Saturation Dosage Research Articles

Along the S‐Curve – How Superplasticizers Affect the Yield Stress of Cement Paste

AbstractIn cementitious systems, superplasticizers have two core purposes. On the one hand, they are used to lower the yield stress of a cement paste without changing the water to cement (w/c) ratio. On the other hand, they can reduce the w/c ratio without changing the yield stress. The relationship between slump flow and dosage of a superplasticizer containing cement paste can be described as an S‐curve. Below a critical dosage, the superplasticizer does not increase the flow. Above this dosage, the flow increases linearly until the saturation dosage is reached. Further addition of polymer will therefore not increase the fluidity of the cement paste. The minimum dosage which corresponds to an onset of increased flow compared to a dispersant free paste is referred to as the critical dosage.In this study, we analysed the dosage curve for three different polymers: a mela‐mine based (MFS), a polycarboxylate ether (PCE) and a polyphosphate ether (PPE) superplasticizer. The dosage curves of each superplasticizer were measured with a slump flow test at two different w/c ratios. To observe even small changes in the ultra‐low dosages, MFS was measured using a rheometer. We have specifically examined the areas defined as critical dosage and saturation dosage. We have found that these definitions need to be revised, not with regards to their values, but in terms of a proper understanding.

Up to the maximum-testosterone dose-dependent effects on anabolic and androgen responsive tissues in orchiectomized rats.

Despite the high number of synthetic androgenic-anabolic steroids, testosterone is still misused for doping in amateur and professional sports. However, only few studies investigated the dose-response effects of testosterone beyond its physiological concentrations and in over 90 years of research, no saturation dosage has been experimentally described for exogenous testosterone administration. We want to elucidate the physiological and pathophysiological effects of supra-physiological testosterone application and close this gap in testosterone dose-response data. Male orchiectomized rats were treated with different testosterone doses ranging from 0.1 to 50mg/kg body weight for 3 weeks. Several physiological endpoints (e.g., body weight, organ and muscle weight, muscle strength, muscle fiber size) were examined during and after the termination of the treatment with an adjusted Hershberger assay, open-field-test, and (immuno-)histologic. The wet weights of androgen responsive organs (penis, prostate, seminal vesicle) showed a significant increase in a dose-dependent manner. Histological evaluation of the prostate showed a significant higher percentage of KI67 positive prostate nuclei in the highest dosage group and an increasing hyperplasia with increasing testosterone administered. A significant anabolic effect was only observed in Levator ani wet weight, and to minor degree for the cardiac muscle. Regarding other skeletal muscles (Musculus soleus and Musculus gastrognemicus), no significant testosterone effects were observed. We showed a significant increasing dosage-response effect for testosterone in androgen responsive organs with saturation at the two highest concentration of 10 and 50mg/kg body weight. The dose-dependent androgenic effects of testosterone were well observable and the anabolic effects on muscle tissue were visible although to a lesser degree, without the support of aerobic exercise and a protein rich diet. Future studies should investigate a combinatorial effect of testosterone and training. Nevertheless, with the chosen range of applied testosterone, we showed a saturation of testosterone effects in prostate, seminal vesicle, penis, and Levator ani.

Effect of Polycarboxylate Superplasticizer in Ordinary Portland Cement and Sulfate Resistant Cement

Polycarboxylate superplasticizers (PCE) are the most widely used admixtures in today’s cementitious construction materials. The molecular structure has a decisive influence on the effectiveness of PCE, which also can be tailored to serve in a different cementitious system. The current study investigates the influence of the backbone charge density of PCE on the rheology, hydration kinetics, and adsorption behavior of ordinary Portland cement (OPC) and sulfate-resistant cement (SRC). The results indicate that regardless of the PCE type, OPC requires a higher amount of PCE to be adsorbed to induce changing of rheological parameters and hydration kinetics. Regardless of the cement type, the PCE with a higher charge density exhibits higher adsorption behavior, corresponding to lower viscosity measurement. Compared to OPC, SRC is more sensitive to the introduction of both PCEs and has a lower saturation dosage, indicating that SRC generally provides better workability properties regardless of the PCE.

