Investigation of the interface of fungal mycelium composite building materials by means of low-vacuum scanning electron microscopy.

Low-vacuum scanning electron microscopy (low-vacuum SEM) is widely used for different applications, such as the investigation of noncoated specimen or the observation of biological materials, which are not stable to high vacuum. In this study, the combination of mineral building materials (concrete or clay plaster) with a biological composite (fungal mycelium composite) by using low-vacuum SEM was investigated. Fungal biotechnology is increasingly gaining prominence in addressing the challenges of sustainability transformation. The construction industry is one of the biggest contributors to the climate crises and, therefore, can highly profit from applications based on regenerative fungal materials. In this work, a fungal mycelium composite is used as alternative to conventional insulating materials like Styrofoam. However, to adapt bio-based products to the construction industry, investigations, optimisations and adaptations to existing solutions are needed. This paper examines the compatibility between fungal mycelium materials with mineral-based materials to demonstrate basic feasibility. For this purpose, fresh and hardened concrete specimens as well as clay plaster samples are combined with growing mycelium from the tinder fungus Fomes fomentarius. The contact zone between the mycelium composite and the mineral building materials is examined by scanning electron microscopy (SEM). The combination of these materials proves to be feasible in general. The use of hardened concrete or clay with living mycelium composite appears to be the favoured variant, as the hyphae can grow into the surface of the building material and thus a layered structure with a stable connection is formed. In order to work with the combination of low-density organic materials and higher-density inorganic materials simultaneously, low-vacuum SEM offers a suitable method to deliver results with reduced effort in preparation while maintaining high capture and magnification quality. Not only are image recordings possible with SE and BSE, but EDX measurements can also be carried out quickly without the influence of a coating. Depending on the signal used, as well as the magnification, image-recording strategies must be adapted. Especially when using SE, an image-integration method was used to reduce the build-up of point charges from the electron beam, which damages the mycelial hyphae. Additionally using different signals during image capture is recommended to confirm acquired information, avoiding misinterpretations.

Safety in Senhance™ Robotic Gastrointestinal Surgery in 530 Patients.

The Senhance Robotic System™ (Asensus Surgical, Durham, NC, USA) has been used in abdominal surgery since 2016, and provides an eye-tracker for camera movement and haptic tactile feedback. Safety aspects are very important in robotic surgery, such as regarding the presence of system malfunctions and surgical outcomes. The data for robotic function in gastrointestinal surgical procedures in 530 patients (colorectal surgery, fundoplication, others) were prospectively listed in the TRUST registry after informed patient consent in three German gastrointestinal surgery centers (center A, N = 46 patients; center B, N = 457; center C, N =27). Adverse events were noted in 14.3% (76/530 patients) of the overall surgeries, with an equal distribution among the procedures. Robotic malfunctions, such as console/camera/arm malfunctions, collisions, or limited motion, were experienced in 5.5 % (29/530 patients), with some differences among the centers (A, 0.0%; B, 4.2%; C, 37%). These differences were explained in terms of team experience and case load. In conclusion, the Senhance™ Robotic System can be safely applied to routine abdominal surgery procedures.

Critical parameters affecting the thermal resistance of alkali-activated aluminosilicate wastes: Current understanding and future directions.

Many research articles and reviews have recognized alkali-activated materials (AAMs) as eco-friendly alternative binders to ordinary Portland cement (OPC) due to their economic andenvironmental advantages. However, few literature surveys reported the physical, mechanical and microstructural changes that occur after the exposure of AAMs to elevated temperatures. Owing to the wide diversity in the properties of aluminosilicates, alkali-activation conditions, and additives, a deep survey is needed to understand how different factors can affect the performance of AAMs under elevated temperatures. Therefore, this review extensively discusses the impact of recent critical parameters, including aluminosilicate compositions, aggregate type and mineral, micro, and nano additives, on the behavior of AAMs under thermal load. It can be concluded that regardless of alkali-activator type and concentration, alkali-activated fly ash shows higher thermal resistance than alkali-activated metakaolin and slag. Moreover, the presence of an adequate amount of calcium can increase the thermal stability of AAMs, while the iron has a varying effect on the thermal resistance of AAMs, either positively or negatively. Compared with all additives and aggregates, using waste glass and lightweight aggregates enhanced the thermal resistance of AAMs. Howerver, some types of aggregate having a binding ability which increase the residual strength after heat exposure. Considering the fineness of materials, evaluating the role of nano and micro materials on the properties of AAMs at high temperatures is reviewed. Based on this survey, several promising topics for future work are suggested.

