Durability of Concrete with Partial Replacement of Portland Cement by Incorporating Reactive Magnesium Oxide and Fly Ash.

In this research, the durability performance of sustainable concrete with the incorporation of reactive magnesium oxide (MgO) and fly ash (FA) was evaluated. The partial replacement of cement with these two materials is an appealing solution for the construction sector due to sustainability benefits and shrinkage reduction. The incorporation of FA by partial replacement of cement was carried out at 0%, 15% and 30%.

Improvement of the Quality of Recycled Concrete Aggregate Subjected to Chemical Treatments: A Review.

The main factor that alters the quality of recycled concrete aggregate (RCA) is the paste adhered to the natural aggregate (NA). Since it causes weakening of the interfacial transition zone (ITZ) between the aggregate and the cementitious paste, it becomes a determining factor for the mechanical behavior of concrete. It turns out that it is critical to enhance this interface by improving the surface of the aggregate or by removing the paste adhered to the NA.

Eurocode Shear Design of Coarse Recycled Aggregate Concrete: Reliability Analysis and Partial Factor Calibration.

This paper contributes to the definition of design clauses for coarse recycled aggregate concrete. One of the main reasons for scepticism towards recycled aggregate concrete is the perceived notion that the heterogeneity of recycled aggregates may increase the uncertainty of the behaviour of concrete. Therefore, the paper uses structural reliability concepts to propose partial factors for recycled aggregate concrete's design for shear failure.

Performance of Mortars with Commercially-Available Reactive Magnesium Oxide as Alternative Binder.

This paper intends to analyze the performance of mortars with reactive MgO, as a sustainable alternative to cement. Six different MgOs from Australia, Canada, and Spain were used in the production of mortars as partial substitutes for cement, namely 5%, 10%, 15%, 20%, and 25% (by weight). MgOs with different levels of reactivity were used to analyze its influence on the performance of MgO mortars.

Magnesia (MgO) Production and Characterization, and Its Influence on the Performance of Cementitious Materials: A Review.

This paper presents a literature review concerning the characteristics of MgO (magnesium oxide or magnesia) and its application in cementitious materials. It starts with the characterization of MgO in terms of production processes, calcination temperatures, reactivity, and physical properties. Relationships between different MgO characteristics are established.

On the Development of a Technical Specification for the Use of Fine Recycled Aggregates from Construction and Demolition Waste in Concrete Production.

The possibility of using recycled aggregates from construction and demolition waste (CDW) in concrete is rather widely agreed upon when it comes to the use of coarse recycled aggregates. However, this is not the case when fine recycled aggregates (FRA) are considered, as it is deemed that these seriously impair the behaviour of concrete. Hence, this work presents a technical specification proposal for the use of FRA from CDW in concrete, to attempt to fill this gap in legislation.

Microstructural Features of Recycled Aggregate Concrete: From Non-Structural to High-Performance Concrete.

The use of concrete-recycled aggregates to produce high-performance concrete is limited by insufficient correlation between resulting microstructure and its influence on mechanical performance reproducibility. This work addresses this issue in a sequential approach: concrete microstructure was systematically analyzed and characterized by scanning electron microscopy and results were correlated with concrete compressive strength and water absorption ability. The influence of replacing natural aggregates (NA) with recycled concrete aggregates (RCA), with different source concrete strength levels, of silica fume (SF) addition and of mixing procedure was tested.

Probabilistic Conversion of the Compressive Strength of Cubes to Cylinders of Natural and Recycled Aggregate Concrete Specimens.

This paper investigates the effect of recycled coarse aggregate incorporation on the relationship between 150 mm cubic and Փ 150 mm cylindrical compressive strength (the reference strength of standards) by comparing data from recycled and natural aggregate concrete compositions in which both cubes and cylinders were tested. A conversion factor from cubic to cylindrical strength is proposed in two versions: A deterministic and a probabilistic one. Such factor has not been studied before and researchers have been converting cubic data as if natural aggregate concrete were tested.

Increased Durability of Concrete Made with Fine Recycled Concrete Aggregates Using Superplasticizers.

