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The duration of concrete transportation to the construction site, its workability and formworkremoval time are significantly affected by the setting time of cement. Therefore, it is of great importance toknow the initial and final setting times of concrete mixtures in construction applications. According to theliterature survey, the setting time of cementitious systems is generally determined on cement paste mixture bythe Vicat test. However, it was understood that a limited number of studies were carried out on thedetermination of the setting time using concrete mixtures. In this study, the effect of cement C3A ratio variationon the initial and final setting times of cementitious systems was determined using mortar mixtures. For thispurpose, mortar mixtures were prepared by using cement having four different C3A content (2%, 3%, 6% and9%). The ratios of water/cement and sand/cement as well as slump-flow values were kept constant as 0.485,2.75 and 27±2 cm, respectively. In order to provide the desired flowability, polycarboxylate ether-based waterreducing admixture (PCE) was used. The initial and final setting times of the mortar mixtures were determinedusing a concrete penetrometer equipment. According to the results, PCE demand to provide the target slumpflow value increased by increasing the cement C3A content. In addition, the setting time values reduction wasobserved with the increase of cement C3A content. It was determined that the results obtained are compatiblewith the literature.

The mining industry is a major economic driver and job creator for many countries. However, mining is associated with geo-hazards and environmental issues, such as the disposal of large volumes of waste, acid mine drainage, and ground subsidence. As a result, efficient mining waste management is crucial for sustainable development. The geotechnical, economic, and environmental benefits of cemented paste backfill (CPB) have piqued the interest of researchers and academicians worldwide, making it an essential aspect of underground mining management. CPB is a thickened cementitious combination of dewatered tailings (70 - 85 wt.%), binders (usually 3 to 8% wt.%), and water used to backfill mine waste into underground mining stopes. Despite being used in small amounts, the cost of cement makes up to 80% of the cost of backfilling operations. In addition, clinker production accounts for 5-8% of global human created carbon dioxide (CO₂) emissions. This predicament necessitates the development of a viable alternative to cement. Partially substituting cement with supplementary cementitious materials like fly ash, blast furnace slag, natural pozzolans, and other materials has been increasingly prevalent in CPB. It is evident that the addition of slag to cement can increase the mechanical strength of CPB at the advanced ages but decreases the strength and suction development due to the slow reaction kinetics in the CPB at the early ages, which may negatively affect the mechanical stability of the CPB, mining cycle, and safety of mineworkers. Moreover, the supply of these materials is limited and may not be enough for the future needs of the industry. Furthermore, there has been a surge in interest in using limestone powder (LS) owing to its abundance, low cost, and lack of environmental costs which are associated with Portland cement - Type 1 (PCI). The addition of LS accelerates hydration at the early ages, thus resulting in high early strength, but the dilution effect can reduce the late strength. The combination of LS and slag in a ternary blended cement can be potentially used as a binder for CPB with acceptable strength development at the early and advanced ages while lowering the cost of the CPB and the carbon footprint of the mining industry. Nevertheless, the rheology, mechanical strength, and stability are important key performance quality criteria for CPB; however, the effect of ternary cement blends on these parameters is not well known. In this research program, the impact of the binary and ternary cement blends on (i) the fresh properties of CPB, such as the rheological properties (yield stress, viscosity) and setting time, and (ii) the strength and suction development of CPB are investigated. To understand the effect of substituting slag with LS in the binary binder in the first phase of the study, binary binders with two differ-ent PCI: Slag proportions of 50/50 and 80/20 are examined with no limestone, followed by replacing slag with an increasing amount of LS from 0 to 20 wt. % of the total binder, with a constant cement content, over a period of 4 hrs (0, 0.25, 1, 2, and 4 hrs) of curing at room temperature. In the second phase, the effect of a ternary binder (PCI-Slag- LS) with varying proportions on the suction development and the mechanical behavior of hardened CPB is investigated over a curing period of up to 90 days. The changes in strength of these binary and ternary binders on the CPB sample are tested for 1, 3, 7, 28, 60, and 90 days. An unconfined compression test (UCS) is conducted to evaluate the strength development. The microstructure of the mixes is examined through mercury intrusion porosimetry (MIP) for changes are validated through monitoring for the development of hydration and suction, electrical conductivity (EC), and temperature, which is carried out for up to 30 days. This is followed by a microstructure analysis with a thermogravimetric/differential thermogravimetric test on fresh and hardened samples. The results of the first phase show that an increase in the percentage of substituted cement in the binary binder (from PCI/Slag 80/20 to 50/50) increases the yield stress of the CPB but decreases the viscosity of the mix. However, the addition of LS as a substitution for slag shows a considerable decrease in the yield stress of the control mix with an increase in viscosity with increasing dosages of LS, thus indicating an improvement in the flowability of CPB. The second phase results indicate that the slow hydration kinetics of slag influences early age suction and strength changes in the binary sample with a high slag content (50/50); however, its latent hydraulic and pozzolanic properties enhance strength gain after 28 days. The addition of 5% limestone to the ternary blend increases the strength gain by up to 7 days compared to the binary control samples. Indeed, the presence of LS influences the rate of hydration of cement and slag through both physical (filler, nucleation, dilution) and chemical (hydrate) effects. However, substituting more than 10% LS for slag affects the mechanical performance at all ages. Overall, up to 50 wt.% slag and 10 wt.% limestone with cement as a ternary binder can be used without significant compressive strength loss. This study demonstrates that the partial substitution of ordinary Portland cement (OPC) with varying percentages of slag and LS is complementary, and overall, the interaction of slag and LS is observed. The optimal use of LS and slag in a ternary system may serve as a sustainable alternative to the commonly used OPC and PCI/Slag binders, thereby reducing the energy consumption and carbon footprint associated with cement. The findings of this study will ultimately help to develop a better understanding of the impact of ternary blends with increasing percentages of LS on the rheology and setting time of CPB mixes and mechanical strength changes in designing an efficient mixing plant, particularly its transport system.

Concrete is one of the composite material consisting of Coarse Aggregate, Fine aggregate, cement and water to cement ratio. All the components of the concrete are very important and affect the properties of the concrete at both fresh stage and hardened stage. Fresh properties of the cement and concrete such as setting time, heat of hydration, consistency and soundness. Various fresh properties of the concrete are Segregation, Bleeding, Hydration and Setting Time. There is great effect of type of water on the both properties of fresh and hardened concrete. There is greater requirement of large quantity of the water for the preparation of the concrete along with its curing. It is always not economical and technically feasible to provide fresh water at the construction site. Hence, waste water is used at the construction site for the preparation of the fresh concrete. Effect of the waste water on the physical properties of the cement and concrete are studied. It is found that there is improvement in the physical properties of the cement and concrete such as setting time, heat of hydration, consistency and soundness.