RefluxStop™ Therapy - a New Minimally Invasive Technology in Anti-reflux Surgery.

The symptoms of gastroesophageal reflux disease (GERD) are very common, but cannot be reliably controlled with medication, as more than 40% of patients suffer troublesome symptoms more than twice a week even when taking maximum doses of proton pump inhibitors (PPI). Until recently, the only surgical option was anti-reflux surgery, usually performed as a hiatal hernia repair and some form of fundoplication. While this is still the gold standard, some centers note high recurrence rates and/or high rates of side effects such as dysphagia, bloating, and post-prandial discomfort. This paper describes a new surgical procedure that controls reflux symptoms through hiatal hernia repair in combination with the implantation of a silicone cube. The cube is implanted near the left side of the esophagus above the lower esophageal sphincter (LES). The details of the procedure, the indications for this new approach, the initial results, and the rate of side effects compared to Nissen fundoplication are described. Implantation of the CE-certified RefluxStop™ (Implantica, Zug, Switzerland) has been used for 3 years and the initial studies show encouraging success rates. In addition, side effects are significantly reduced. These results must be evaluated in further studies.

Single-Center Results of Colorectal Procedures Performed with Fully Articulated Laparoscopic Artisential® Devices.

INTRODUCTION: The ArtiSential® line of products from LivsMed (Seongnam, Republic of Korea) are fully articulated hand-held laparoscopic instruments, possessing end-effectors that closely imitate those of surgical robots with regard to shape and dexterity. Feasibility and safety studies describing the initial experiences with these devices in upper and lower gastrointestinal as well as thoracic surgery have been published. This report presents the outcomes of the largest cohort to date of colorectal procedures performed with Artisential® instruments in a single center. MATERIALS AND METHODS: Between September 2020 and May 2022, prospective data were collected from patients undergoing ArtiSential®-assisted laparoscopic surgery. A retrospective data analysis was performed for all patients who underwent ArtiSential®-assisted surgery for colorectal indication. Indications for colorectal surgery included rectal and colon cancer, complicated diverticular disease, inflammatory bowel disease, obstructed defecation syndrome, endoscopically nonresectable adenomas and chronic anastomotic fistula following a low anterior resection (LAR). RESULTS: A total of 73 patients (49 males, 24 females) underwent Artisential®-assisted colorectal surgery. The median age of the patients was 62 years (range 34-88) and the median body mass index (BMI) was 27 kg/m2 (range 19-51). Indications for surgery were colorectal malignancy (n=55, 75%), complicated diverticular disease (n=11, 15%), obstructed defecation syndrome (n=3, 4.1%), inflammatory bowel disease (n=2, 2.7%), endoscopically nonresectable adenomas (n=1, 1.4%) and chronic anastomotic fistula following LAR (n=1, 1.4%). The median operative time was 240 minutes (range 95-458). There were no conversions to standard straight-stick laparoscopy or to laparotomy, and no intraoperative complications. All patients who were operated upon for colorectal malignancy had an adequate oncological resection (R0=100%). The median length of stay was 7 days (range 3-36). The overall complication rate was 10.9 % (Clavien-Dindo II: 1 patient, Clavien-Dindo IIIb: 7 patients). There were two readmissions, one unrelated, and no mortalities. CONCLUSIONS: This larger series confirms the results of previous reports on the safety and feasibility of Artisential® use in complex laparoscopic colorectal surgery. To examine potential benefits in outcome, comparative studies involving Artisential®, robotic-assisted and standard laparoscopic surgery are needed.

