Biopolymers are very favorable materials produced by living organisms, with interesting properties such as biodegradability, renewability, and biocompatibility. Biopolymers have been recently ...considered to compete with fossil-based polymeric materials, which rase several environmental concerns. Biobased plastics are receiving growing interest for many applications including electronics, medical devices, food packaging, and energy. Biopolymers can be produced from biological sources such as plants, animals, agricultural wastes, and microbes. Studies suggest that microalgae and cyanobacteria are two of the promising sources of polyhydroxyalkanoates (PHAs), cellulose, carbohydrates (particularly starch), and proteins, as the major components of microalgae (and of certain cyanobacteria) for producing bioplastics. This review aims to summarize the potential of microalgal PHAs, polysaccharides, and proteins for bioplastic production. The findings of this review give insight into current knowledge and future direction in microalgal-based bioplastic production considering a circular economy approach. The current review is divided into three main topics, namely (i) the analysis of the main types and properties of bioplastic monomers, blends, and composites; (ii) the cultivation process to optimize the microalgae growth and accumulation of important biobased compounds to produce bioplastics; and (iii) a critical analysis of the future perspectives on the field.
With the availability of commercial Natural cements (NC) for the conservation purposes raises a fundamental question about the compatibility between historic and repair mortars. The properties of ...Natural cements are dependent on the geological location of the raw material extraction and also on the production parameters, both having an impact on the final properties of the mortars produced from each distinct. Therefore, the significance of preservation of 19th and 20th century heritage and selection of the proper binder compatible with the original materials necessitate the study of existing NCs, that nowadays are produced by several manufacturers. This work provides a complex study of the mortars prepared from three NCs available in the market: Groupe Prompt Vicat, France (NCPV); Cemento Collet Marfil (NCM) and Cemento Natural Tigre (NCT), both from Spain. Various mortar sets based on individual NC containing different binder/aggregate ratios and air lime additions were analyzed after 28, 60, and 90 days of curing with the focus on their mineralogical composition (XRD), morphology (SEM), mechanical (flexural and compressive strength), and physical properties such as water absorption by capillarity, water vapor permeability, and water vapor diffusion resistance. Mortars prepared from NCPV, NCM, and NCT show distinct physical-mechanical properties with varying binder/aggregate ratio and air lime addition. This study shows that the NC variability should be taken into consideration when selecting materials for the conservation and rehabilitation of historic renders and plasters. Based on the comparison with original NC mortars, several NC mortars developed in this study show adequate properties for conservation of the buildings from late 19th and early 20th century in terms of compressive strength (>12 MPa), water absorption by capillarity (<20 kg·m−2·h−0.5), water vapor permeability (<4 × 10−10 kg·s−1·m−1·Pa−1), and water vapor diffusion resistance (<28) values.
The popularity of natural cement (Roman cement) in buildings from the late 19th and the beginning of the 20th century and the high diversity of characteristics of natural cement demand research of ...mortar and binders used in the buildings of this period in Portugal. Understanding the type of binder used in the historic buildings will help the project/intervention team to make the best decisions in terms of the development of compatible mortars for historical conservation purposes. Casa Barbot is one of the Art Nouveau examples of the beginning of the 20th century in Portugal. The garden of this building is characterized by peculiar elements in terms of materials and architecture. Full characterization of the mortars employed in the construction of this building as well as identification of the used binder is the main objective of this study. The study comprises a wide range of laboratory characterization techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD), petrography, open porosity, density, water absorption by capillarity, and compressive strength. The results show the diversity of compositional characteristics in the mortars used in the decorative elements in the period garden of Casa Barbot. All mortars are composed of Portland cement with a mix of additives such as blast furnace slag, limestone filler, air lime, and the occasional presence of charcoal. The results raise doubt about the use of natural cement as stated in the historical documents. This study will broaden the scientific knowledge of the materials of that period in Portugal to provide a comprehensive plan for the preservation of historical buildings.
Waste valorisation as secondary or alternative raw materials in several sectors products and processes has been an important way to implement a more sustainable and circular way to manage the ...efficient use of natural resources. This action contributes not only to save natural resources but also to prevent sending large amounts of wastes, some of them dangerous, to landfill disposal, creating a major environmental, economic and social impact. To promote circular economy, this work attempts to demonstrate the environmental gains in a competitive way, by bringing together in an industrial symbiosis action, two large producing sectors (the pulp and paper industry and concrete construction sector), which are also able to consume significant amounts of resources and to generate large amounts of wastes. A sustainability evaluation based on a life cycle and circular approach is presented and discussed using a simple case study performed at real industrial scale. The lime ash waste from the pulp and paper industry is used to replace 100% of the natural filler used in precast concrete production and the impacts and benefits from the technical, environmental, economic and social level were assessed. It was demonstrated that this simple action causes positive impacts in the evaluated dimensions of sustainability without causing any changes in production time and causes no degradation on relevant concrete properties.
•Biochar factors affecting the performance of cementitious materials are reviewed.•Effect of biochar addition on the properties of cement composites is reviewed.•A roadmap is provided for the ...selection of biochar into the cement composites.•An optimum biochar dosage as filler and cement replacement is introduced.
