Utilization of quarry dust and periwinkle shell ash in concrete production.

The usage of plentiful raw discarded resources in the manufacturing of concrete has proven to be a sustainable and environmentally beneficial method of making concrete for a variety of purposes. In this study, the physical and mechanical properties of concrete made by partially and fully substituting fine aggregates and ordinary Portland cement with periwinkle shell ash and quarry dust (5%, 10%, 15%, 20%, and 100%), respectively, were examined. The ratio of water to cement utilized for the concrete mixture, 1:2:4, was 0.60. Fresh concrete underwent a slump test, and then 150-mm cubes of cured concrete were subjected to density, compressive strength tests, and morphological and structural property characterizations. The concrete without the waste materials gave an optimum compressive strength of 22.9 N/mm2 as opposed to those that were partially replaced, having 18.8-15.1 N/mm2. The concrete samples with full replacements of periwinkle shell ash and quarry dust have compressive strengths lower than 13.8 N/mm2. All the concrete samples produced with partial and full replacements are in the class of normal concrete, but only those with partial replacements of up to 20% can be utilized for load-bearing and non-load-bearing applications. Opting for these alternative waste materials implies taking steps towards creating a cleaner and healthier planet for now and the future.

Root canal irrigants effect on the compressive strength and calcium ion release of Biodentine.

Compressive strength and calcium ion release are integral properties of Biodentine for its enhanced efficiency. The present study evaluated the effects of Dual Rinse HEDP (DR HEDP), ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) on the calcium ion release and compressive strength of Biodentine. Eighty Biodentine specimens were moulded and randomly divided into four groups (n = 20). Samples in group 1 were treated with 17 % EDTA; group 2 with DR HEDP; group 3 with 2.5 % NaOCl; and group 4 with distilled water. Samples were immersed in 10 mL of the test solutions for 1 min. The mean concentration of the calcium ion released was measured using atomic absorption spectrophotometry. The remaining 40 samples were tested for their compressive strength. Significant differences were determined among all the irrigants tested for calcium ion release and compressive strength. Samples treated with NaOCl had the lowest calcium ion release, while samples treated with 17 % EDTA had the largest calcium ions. No significant differences were measured between DR HEDP or distilled water. For compressive strength, samples treated with 2.5 % NaOCl had the lowest strength, while the highest values were obtained with distilled water. There was a significant difference between DR HEDP and EDTA, in which EDTA reduced the compressive strength significantly more than DR HEDP. DR HEDP had less detrimental effect on the calcium ion release and compressive strength of Biodentine.

Comparative Analysis of Antimicrobial Properties and Physical Properties of Mineral Trioxide Aggregate Mixed With Distilled Water, Chlorhexidine, and Sodium Hypochlorite Solutions: An In Vitro Study.

BACKGROUND:  Endodontics widely uses mineral trioxide aggregate (MTA) because of its excellent sealing ability, biocompatibility, and capacity to promote healing. However, the effectiveness of MTA can vary depending on the blending solution used. Endodontics commonly employ chlorhexidine (CHX) and sodium hypochlorite (NaOCl), but their impact on MTA's properties necessitates further investigation. MATERIALS AND METHODS: We blended MTA with the specified solutions and prepared it for testing according to the manufacturer's instructions. The study was divided into four groups: group 1 involved MTA blended with distilled water, group 2 consisted of MTA blended with 0.12% CHX solution (PerioGard, Colgate-Palmolive, Osasco, Brazil), group 3 included MTA blended with 0.2% CHX solution (Corsodyl, GlaxoSmithKline Consumer Healthcare, England, UK), and group 4 comprised MTA blended with 5% NaOCl (Azure Research Lab Pvt. Ltd., New Delhi, India). The antimicrobial activity of each group was assessed using the agar diffusion method against Enterococcus faecalis, Candida albicans, and Streptococcus mutans. We measured the compressive strength at 1, 3, 7, and 21 days using an Instron universal testing machine (Hounsfield Test Equipment, Redhill, UK). Statistical significance was evaluated through one-way ANOVA and Kruskal-Wallis tests, with p values <0.05 considered significant. RESULTS:  Group 3 (MTA blended with 0.2% CHX) exhibited the highest antimicrobial efficacy, with significantly larger inhibition zones against Enterococcus faecalis (25.25 ± 0.21 mm vs. 13.33 ± 0.12 mm, p = 0.011), Candida albicans (29.58 ± 0.24 mm vs. 16.97 ± 0.16 mm, p = 0.004), and S. mutans (26.37 ± 0.15 mm vs. 14.55 ± 0.25 mm, p = 0.027). Group 4 (MTA blended with 5% NaOCl) showed the highest compressive strength at one and three days (p = 0.032 and p = 0.021, respectively), but by 21 days, group 2 demonstrated the greatest compressive strength (p = 0.044). CONCLUSION:  MTA mixed with 0.2% CHX provides superior antimicrobial properties, making it suitable for enhanced microbial control in endodontic treatments. Conversely, MTA mixed with 0.12% CHX offers optimal long-term compressive strength. These findings guide selecting MTA formulations to maximize performance based on clinical needs.