First Pediatric Pyeloplasty Using the Senhance® Robotic System-A Case Report.

A pediatric robotic pyeloplasty has been performed with the Senhance® robotic system for the first time in January 2021 on a 1.5-year-old girl with symptomatic ureteropelvic junction stenosis. A Senhance® robotic system (Asensus Surgical® Inc., Durham, NC, USA) with three arms and 5 mm instruments was used, providing infrared eye tracking of the 5 mm camera and haptic feedback for the surgeon, facilitating suturing of the anastomosis and double-J stent insertion. The robotic surgery lasted 4.5 h, was uneventful and successful, without recurrence of the ureteropelvic junction obstruction after six months, and with normal development of the patient's growth and organ function. The use of the robotic system was shown to be safe and feasible; long term follow-up will be conducted subsequently in pediatric surgery.

Development of a sample preparation procedure for Sr isotope analysis of Portland cements.

The 87Sr/86Sr isotope ratio can, in principle, be used for provenancing of cement. However, while commercial cements consist of multiple components, no detailed investigation into their individual 87Sr/86Sr isotope ratios or their influence on the integral 87Sr/86Sr isotope ratio of the resulting cement was conducted previously. Therefore, the present study aimed at determining and comparing the conventional 87Sr/86Sr isotope ratios of a diverse set of Portland cements and their corresponding Portland clinkers, the major component of these cements. Two approaches to remove the additives from the cements, i.e. to measure the conventional 87Sr/86Sr isotopic fingerprint of the clinker only, were tested, namely, treatment with a potassium hydroxide/sucrose solution and sieving on a 11-µm sieve. Dissolution in concentrated hydrochloric acid/nitric acid and in diluted nitric acid was employed to determine the 87Sr/86Sr isotope ratios of the cements and the individual clinkers. The aim was to find the most appropriate sample preparation procedure for cement provenancing, and the selection was realised by comparing the 87Sr/86Sr isotope ratios of differently treated cements with those of the corresponding clinkers. None of the methods to separate the clinkers from the cements proved to be satisfactory. However, it was found that the 87Sr/86Sr isotope ratios of clinker and cement generally corresponded, meaning that the latter can be used as a proxy for the clinker 87Sr/86Sr isotope ratio. Finally, the concentrated hydrochloric acid/nitric acid dissolution method was found to be the most suitable sample preparation method for the cements; it is thus recommended for 87Sr/86Sr isotope analyses for cement provenancing.

Erratum: Von-Wolff et al. Testing of Eluates from Construction Products for Potential Environmental Effects Due to the Behaviour of Enchytraeus albidus. Materials 2021, 14, 294.

In the original version of our article [...].

The Artisential® Articulated Laparoscopic Forceps: A Dry Lab Study to Examine Dexterity and Learning Effects in Operators with Different Levels of Laparoscopic Experience.

PURPOSE: The advent of robotic surgery has highlighted the advantages of articulation. This dry-lab study examined the dexterity and learning effect of a new articulated laparoscopic instrument: the ArtiSential® forceps (LIVSMED, Seongnam, Republic of Korea). METHODS: A peg board task was designed. Three groups of volunteers with varying levels of laparoscopic expertise were organized to perform the task: expert, intermediate and novice. The participants performed the task using articulated and straight instruments, once before a 30-min training session and once afterwards. The times required to perform the task were recorded. The performances were analyzed and compared between the groups as well as between the straight and articulated instruments. RESULTS: The experts were significantly faster than the novices with both instruments before the 30-min training session (p = 0.0317 for each instrument). No significant time difference was found among the three groups after the 30-min training session. The decrease in the time required to perform the peg-transfer task with the articulated instrument was significantly greater in the novice and intermediate groups (p = 0.0159 for each group). No significant difference in time reduction was observed between the groups with the straight instrument. Regardless of the user, the articulated device was associated with faster task performance than the straight device after 8 hours of training (p = 0.0039). CONCLUSION: The ArtiSential® articulated device can improve dexterity. A significantly greater learning effect was observed in the novice and intermediate groups in comparison with experts. A plateau in the learning curve was observed after a few hours of training.