The activity of sewage sludge ash (SSA) is not high; ground granulated blast slag (GGBS) has a high calcium oxide content that can accelerate polymerization rates and exhibit better mechanical performance. In order to improve the engineering application of SSA–GGBS geopolymer, it is necessary to conduct a comprehensive evaluation of its performance and benefits. In this study, the fresh properties, mechanical performance and benefits of geopolymer mortar with different SSA/GGBS, modulus and Na2O contents were studied. Taking the economic and environmental benefits, working performance and mechanical performance of mortar as evaluation indexes, the entropy weight TOPSIS (Technique for Order Performance by Similarity to Ideal Solution) comprehensive evaluation method is used to evaluate the geopolymer mortar with different proportions. The results show that as SSA/GGBS increases, the workability of mortar decreases, the setting time first increases and then decreases, and the compressive strength and flexural strength decrease. By appropriately increasing the modulus, the workability of the mortar decreases and more silicates are introduced, resulting in increased strength in the later stage. By appropriately increasing the Na2O content, the volcanic ash activity of SSA and GGBS is better stimulated, the polymerization reaction is accelerated, and the early strength increases. The highest Ic (integrated cost index, Ctfc28) of geopolymer mortar is 33.95 CNY/m3/MPa, and the lowest is 16.21 CNY/m3/MPa, which is at least 41.57% higher than that of ordinary Portland cement (OPC). The minimum Ie (embodied CO2 index, Ecfc28) is 6.24 kg/m3/MPa, rising up to 14.15 kg/m3/MPa, which is at least 21.39% lower than that of OPC. The optimal mix ratio is a water–cement ratio of 0.4, a cement–sand ratio of 1.0, SSA/GGBS of 2/8, a modulus content of 1.4, and an Na2O content of 10%.

The effects of limestone powder (LP) of different fineness on the packing density, strength and hydration behaviour of cement blended with a high volume of LP were studied using Vicat setting time tests, strength tests, isothermal calorimetry and scanning electron microscopy. Three different LP fineness values were examined and it was found that cement replacement by LP with the smallest median particle size produced the highest density. The compressive strength of the blended cement mortar increased with increasing LP fineness. The packing densities of the blended cement were used to infer the evolution of mechanical strength of the blended cement mortar. The addition of LP with a median particle size smaller than that of cement accelerated the hydration of cement in the acceleration period. Compared with LP with a median particle size smaller than that of cement, the production rate of nuclei of cement blended LP with a median particle size larger than that of cement decreased with increasing amounts of LP replacement, while the growth rate of nuclei increased with increasing amounts of LP replacement.

With introduction into endodontics, bioceramic-based sealers have gained considerable popularity for excellent properties. The aim of this study was to investigate the physicochemical properties of a novel bioceramic silicone-based sealer, GuttaFlow Bioseal, and measure heat flow of setting reactions.Film thickness, flow, working and setting time of Bioseal were compared with other 4 kinds of sealers: iRoot SP, AH Plus, RoekoSeal and GuttaFlow2. Differential scanning calorimetry test was performed to measure heat flow.Bioseal demonstrated the highest film thickness of 44 μm, double to triple that of the other 4 sealers (P 0.05). The highest flow was detected in iRoot SP and RoekoSeal, with values of 27.35 and 27.20 mm, while GuttaFlow2 and Bioseal had the lowest of 22.31 and 21.43 mm (P 0.05). For each sealer, working time at 37 °C was shorter than that at 23 °C (P 0.05). At 37 °C, Bioseal had the shortest working and setting time of 4.5 and 16.3 min, while iRoot SP showed the longest of 105.0 and 571.7 min (P 0.05). Differential scanning calorimetry test revealed that setting process of all the tested sealers was exothermic. Bioseal reached an exothermic peak at 14 min, with almost 1.5 times peak intensity of GuttaFlow2 and RoekoSeal. Whereas iRoot SP and AH Plus reached an exothermic peak 5 h after mixing, with intensity 1/2 to 2/3 that of Bioseal.The novel bioceramic silicone-based sealer Bioseal showed intense and fast exothermic reactions with characteristic physicochemical properties.

This paper explores hybrid alkaline cement composites with high cement content over 50%. Calcium (Ca) accelerates the strength development and improves the compressive strength of geopolymer. However, the mixing proportion of Ca in geopolymer has been limited because Ca significantly decreases the flow of fresh geopolymer. This study resolves the flow decline issue by mixing a part of the initial mixing water with cement before adding it into a metakaolin-based geopolymer, which is named hybrid alkaline cement composites (HACC) in this study. The cement/(metakaolin + cement) ratio investigated is up to 85%. Based on the initial setting time and compressive strength results, some unique characteristics of the HACC are observed: i) the material is set within 10 min and the 28-day compressive strength is over 80 MPa with 1:1 mixing ratio of geopolymer and cement paste, and ii) the compressive strength of HACC is not always higher with a lower w/c ratio of cement paste.

High mud content in the sand has a negative impact on cement mortar but there is little research on Alkali-activated slag (AAS) mortar. In order to explore the impacts of mud content in the sand on the performance of AAS mortar, this paper used sand that contains silt, clay, and a mixture of silt and clay; tested the setting time of AAS with different mud contents of 0%, 2%, 4%, 6%, 8%, and 10%; and measured the unconfined compressive strength and beam flexural strength of 3 d, 7 d, and 28 d AAS mortar specimens. The microstructure of AAS mortar with different kinds of mud was observed by scanning electron microscope (SEM), the elemental composition of the hydration product was tested by energy dispersive spectroscopy (EDS), and the AAS interaction mechanism with different kinds of mud was analyzed. The main conclusions are: the higher the mud content in the sand, the shorter the initial setting time and the longer the final setting time of AAS, mainly because the mud in the sand affects the hydration process; mud content above 4% causes a rapid decrease in the compressive and flexural strengths of AAS mortar, mainly because the mud affects the hydration process and hinders the bonding of the hydration product with the sand. When there is no mud in the sand, the main hydration product of AAS is dense calcium-alumina-silicate-hydrate (C-A-S-H) gel. When the sand contains silt, the hydration product of AAS is loose C-A-S-H gel. When the sand contains clay, the hydration products of AAS contain C-A-S-H gel and a small amount of sodium-aluminum-silicate-hydrate (N-A-S-H), and needle-like crystals. Loose gel and crystals have a negative effect on the AAS mortar strength.

The setting time of alkali-activated slag (AAS) binders is extremely short, while traditional retarders of Portland cement may be invalid for AAS. To find an effective retarder with a less negative impact on strength, borax (B), sucrose (S), and citric acid (CA) were selected as potential retarders. The setting time of AAS with different admixtures dosages of 0%, 2%, 4%, 6%, and 8%, and the unconfined compressive strength and beam flexural strength of 3 d, 7 d, and 28 d AAS mortar specimens were tested. The microstructure of AAS with different additives was observed by scanning using an electron microscope (SEM), and the hydration products were analyzed by energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD), and thermogravimetric analysis (DT-TGA) to explain the retarding mechanism of AAS with different additives. The results showed that the incorporation of borax and citric acid could effectively prolong the setting time of AAS more than that of sucrose, and the retarding effect is more and more obvious with the increase in borax and citric acid dosages. However, sucrose and citric acid negatively influence AAS’s unconfined compressive strength and flexural stress. The negative effect becomes more evident with the increase in sucrose and citric acid dosages. Borax is the most suitable retarder for AAS among the three selected additives. SEM-EDS analysis showed that the incorporation of borax does three things: produces gels, covers the surface of the slag, and slows down the hydration reaction rate.

