans, animals, and the environment. To address this issue, numerous studies have investigated the use of various additives in cement to reduce carbonation, thus enhancing the cement’s resistance to supercritical (sc) CO2 and maintaining its integrity. This paper provides a comprehensive review of current research on cement carbonation tests conducted by different authors. It includes detailed descriptions of the additives used, testing setups, curing conditions, methodologies employed, and experimental outcomes. This study will help to provide a better understanding of the carbonation process of the cement sample exposed to a CO2-rich environment, along with the pros and cons of the additives used in the cement. A significant challenge identified in this research is the lack of a standardized procedure for conducting carbonation tests, as each study reviewed employed a unique methodology, making direct comparisons difficult. Nonetheless, the paper provides an overview of the most commonly used temperatures, pressures, curing durations, and carbonation periods in the studies reviewed.

Potentiality of Nano Pb2O3–Enhanced Cement as a Nuclear Radiation Shield for Radiation Therapy Facilities

In the present investigation, the gamma and neutron shielding parameters of nano Pb2O3 incorporated into cement in proportions ranging from 0 to 5 wt% were determined using EpiXS and NGCal software. It was observed that the mass attenuation coefficient decreased with increasing photon energy. The introduction of higher concentrations of nano Pb2O3 into the cement resulted in a marked increase in the Pb K-edge. Cement samples enhanced with Pb2O3 content exhibited a pronounced peak in the effective atomic number in the lower energy regions. The exposure buildup factor showed a decrease in its value with increasing Pb2O3 content. Among the compositions used, pure cement with no Pb2O3 addition demonstrated a superior mass attenuation factor for both thermal and fast neutrons. A blend of 95% cement with 5% Pb2O3 emerged as the most effective gamma-ray shielding material within the tested energy range. A comparative analysis of this mix with other concrete types was conducted to evaluate its effectiveness as a shielding material. The findings suggest that this composition could benefit medical imaging and radiation therapy facilities.

Analysis of Cement properties using Hyperspectral Remote Sensing methods

Abstract. Understanding building material properties can play a key role in analyzing the health of structural elements in buildings. However, the field and laboratory tests can be laborious, time-consuming, and cost-intensive. Generally, the standard tests employed for characterizing the material properties are destructive in nature, but in the recent past, non-destructive testing (NDT) has given us the ease of understanding the material properties. Hyperspectral remote sensing technology has been exploited as one of the NDT methods for assessing the properties of building components. This study aims to investigate the quality information about cement using the hyperspectral remote sensing method and correlate it with the results of traditional quality testing methods. The materials used in the experiments included Ordinary Portland Cement (OPC), Portland Pozzolana Cement (PPC), and White Portland Cement (WPC). The cement samples were studied and experimented with for the identification of their types, and their temporal variability and changes in their spectral properties on which the strength of the samples depended were further checked. The study concluded that for OPC, PPC, and WPC, the absorption range is 1970 nm to 2020 nm, which is mainly due to the presence of different chemical compounds in cement. Also, the spectral reflectance decreases with time, and it can be concluded that in the present work, the strength of cement decreases with the decrease in spectral reflectance. Hence, Cement properties can be found using hyperspectral remote sensing data.

Enhancing Compressive Strength of Cement by Indigenous Individual and Co-Culture Bacillus Bacteria

Using a Taguchi experimental design, this research focuses on utilizing indigenous bacteria from the Danube River to enhance the self-healing capabilities and structural integrity of cementitious materials. Bacillus licheniformis and Bacillus muralis were used as individual bacterium or in co-culture, with a concentration of 8 logs CFU, while the humidity variation involved testing wet and wet–dry conditions. Additionally, artificial neural network (ANN) modeling of the compressive strength of cement samples results in improvements in compressive strength, particularly under wet–dry conditions. By inducing targeted bacterial activity, the formation of calcium carbonate precipitates was initiated, which effectively sealed formed cracks, thus restoring and even enhancing the material’s strength. In addition to short-term improvements, this study also evaluates long-term improvements, with compressive strength measured over periods extending to 180 days. The results demonstrate sustained self-healing capabilities and strength improvements under varied environmental conditions, emphasizing the potential for long-term application in real-world infrastructure. This study also explores the role of environmental conditions, such as wet and wet–dry cycles, in optimizing the self-healing process, revealing that cyclic exposure conditions further improve the efficiency of strength recovery. The findings suggest that autochthonous bacterial co-cultures can be a viable solution for enhancing the durability and lifespan of concrete structures. This research provides a foundation for further exploration into bio-based self-healing mechanisms and their practical applications in the concrete industry.