Testing of Eluates from Waterproof Building Materials for Potential Environmental Effects Due to the Behavior of Enchytraeus albidus.

In order to determine the potential environmental impact of construction products, it is necessary to evaluate their influence on organisms exposed to them or their eluates under environmental conditions. The behavior of the white worm Enchytraeus albidus is a useful tool for assessing the potential environmental impact of construction products in contact with water and soil. This study investigates the environmental effects of eluates from two construction products, a reactive waterproofing product, and an injection resin, on the reproduction and avoidance behavior of E. albidus. The eluates were prepared according to existing guidelines. The soil used for the tests was moistened with the eluates of the construction products. The reproduction results of the worms were collected after six weeks of exposure. Offsprings were counted under the microscope and statistically analyzed. Results from the avoidance behavior were collected after 48 h of exposure, and results were compared with the reproduction results. The eluates from both construction products induced significant changes in the reproduction behavior of E. albidus. Undiluted or only slightly diluted eluates of the injection resin drastically reduced the reproduction of the worms, whereas the leaches of the reactive waterproofing product only had a minor effect. The avoidance results for the injection resin indicates that its presence in the habitat is clearly detrimental to the survival of E. albidus, while the avoidance results for the waterproofing resin showed an initial avoidance of the eluates, but no harmful effects were observed. The avoidance test is a way of rapid toxicity screening of environmental samples when time is a critical parameter to measure possible environmental effects. This study shows that ecotoxicological tests using Enchytraeids are a valuable and important tool for understanding the mode of action of eluates from construction products in the environment.

The TransEnterix European Patient Registry for Robotic-Assisted Laparoscopic Procedures in Urology, Abdominal, Thoracic, and Gynecologic Surgery ("TRUST").

INTRODUCTION: Robotic surgery was first introduced in the mid-1980s, and at the end of the '90s, the da Vinci® System (Intuitive Surgical Inc., Sunnyvale, California) was introduced in Europe and held a monopoly for years afterward. In 2016, Senhance™ digital laparoscopic platform (TransEnterix Inc., Morrisville, North Carolina) came to the market. This new platform is based on laparoscopic movements and is designed for laparoscopic surgeons. This study shows the surgical outcomes of patients after different visceral, colorectal, gynecological, and urological surgical procedures done with the Senhance™ digital laparoscopic platform with a focus on safety. MATERIALS AND METHODS: The study population consists of 871 patients who underwent robotic surgery with the Senhance™ platform. The most common procedures were hernia repairs (unilateral and bilateral), cholecystectomies, and prostatectomies. The procedures were performed in five centers in Europe between February 2017 and July 2020 by experienced laparoscopic surgeons. RESULTS: 220 (25.3 %) out of 871 patients had a unilateral hernia repair, 70 (8.0%) a bilateral hernia repair, 159 (18.3%) underwent a cholecystectomy, and 168 (19.3%) a prostatectomy. The other procedures included visceral, colorectal, and gynecological surgery procedures. The median docking time was 7.46 minutes for the four most common procedures. The duration of surgery varied from 32 to 313 minutes, the average time was 114.31 minutes. Adverse events were rare overall. There were 48 (5.5 %) adverse events out of 871 patients, 24 of them (2.8 % of all cases) were severe. Out of all 24 severe adverse events, five events (20.8%) were likely related to the robot, 17 events (70.8%) were unlikely related to the robot, and two events (8.3%) could not be categorized. Regarding complications following unilateral hernia repairs, data from 212 patients was available. Thirteen (6.1%) complications occurred, and six of those (2.8%) were serious. Out of 68 patients with a bilateral hernia repair, six patients (8.8%) developed complications, three of which were severe (4.4%). The complication rate was 2.8% in the patients following a cholecystectomy (4/144); two of them serious. After prostatectomy, six out of 141 patients (4.3 %) had complications; one serious (0.7%) No mortality was observed. Data about unplanned conversions to laparoscopic surgery could be collected from 761 patients which is a rate of 3.7%. There were 12 conversions out of 760 procedures to open surgery (1.6%). CONCLUSIONS: Our series shows these procedures are safe and reproducible. The findings suggest that the surgical results after robotic surgery with the Senhance™ system are promising. Long-term data regarding complication rates should be the subject of future studies.