Insights into the efficiency loss of naphthalene superplasticizer in alkali-activated slag pastes

This paper investigates the effect of naphthalene superplasticizer (NS) on the fluidity of four different (activated by Na2SO4, Na2CO3, NaOH and waterglass (WG)) alkali-activated slag (AAS). The adsorption behaviors, solubility, chemical and physical stability, and diffusion properties of NS in alkali activator solutions were comprehensively evaluated. The results indicate that the working efficiency of NS in AAS (at the same Na2O%) followed the order of activators: Na2SO4, Na2CO3 or NaOH, and WG, which losses its efficiency by 45%, 85%, 85%, and 100% when compared to that in slag-water pastes (i.e. using the same saturation dosage of NS as in slag-water paste, 0.75 wt%). In the alkali activator solutions, the NS remained chemically stable; however, it formed micelles and its physical stability reduced. The formation of micelles of NS was clearly captured by transmission electron microscopy (TEM), which is responsible for its lower solubility and mobility in these solutions. The decrease of solubility and mobility of NS in the alkali activator solutions reduced the adsorption and dispersion efficiency of NS in AAS pastes.

Compatibility of Ether-Based Poly-Carboxylate Superplasticizer with Mineral Admixtures Blended with OPC

The marsh cone test is a defined procedure to determine the quantitative fluidity of cement with mineral admixtures along with the saturation dosage and the efficiency of the superplasticizer (SP). In the present study, three mineral admixtures, micro-silica (MS), fly ash (FA), and ground granulated blast furnace slag (GGBFS) were used as cement replacement. Poly-carboxylate ether-based superplasticizer was used as a chemical admixture. Blends of cement and mineral admixtures with water/binder (w/b) ratios ranging from 0.40 to 0.60 at every interval of 0.05 were examined against the different dosages for SP. All the binder mixes reached a saturation dosage for SP, after which there is no change in the fluidity of the mix. The obtained dosage is considered the maximum amount of SP added to the concrete with the respective binder type. The replacement percentage of cement with mineral admixture also affected the fluidity of the binder mix. A decrease in the fluidity of binder mix was observed on increasing the amount of mineral admixture in it. At a higher w/b ratio, a significantly less SP dosage is required to attain saturation point and vice-versa. Based on the experimental investigation, it is concluded that the efficiency of SP depends on its dosage, the w/b ratio, the type and amount of mineral admixture.

Effect of Entropy Index-Targeted Dextromeetomidine on Postoperative Neurocognitive Function in Elderly Patients with Gastrointestinal Tumors

Objective: To investigate the effect of entropy index targeted monitoring combined with dexmedetomidine infusion on cognitive function after thoracic and abdominal surgery in elderly patients. Methods: 60 elderly patients undergoing abdominal surgery in our hospital on October ~2017 and October 2019 were selected, ASAⅡ~ grade III, and the random digital table method was divided into 3 groups ,20 cases in each group. entropy index monitoring combined with dexmedetomidine group (D1 group), entropy index monitoring combined with dexmedetomidine group (D2 group) and dexmedetomidine monitoring combined with saline group (D0 group). All patients were subjected to sequential rapid induction of endotracheal intubation general anesthesia. D1, D2, the group was injected with 0.5μg/kg dexmedetomidine hydrochloride intravenously in the first 15 min of induction, followed by a 0.3μg•kg-1•h-1, 0.6μg•kg-1•h-1 maintenance pump until 30 minutes before the end of operation, respectively. The D0 group was injected with the same amount of saline intravenously before induction, and then maintained with the same amount of saline. D1 and D2 groups were calibrated at 40~60. preoperative (T1), tracheal intubation immediate (T2),30 min after operation (T3) and extubation immediate (T4) M after operation were compared in 3 groups AP (mmhg), hr (sub/ min), blood oxygen saturation (SpO2) and intraoperative anesthetic dosage, vasoactive drug use, and postoperative recovery status; simple intelligent mental state examination scale (MMSE) test was completed 1 day before ,1 day after ,3 days after and 7 days after operation to record the incidence of perioperative neurocognitive disorders (PND). To detect the necrosis factor-α(TNF-α) and C-reactive protein (CRP) of the above-mentioned concurrent serum tumors; Results Compared with D0 group, the MAP of D1 group and D2 group decreased significantly and the HR slowed down significantly (P<0.05), The MAP, HR of T3, T4 in D2 group was significantly decreased compared with that in the D1 group (P<0.05), but the difference was not significant at all time points (0.05);The respiratory recovery time (min), dialling time (min) and restoring directional force time (min) were significantly shortened compared with the D0 group and the D2 group, and the consumption of propofol and sufentanil during the operation was significantly decreased. Compared with the D2 group, the use of vasoactive drugs in the D1 group was significantly decreased (P<0.05). The TNF-α, CRP of patients in the first day and the third day were higher than those in the first day of operation, but the TNF-α, CRP of D1 group and D2 group were lower than those in the D0 group (0.05). The MMSE scores of l days and 3 days after operation in D1 and D2 groups were higher than those in D0 groups. Significantly decreased (P<0.05), and there was no significant difference between the groups 7 days after operation (P>0.05): Conclusion entropy index targeted monitoring combined with dexmedetomidine infusion (0.3μg/kg/h) in the elderly patients during surgery can improve the intraoperative and postoperative hemodynamic stability, can improve the perioperative neurocognitive disorders of patients, worthy of clinical promotion.