A comparative study has been carried out in the current work to investigate the influence of three additives [ namely ; Polyvinyl Acetate (PVA), Tree Glue Powder (TGP) and Silica Fume (SF)] on two fundamental characteristics of Local Plaster of Paris (LPOP) (namely; Setting Time and Compressive Strength) in order to enhance both of them (together). This target had been achieved firstly; by adding each additive individually, secondly; by adding each one of them with another one (dually), and thirdly; by adding all of them together (triple addition). The experimental work contains preparing eight LPOP mixtures based on the weighted content of those additives (1.0% for TGP, 4.0% for PVA and 1.2% for SF) as well as the reference mixture (i.e. a mixture free of additives). All the aforementioned mixtures had a (Water / Plaster = 0.5). It was found that; adding each additive individually, enhances one of the aforementioned characteristics and decrease the other, whereas adding two of them dually, was found either to significantly enhance one characteristic and mitigate the decreasing in the other, or slightly enhance one of them. Finally, It was also found that adding all the three additives together, gives the optimum enhancement for both characteristics together (precisely: 23.8% for the compressive strength and310.4% for the setting time)..

Introduction. Due to the multicomponent composition, cement based concrete has a high potential for improving technical characteristics by controlling technological processes or the quality of raw materials, which makes it possible to develop composites with specified requirements for the construction of modern resource and energysaving buildings, including for the northern territories of Russia. With the transition to the micro level of the formation of the structure of cement based concretes, new opportunities open up for the directed regulation of properties. Based on this, in order to improve the quality of concrete by improving the structure of the hardened cement paste, a method was proposed for introducing modifiers into the mixture, which directly affect the new growths in the ‘cement-water’ system, which makes it possible to control the process of structure formation of the hardened cement paste.Materials and methods. Research has been carried out using test methods set out in national standards and physical and chemical analysis: thermal analysis and scanning electron microscopy. The results of a study of the effect of complex modifying additives (CMA) based on an aqueous solution of glyoxal and organic acids on the rheological and strength properties of hardened cement paste are presented, the regularities of the processes and the mechanism of structure formation of the modified cement paste are determined.Results. The optimal compositions of a cement based composition based on an aqueous solution of glyoxal have been determined. On the first day of hardening of hardened cement paste with CMA, including polylactic acid and an aqueous solution of glyoxal, as well as lactic acid and an aqueous solution of glyoxal, the strength increases by 23.5%, and at 28 days of age - up to 63% compared to the control composition. Physicochemical studies found that in hardened cement paste with CMA based on an aqueous solution of glyoxal and organic acids, the density and homogeneity of the structure increases, and the content of low-basic hydrosilicates also increases.Conclusion. The developed complex additives are recommended for use in the production of cement based concretes with the required rate of structure formation and high strength.

Cementing is one of the important steps in well construction. This chapter shows how to calculate the amount of additives required for mixing the different types of cement slurries. These additives provide properties of fluid loss, setting time and rate (i.e., acceleration or retardation), and reducing the friction to prevent high pump pressures on deep high-density casing jobs. Calculations to provide the proper placement for support of the casing and to ensure that the casing is anchored to prevent casing shoe movement after the cement is pumped are detailed. Other important cementing operations include pumping and placing open hole plugs and balancing the pressures, so the plug will not “U-Tube” when the pipe is removed from the plug. Finally, it is important to determine if the casing will move up (called “hydraulicing”) the hole as the different density cement slurries are pumped in place.

This study extended blending proportion range of ordinary Portland cement (OPC) and calcium sulfoaluminate (CSA) cement blends, and investigated effects of proportions on setting time, workability, and strength development of OPC-CSA blend-based mixtures. Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were conducted to help understand the performance of OPC-CSA blend-based mixtures. The setting time of the OPC-CSA blends was extended, and the workability was improved with increase of OPC content. Although the early-age strength decreased with increase of OPC content, the strength development was still very fast when the OPC content was lower than 60% due to the rapid formation and accumulation of ettringite. At 2 h, the OPC-CSA blend-based mortars with OPC contents of 0%, 20%, 40%, and 60% achieved the unconfined compressive strength (UCS) of 17.5, 13.9, 9.6, and 5.0 MPa, respectively. The OPC content had a negligible influence on long-term strength. At 90 d, the average UCS of the OPC-CSA blend-based mortars was 39.2 ± 1.7 MPa.

Gypsum deposits are wide spread in Zurbatiyah area, Eastern of Iraq, especially in Fatha Formation. Gypsum deposits have been known as a suitable materials for gypsum plaster industry. Sawdust and Palm fibers powders have been added in different ratios to gypsum plaster material mixture to improve their industrial properties. Addition of 0 %,1 %, 5%, 10% and 15 % pass of 4.75 mm size of sawdust and palm fibers powder and 0 %, 1 %, 5%, 10% and 15 % pass of 5.60 mm size of sawdust and palm fibers powder to gypsum plaster material mixture. This ratios showed results of consistency (35-75 ml/gm), setting time (11-20 min) and compressive strength (2.2-4.4 N/mm2) for sawdust powders size 4.75 mm, whereas the results of consistency (35-63 ml/gm),setting time (11-21 min) and compressive strength (2.0-4.2 N/mm2) for palm fibers powders size pass of 4.75 mm. The addition of 1% and 5% pass of 4.75 mm sawdust and palm fibers powder to gypsum plaster material mixture showed an improvements in consistency(37-41ml/gm), (36-40ml/gm) setting time (13-14 min), (12-13 min) and compressive strength (4.2-4.4 N/mm2), and (4.1-4.2 N/mm2) for sawdust and palm fibers respectively. Also the addition of 1 % and 5 % pass of 5.60 mm sawdust and palm fibers powder showed consistency (40-45 ml/gm), (39-44 ml/gm), (14-15 min.), (12-13min.), (3.5-4.2 N/mm2), and (3.0-4.1 N/mm2), for sawdust and palm fibers respectively. In general, the results of current study conform the requirements of the Iraqi standard specification No. 28 (1988) and ASTM C28, C472 (2010) for ordinary gypsum plaster industry.

The main objective of this research was to analyse four dental gypsum products by brazilian dentists, according to the proposed American Dental Association specification for Dental Gypsum Products. (Six Draft) Iuated: consistency, setting time, compressive strenght, setting expansion and reproduction of detail. Only one the products tested (products tested (product D) met all the requirements. The other three products, (A, B and C) althought and reproduction of detail requirements, failed with regard to setting time and setting expansion requirements.

Additives were selected and a method for modifying the structure of gypsum-containing materials for construction purposes and a method for their dispersion were developed. Based on the selected modifiers, effective compositions of composite gypsum-containing materials based on local and secondary raw materials were developed, and an increase in their strength and resistance to water was established.