First Clinical Use of 5 mm Articulating Instruments with the Senhance® Robotic System.

INTRODUCTION: While the well-known DaVinci ® robotic system (Intuitive Surgical, Inc., Sunnyvale, CA) uses 8 mm articulated instruments, the Senhance ® robotic system (TransEnterix, Morrisville, NC), available since 2016, uses 5 mm instruments, which is the standard size in laparoscopy. We report here the first 43 procedures using 5 mm articulating instruments with the Senhance ® system (TransEnterix). METHODS: From September 9, 2019, to January 15, 2020, we performed 43 various robotic-assisted abdominal procedures. Before the first clinical intervention, the surgeons and surgical nurses were trained in the handling and operation of the articulating instruments. The main procedure was Inguinal Hernia Repair with the TAPP technique. We performed the operations with a 5 mm articulating bipolar forceps and a 5 mm articulating needle holder. In all cases, the Senhance ® (TransEnterix) articulating instruments were inserted through a 5 or 10 mm trocar, connected to the robotic arm and used for tissue dissection (inguinal hernia repair, cholecystectomy, and sigmoid resection) on the left hand of the robot arm and for suturing (inguinal hernia repair) on the right hand of the robot arm. RESULTS AND DISCUSSION: We observed technical issues in three patients: two resulted from user error and one occurred due to a software update. No technical issues were observed in the remaining 40 cases. There were two unscheduled conversions to laparoscopic surgery and no conversions to open surgery. No case of damage to surrounding tissue was observed. In one case, the branches of the grasper were jammed due to severe clot buildup after extensive coagulation following a strong bleed. After unproblematic laparoscopic bleeding control, robotic surgery was continued. There were no further intraoperative or early postoperative complications. The first impression of the participating surgeons and surgical nurses was that the smaller instruments were easy to handle after special training and offered a wider range of movement within the surgical field. All of the surgeons involved saw advantages with the use of 5 mm articulating instruments. CONCLUSION: Senhance ® (TransEnterix) 5 mm articulating instruments are technically stable and can be safely used in various abdominal procedures. The initial results suggest that these 5 mm articulating instruments can be a supportive tool in further robotic surgery, providing advantages in suturing and dissection with less risk of injury to surrounding tissue.

A Systematic Study on Polymer-Modified Alkali-Activated Slag-Part II: From Hydration to Mechanical Properties.

The effect of styrene-acrylate (SA) polymer latex on alkali-activated slag (AAS) was systematically studied in the aspects of hydration, hydration products, pore structure and mechanical properties through the combined analytical techniques including calorimetry, X-ray diffraction, thermogravimetric analysis, mercury intrusion porosimetry, and mechanical measurement. It was found that the addition of SA does not retard the AAS hydration, but slightly accelerates it, possibly due to the increasing ion diffusion through the loosely structured hydration products. Pore structure analysis indicates that the addition of polymer increases the cumulative pore volume and the portion of pores with size >100 nm in the hardened AAS paste. The addition of SA latex results in a continuous decrease of the compressive strength, but the flexural strength firstly increases and then decreases with the increase of polymer dosage. The polymer dosage of 2.5 wt % is optimal when applying polymer latex in the AAS system in this study.