Does Cement Viscosity Impact Antibiotic Elution and In Vitro Efficacy Against Common Prosthetic Joint Infection Pathogens?

Polymethylmethacrylate (PMMA) antibiotic-laden bone cement (ALBC) is commonly used in total joint arthroplasty to treat and potentially prevent prosthetic joint infection (PJI). Multiple properties impact the elution characteristics of antibiotics from PMMA-based ALBC, including viscosity. What is not known is how medium-viscosity cement formulations affect antibiotic elution and how different cement products from different manufacturers compare regarding reaching the minimum inhibitory concentration (MIC) of antibiotics for common PJI-causing organisms in an in vitro setting. (1) Does cement viscosity impact in vitro antibiotic elution characteristics when comparing medium-viscosity ALBC and high-viscosity ALBC formulations from the same manufacturer against four common PJI pathogens? (2) Does the manufacturer of the PMMA-based ALBC product and the type of aminoglycoside (gentamicin versus tobramycin) impact the in vitro antibiotic elution against four common PJI pathogens? Three different PMMA-based ALBC products, including Palacos® R (high viscosity) plus gentamicin (PR+G), Palacos (medium viscosity) plus gentamicin (PMV+G), and Simplex™ P (low viscosity) plus tobramycin (SP+T), and controls for each cement type, including Palacos R, Palacos medium viscosity, and Simplex P, were evaluated. These cements were tested against four common PJI pathogens: methicillin-sensitive Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), methicillin-sensitive S. epidermidis (MSSE), and methicillin-resistant S. epidermidis. A 5-day elution protocol was observed using uniform cylindrical cement samples of each cement product. Each analysis was run with three separate lots of cement, with four samples created per lot and each sample run in duplicate. Standard curves with known antibiotic concentrations were created. Kirby-Bauer assays were then used to determine the zone of inhibition for each cement product against the four common PJI pathogens. The eluted antibiotic concentration was extrapolated for each product over 5 days to determine the interpolated antibiotic concentration for each of the 5 days. Area under the curve (AUC) was calculated as a surrogate for total antibiotics eluted over the 5-day period. Cement viscosity does not impact antibiotic elution characteristics when comparing a medium-viscosity ALBC and a high-viscosity ALBC from the same manufacturer. The cement products from two manufacturers containing different types of aminoglycosides differ in their in vitro activity over a 5-day period against four common PJI pathogens. There was no difference in interpolated antibiotic concentration against MSSE on Day 1 between PMV+G cement and PR+G (high-viscosity) (mean ± SD medium-viscosity cement gentamicin concentration 73.6 ± 14.0 µg/mL versus high-viscosity gentamicin concentration 80.3 ± 15.5 µg/mL, mean difference -6.8 [95% confidence interval (CI) -27 to 40]; p = 0.9); there was, however, greater interpolated effective antibiotic in PR+G when compared with tobramycin concentration of SP+T (80.3 ± 15.5 µg/mL versus 199.9 ± 81 µg/mL, mean difference -120 [95% CI -153 to -86]; p < 0.001). All antibiotic cement products had zones of inhibition that corresponded to an interpolated concentration above the MIC (> 32 mg/L) for all organisms on Day 1. Concentrations were maintained above the MIC even at Day 2 for only MRSA and MSSE for PMV+G and PR+G. Concentrations dropped below the MIC after Day 1 for all organisms for SP+T. Similar results were seen in the AUC, which was used as a surrogate for total antibiotics eluted over 5 days, where PMV+G and PR+G both had greater antibiotics eluted over 5 days than SP+T except for MSSE, which demonstrated no difference in the AUC. In this study, medium-viscosity ALBC demonstrated similar elution properties compared with high-viscosity ALBC from the same manufacturer. Both the medium- and high-viscosity ALBC cement products from Palacos demonstrated superior in vitro antibiotic elution properties and activity against four common PJI pathogens compared with low-viscosity ALBC from Simplex over a 5-day period. This in vitro study suggests that a surgeon may choose to use Palacos medium-viscosity ALBC (PMV+G) in total joint applications without impacting the in vitro antibiotic elution properties compared with Palacos high-viscosity ALBC (PR+G), and that both the medium- and high-viscosity formulations of ALBC from Palacos may have improved activity against three of four common PJI pathogens compared with Simplex low-viscosity ALBC (SP+T). However, more related research is needed to determine the in vivo activity of these ALBC products and the overall efficacy of routine use of ALBC in general.