Effect of Filler Type, Fineness, and Shape on the Properties of Nonfibrous UHPC Matrix

Fillers have been commonly used to replace a portion of cement in ultra-high-performance concrete (UHPC) for economic and eco-friendly purposes. However, mostly only the type and amount of filler are addressed, and limited efforts have been made on the size and shape effects of filler. This study used inert mineral fillers with different morphologies (approximately spherelike versus needlelike) to study the effect of the shape and different particle sizes (fineness) within the same filler type to study the effect of the size. A systematic study was carried out to investigate these effects on the workability, strength, hydration, modification of the particle-size distribution (PSD), and microstructure of the designed nonfibrous UHPC matrixes. The mixture proportion design is based on a modified Andreasen and Andersen model, and three mixtures devoid of fillers were prepared firstly to study the effect of superplasticizer dosage on the UHPC matrix to determine the saturation dosage. Results reveal that larger-sized approximately spherelike filler (limestone or quartz) results in a slightly negative effect on the strength, whereas larger-sized needlelike wollastonite enhances the strength of the mixture. The mixtures with 20% substitution of cement by the seven different fillers obtained increased workability, decreased cost, and higher strength or no more than 4% strength reduction compared with the control mixture devoid of filler. This quantification of size and shape effects of fillers will provide an effective theoretical basis, and particular fillers could be intelligently chosen in the engineering practice for the production of UHPC.

Polycarboxylate ester adsorption on cement grains: Influence of polydispersity

Although in academic and industrial practice polymers are typically described by their average molecular parameters, most often they display a polydispersity both in size and in properties. In this paper, we focus on the influence of polydispersity on the adsorption of polycarboxylate ester on cement grains and on its influence on the definition of a so-called affinity of the polymer to the surface. We first show that a constant fraction of a polydisperse polycarboxylate ester always adsorbs no matter the availability of adsorption sites. We moreover suggest from our measurements and from scaling laws from literature that the degree of polydispersity in the structure of polycarboxylate ester should affect adsorption at both low and intermediate dosages and hydrodynamic radii in solution. However, it shall not have a major influence on polymer layer thickness or saturation dosage.

A study on compatibility of superplasticizers with high strength blended cement paste

Adoption of High-Performance Concrete (HPC) made with low water to binder ratios in practical applications are being encouraged widely for enhanced development of high early strength and durability. The type of superplasticizers incorporated, highly influences the development of HPC. At low water-cement ratio, HPC is made workable by the incorporation of superplasticizers. The wrong proportion of cement and admixture in a mix causes low fluidity, rapid/delayed setting, segregation, bleeding etc. Therefore, it is important to underline the interaction mechanism between cement and superplasticizer for the better utilization of concrete. As more blended cements are used now a day, it is imperative to investigate the compatibility of superplasticizers in such paste systems. In this study, the saturation dosages and compatibility of sulphonated naphthalene formaldehyde (SNF) and poly carboxylate ether (PCE) superplasticizers with cement paste prepared from Ordinary Portland Cement (OPC) 53 grade, Portland Pozzolana Cement (PPC) and Slag cement (PSC) for different water-binder (w/b) ratios are analysed using the marsh cone test and mini slump test. As per the result obtained, PSC was found to have higher saturation dosages than OPC and PPC. The optimum dosages for PCE admixture are lower than that for SNF as their mechanism of action are different.