Natural Fiber-Stabilized Geopolymer Foams-A Review.

The development of sustainable, environmentally friendly insulation materials with a reduced carbon footprint is attracting increased interest. One alternative to conventional insulation materials are foamed geopolymers. Similar to foamed concrete, the mechanical properties of geopolymer foams can also be improved by using fibers for reinforcement. This paper presents an overview of the latest research findings in the field of fiber-reinforced geopolymer foam concrete with special focus on natural fibers reinforcement. Furthermore, some basic and background information of natural fibers and geopolymer foams are reported. In most of the research, foams are produced either through chemical foaming with hydrogen peroxide or aluminum powder, or through mechanical foaming which includes a foaming agent. However, previous reviews have not sufficiently addresses the fabrication of geopolymer foams by syntactic foams. Finally, recent efforts to reduce the fiber degradation in geopolymer concrete are discussed along with challenges for natural fiber reinforced-geopolymer foam concrete.

The Effect of Lightweight Concrete Cores on the Thermal Performance of Vacuum Insulation Panels.

The performance of vacuum insulation panels (VIPs) is strongly affected by several factors, such as panel thickness, design, quality of vacuum, and material type. In particular, the core materials inside VIPs significantly influence their overall performance. Despite their superior insulation performance, VIPs are limited in their widespread use as structural materials, because of their low material strength and the relatively expensive core materials. As an alternative core material that can compensate these limitations, foamed concrete, a type of lightweight concrete with very low density, can be used. In this study, two different types of foamed concrete were used as VIP core materials, with their effects on the thermal behavior of the VIPs having been evaluated using experimental and numerical methods. To confirm and generate numerical models for VIP analysis, micro-computed tomography (micro-CT) was utilized. The obtained results show that insulation effects increase effectively when panels with lightweight concrete are in a vacuum, and both foamed concrete types can be effectively used as VIP core materials.

Interaction of Different Charged Polymers with Potassium Ions and Their Effect on the Yield Stress of Highly Concentrated Glass Bead Suspensions.

The interaction of different charged polymers, namely anionic polycarboxylate superplasticizer (PCE) and neutral polyethylene glycol (PEG) with potassium ions, and their effect on the yield stress of highly concentrated glass bead suspension (GBS), were studied under different concentrations of potassium ions ([K+]). It was found that, compared to the neutral PEG, the negatively charged PCE can be adsorbed on glass beads (GB), and then decreases the yield stress of GBS. The increasing concentration of free polymer in the interstitial liquid phase with the increased polymer dosage leads to the higher yield stress of GBS, which may be caused by the higher depletion force. In addition, this effect is also related to the charge density of the polymer and the [K+] in the solution. Along with the increase in [K+], the yield stress of GBS increases significantly with the addition of PCE, but this cannot be observed with PEG, which indicates that potassium ions can interact with negatively charged PCE instead of the neutral PEG. At last, the interparticle forces between two single GB with adsorbed PCE in solutions containing [K+] and PCE were measured by colloidal probe atomic force microscopy to better understand the interaction of the charged polymer with counterions.

Investigation of the Incompatibilities of Cement and Superplasticizers and Their Influence on the Rheological Behavior.