On the Initial Fabric of Naturally Occurring and Reconstituted Weakly Cemented Geomaterials

The understanding of naturally occurring materials such as clay, sand, hard and soft rocks under a common theoretical framework has been a topic of persistent research interest. Over the past few decades, various sample reconstitution techniques have been developed in the literature to mimic in situ conditions, and to parse carefully the influence of various components in a cohesive-frictional geomaterial such that their behavior can be folded into the broad ambit of a continuum mechanics framework. The initial fabric of natural rock specimens is compared with reconstituted cemented sand samples using X-ray computed tomography (XRCT) scans. The efficacy of laboratory reconstitution techniques in replicating the initial microstructural features of natural rocks is evaluated here. Additionally, discrete element method (DEM) protocols which are often employed in generating cohesive granular ensembles are employed here and compared against the naturally occurring and artificially reconstituted fabric. A significant difference is observed in the grain boundaries of reconstituted and naturally occurring rocks. Additionally, the arrangement of particles, the orientation of grain contacts, and their coordination number are examined to assess the efficacy of laboratory-reconstituted specimens at micro-length scale.

Measurement of radioactivity and hazard index of Gonadal dose in selected Cement samples in Iraq.

Given the importance of cement as a basic material in construction, this study was undertaken to evaluate the level of radioactivity in a selected group of cement samples most used in construction to determine whether they are safe for human health. In this investigative study, nine samples of cement, both domestic and imported, that are often used in construction projects in Iraq were gathered. A NaI (Tl) gamma-ray spectrometer (3"x3") was used to measure the radioactivity in the samples. The average specific activity levels in the tested cement samples were 11.373±0.522, 5.795 ± 0.230, and 179.123±2.207 Bq/Kg, respectively. Also calculated was the average of the radium, which was equivalent to 33.449±1.022 Bq/kg. As for the risk indicators, the internal risk coefficient was 0.121±0.004 and external risk coefficient was 0.090 ±0.002. While studying the radiation doses, the values of effective annual internal dose was 0.080 mSv/y, external dose rates were 0.020 mSv/y, absorbed dose ratio was 16.321±0.476 nGy/h, and gamma index was 0.253±0.007. In the end, and depending on what was studied from various variables, with an average of 115.59 Sv/y, the annual gonadal equivalent dose risk (AGED) was calculated. The world average values were used to compare all the results. Finally, it was discovered that the radiation parameter levels of none of the samples had a detrimental effect on human health.

Tensile strength and failure mechanism of rock–cement sample: Roles of curing temperature, nano-silica and rock type

Understanding the tensile strength and failure mechanism of rock–cement interfacial transition zone (ITZ) is of vital significance to the sealing integrity of cement sheath under downhole condition. Taking advantage of multiple techniques, i.e., digital image correlation (DIC), nano-indentation, XRD-Rietveld analysis, 29Si MAS solid NMR, and SEM-EDX, this study is devoted to investigating the impacts of curing temperature, rock type, and the addition of nano-silica (NS), on the tensile strength and failure mechanism of rock–cement sample. The experimental results show that both the curing temperature and the addition of NS leads to the formation of more C-S-H, which densifies the ITZ microstructure and responsible for high tensile strength of rock–cement samples; the tensile strengths of shale-cement samples are consistently higher than those of sandstone-cement sample; the crack velocities for rock–cement samples under three-point bending tests are approximately 1 mm/s, the crack velocities for rock–cement samples are slowed down when the NS is incorporated in cement paste, but they are independent on the rock type and curing temperature.