The growing use of blends of low- and high-calcium solid precursors in combination with different alkaline activators requires simple, efficient, and accurate experimental means to characterize their behavior, particularly during the liquid-to-solid transition (setting) at early material ages. This research investigates slag-fly ash systems mixed at different solution-to-binder (s/b) ratios with sodium silicate/sodium hydroxide-based activator solutions of varying concentrations. Therefore, continuous non-destructive tests—namely ultrasonic pulse velocity (UPV) measurements and isothermal calorimetry tests—are combined with classical slump flow, Vicat, and uniaxial compressive strength tests. The experimental results highlight that high alkali and silica contents and a low s/b ratio benefit the early-age hydration, lead to a faster setting, and improve the early-age strength. The loss of workability, determined from the time when the slump flow becomes negligible, correlates well with ultrasonic P-wave velocity evolutions. This is, however, not the case for Vicat or calorimetry tests.

Liquid accelerating agents have the advantages of simple operation and fast construction, and have become indispensable admixtures in shotcrete. However, most liquid accelerating agents in the market at present contain alkali or fluorine, which adversely affect concrete and seriously threaten the physical and mental health of workers. Therefore, in view of the above deficiencies, it is necessary to develop a new type of alkali-free fluorine-free liquid accelerating agent. In this paper, the polyaluminum sulfate early strength alkali-free liquid accelerator is prepared using polymeric aluminum sulfate, diethanolamine, magnesium sulfate heptahydrate and nano-silica. The influence of this agent on the setting time of fresh cement paste and compressive strength of the corresponding cement mortar is determined. Thermogravimetric analysis curves, X-ray diffraction and scanning electron microscopy images are obtained to investigate the mechanism. Findings show that the initial setting time and the final setting time of cement paste are 2 min 30 s and 7 min 25 s. The compressive strengths of cement mortar cured for 1 d, 28 d and 90 d are 2.4 MPa, 52.2 MPa and 54.3 MPa respectively. Additionally, the corresponding flexural strengths are 3.4 MPa, 9.8 MPa, 11.8 MPa. When the mass rate of accelerator is 7%, the mechanical strengths of cement mortar are the highest. The additions of fly ash and blast furnace slag can affect the mechanical of cement mortar mixed with accelerator. When the mass ratio of the fly ash and blast furnace slag is 15%, the mechanical strengths of cement mortar reach the highest. Moreover, the hydration heat release rate of cement is increased by the accelerator and the corresponding time of hydration heat peak is decreased by the accelerator. The accelerator can decrease the amount of needle-like hydration products and improve the compactness. The mechanical strengths are improved by consuming a large amount of Ca(OH)2 and forming more compact hydration products. It is recommended that the optimum dosage range of the polyaluminum sulfate early strength alkali-free liquid accelerator is 7%.

Aim: The setting time of glass ionomer cement is important in terms of the sensitivity of the cement to moisture and working conditions in the early period. In restorative materials, there may be differences in the setting times with the preheating process. Therefore, the aim of the study is to compare the setting times of glass ionomer cements prepared at four different temperatures (4 °C, 23 °C, 39 °C, and 55 °C).Methods: In this study, discs prepared from radiopaque glass ionomer cement preheated at four different temperatures (4 °C, 23 °C, 39 °C, 55 °C) were evaluated and their setting times were compared. Glass ionomer cement, which was reached to preheat values by keeping it in the refrigerator, keeping it at room temperature, and using a composite heating device to bring it to 39 ºC and 55 ºC, was placed on a glass layer and mixed. It was placed on 10 mm diameter and 2 mm thick silicone discs. Vicat penetration test was used to measure the setting time. The obtained data were analyzed statistically by using One Way ANOVA and t-test. Results: A statistically significant difference was observed between the setting times of the glass ionomer cement at four different temperatures (p, Amaç: Dental restoratifler arasında önemli yeri olan cam iyonomer simanlarının sertleşme süresi, simanın erken dönemde neme karşı hassasiyeti ve çalışma koşulları göz önüne alındığında büyük önem arz etmektedir. Restoratif materyallerde ön ısıtma işlemi ile sertleşme sürelerinde farklılıklar oluşabilmektedir. Bu nedenle; çalışmanın amacı, dört farklı sıcaklıkta (4 °C,23 °C,39 °C,55 °C) hazırlanan cam iyonomer simanların sertleşme sürelerinin karşılaştırılmalı olarak değerlendirilmesidir.Gereç ve yöntem: Bu çalışmada dört farklı sıcaklıkta hazırlanmış olan (4 °C, 23 °C, 39 °C, 55 °C) radyoopak cam iyonomer simandan (R&D Series Nova Glass-L, Imicryl, Konya, Turkey) hazırlanan diskler değerlendirilerek sertleşme süreleri karşılaştırıldı. Buzdolabında bekletilerek, oda ısısında bekletilerek ve 39 ºC ve 55 ºC sıcaklığa getirmek için ise kompozit ısıtma cihazı (Micerium, S.p.a., Avegno GE, Italya) kullanılarak ön ısı değerlerine ulaştırılan cam iyonomer siman bir cam tabakaya (100 mmx100 mmx4 mm) yerleştirilerek karıştırıldı. 10 mm çapında ve 2 mm kalınlığında silikon disklere yerleştirildi. Sertleşme süresini ölçmek için Vicat penetrasyon testi kullanıldı. Elde edilen veriler One Way ANOVA ve t testi ile analiz edilerek istatistiksel olarak değerlendirildi.Bulgular: Cam iyonomer simanın dört farklı sıcaklık derecesinde sertleşme süreleri arasında istatistiksel açıdan anlamlı fark gözlendi. (p

When formulating cementitious composites with plant particles, the cement setting may be disrupted by the compounds extracted from the plant. An experimental programme is proposed to analyse the in...

This paper investigates the effectiveness of polysaccharide-based biopolymers (natural and semi-synthetic) on the setting time, compressive strength, and microstructural properties of alkali-activa...

Calcium hydroxide (Ca(OH)2 has been recently synthesized from natural Indonesian limestone to be used as an intracanal medicament for root canal infection. Ca(OH)2 is applied into the infected root canal in a non-setting paste form to release calcium and hydroxyl ions which elevates the pH and provide an antimicrobial effect to pathogenic bacteria. To form an injectable paste, Ca(OH)2 powder has to be mixed with a proper solvent to produce optimal consistency, ion dissociation, and maintain its property as a non-set material. Solvent is an important factor affecting ion dissociation and preserving its non-setting paste condition. The aim of this study is to synthesize Ca(OH)2 powder from Indonesian limestone, and evaluate the setting time of Ca(OH)2 paste from mixture of Ca(OH)2 powder synthesized from Indonesian limestone (limestone Ca(OH)2) with various solvent, to evaluate which solvent serve best to prevent the Ca(OH)2 paste from setting, to form an ideal paste be used as an intracanal medicament. This study consists of 5 groups (n=5); commercially Ca(OH)2 paste (Calcipex II) as positive control, Ca(OH)2 powder (Merck) + distilled water as negative control, limestone Ca(OH)2 powder + natrium carboxy methylcellulose (Na CMC) as group 1, limestone Ca(OH)2 powder + propylene glycol (PG) as group 2, and limestone Ca(OH)2 powder + polyethylene glycol (PEG) as group 3. Setting time evaluation was measured according to ISO 9917 by vicat needle in 37°C to mimic the physiological body condition. Results were analyzed by One Way Anova test and Post Hoc Tukey test. The result of this study showed that the setting time of Ca(OH)2 paste mixed with Na CMC solvent was 1:04 hours, PG 72:15 hours, and PEG did not harden until 7 days of observation. PEG is a hygroscopic high viscosity solvent, resulting in low and steady molecule interaction, thus prolonged its setting time. From this study it can be concluded that PEG inhibit Ca(OH)2 setting reaction up to 7 days and might be used as solvent for Ca(OH)2 paste as intracanal medicament.