Performance evaluation of self-compacting concrete containing volcanic ash and recycled coarse aggregates

Sustainable development in concrete technology can be achieved via conservation of primary materials and enhancement of the durability of concrete structures. Accordingly, in this study, self-compacting concrete (SCC) was developed economically, using sustainable materials such as volcanic ash (VA) and recycled coarse aggregates (RCA). The flow behavior, mechanical properties, and durability performance were evaluated and compared for the developed mixes. Six concrete mixes with different compositions, including the replacement of ordinary Portland cement and normal coarse aggregates (NCA) with 30% VA and 30% RCA, respectively, were prepared using the saturation dosages of superplasticizer (SP) and viscosity modifying admixture (VMA) obtained from the paste study. SCC could be developed with the selected compositions through a two-stage mixing method, and it was observed that the replacement of NCA with 30% RCA did not adversely affect the mechanical properties. A modification in the microstructure could be observed with the incorporation of SP, VA, and VMA. Further to this, the reduction in the durability properties with the incorporation of VA and RCA was compensated with a ternary mix containing ground granulated blast-furnace slag. In general, the SCC incorporating regional and local materials such as VA and RCA could be used, based on the durability indices developed through this study, and considered as a viable alternative to meet the raw material shortage in Kuwait.

Mix-design and properties of self-compacting concrete made with calcareous tuff

This paper focuses on the possibility of using calcareous tuff (CT) in self-compacting concrete (SCC) production. In concrete mixtures, CT is used as sand and its fines as partial cement replacement. Mixtures are prepared with three different sand/mortar ratios (S/M) of 0.40, 0.45 and 0.50 with a varying superplasticiser content (SP). Cement was substituted by fines of calcareous tuff (CTF) with percentages of 0, 5, 10, 15, 20, 25 and 30% for S/M ratios of 0.40 and 0.45 with a varying SP dosage up to the superplasticiser saturation dosage (SSD). The filling, passing ability and segregation resistance tests are used to assess the fresh properties of SCC. The compressive strength of SCC was also determined at 3, 7, 28 and 56 days. The results show that the use of CT improves the flowability and stability of both SCM and SCC. SCC mixtures made with CT satisfy the specifications and guidelines for SCC production. The maximum strength obtained at 28 days was with mixtures SCC incorporating 10% of CTF, which revealed clearly the good adhesion between CT and cement matrix. Finally, CT constitutes a good local eco-material, abundantly available, for the SCC design.

Caracterización en salud oral y hábitos de higiene oral en pacientes con enfermedad renal crónica

Objetivo: determinar el estado de salud oral de pacientes con enfermedad renal crónica atendidos en un centro de terapia renal y su relación con marcadores nutricionales, inflamatorios y dosis de eritropoyetina. 
 Pacientes: todos los pacientes con enfermedad renal crónica atendidos en RTS sucursal Caldas en programas predialítico, postrasplante renal, hemodiálisis y diálisis peritoneal, con más de tres meses ininterrumpidos de asistencia en uno de esos programas, haber aceptado su participación en el estudio, contar con los paraclínicos necesarios para el estudio y registro de dosis administrada de eritropoyetina. 
 Métodos: trescientos treinta y seis pacientes cumplieron con los criterios de inclusión: 24 (7%) en prediálisis, 164 (49%) en hemodiálisis, 114 (34%) en diálisis peritoneal y 34 (10%) en postrasplante renal. Se establecieron los datos demográficos y se evaluaron los índices de placa (higiene oral), salud periodontal, experiencia en caries COP-D (cariados, obturados, perdidos – diente), y diagnóstico estomatológico. También resultados de exámenes paraclínicos indicadores de estado inflamatorio tales como albúmina, ferritina y porcentaje de saturación de transferrina, además la dosis administrada de eritropoyetina. 
 Resultados: la población de pacientes en prediálisis y postrasplante renal no arrojó datos suficientes para ser incluida en el análisis estadístico. De los pacientes en diálisis 63% presentaban buena higiene oral, 33% regular, y sólo 3% tenían mala higiene oral, a pesar de ello la prevalencia de enfermedad periodontal fue alta afectando a 75% de los pacientes llegándose a presentar gingivitis severa en 35-38% de los pacientes. Por el índice COP-D se observó que la prevalencia en caries fue alta. Por lo disperso de los resultados de laboratorio de marcadores inflamatorios no fue posible determinar correlación alguna entre ellos y salud periodontal o dosis de eritropoyetina. 
 Conclusiones: la higiene oral de los pacientes en diálisis es satisfactoria, pero a pesar de ello presentan alta prevalencia de enfermedad periodontal y caries, ello sugiere que factores relacionados con el medio urémico, modificaciones en el PH y flujo salival favorecen su aparición. La evaluación de estos parámetros en estudios posteriores podría ofrecer resultados más concluyentes, al igual que la utilización de marcadores inflamatorios más sensibles. La evaluación precoz de todos los pacientes con ERC por odontología es prioritaria para evitar la aparición de enfermedad periodontal