MODIFICATION OF GLASS IONOMER FILLING MATERIAL BY METAL NANOPARTICLES AND THEIR COMPOUNDS: EFFECT ON ANTI-MICROBIAL ACTIVITY

Background: Glass ionomer filling materials are widely used in stomatology, but do not have an antimicrobial effect that effectively prevents the development of secondary and recurrent dental caries. Researchers are attempting to modify these materials by introducing various biologically active additives into them. The aim of the study was to evaluate the antimicrobial properties of a dental ionomer filling material modified withadditives based on high–energy nanoparticles of silver, copper, titanium and their compounds. Material and methods: Colloidal aqueous and alcoholic solutions of metals and their oxides with stabilizers were obtained by the electroerosion method. Citric acid, cetylpyridinium chloride and Trilon B were used as stabilizers. The zeta potential and the distribution of particles of the dispersed phase in solutions were measured. Samples of dental glass ionomer cement "Cemion-Aqua" were impregnated with colloidal solutions of nanoparticles. The microbiological activity of glass ionomer fillings samples in relation to plaque was determined by disc diffusion and suspension methods. Results: The results showed that modification of glass ionomer cement samples with silver hydrosols in citric acid solutions with concentrations of 0.04% and 0.0025% increases the zone of radial lysis of microbial plaque colonies around the cement samples by 1.5 and 2.5 times compared with the control. By the suspension method, it was determined that silver hydrosols in a solution of citric acid and without it reduce the formation of colonies of microorganisms to several units up to 72 hours of exposure compared with the control. And copper hydrosols in solutions of cetylpyridinium chloride prevent an increase in the number of colonies of microorganisms after 24 hours of exposure compared with the control. Silver hydrosol in a solution of citric acid with a concentration of 0.0025% and silver alcohol sol reduce the number of colonies of microorganisms to several units after 3 hours of exposure.

The Effects of Metakaolin on the Properties of Magnesium Sulphoaluminate Cement.

Magnesium sulphoaluminate (MSA) cement has good bonding properties and is suitable as an inorganic adhesive for repairing materials in civil engineering. However, there are still some problems with its use, such as its insufficient 1 day (d) strength and poor volumetric stability. This paper aims to investigate the influences of metakaolin (MK) on the physical and mechanical properties of magnesium sulphoaluminate (MSA) cement. The hydration products and microstructures of typical MSA cement samples were also analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The results showed that the addition of metakaolin reduces the fluidity and shortens the setting time of the MSA cement. The initial setting time and final setting time shortened maximally by 15-27 min and 25-48 min, respectively, with the addition of 10-30% metakaolin. Moreover, the compressive strength and flexural strength of the MSA cement improved significantly with the addition of 10-30% metakaolin at a curing age of 1 d. Compared with the compressive and flexural strengths of the control sample at 1 d, the compressive strengths of the modified samples showed obvious increases of 98%, 101%, and 109%, and the flexural strengths increased by 39%, 31%, and 26%, respectively, although they decreased slightly when the curing ages were 7 d, 14 d, and 28 d. The addition of 10% metakaolin improved the water resistance of the MSA cement immersed in water for 7 d and resulted in even higher water resistance at 28 d. The addition of 10-30% metakaolin improved the volumetric stability of the MSA cement with increasing dosages before 28 d of ageing. XRD and SEM-EDS analyses showed that the metakaolin accelerated the early hydration reaction and optimised the phase composition of the MSA cement. The results indicate that the addition of 10-20% metakaolin improved the strength after 1 d of ageing, water resistance, and volumetric stability of the MSA cement, providing theoretical support for the application of MAS cement as an inorganic bonding agent for repairing materials.

Technology of Manufacturing Hollow Soil-Cement Blocks

The author analyzed technological solutions for the production of blocks from soil cement. It is proposed to make soil cement blocks from portland cement brand 400 in the amount of 20 % of the mass of soil and water. Experimental addition of fly ash to the solution in different amounts depending on the cement content. It is proposed to add ash removed from the Darnytsya thermal power plant, which was sifted through a 4 mm sieve, because the ash contains a significant amount of impurities. The content of inclusions from 1 to 4 mm was up to 40 %. It is proposed to make blocks from soil cement with the addition of fly ash with the aim of improving the thermotechnical properties. It is proposed to make soil-cement blocks with two voids. To ensure high-quality compaction of products in forms, the moisture content of the content for most soils should be within 14–23 %. The maximum force that the sample can withstand was taken as a destructive load. It was decided that the use of fly ash as part of the mixture in the production of soil cement gives a positive effect. With an increase in the period of exposure of samples in water to 90 days, the average compressive strength of soil cement samples without additives and with the addition of the appropriate percentage of fly ash increases.