Aluminium dross is generated when resmelting process is done in an aluminium industry to recover residual aluminium, wherein primary dross is taken as a raw material. It is completely a waste product and hazardous to dispose it into landfills. This is rich in aluminium oxide and having traces of few heavy metals. It is necessary to check the eco-friendly methods of solidification of this material. One of the feasible methods of solidifying the industrial wastes is using them in production of cement concrete. In this study, behaviour of aluminium dross as a partial replacement for Ordinary Portland Cement is evaluated. Aluminium dross is replaced at 5, 10, 15 and 20% of Ordinary Portland Cement. Consistency and setting time of cement paste samples were determined which shows a lag in setting time of paste. Workability and setting time of concrete mixes with 5, 10, 15 and 20% of Aluminium dross as a binder, were evaluated. Retardation of setting time and increase in the workability are the main observations of this study. As the percentage of aluminium dross increases, the setting time also increases. This may be considered as a reason to utilize such concrete mixes in hot weather conditions wherein delayed setting time is an added advantage. Therefore, retardation of setting time is the positive impact of aluminium dross. Keeping in view of the fact that there can be a reduction in strength with increased binder replacement and the workability requirements, only up to 20% of aluminium dross was replaced in the present study.

The purpose of this study was to evaluate the effects of a shrinkage reducing agent (SRA) and Portland expanded cement (PEC) on the fluidity, mechanical properties, and shrinkage performance of ultrahigh-performance concrete (UHPC). The results indicated that the fluidity of the fresh UHPC mortar initially decreased and then increases along as a function of SRA dosage. When the dosage of SRA was 1%, the UHPC mortar fluidity was at its minimum. For dosages exceeding 1%, the additional water-binder ratio of the mortar increased, which in turn increased the UHPC fluidity. That is, the SRA delayed the cement hydration and increased the setting time, which is not conducive for early strength development of UHPC. As the SRA dosage was increased (i.e., 0%–2%), the autogenous shrinkage of UHPC decreased significantly such that even a small dosage of about 0.5% SRA was able to effectively reduce drying shrinkage. From the study results, it was also observed that PEC accelerated the loss of fluidity in the fresh UHPC and concurrently promoted the early strength development of UHPC. At 75% PEC content, the strength enhancement effects tended to be stable. This means that although the addition of PEC will potentially increase the autogenous shrinkage of UHPC, it has the positive effect of inhibiting drying shrinkage provided that the PEC dosage is controlled within the 25%–50% range. Furthermore, morphological analyses using a scanning electron microscope (SEM) indicated that an increase in the SRA dosage loosens the UHPC microstructure, with the formation of the hydration products remaining incomplete, thus ultimately causing the UHPC strength to decrease. Overall, the study findings indicated that 2% SRA and 25%–50% PEC can effectively reduce the shrinkage of UHPC and are, therefore, recommended as the optimum dosages.

The effect of the water-to-cement ratio on cement paste microstructural development was investigated using electrical resistivity measurements and computer modelling. Three cement pastes with 0.3, 0.35, and 0.4 w/c ratios were used in this study. The electrical resistivity measurements curve as a function of time for the three pastes shows that the lower the w/c ratio the higher the electrical resistivity through the whole time. The effect of overall porosity and initial distances between particles significantly influence the measurements. Although low w/c ratio paste has low liquid electrical resistivity comparing to other samples, still has high bulk electrical at all ages. The influence of particles proximity due to lower water amount was interpreted through monitoring the electrical resistivity development and computer illustration. The demonstration provides more explanation about the importance of water-to-cement ratio. Through the conducted experiments, empirical correlations were developed regard predicting compressive strength and autogenous shrinkage of cement pastes when all parameters are related to porosity. Setting time was also predicted by monitoring the critical points on the electrical resistivity curve. Scanning electron microscopy (SEM) was employed to elucidate the effect of the w/c ratio on the morphology of hydration products, and it was observed that high w/c ratio paste has more fibers per unite area comparing to lower w/c ratio pastes due to the long distances between hydrates for expanding.

The built-in temperature difference (BITD), defined as the temperature difference between the top and bottom of a slab at the final setting time, is an important parameter for analysing curling stress and slab deformation in concrete pavements. However, the available methods for estimating this parameter are very limited. A method to predict the BITD in a concrete pavement was therefore developed. To do this, a numerical model was developed to predict the temperature distribution in a concrete slab at early age using a transient one-dimensional finite-difference method. A mathematical equation for predicting concrete final setting time presented in the literature was used and incorporated in the numerical model to predict the BITD. The results of the numerical model showed good agreement with field data. Using the proposed model, the effects of climatic conditions, placement time, pavement thickness and concrete mix proportion on the BITD were also evaluated. The results showed that climatic conditions, placement time and concrete mix proportion have substantial effects on the BITD, whereas pavement thickness has only a slight effect. The proposed model can be used to predict the BITD in concrete slabs for given concrete mix design, placement time, pavement thickness and environmental conditions.

Steel fibers and their aspect ratios are important parameters that have significant influence on the mechanical properties of ultrahigh-performance fiber-reinforced concrete (UHPFRC). Steel fiber dosage also significantly contributes to the initial manufacturing cost of UHPFRC. This study presents a comprehensive literature review of the effects of steel fiber percentages and aspect ratios on the setting time, workability, and mechanical properties of UHPFRC. It was evident that (1) an increase in steel fiber dosage and aspect ratio negatively impacted workability, owing to the interlocking between fibers; (2) compressive strength was positively influenced by the steel fiber dosage and aspect ratio; and (3) a faster loading rate significantly improved the mechanical properties. There were also some shortcomings in the measurement method for setting time. Lastly, this research highlights current issues for future research. The findings of the study are useful for practicing engineers to understand the distinctive characteristics of UHPFRC.

In high pressure water-rich formation, the grout is diluted by groundwater, could not develop early strength as quickly as possible for the dissipation of cementing material, failed to fill effectively the space between the segment and formation, which is unhelpful to control segment floating. In this study, by adding a variety of organic and inorganic materials to reduce grout setting time, meanwhile ensure the low loss of fluidity, high anti-aqueous dispersions, low shrinkage, finally, to achieved better effect than Two-component grouting.

