Microparticles, microspheres, and microcapsules are widely used constituents of multiparticulate drug delivery systems, offering both therapeutic and technological advantages. Microparticles are generally in the 1–1000 µm size range, serve as multiunit drug delivery systems with well-defined physiological and pharmacokinetic benefits in order to improve the effectiveness, tolerability, and patient compliance. This paper reviews their evolution, significance, and formulation factors (excipients and procedures), as well as their most important practical applications (inhaled insulin, liposomal preparations). The article presents the most important structures of microparticles (microspheres, microcapsules, coated pellets, etc.), interpreted with microscopic images too. The most significant production processes (spray drying, extrusion, coacervation, freeze-drying, microfluidics), the drug release mechanisms, and the commonly used excipients, the characterization, and the novel drug delivery systems (microbubbles, microsponges), as well as the preparations used in therapy are discussed in detail.

Microparticles, Microspheres, and Microcapsules for Advanced Drug Delivery

A review on concrete surface treatment Part I: Types and mechanisms

Thermal properties and applications of microencapsulated PCM for thermal energy storage: A review

Using recycled aggregate s from construction and demolition waste can preserve natural aggregate resources, reduce demand of landfill, and contribute to sustainable built environment. This study provides a comprehensive review on recycled aggregate (RA) and recycled aggregate concrete (RAC) regarding their history, recycling, reuse and manufacture process, inherent defects (e.g. existing of additional interfacial transition zones in RAC), and materials properties. Specifically, these properties of RAC include fresh concrete workability, physical and chemical properties (i.e. density, carbonation depth, and chloride ion penetration), mechanical properties (i.e. compressive, flexural, and splitting tensile strength as well as elastic modulus), and long-term performance (i.e. freezing-thawing resistance, alkali-silica reaction resistance, creep, and dry shrinkage). On top of that, methods for improving RAC mechanical properties and long-term performance are summarized and categorized into three groups, i.e. (1) reduction of recycled aggregate porosity, (2) reduction of old mortar layer on recycled aggregate surface, and (3) property improvement without recycled aggregate modification (i.e. different concrete mixing design and addition of fibre reinforcement). Next, current regression-based models and artificial intelligence models on the prediction of compressive strength, modulus, and compressive stress-strain curves of RAC are reviewed and the ir limitations of those models are discussed. Furthermore, the state-of-the-art RAC applications are presented. Additionally, challenges of RAC application are reviewed taking China as an example. The link between material from CDW and EU green policy are discussed by analysing the previous research projects funded by European Commission. Finally, future perspectives of RAC research focus are discussed, i.e. development of “green” treatment methods on recycled aggregate s , further direction on nanoparticle application in RAC, and the establishment of database for RAC strength prediction.

A Comprehensive Review on Recycled Aggregate and Recycled Aggregate Concrete

Fiber-reinforced polymer (FRP) composites are extensively used in advanced concrete technology given their superiority over traditional steel reinforcements. These materials possess high strength capacity and corrosion resistance and can be employed as the main reinforcements in combination with adhesives and anchorages to strengthen reinforced concrete (RC) beam members. RC beams are designed to provide resistance against flexure , shear, torsion, fatigue, impact, and blast loading. The strength and ductility of RC beams can be improved via FRP strengthening techniques with a combination of fibers. The overall strength of FRP composites in RC beams is controlled by fiber type , configuration, and materials and strengthening technique. This review focuses on the characteristics and behaviors of FRP-strengthened RC beams under various loading conditions. It also presents the typical FRP composites with the properties, features, and applications. This review demonstrates that FRP composites can be used to recover the strength of damaged and corroded beams and exhibit good durability and insulation performance. It also provides a straightforward perspective of strengthening and retrofitting techniques for RC beams using FRP composites.

Strengthening of reinforced concrete beams by using fiber-reinforced polymer composites: A review

An environmentally friendly method to improve the quality of recycled concrete aggregates

Internal curing of high performance concrete using cenospheres

Phase change materials (PCMs) can enhance the building energy efficiency through thermal energy storage and thermal regulation. Microencapsulated PCMs (MEPCMs) provide a better utilization of PCMs with building materials. This study proposes a novel method to encapsulate PCMs into cenospheres which are hollow fly ash particles generated in coal burning power plants with size ranging from a few micrometers to hundreds of micrometers. The shell of the cenosphere inherently has some small pores which are sealed by a thin layer of glass-crystalline film. By removing this film through chemical etching, these holes can be exposed, providing paths for PCMs moving into the internal void of cenospheres. A thin layer of silica is coated on the PCM loaded cenospheres to prevent the possible leakage of liquid PCMs. The produced PCM microcapsules are referred to as CenoPCM, which can be directly added into traditional construction and building materials such as concrete to produce thermally active concrete. Prototype thermally active cement mortar integrated with the produced CenoPCM capsules have also been manufactured and characterized for its mechanical and microstructural properties. The characterizations showed that there was only minor reduction in strength and the mortar remained strong enough for building application. From this work, it is found that the produced CenoPCM capsules have great potential to be added into construction materials for reducing energy consumptions in buildings.

/pdf/integrating-phase-change-materials-into-concrete-through-1w9p03lql6.pdf

Integrating phase change materials into concrete through microencapsulation using cenospheres

This study explores a novel beneficial utilization of CO2 in ordinary Portland cement (OPC) based concrete. In existing studies, CO2 is mainly added into concrete through accelerated carbonation of fresh or hardened concrete, which is limited by the low diffusion of CO2 into the concrete. In addition, a high CO2 concentrated environment is needed to carbonate the concrete, making the existing methods only applicable to pre-cast concrete. Aiming to eliminate these limitations in the existing methods, this study proposes to directly add gaseous CO2 into fresh concrete mix as an admixture through a two-step mixing approach, pre-carbonation method. In this method, CO2 is first absorbed into a slurry of calcium-rich cementitious material in the first step, and then blended with the rest ingredients to produce concrete in the second step. This method can in-situ produce nano to sub-micro CaCO3 particles in fresh concrete, providing extra heterogenous nucleation sites for the hydration of OPC. Therefore, the hydration of OPC can be greatly improved, as evidenced by the calorimetry testing result. The addition of CO2 also produces more ettringite in the produced mortar, as revealed by X-Ray Diffraction and Thermogravimetric analysis. As a result, the overall volume of the hydration products of the OPC is increased, leading to denser microstructure of the mortar samples. For these reasons, the compressive strength of the cement mortar samples can be significantly improved by the proposed method.

Jialai Wang

Papers

An environmentally friendly method to improve the quality of recycled concrete aggregates

Internal curing of high performance concrete using cenospheres

Integrating phase change materials into concrete through microencapsulation using cenospheres

Carbon dioxide as an admixture for better performance of OPC-based concrete

Surface treatment of concrete bricks using calcium carbonate precipitation