Current and potential materials for the low-carbon cement production: Life cycle assessment perspective

Given the carbon-intensive nature of cement production, conducting a comprehensive environmental evaluation using life cycle assessment (LCA) modeling is paramount to achieving eco-friendly cement standards. This study meticulously compiles and evaluates LCA findings from diverse analyses of current and potential supplementary cementitious materials (SCMs) within the blended cement sector. It underscores the impact of the functional unit (FU) within the LCA approach, supply chain considerations, and technical and regulatory factors on the sustainability of blended cement mixtures. Most of LCAs studied herein show that integrating SCMs into the cement matrix typically reduces land use, energy consumption, and greenhouse gas (GHG) emissions, thereby lowering the global warming potential (GWP) of ordinary portland cement (OPC) samples from 831 to 980 kg of CO2-eq to 768-481 kg of CO2-eq per ton of cement. However, in some instances, environmental indicators like abiotic depletion potential-elements (ADP-E) and human toxicity potential (HTP) rise due to increased mining, electricity, and transportation demand for SCMs. Regarding the environmental potential of alkali-activated cementitious materials and low-carbon clinker formulations, we found that limitations arise in fully replacing OPC due to global raw material availability constraints, rendering them economically unfavorable and impeding their widespread adoption. Among the SCMs examined in this study, clays, which are more widely available compared to industrially sourced materials like fly ash, slag, and silica fume, exhibited a more favorable environmental profile when evaluated using a mass-based FU. Incorporating compressive strength into the FU resulted in greater environmental benefits from high-strength blendedcement composites. However, this approach might lead to inaccurate results because higher strength does not always correspond to a lower environmental impact. Thus, establishing a FU that accurately reflects the environmental impact of blended cement and its composites (e.g., concrete and mortar) is crucial. Despite the potential of various pozzolanic materials to reduce clinker content in cement mixtures, their wide utilization remains restricted due to the absence of widescale market-based initiatives, green procurement strategies, and effective policy measures, which hampers their industrial and public acceptance. Consequently, governmental support is essential for developing and integrating sustainable cement solutions.

Reinforcement of hydroxyapatite bone cement via thin glycerol-citrate polyester infiltration: Microstructural, mechanical and in-vitro evaluation

The development of calcium phosphate cements (CPCs) incorporating biopolymers, such as thermoplastic polylactides, is known as an efficient strategy to enhance the physico-chemical, biological, and mechanical properties of CPCs. However, the use of thermosetting polyol citrates as fillers in CPCs has rarely been reported. Hence, the main goal of the present work was to produce composite CPCs based on tetracalcium phosphate–monetite cement matrix (C) and glycerol-citrate polyester (GCA) and to thoroughly study the effect of GCA addition on microstructural, micro, and nano-mechanical as well as in-vitro cellular properties of final cement composites. The GCA polymer was synthesized by esterification of glycerol with citric acid and coated on the C cement powder matrix at a concentration of 2.5 wt% by infiltration in ethanol solution. Two systems were prepared, by drying the composite powder at 105 and 170 °C (denoted as GCA/C105 and GCA/C170), while the respective composite cements were produced by mixing the powders with the 2 wt% of NaH2PO4 liquid phase. The results showed that the GCA polyester had no significant effect on the hydrolysis and transformation of the original cement matrix, and the nanocrystalline hydroxyapatite (Hap) was found as the main hydration product in all types of cement. The cement setting time decreased slightly with the GCA addition. On the other hand, a significant increase in mechanical properties was reached by introducing the GCA polyester into the CPC matrix, achieving more than a 70 % increase in the compressive strength, and about 50 % and 20 % in micro and nanohardness values compared to that obtained for the original C cement sample. The nanoindentation analysis revealed that the improved compressive strength and hardness were due to the stronger boundaries between the platelet-like hydroxyapatite particles in GCA-doped cements and partially caused by the denser, less porous, and more compact microstructures. The results of in-vitro cytotoxicity testing revealed high proliferation activity of the osteoblastic cells in all cement extracts, providing useful information for designing novel composite cements with the potential to be applied as bone substitute materials.