This research was planned to study the effect of water-reducing admixtures on the properties of cement paste and concrete. These properties included setting time of cement paste, consistency of fresh concrete and compressive strength of hardened concrete. The main veritables taken into consideration in this study were cement content, water/cement ratio and admixture/cement ratio. A comparison was made between the properties of concrete according to the usage of the optimum dose of the admixture as a result of the experimental test results and the properties of concrete when the dose recommended by the producer was used. Great improvement was achieved in both the workability of fresh concrete and the compressive strength of hardened concrete when optimum dose of the water-reducing admixture was used which depends on many factors among which are the cement content and water content. The initial and the final setting time of cement increase with the increase of the water-reducing admixture in the cement poste. However, the limits of the setting time recommended by the specifications have to be taken into consideration when determining the optimum dose of the admixture.

In this paper, a high-performance geopolymer grouting material based on slag and fly ash was developed and the properties were investigated. The fluidity, setting time, compressive strength, water resistance and drying shrinkage were studied to evaluate the workability and mechanical properties of geopolymer grouting material (GGM). X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to analyze the microstructural performance of GGM. The results show that the concentration of alkaline activator and slag content plays a significant role in properties of GGM and the optimum formula has been obtained. In the course of the study, the effect of concentration of alkaline activator and the content of slag on the workability and mechanical performance of GGM is different. All properties of geopolymer were considered comprehensively, the slag content and concentration of alkaline activator were 70% and 37%, which indicated that the geopolymer grouting material made from slag and fly ash could meet the requirements of concrete reinforcement well and was friendly to the environment.

In this work, novel magnesium calcium phosphate/sodium alginate composite cements were successfully fabricated with a proper setting time (5–24 min) and high compressive strength (91.1 MPa). The physicochemical and biological properties of the cement in vitro were fully characterized. The composite cements could gradually degrade in PBS as the soaking time increase, and the weight loss reached 20.74% by the end of 56th day. The cements could induce the deposition of Ca–P layer in SBF. Cell experiments proved that the extracts of the composite cements can effectively promote the proliferation and differentiation of the mouse bone marrow mesenchymal stem cells (MSCs). These preliminary results indicate that the magnesium calcium phosphate/sodium alginate composite cements could be promising as potential bone repair candidate materials.

One of the latest innovations in nano-technology is the use of Micro-Nano Air Bubbles (MINAB) as a substitute for water in concrete. Using MINAB as a substitute for water used in concrete can be used to improve the properties of concrete. The use of super- Plasticizer can have an effective role in reducing negative effects MINAB on concrete properties. In this study, to investigate the effects of MINAB with water in concrete in the presence of different super- Plasticizer percentages, the effect of MINAB on the setting time, cement mortar flow and compressive strength of cement mortar is investigated. For this purpose, 16 samples of VICT needles, 48 samples of cement mortar and 16 samples of cement mortar flow were used to check the curing time, compressive strength and cement flow with different percentages of super- Plasticizer (0.5, 0.9 and 1.4) were tested in the presence and absence of MINAB. The results showed that the compressive strength of cement mortar with MINAB increased by 16 and 7%, relative to water at 7 and 28 days respectively. The compressive strength of cement mortar with MINAB has increased in presence of super- Plasticizer in comparison to cement mortar with water in presence of super- Plasticizer at the age of 7 and 28 days, with the highest resistance in 0.5% super- Plasticizer, which increased by 21% at 7 days and increased by 10% at the age of 28.

Water is one of the main constituents of concrete. Although many types of water exist, fresh water is the mostly used in concrete industry. Fresh water is expected to be in a great shortage by 2050 according to UN world water development report. Incorporating seawater in concrete mixture can help in the expected problem of scarcity of fresh water. Also, in many cases seawater may be the only available water especially in coastal regions. Many reports mention various possibilities of using seawater in concrete without detrimental effect on concrete properties. In this study another beneficial effect of seawater over tap water was concluded. Setting tests of cement paste mixed with seawater was determined using Vicat apparatus and compared to tap water. Compressive strength tests at the age of 28 days of Portland cement concretes with varied quantity of cement i.e. 300, 350, 400, 450, and 500 kg, and mixed with seawater was also performed and compared to tap water. The results show that seawater affects standard consistency of cement paste and two percent increase was required in order to attain the same consistency as tap water. It shows also seawater slightly accelerates initial setting of cement but the effect is not so pronounced so as to cause a trouble in concrete and final setting time almost remains unaltered. Compressive strength tests show an increase in concrete strength mixed with seawater for all tested mixtures and depending on quantity of cement. It also shows a beneficial effect of seawater on compressive strength of rich concrete with quantity of cement 450 and 500 kg over tap water. Doi: 10.28991/cej-2021-03091695 Full Text: PDF

The mould-ability of concrete into intricate forms and the versatility of its constituent materials has made concrete to be the most preferred construction material. However, in developing nations such as Nigeria, poor quality of concrete is listed among the common causes of building collapse. Thus, this study investigated the effects of chemical compounds of four commonly used local ordinary Portland cement brands on the compressive strength of normal concrete. The cement was labelled brands A, B, C, and D, respectively, while all the other constituent materials remained constant in this study. The HACH DR 200 direct reading spectrophotometer method was used to analyze the composition of the oxide in each of the cement samples, while the Bogue composition formula was used to estimate the compound compositions of the cement samples. A designed mix proportion of 1:2:4 (cement: sand: granite) at water-cement ratio (w/c) of 0.6 was used to produce the concrete with an expected target strength of 25 N/mm2. Also, the initial and final setting time of the cement samples and the workability of the concrete mixes were determined. Forty-Eight (48) numbers cube samples were cast and tested for compressive strength at 3, 7, 14, and 28 curing days, respectively, using a 150 mm concrete cubes. The result shows the setting time of the cement samples to be within an acceptable period. Also, results indicated that the cement brands have a significant percentage of Tricalcium Silicate (C3S) content and low percentage Dicalcium Silicate (C2S) content responsible for faster hydration rate and higher early strength gain of the concrete. However, it was observed that a higher percentage of Tricalcium aluminate (C3A) leads to higher strength gain from 7 to 28 days of curing age.

Infrastructure development is followed by an increase in demand for ready-mix concrete (RMC). Some failures in delivering RMC on time would delay construction performance or the truck would need to wait at the construction site, so the delivered concrete became useless if it exceeded the concrete setting time limit. This research optimizes the supply chain of ready mix concrete based on real-time data from a batching plant in Surabaya by using the metaheuristic method. The metaheuristic method used in this research are Particle Swarm Optimization (PSO) and Symbiotic Organisms Search (SOS), and also compares the performance of both metaheuristic algorithms, because both algorithms have proven effective in solving various optimization problems. The objective function of this research is to minimize the total waiting times of mixer trucks. The results showed that the SOS algorithm has better performance than the PSO algorithm, which gets lower total waiting times of 100,863 hours.