Investigating the Influence of Additive Manufacturing and Ultrasonic Coating Parameters on Biopolymeric Scaffold Performance Using Response Surface Methodology.

Triply periodic minimal surface (TPMS) scaffolds have gained attention in additive manufacturing due to their unique porous structures, which are useful in biomedical applications. Unlike metallic implants that can cause stress shielding, polymeric scaffolds offer a safer alternative. This study is focused on enhancing the compressive strength of additive-manufactured polylactic acid (PLA) scaffolds with a diamond structure. The response surface methodology (RSM)-based experimental design was developed to study the influence of printing parameters. The fused deposition modeling (FDM) process parameters were optimized, achieving a compressive strength of 56.2 MPa. Subsequently, the scaffolds were fabricated at optimized parameters and underwent ultrasonic-assisted polydopamine coating. With the utilization of the RSM approach, the study examined the effects of ultrasonic vibration power, coating solution concentration, and submersion time on compressive strength. The optimal coating conditions led to a maximum compressive strength of 92.77 MPa-a 65.1% improvement over the uncoated scaffold. This enhancement is attributed to the scaffold's porous structure, which enables uniform coating deposition. Energy-dispersive x-ray spectroscopy confirmed the successful polydopamine coating, with 10.64 wt% nitrogen content. These findings demonstrate the potential of ultrasonic-assisted coating in improving the mechanical properties of PLA scaffolds, making them suitable for biomedical applications.

Recycle of steel slag as cementitious material and fine aggregate in concrete: mechanical, durability property and environmental impact.

Using steel slag (SS) as cementitious material and fine aggregate in concrete is an effective and environmental method for SS consumption and cost reduction. In this paper, SS was recycled in large volumes in concrete as partial cementitious material and fine aggregate. The compressive strength and reaction mechanism of cementitious material with different SS powder contents including 20%, 25%, 30%, and 35% were presented. The results indicated that 20% of SS powder improved the compressive strength by 34.57% and the hydration products were ettringite (AFt) and calcium silica hydrate(C-(A)-S-H). Furthermore, the mechanical and durability performance of concrete with SS as fine aggregate were investigated. When the SS substitution rate was 75%, the compressive strength was increased by 37.83%. The volume shrinkage rate and 28d-carbonation depth were reduced nearly by 64% for 90 days and 2.33 mm, respectively. The chloride ion penetration resistance reached the optimal grade Q-V and abrasion resistance was improved by nearly 24%. Along with the reduced CO2 by 210-294 kg/m3 and the decreased cost by 12.61 USD/m3, it is regarded as an effective method to consume steel slag. As such, this research provided a scientific and systematic basis for the large-scale disposal and utilization of industrial waste residues as well as recycled materials preparation.

Mechanical properties of aeolian sand cemented via microbially induced calcite precipitation (MICP).