Superplasticizer and Shrinkage Reducing Admixture Dosages for Microfine Cement in Grout Systems

Grouts have numerous applications including crack repair as maintenance in construction industries. Microfine cements are intensively used for high strength mortar and grout products. They are ideal for injection grouting in structural repair. Such grouts should have suitable rheological properties to be injectable, especially those used in repair and rehabilitation. The use of superplasticizers (SP) in these products is thus becoming increasingly crucial to achieve favorable workability and viscosity properties. A difficulty in such grouts is the plastic shrinkage due to finer particles used. It is thus necessary to determine optimum SP and shrinkage reducing admixture (SRA) dosages for a microfine cement based grout. In this study, a saturation dosage was decided from two Polycarboxylate ether (PCE) based SPs in relation to neat cement using slump flow and rheological parameters. A range of grout mixtures was formulated containing micro silica (MS) and fly ash (FA), and tested for suitable rheological and mechanical parameters. Based on the results, a grout mixture with MS and FA was selected to determine optimum SRA content. According to the results, a SP dosage of 3% by weight of neat cement is sufficient to achieve saturation. The grout material including MS and FA can produce comparable properties to neat cement grout. MS is found to improve compressive strength within the range considered, whereas a higher FA content provides favourable rheological properties. Finally, a SRA dosage of 4%, which could reduce the shrinkage by about 43% after 28d days, is determined for the grout system.

Investigations on compatibility of cement-superplasticizer interaction and its influence on mortar workability incorporating copper slag as fine aggregate

Interaction between cement and water is a complex phenomenon to understand. Sometimes achieving the desired results is quite challenging due to the contrast spotted in the characteristics of cement, type and dosage of superplasticizers (S.P) as the behaviour is insignificant. Influence of different types of cement fineness on pastes with different superplasticizers which represents the compatibility between cement with water reducing admixture in order to obtain well-defined saturation dosage and with the partial replacement of fine aggregates (F.A) by copper slag (C.S) to study the mortar behaviour is focused in this work. A methodology based on fundamental properties of cementitious systems using marsh cone and mini-slump cone tests results to identify the suitable and compatible combinations between cement and superplasticizers for the enhancement of flow behaviour of mortar mixes.

Temperature Influence on Rheology of Superplasticized Pozzolana Cement and Modeling Using RKS Algorithm

Rheology deals with flow and deformation of matter under applied force. The study of rheological response of superplasticized portland pozzolana cement pastes subjected to a stepwise loading at three levels of temperature using Herschel–Bulkley and Bingham flow models is presented here. Rheological tests were done in a temperature-controlled coaxial cylinder viscometer (Brookfield DV-II). Cement pastes were prepared at a water–cement ratio of 0.37 using four types of portland pozzolana cement (PPC) and superplasticizers (SP) of four different families. Saturation dosages of the superplasticizers were obtained through Marsh cone and mini slump tests. Rheological tests were done on superplasticized cement paste mixes for three levels of dosages viz., lower than the saturation dosage, saturation dosage, and higher than the saturation dosage. Cement paste samples were subjected to shear rates ranging from 30 to 65 S−1 in the viscometer and the resultant shear stress was measured. Rheological parameters were obtained at three test temperatures (15, 27, and 35°C) by fitting the second cycle downward flow curves using Bingham model and Herschel–Bulkley model. These parameters were analyzed and used for modeling through random kitchen sink algorithm. The variation of predicted and measured values of the rheological parameters were compared and validated. It was observed that the model could effectively predict the rheological parameters within the experimental domain.