The purpose of this study was to compare the physical properties and cytocompatibility of contemporary calcium silicate-based sealers. Four calcium silicate-based sealers (BrightEndo MTA sealer, CeraSeal, EndoSeal TCS and One-Fil) were compared to an epoxy resin-based sealer (AH Plus). Flow, setting time, radiopacity and dimensional change were evaluated according to ISO 6876 standards. Cytotoxicity on human periodontal ligament fibroblast (hPDLF) cells was compared for biological properties using MTT assay. The surface of the sealer was analysed using scanning electron microscopy to evaluate cell attachment. Flow and radiopacity of all sealers met ISO standards, while setting time and dimensional stability did not meet the ISO standards. Calcium silicate-based sealers showed favourable cytocompatibility, and hPDLF cells were well attached to the calcium silicate-based sealers. Calcium silicate-based sealers have clinically acceptable flow and radiopacity, and cytocompatibility. However, these sealers had longer setting time and higher dimensional change than those required by ISO 6876.

Environmental threats posed by the cement manufacturing industry and agro-industrial waste discharge have shifted the direction of research towards building sustainable construction without compromising the technical merits of the developed binders. Date palm trees are one of the highest numbers of trees in the world whose generated wastes can be beneficially recycled and reused by the concrete industry. In this study, ordinary Portland cement (OPC) and date palm frond ash (DPFA)-based binders were synthesized by varying ratio of DPFA/(OPC + DPFA) between the range of 0 to 0.3 at an interval of 0.1. Both base materials were characterized by physical, chemical, and thermal techniques. The developed binders were assessed by flow, setting time, and compressive strength up to 360 days of curing. Scanning electron microscopy (SEM) was performed to complement the strength results. It is postulated that the DPFA/(OPC + DPFA) ratio of up to 0.2 outperforms the DPFA-free binder in terms of the overall performance. The properties of binders were negatively affected by the total precursor composition ratio of CaO/SiO2 and Al2O3/SiO2 below 2.06 and 0.18, respectively. The optimum synergy of OPC–DPFA resulted in superior microstructural density attributed to the uniform skeletal framework of gel products. Strengths, weaknesses, opportunities, and threats analysis of the use of DPFA in cementitious materials showed that there is a high potential for its use in terms of sustainability and economic benefits. However, various weaknesses and threats associated with the use of DPFA as a cementitious material need to be resolved.

There are many factors affecting the characteristics of cement-fly ash slurry in practical engineering. Thus, this paper studies the influence of multifactors on the fluid properties of cement-fly ash slurry based on water-cement ratio ( w / c ) (0.75, 1, 1.25, and 1.5), fly ash content (0%, 10%, 20%, 30%, 40%, and 50%) and temperature (20°C, 40°C, 60°C, and 80°C). The bleeding ratio, initial setting time, final setting time, and viscosity were analyzed under coupling conditions. It is found that the water-cement ratio ( w / c ) is the main factor that affects the rheological properties and bleeding rate of slurry. The temperature affects the stability of the slurry in terms that the bleeding ratio of the slurry decreases as the temperature increases. The addition of fly ash enhances the stability of the slurry under different temperature conditions.

The bio-clogging using bacteria can be an eco-friendly and sustainable alternative to conventional grouting methods for seepage control. However, it remains unclear to date how the dilute concentration of bacterium and medium during field installation can affect the setting time of bacterium and its correlation with permeability reduction. In this study, the setting time of bacterium and its effectiveness in permeability reduction were addressed through experimental and theoretical investigations. A series of sand column was cultivated using different concentrations of Leuconostoc mesenteroides and culture medium. The distribution and composition of the bacterial product (i.e. dextran) were observed by refractometer, scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS). Soil permeability was recorded using a constant head test. The results revealed that bacterium was effective to produce dextran at the setting time of about 5 d after installation. This dextran can reduce the permeability of bio-mediated soil by two orders of magnitude, even without culture medium supply. In general, the dextran production decreased proportionally with increase of bacterium and medium concentration. However, at 50% bacterium and medium concentration by weight, it still has a significant influence on permeability reduction with similar setting time, compared to 100% concentration.

Establishing a bridge foundation when there is a top layer of weak soils normally requires the application of deep foundations such as piles. Driving prestressed-precast concrete piles (PPCP) is one of the options among various types of piles and installation methods. However, it often happens that shipping and transportation constraints limit the length of precast prestressed pile segments that can be delivered to the bridge site. Therefore, the length of pile segments may be smaller than the length required to establish adequate resistance, and splicing of pile segments becomes necessary. The review reported in this paper aims at identifying and analyzing the available splice systems to be able to build upon the existing experiences when considering the development of new alternatives. The existing splice systems were compared based on capacity, ductility, durability, and ease of installation. As importantly, a thorough investigation was also conducted on the existing filler or bonding materials used for PPCP splicing to help the selection of the most applicable material. The review identified a set of filler/bonding material with rapid strength gain, workability and setting time suitable for establishing splices. This research was deemed necessary since there has been little or no recent innovation related to the PPCP splices. This paper combines in one place all available information on this subject and will help the researchers to understand the existing systems as well as the types of materials used for splicing. The results of this study are expected to motivate new ideas on more effective, durable, and economic systems for establishing PPCPs splices.

Objective: The purpose of this study was to investigate the effect of the incorporation of chitosan nanoparticles into epoxy resin-based sealer on its setting time, flowability and solubility. Methods: This study was divided into three evaluations: setting time, flowability, and solubility of sealers. Each study used 20 samples, which were divided into two groups. Group 1, epoxy resin-based sealers, and group 2, epoxy resin-based sealers mixed with chitosan nanoparticles. The Gilmore needle was used to observe the setting time, a simple press method based on ISO 6876 was employed to evaluate the flowability of the sealer, and the solubility test, which was according to ISO 6876 standard, was used to determine the solubility of sealers. The surface structure of the sealers before and after the solubility test was observed under Scanning Electron Microscopy (SEM). The data obtained from each study were analyzed by an unpaired t-test with a degree of significance of 95%. Results: The results showed that the setting time of epoxy resin and epoxy resin incorporated with chitosan were 567±30.20 and 572.5±27.91 min, flowability was 25.06±0.89 and 23.18±1.06 mm, and solubility was 0.0051%±0.0016 and 0.0045%±0.0018, respectively. No significant difference occurred between epoxy resin-based sealer and epoxy resin-based sealer mixed with chitosan nanoparticles in setting time, flowability, and solubility of sealers (*P>0.05). Conclusion: The incorporation of chitosan nanoparticles produced a similar effect in setting time, flowability, and solubility as the epoxy resin-based sealer. Thus, epoxy resin-based sealer mixed with chitosan nanoparticles had acceptable properties in setting time, flowability, and solubility based on ISO 6876 standards.