The cementation of desert aeolian sand is a key method to control land desertification and dust storms, so an economical, green and durable process to reach the binding between sand grains needs to be searched. The method based on the microbially induced calcite precipitation (MICP) appeared in recent years as a promising process that proved its efficiency. The feasibility of the MICP technique to treat aeolian sand composed by low clay content, fine particles, low water content and characterized by weak permeability was demonstrated in the present paper. The effects of initial dry density, cementation number and curing time on the permeability and strength of MICP-treated aeolian sand were investigated using permeability tests and unconfined compressive strength (UCS) tests. The microstructure of aeolian sand was observed by scanning electron microscopy (SEM) tests and X-ray diffraction (XRD), aiming to reveal the solidification principle of MICP. The tests result indicated that when the initial dry density and the cementation number rose, the hydraulic conductivity of aeolian sand decreased while the mechanical strength given by UCS values improved. When the initial dry density was 1.65 g/cm3, the curing time was 3 h and the cementation number reached 20, the hydraulic conductivity and UCS reached 0.00151 cm/s and 1050.30 kPa, respectively. With increasing curing time, the hydraulic conductivity first decreased, followed by an increase, while the UCS exhibited an up and then a downtrend. Furthermore, the correlation between UCS values and the CaCO3 content reached a high R2 value equal to 0.912, which confirmed that the cementation occurred in sandy material and governed the soil strengthening. Indeed, the calcium carbonate crystals observed by SEM and XRD enhanced the friction between particles when they wrapped around the sand grains surface, while carbonates reduced the soil permeability when filling the pores and sticking the sand particles together. Finally, the theoretical and scientific knowledge brought by the present study should help in managing sand in desert areas.

Experimental Investigation and Machine Learning Prediction of Mechanical Properties of Rubberized Concrete for Sustainable Construction.

Concrete is widely used in civil engineering applications and the natural aggregates which used in concrete are scarce, but its demand is increasing. The disposal of rubber tyres poses a significant environmental challenge, as their decomposition releases harmful chemicals into the soil and water bodies over many years. Decomposition of tyres should be done in a smart way and hence came the emergence of mixing recycled rubber crumbs into concrete as Rubberised Concrete (RC). This paper provides an in-depth analysis of the mechanical properties of concrete such as Compressive Strength (fck), Tensile Strength (ft), Flexural Strength (fcr) of 7, 14, 28 days in replacement of fine aggregate with fine rubber (FR), and Coarse Aggregate with Coarse Rubber (CR). The results indicate that RC is more suitable for structural applications, including Reinforced Concrete columns, beams, slabs, than conventional concrete. The primary objective of the article is to explore the potential use of recycled rubber crumbs in concrete, referred to as Rubberised Concrete (RC), and to analyze its mechanical properties such as compressive strength, tensile strength, and flexural strength over different curing periods. Additionally, machine learning (ML) based prediction model has been developed for various strength characteristics of concrete mixtures at 28 days. The hyperparameter optimization using Grid Search CV with fivefold cross-validation have been performed to obtain the best hyperparameters. The model's performance is evaluated using metrics like MAE, MSE, RMSE, and R-squared values. Results reveal varying performances among different ML algorithms for predicting flexural, tensile, and compressive strengths.

Utilizing industrial wastewater sludge-derived biochar for enhancing strength and microstructure of soft soil- An infrastructure application of wastewater sludge.

This study proposes a waste-to-value approach; specifically focusing on the utilization of industrial wastewater sludge (IWS) derived pyrolytic biochar (PBC) as an alternative to conventional carbon positive soil stabilizing materials. The IWS was subjected to thermogravimetric analysis (TGA) in N2 environment which suggested the pyrolysis temperature of 450 °C for the synthesis of PBC. Five different dosages of PBC by weight were mixed with the soft soil (SS) and unconfined compressive strength (UCS) values were examined across the various curing periods. Test results confirmed that UCS and stiffness values of soil-PBC matrix increased 4-5 and 5-6 times to that of virgin soil respectively. The PBC increased the cation exchange capacity (CEC), point of zero charge (pHpzc), alkalinity, and water holding capacity of the soil thereby assisted to initiate pozzolanic reactions. Various spectroscopic techniques were performed to investigate the strength development mechanism. Free oxide of calcium (CaO) in PBC disturbed the laminated structure of soil, reacted with oxides of silica (SiO2) and other silicates of aluminum thereby densifying the soil-PBC structure. Further, leaching test was performed on soil-PBC matrices to evaluate the environmental viability of the PBC. The statistical significance of the test results was confirmed using the Analysis of Variance (ANOVA) technique. Overall, this study concludes that PBC has the potential to serve as an environmentally friendly alternative to conventional soil stabilizing materials.