Optimization of superplasticizer in portland pozzolana cement mortar and concrete

Chemical Admixtures are added to concrete at the time of mixing of its constituents to impart workability. The requirement of right workability is the essence of good concrete. It has been found that the use of optimum use of admixtures is very important since low dosage may result in loss of fluidity and over dosage could lead to segregation, bleeding, excessive air entrainment etc in concrete. Hence it is essential to find optimum dosage of superplasticizer for getting good strength and workability. But large number of trial tests are required in the field to find the saturation dosage of superplasticizer in concrete which requires more materials and consume more time. The paper deals with developing a co-relation between the quantity requirements of superplasticiser in mortar to that of cement concrete to get good workability. In this work for preparing mortar and concrete 4 brands of locally available Portland pozzolana cement (PPC) and superplasticizer (SP) belonging to 4 different families namely Polycarboxylate Ether (PCE), Lignosulphate (LS), Sulfonated Naphthalene Formaldehyde (SNF) and Sulfonated Melamine Formaldehyde (SMF) are used. Two different brands of SP’s are taken from each family. Workability study on the superplasticized mortar with cement to sand ratio 1:1.5 and water cement ratio of 0.4 was performed using marsh cone and flow table test and workability study on the concrete with same cement/sand ratio and water cement ratio was done using slump cone and flow table test. Saturation dosage of superplasticizer in mortar and concrete determined experimentally was compared to study the correlation between two. Compressive strength study on concrete cubes were done on concrete mixes with a superplasticizer dosage corresponding to the saturation dosage and a comparative study were done to analyse the improvement in the compressive strength with addition of superplasticizer from different family.

Coupled effect of superplasticizer dosage and fly ash content on strength and durability of concrete

The incorporation of fly ash in concrete enhanced the durability of portland cement concrete more effectively. Fly ash is incorporated as a mineral admixture because of its advantageous properties like pozzolanic reaction and pore refinement. At the point when fly ash is added in concrete, calcium hydroxide, liberated during cement hydration, reacts with the reactive silica present in fly ash and forms calcium silicate hydrate(C-S-H) gel. This research investigates the influence of fly ash in conjunction with four different superplasticizers (SP) namely Polycarboxylate ether (PCE), Lignosulphonate (LS), Sulphonated Melamine Formaldehyde (SMF) and Sulphonated Naphthalene Formaldehyde (SNF) and on the mechanical and durability properties of concrete. Concrete was made with different levels of class F flyash replacement (0,15, 25, and 35% by mass) of cement, the w/c ratio were maintained constant as 0.37 and the superplasticizer dosage corresponding to saturation dosage. The saturation dosage of superplasticizer is measured by conducting marsh cone and minislump tests. The mechanical and durability properties tested were compressive strength, splitting tensile strength and Sorptivity. PCE based superplasticizers are found to be more effective. Modification in the mechanical by increase in later age strength and durability properties by increase of the concrete was observed with the addition of fly ash and superplasticizer in control mix

Ultrasound-guided supine lumbar plexus block versus iliac fascia block for analgesia in older adult patients undergoing hip replacement: a randomized controlled trial