Environmental degradation caused by deforestation activities for harvesting of limestone from the hills and its calcination process at cement factory along with disposal of cockle shell waste from fisheries industries is in need of resolution. In view of sustainable green environment, approach of utilizing cockle shell waste as partial cement replacement in cement production would reduce pollution caused by both industries. Thus, this research investigates the effect of cockle shell powder as partial cement replacement on setting time and compressive strength of mortar. A total of five types of mortar mixes consisting different percentage of cockle shell powder as partial cement replacement from 0%, 10%, 20%, 30%, and 40% by weight of cement were prepared. Setting time test were conducted on fresh paste. All specimens were subjected to water curing until the testing age. Compressive strength test were conducted on hardened mortar cubes at 3, 7 and 28 days. Finding shows that integration of cockle shell powder as partial cement replacement influences the setting time and compressive strength of mortar. Suitable combination of 10% cockle shell powder successfully enhances the compressive strength of mortar. Conclusively, success in transforming the cockle shell waste to be used as partial cement replacement in mortar production able to reduce cement consumption, save landfill usage for trash dumping and promote cleaner environment for healthier lifestyle of community nearby.

Une manière de valoriser les matières minérales, localement disponibles, est de les traiter et de les incorporer dans les matériaux de constructions. Les investigations menées dans ce travail portent sur le kaolin disponible dans la région de Kétou de la partie Sud-Est du Bénin. Le kaolin est conditionné de trois manières différentes donnant lieu à trois types: le kaolin brut, le kaolin étuvé à 105°C et le kaolin cuit à 800°C. Les liants hydrauliques obtenus à partir de ces trois types de kaolins, réduits en poudre et substitués au ciment Portland dans les proportions pondérales de 0%, 5%, 10%, 15%, 20%, 25% et 30% ont servi à préparer des mortiers qui ont été soumis aux essais mécaniques. Le temps de prise et de stabilité et les résistances mécaniques de ces ciments ont été déterminés. Les résultats ont montré qu’il est possible, tout en respectant les exigences normatives, d’obtenir du ciment du type CEMII 32,5R avec 25% de kaolin cuit à 800°C et 75% de ciment Portland. A manner of developing the mineral matters, locally available is to treat and incorporate them in building materials. The investigations carried out in this work concern the kaolin available in the South-eastern part of Benin. The kaolin is conditioned in three different ways giving place to three types: the raw kaolin, the kaolin dried at 105°C and the kaolin calcined at 800°C. Kaolin- blended Portland cement mortars are obtained from these three types of kaolin with partial replacement of cement in proportion of 0 %, 5 %, 10 %, 15 %, 20 %, 25 % and 30 % by weight. The setting time and stability and mechanical strength of these cements have been determined. The results showed that while meeting the normative requirements, it is possible to obtain cement type CEMII 32.5 R with 25% replacement of kaolin calcined at 800° C.

The development of biomaterials that exhibit profound bioactivity and stimulate stem cell differentiation is imperative for the success and prognosis of vital pulp therapies. The objectives were to (1) synthesize calcium strontium silicate (CSR) ceramic through the sol–gel process (2) investigate its physicochemical properties, bioactivity, cytocompatibility, and its stimulatory effect on the differentiation of human dental pulp stem cells (HDPSC). Calcium silicate (CS) and calcium strontium silicate (CSR) were synthesized by the sol–gel method and characterized by x-ray diffraction (XRD). Setting time, compressive strength, and pH were measured. The in vitro apatite formation was evaluated by SEM-EDX and FTIR. The NIH/3T3 cell viability was assessed using an MTT assay. The differentiation of HDPSC was evaluated using alkaline phosphatase activity (ALP), and Alizarin red staining (ARS). Ion release of Ca, Sr, and Si was measured using inductive coupled plasma optical emission spectroscopy (ICP-OES). XRD showed the synthesis of (CaSrSiO4). The initial and final setting times were significantly shorter in CSR (5 ± 0.75 min, 29 ± 1.9 min) than in CS (8 ± 0.77 min, 31 ± 1.39 min), respectively (p < 0.05). No significant difference in compressive strength was found between CS and CSR (p > 0.05). CSR demonstrated higher apatite formation and cell viability than CS. The ALP activity was significantly higher in CSR 1.16 ± 0.12 than CS 0.92 ± 0.15 after 14 d of culture (p < 0.05). ARS showed higher mineralization in CSR than CS after 14 and 21 d culture times. CSR revealed enhanced differentiation of HDPSC, physicochemical properties, and bioactivity compared to CS.

In this research, a mechanochemically activated geopolymer (MG) grout is adopted to activate slag, fly ash, sodium hydroxide, and sodium silicate by dry grinding in a ball mill for 2 h, after which water is the only additive required to initiate the geopolymerization reaction. A conventionally activated geopolymer (CG) grout was also evaluated for comparison purposes. Twenty-four different slag and fly ash mixtures have been prepared at different slag/fly ash ratios (0S100F, 50S50F, 75S25F, and 100S0F) at three different molarities of sodium hydroxide (1.25, 2.5, and 3.75) to assess the behavior of both MG grout and CG grout. A series of tests were examined, such as rheological characteristics, setting time, bleeding, unconfined compressive strength (UCS), ultrasonic pulse velocity (UPV), and scanning electron microscopy (SEM). The experimental results showed that the mechanochemical activation technique reduced the rheological characteristics and fresh properties (setting time and bleeding) of geopolymer grout compared to the conventional activation process. Considering mechanical properties, both UCS and UPV of MG grout were higher than that of CG grout. Furthermore, slag content and sodium hydroxide concentration significantly affected the rheological, fresh, and mechanical properties of all geopolymer grouts regardless of the activation method. Both the rheological characteristics and mechanical properties were increased considerably with the increase in molar concentration and slag content. Whereas the bleeding capacity and setting time dramatically reduced with the increase of molar concentration and slag content.

The composite gelling system of chlorine and magnesium thioxide was prepared by mixing different mass fractions of magnesium sulfate solution into MOC. Detailed studies regarding the influences of magnesium sulfate replacing magnesium chloride on the setting time, compressive strength, and water resistance of magnesium oxychloride cement (MOC) have been carried out in this paper. The phase composition and micro morphology of the hydration products in the mixed system were analyzed by XRD and SEM. The results show that the addition of magnesium sulfate prolongs the setting time and reduces the compressive strength of the mixed MOC. Compared with the primordial MOC system, the water resistance of the mixed system improved, with the mixed system exhibiting optimal water resistance when the mass fraction of magnesium sulfate was 30%. The phases of the mixed system were composed of 5Mg(OH)2·MgCl2·8H2O and 5Mg(OH)2·MgSO4·7H2O phases. The microscopic morphology shows that the interior of air-cured MOC was composed of a large number of needle-like crystals, and continuous crystal structures have close contact and a strong bonding force. Cracks and pores appear on the surface after submerging in water, and the crystallization state of the internal crystals becomes worse. The compressive strength and water stability of MOC were closely related to the crystal morphology.

Searching for low environmental impact materials for use in mortars, lime-metakaolin binders can be a great alternative. However their long hardening process does not please this binder be used in current constructions. Little is known about its workability and setting time. Therefore, this work studied the rheological behavior and the influence of a setting accelerating agents in pastes containing limemetakaolin. The initial results showed that metakaolin contributed to lower yield strength in relation to the lime paste, but the setting time was still very long.