Evaluation of dental cements derived from mixtures of highly reactive ionomer glasses and bottle glass: Cement manipulation, mechanical, fluoride ion releasing, radiopaque and setting properties.

OBJECTIVES: To evaluate the mechanical properties, fluoride release, radiopacity, and setting characteristics of dental cements derived from highly reactive ionomer glasses and bottle glass mixtures. METHODS: Two highly reactive glass series, LG99 and LG117, were synthesized, milled, sieved, and characterized using XRD and laser particle size analysis. These glasses were mixed with predetermined ratios of ground bottle glass, poly(acrylic acid), and aqueous tartaric acid to form glass ionomer cements. The cements' working time (WT), setting time (ST), fluoride release, radiopacity, compressive strength (CS), and elastic modulus (EM) were evaluated. Mean differences in CS were analyzed using multivariate ANOVA with Tukey's post hoc test at p = 0.05. RESULTS: The WT and ST for both groups ranged from 1.5 to 2.5 min. LG99 series cements showed significantly higher CS (∼65 MPa) and EM (∼2 GPa) than LG117 series (p < 0.05). Both series showed similar fluoride release profiles, peaking at 1.2 mmol/L at 28 days. Radiopacity for LG99 ranged from 0.97 to 1.34, while LG117 ranged from 0.60 to 0.95. Solid state 27Al magic-angle spinning-nuclear magnetic resonance (MAS NMR) confirmed the presence of Al(IV) and Al(VI), indicating setting completion by one day for both series. Bottle glass showed a chemical shift at 55.8 ppm, overlapping with LG99's Al(IV) signal. The 19F MAS NMR spectra revealed Al-F and F-Sr(n) species in all glasses, with LG117 forming CaF2 after one day in deionized water. CONCLUSION: Mixtures of highly reactive ionomer glass and bottle glass produced cements with satisfactory properties for dental applications. Further research is needed to optimize their formulation and properties.

Evaluating mechanical and biological responses of bipolymeric drug-chitosan-hydroxyapatite scaffold for wounds: Fabrication, characterization, and finite element analysis.

This study aims to explore the potential of a scaffold composed of drug-chitosan-hydroxyapatite (HA) in improving tissue treatment. The focus of the investigation lies in analyzing the physical and biological properties of the scaffold and evaluating its mechanical characteristics through finite-element analysis. To synthesize microcapsules containing dextran-diclofenac sodium, the electrospraying method was employed. The drug-chitosan-HA scaffold with varying volume fractions (VF) of the synthesized microcapsules (10, 15, and 20) was fabricated using the freeze-drying technique. Microscopic and scanning electron microscopy (SEM) images were utilized to evaluate the morphology, shape, and size of the microcapsules, as well as the porosity of the scaffolds for wound healing purposes. The mechanical properties of the synthesized microcapsules were determined via a nanoindentation test, while the mechanical behavior of the fabricated scaffolds was assessed through compression testing. Additionally, a multiscale finite-element model was developed to predict the mechanical properties of tissue scaffolds containing pharmaceutical microcapsules. The findings indicate that the incorporation of drug-chitosan-hydroxyapatite into the tissue significantly enhances both mechanical and biological responses. The mechanical evaluations demonstrate that the drug-chitosan-hydroxyapatite tissue exhibits excellent resistance to pressure, making it a suitable protective covering for skin wounds. Moreover, biological evaluations reveal that an increase in scaffold porosity leads to higher swelling behavior. The scaffold containing 20 % pharmaceutical microcapsules demonstrated the greatest swelling and desirable antibacterial properties, thereby indicating its potential as an effective wound dressing. Furthermore, a multiscale finite-element model was developed to predict the mechanical properties of tissue containing pharmaceutical microcapsules. The results indicated that the average size of the microcapsules was in the range of 170 to 180 µm, and the porosity of the prepared tissue was between 52 % and 61 %. The experimental compressive properties revealed that an increase in the volume fraction of the embedded microcapsules led to an increase in the maximum compressive stress and compressive modulus of the scaffolds by up to 54.95 % and 53.18 %, respectively, for the scaffold containing 20 % VF of pharmaceutical microcapsules compared to the specimen containing 10 % VF. In conclusion, the developed scaffold has the potential to serve as an effective wound dressing, with the ability to provide structural support, facilitate controlled drug release, and promote wound healing.