Background and objectives: Anesthesia is an important part of hip replacement in older adult patients. Lumbar plexus block and iliac fascia block are common block methods in hip replacement. This study will compare the analgesic effects of ultrasound-guided supine lumbar plexus block and multi-angle multi-point iliac fascia block during hip replacement in older adult patients. The result will identify the optimal analgesic regimen. Methods: This prospective, single-center (Lu’an Civily Hospital in China), randomized controlled trial will include 208 older adult patients who are scheduled to undergo hip replacement. The patients will be randomly assigned to one of two groups (n = 104/group). In the lumbar plexus-block group, patients will undergo supine lumbar plexus block, general anesthesia using a laryngeal mask airway, and subsequent hip replacement. In the iliac fascia-block group, patients will undergo multi-angle multi-point iliac fascia block, general anesthesia using a laryngeal mask airway, and subsequent hip replacement. After surgery, all patients will be followed up for 24 hours. Results: The primary outcome measure of this study is a Visual Analog Scale score obtained 24 hours post-surgery, which will be used to evaluate the postoperative analgesic effect. The secondary outcome measures are Visual Analog Scale scores at 2, 6 and 12 hours post-surgery, heart rate at various time points during the surgery (laryngeal mask placement, T0; surgical incision, T1; surgical reaming, T2; prosthesis implantation, T3; incision suture, T4; and resuscitation, T5), mean arterial pressure, blood oxygen saturation, intraoperative sufentanil, perdipine, and ephedrine dosages, total amount of intravenous patient-controlled analgesics at 2, 6, 12, and 24 hours post-surgery, and incidence of adverse reactions. Results of a pilot study involving 60 older adult patients who underwent hip replacement during March 2018 through September 2018 showed that intraoperative sufentanil, perdipine, and ephedrine dosages were significantly lower in the lumbar plexus-block group (n = 30) than in the iliac fascia-block group (n = 30; P Conclusion: Results from this study will provide evidence indicating whether ultrasound-guided supine lumbar plexus block in combination with general anesthesia can more effectively maintain stable hemodynamic indices during hip replacement and whether it results in more encouraging postoperative analgesic effects in older adult patients than multi-angle multi-point iliac fascia block. Ethics and trial registration: This study was approved by the Medical Ethics Committee of Lu’an Civily Hospital in March 2018 (approval No. PJ2018-001). The study protocol version is 1.0. Patients participating in this study will provide their written informed consent after fully understanding the study protocol. This study was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR1800019888).

Effect of superplasticizers on the rheological properties of fly ash incorporated cement paste

The rheology is a study of flow of matter. Rheological behavior of cement paste changes with composition of cement, amount of mineral and chemical admixtures, family of superplasticizer, temperature etc. This paper explores the influence of superplasticizer dosage, superplasticizer family and mineral admixture dosage on the rheological behavior of cement paste. For this purpose cement pastes were prepared at a water cement ratio of 0.37 using OPC and different percentage of fly ash (15, 25, 35) and different dosages of superplasticizer (one from each family). Four families of superplasticizer used for this study are polycarboxylate ether, sulphonate melamine formaldehyde, sulphonate naphthalene formaldehyde and lignosulphates. Rheological tests were performed in a coaxial cylinder viscometer (Brookfield DV-II). Saturation dosage of the superplasticizers in the cement paste mixes with different percentage of fly ash replacement were obtained through marsh cone and mini slump tests on cement paste. Cement pastes were placed in the sample chamber of coaxial cylinder viscometer and shear stress produced measured with known shear rate ranging from 30 S to 65 S-1 applied to the fluid through the spindle. Rheological parameters like yield stress and plastic viscosities were calculated using Bingham and Herschel bulkley model. Change in rheological parameters of the cement paste with fly ash replacement percentage, superplasticizers dosage and family were measured and comparison is made

Mixture design and early age investigations of more sustainable UHPC

This paper deals with the possibility to make the Ultra-High Performance Concrete (UHPC) as an environmentally friendly, through cement replacement with Blast Furnace Slag (BFS) and considering its cost and its early age performance. Thereby, a preliminary investigation is carried out, to design an UHPC with local materials and where Silica Fume (SF) is partially replaced with crushed quartz. The results showed that, from a mixture standpoint: i) the use of high energy mixer is necessary to ensure a homogeneous and workable mixture; ii) the polycarboxylate superplasticizer with chemical structure of acrylic polymer (ACP1) and saturation dosage of 1.8% gives better workability for UHPC, compared to other six superplasticizers; iii) despite its negative effect on slump flow, Grey Silica Fume (silicium) ensures better compressive strength at early age, than Light one (zirconium). Results showed also that for 30% of cement replacement, the nucleation effect of BFS particles prevails and induces an acceleration of setting and hydration reaction of cement. For BFS contents of 50 and 80%, the dilution effect is dominating, which decelerates the setting and hydration reaction and decreases the peak of heat flow. BFS addition also affects the strength development. At 3 days, the strengths of the blended mixtures of UHPC with 50 and 80% of BFS were decreased by 26 and 66% respectively, while in contrast, there was a slight increase in the strength (+3%) with 30% of BFS compared to the reference mixture (UHPC1). For UHPC containing 80% of BFS, the use of chemical activator of potassium hydroxide, with a concentration of [KOH]3, causes slag’s dissolution and reaction, which in turn improves the compressive strength by 42% and 11%, at 3 and 7 days, respectively.