This paper evaluates the influence of two superplasticizers (SP) on the durability properties of concrete made with fine recycled concrete aggregate (FRCA). For this purpose, three families of concrete were tested: concrete without SP, concrete made with a regular superplasticizer and concrete made with a high-performance superplasticizer. Five volumetric replacement ratios of natural sand by FRCA were tested: 0%, 10%, 30%, 50% and 100%.

Microstructure of Concrete with Aggregates from Construction and Demolition Waste Recycling Plants.

This paper intends to analyze the microstructure of concrete with recycled aggregates (RA) from construction and demolition waste from various Portuguese recycling plants. To that effect, several scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were performed. Various concrete mixes were evaluated in order to analyze the influence of the RA's collection point and consequently of their composition on the mixes' characteristics.

Microstructural characterization of concrete prepared with recycled aggregates.

Several authors have reported the workability, mechanical properties, and durability of concrete produced with construction waste replacing the natural aggregate. However, a systematic microstructural characterization of recycled aggregate concrete has not been reported. This work studies the use of fine recycled aggregate to replace fine natural aggregate in the production of concrete and reports the resulting microstructures.

Gastrobronchial fistula after sleeve gastrectomy and gastric bypass: endoscopic management and prevention.

Gastrobronchial fistula (GBF) is a serious complication following bariatric surgery, whose treatment by thoracotomy and/or laparotomy involves a high morbidity rate. We present the outcomes of endoscopic management for GBF as a helpful technique for its healing process. This is a multicenter retrospective study of 15 patients who underwent gastric bypass (n = 10) and sleeve gastrectomy (n = 5) and presented GBF postoperatively (mean of 6.

Small erosion of adjustable gastric band: endoscopic removal through incision in gastric wall.

The erosion of a laparoscopic adjustable gastric band (LAGB) can cause pain that is not controlled by analgesics. In such cases, early endoscopic removal may be indicated, but only when gastric penetration is greater than 50%. We report the case of a patient with severe shoulder pain due to a small area of LAGB erosion, which was treated with early endoscopic removal through an incision in the gastric wall.

Treatment of ring slippage after gastric bypass: long-term results after endoscopic dilation with an achalasia balloon (with videos).

Background: Silastic rings are used in gastric bypass procedures for the treatment of obesity, but ring slippage may lead to gastric pouch outlet stenosis (GPOS). Conventional management has been ring removal through abdominal surgery.

Objective: To describe a novel, safe, minimally invasive, endoscopic technique for the treatment of GPOS caused by ring slippage after gastric bypass.

Laparoscopic greater curvature plication: initial results of an alternative restrictive bariatric procedure.

Background: Vertical sleeve gastrectomy (VSG) is a surgical technique that involves resection of a significant portion of the stomach. This surgery is sometimes associated with gastric leaks, which can be difficult to treat. The present study reports findings from laparoscopic greater curvature plication (LGCP), which is an alternative bariatric procedure similar to VSG but without the need for gastric resection.

Endoscopic removal of eroded adjustable gastric band: lessons learned after 5 years and 78 cases.

Background: One of the complications of laparoscopic adjustable gastric banding is intragastric erosion, leading to a revisional procedure to remove the band. Our aim was to present the procedure and results of endoscopic band removal in a 5-year multicenter experience from the Gastro Obeso Center and Universidade de São Paulo, São Paulo, and Universidade Federal de Pernambuco, Recife, Brazil.

Methods: From 2003 to 2008, 82 patients were diagnosed with band erosion.

Translumenal endoscopic drainage of abdominal abscess due to early migration of adjustable gastric band.

We describe the case of early band migration that developed into intraabdominal infection treated by natural orifice translumenal endoscopic surgery. A 40-year-old man was seen 4 years after gastric band placement. He complained of epigastric pain and fever.

Hypovolemic shock due to intragastric migration of an adjustable gastric band.

Migration of the adjustable gastric band (AGB) is a serious complication which usually does not require emergency treatment, except when there is a risk to life. We report a 30-year-old patient who presented with syncope, melena and hypovolemic shock due to the intragastric erosion of an AGB, 13 months after laparoscopic band placement. The diagnosis of migration had been made 7 months after placement, and bleeding only occurred 6 months later.