Synthetic Clay Application to Reduce the Segregation of Barite-Based Oil-Well Cement.

In the oil and gas industry, cement segregation is a significant concern that can have disastrous consequences, such as the failure of cement. The change of hardened cement's properties is observed, resulting in a decrease in its strength and an increase in its permeability. Therefore, providing some solutions to prevent this is crucial. The objective of this study is to assess the efficacy of synthetic clay in mitigating the problem of segregation in cement having barite. Six concentrations of synthetic clay were used to prepare six heavy-weighted cement samples with a high density of 18 lb/gal using the barite weighting material. The approaches of density distribution and nuclear magnetic resonance (NMR) were employed to characterize the heterogeneity in the hardened cement samples with the aim of identifying the potential of cement segregation. Then, the optimum concentration of the synthetic clay was selected and its effects on the rheological, strength, petrophysical, and elastic properties were evaluated and compared with the properties of the base cement (without synthetic clay). The results showed that 0.4% by weight of cement (BWOC) synthetic clay was the optimum concentration, which yielded the minimum cement segregation as represented by a 61% reduction in the density variation compared to the control specimen. The results obtained from the NMR technique validated the findings of the density distribution method, indicating that the porosity distribution of the synthetic clay cement with a concentration of 0.4% BWOC exhibited uniformity across its top, middle, and bottom sections, with a slight deviation window, while the porosity distribution of the control cement specimen displayed noticeable variation. Moreover, the synthetic clay had better properties than the control cement specimen. For example, the rheological properties were improved as represented by a 22% reduction in plastic viscosity and 42 and 11% increase in the yield point and gel strength, respectively. Compared to the base cement, the compressive and tensile strength were increased by 39 and 43%. The synthetic clay decreased the permeability and porosity by 73 and 24%, respectively. The synthetic clay enhanced the elastic properties as represented by a 1.5% reduction in Young's modulus and a 1.3% increase in Poisson's ratio compared to the base cement sample.

Drilling mud contamination effect on wellbore cement strength: An experimental investigation

Cementing is an essential downhole operation during the drilling of oil, gas, and geothermal wells, with the primary objective of providing structural support and a seal in the wellbore. It is important to attain adequate cement strength to preserve well integrity, inhibit fluid movement, enhance zonal isolation, and hold the wellbore casing in place. However, a significant challenge arises from the potential contamination of the cement by drilling mud (DM) during the placement process. This study aims to assess the impact of both water-based drilling mud (WBDM) and oil-based drilling mud (OBDM) contamination on the strength of API Class G wellbore cement by comprehensively investigating the underlying causes and the mechanism of strength degradation. Following a systematic methodological approach and the guidelines provided by API and ASTM, cement slurries were prepared and contaminated with DM at 10 %, 20 %, and 30 % concentrations by volume. Subsequently, both neat and contaminated samples were cured for 1, 3, 7, and 14 days, after which a series of uniaxial compressive strength (UCS) tests were conducted, and the results were further reinforced by microstructural and petrophysical property analysis. The results demonstrate that both WBDM and OBDM contamination significantly reduce cement strength, irrespective of curing time. Though the effect of OBDM contamination appears to be more pronounced, the effect of WBDM contamination is also remarkable. After final curing of 14 days, WBDM-contaminated cement samples exhibited an average strength reduction of 45.06 %, while OBDM contamination led to a 66.32 % reduction in strength compared to the neat cement with 30 % contamination. Additionally, for the same curing time and contamination percentage, porosity was found to be increased by 71.18 % and 91.33 %, respectively. The mechanism of neat and contaminated cement hydration is explained with the support of SEM-EDS tests, which confirmed the presence of contamination and revealed how two different drilling muds generate dissimilar pore structures within the cement sheath, affecting the hydration and ultimately contributing to the observed reduction in strength. The findings quantify the negative impact of WBDM and OBDM contamination on wellbore cement, emphasizing the importance of mitigating mud contamination during cementing operations.