The rheological behavior of cement paste and the improvement of its flowability takes center stage in many research projects. An improved flowability can be achieved by the addition of superplasticizers (SP), such as polycarboxylate ethers (PCE). In order to be able to use these PCEs effectively and in a variety of ways and to make them resistant to changes in the environment, it is crucial to understand the influence of SPs on cement hydration. For that reason, the topic of this paper was the incompatibility of a specific SP and an ordinary Portland cement (OPC). The incompatible behavior was analyzed using rheological tests, such as the spread flow test and penetration test, and the behavior was compared by means of an ultrasound technique and explained by the phase content measured by in-situ X-ray diffraction (XRD) the heat evolution measured by calorimetry, and scanning electron microscope (SEM) images. We showed that the addition of the SP in a high dosage led to a prevention of the passivation of the most reactive and aluminum-containing clinker phases, aluminate and brownmillerite. This induced the aluminate reaction to take place in the initial period and led to an immediate stiffening of the cement paste and, therefore, to the complete loss of workability. The results showed that in addition to the ettringite, which began to form directly after water addition, hemicarbonate precipitated. The fast stiffening of the paste could be prevented by delayed addition of the SP or by additional gypsum. This fast stiffening was not desirable for SPs, but in other fields, for example, 3D printing, this undesirable interaction could be used to improve the properties of printable mortar.

Photocatalytic Activity and Mechanical Properties of Cements Modified with TiO2/N.

In this paper, studies of the mechanical properties and photocatalytic activity of new photoactive cement mortars are presented. The new building materials were obtained by the addition of 1, 3, and 5 wt % (based on the cement content) of nitrogen-modified titanium dioxide (TiO2/N) to the cement matrix. Photocatalytic active cement mortars were characterized by measuring the flexural and the compressive strength, the hydration heat, the zeta potential of the fresh state, and the initial and final setting time. Their photocatalytic activity was tested during NOx decomposition. The studies showed that TiO2/N gives the photoactivity of cement mortars during air purification with an additional positive effect on the mechanical properties of the hardened mortars. The addition of TiO2/N into the cement shortened the initial and final setting time, which was distinctly observed using 5 wt % of the photocatalyst in the cement matrix.

Relating Ettringite Formation and Rheological Changes during the Initial Cement Hydration: A Comparative Study Applying XRD Analysis, Rheological Measurements and Modeling.

In order to gain a deeper understanding of the rheological development of hydrating ordinary Portland cement (OPC) pastes at initial state, and to better understand their underlying processes, quantitative X-ray diffraction (XRD) analysis and rheological measurements were conducted and their results combined. The time-dependent relation between phase development and flow behavior of cement paste was investigated at two different temperatures (20 and 30 °C), over a period of two hours. Regarding the phase development during hydration, ettringite precipitation was identified as the dominant reaction in the first two hours. For both temperatures, the increasing ettringite content turned out to correlate very well with the loss of workability of the reacting cement paste. An exponential relationship between ettringite growth and flow behavior was observed that could be explained by applying the Krieger-Dougherty equation, which describes the influence of solid fraction on the viscosity of a suspension.

Influence of Nanosilica on Mechanical Properties, Sorptivity, and Microstructure of Lightweight Concrete.

This study presents the results of an experimental investigation of the effects of nanosilica (NS) on the strength development, transport properties, thermal conductivity, air-void, and pore characteristics of lightweight aggregate concrete (LWAC), with an oven-dry density <1000 kg/m3. Four types of concrete mixtures, containing 0 wt.%, 1 wt.%, 2 wt.%, and 4 wt.% of NS were prepared. The development of flexural and compressive strengths was determined for up to 90 days of curing. In addition, transport properties and microstructural properties were determined, with the use of RapidAir, mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) techniques. The experimental results showed that NS has remarkable effects on the mechanical and transport properties of LWACs, even in small dosages. A significant improvement in strength and a reduction of transport properties, in specimens with an increased NS content, was observed. However, the positive effects of NS were more pronounced when a higher amount was incorporated into the mixtures (>1 wt.%). NS contributed to compaction of the LWAC matrix and a modification of the air-void system, by increasing the amount of solid content and refining the fine pore structure, which translated to a noticeable improvement in mechanical and transport properties. On the other hand, NS decreased the consistency, while increasing the viscosity of the fresh mixture. An increment of superplasticizer (SP), along with a decrement of stabilizer (ST) dosages, are thus required.