Increasing cement production in construction sector and waste generation in industrial sectors are of the major sources of CO2 emission. For decades, it has been the concern of environmentalists to convince constructors and researchers to find sustainable solutions targeting aforementioned problems. The attempts focused on identification of wastes to be successfully complied with construction materials. Biochar has recently received attention due to several environmental and technological advantages, shortly include carbon sequestration, low thermal conductivity, chemical stability and low flammability. For this reason, biochar is recognized as an efficient candidate for cement or lightweight aggregates replacement in building materials. Biochar addition could result in a reduction of capillary absorption in mortar paste. Besides, its addition accelerates cement hydration and restricts shrinkage cracking in cement mortar. The present review categorizes all the biochar critical features affecting the performance of cementitious materials. The effect of biochar addition as filler and cement replacement on the workability, hydration, mechanical and transfer properties of cement paste/composites is reviewed in this paper. From the data collection, an optimum biochar content around 2% is shown to contribute to the improvement of mechanical properties. The gaps in the literature are identified and the future research plans are proposed.
Incorporation of biochar in cementitious materials is a promising solution in the mitigation of environmental pollutants by partially cutting off the consumed ordinary Portland cement and reducing ...the amount of waste disposal in landfills. This work studied the partial replacement of cement by biochars having a different chemical composition and its effect on the performance of cement mortars. The feedstocks for biochar production were selected from biomass wastes produced in agro-industrial and forestry sectors in Portugal. They included olive stone, rice husk and wood chips from residual forest biomass. Biochars were produced at 500 ℃ using a slow pyrolysis process. The biochars were added at different cement replacement rates; 0.5, 1, 2 and 4 wt% of cement weight. XRD and TGA were used to elaborate the effect of biochar on the hydration products. Effect of biochar addition on the capillary water absorption, compressive and flexural strength of cement mortar was analyzed. The results suggested that the biochars contributed to the promotion of hydration products. Cement replacement with 4 wt% olive stone and rice husk biochars was associated with a slight increase of 28-days compressive strength. Rice husk biochar showed the best long-term mechanical performance due to its pozzolanic reaction in the matrix. No significant changes were observed in the water absorption of cement mortar after the addition of 4 wt% biochar as cement replacement. The research outcomes suggested the beneficial effect of cement replacement with biochars from olive stone and rice husk up to 4 wt% with comparable properties.
Textile Reinforced Mortars (TRMs) have received extensive attention for externally bonded reinforcement of historical and masonry structures. Despite this recent attention, the available information ...on the test methods and mechanical performance of TRMs at different scales are limited. Extensive experimental results are still necessary for development of design formulas and application guidelines. This paper presents a multi-level experimental investigation on the performance of Steel Reinforced Grouts (SRGs) as a common TRM type. The focus is not only on the mechanical characterization but also the test methods and practical challenges. The tests include materials characterization, fiber-to-mortar bond characterization, tensile tests on TRM composite, and TRM-to-masonry bond characterization tests. The tests are performed on three different SRG systems made of pozzolanic lime-based and geopolymeric-based mortars as sustainable matrices for strengthening and restoration applications.
Display omitted
•A multi-level experimental characterization of steel reinforced grouts is presented.•The tests include mechanical characterization of materials, bond behaviour and the composite system.•Two lime-based and one geopolymeric-based mortar are used as the matrix of the SRG system.•A critical discussion is given on the test methods and procedures as well as the obtained results.
Externally bonded reinforcement (EBR) of masonry structures with Fiber Reinforced Polymers (FRPs) has received extensive attention during the last years. Despite the vast literature on mechanics and ...short-term performance, the durability and long-term performance of these systems still remain insufficiently studied. Structures are subjected to harsh environments such as coupled temperature and moisture variations (hygrothermal conditions) during their service life. A clear understanding on the performance of the strengthening system under these conditions is critical at the design stage.
This paper presents an experimental investigation on the effect of long-term hygrothermal conditions on FRP-strengthened masonry components. The focus is on the interfacial bond behavior and materials mechanical properties. The effect of mechanical surface treatment on the bond durability is also investigated.
This study presents an investigation addressing the effect of environmental conditions on the thermal properties of a cold curing epoxy resin used in repair and strengthening of masonry structures. ...The exposure conditions consist of laboratory indoor conditions (IC), long-term water immersion (WI), hygrothermal exposure (HG) and outdoor real exposure conditions (OC). The changes in the glass transition temperature, Tg, relaxation enthalpy and enthalpy peak temperature are monitored with Differential Scanning Calorimetry (DSC). Different measurement techniques for obtaining the Tg from DSC curves are also presented and discussed. The results showed a reduction of Tg in WI tests due to plasticization, which reversed at long-term periods. In HG conditions, post-curing of epoxy resin led to an increment of Tg. It was observed that the changes of Tg in OC conditions in the studied environment have a good correlation with the moisture absorption level and the obtained results from WI tests.
•The bond behavior in NSM system was investigated by testing 36 FRP-strengthened bricks.•A new test setup was developed to avoid the pre-compression load before test.•Majority of specimens failed at ...the adhesive-to-brick interface.•Accuracy of existing bond prediction models was evaluated using a large database.•A fracture-based model was proposed in this study to predictthe bond strength.
Near Surface Mounted (NSM) reinforcement is an interesting technique for seismic strengthening of masonry and historical structures. Despite having several advantages compared to conventional techniques, little attention has been given to understanding the involved mechanisms (such as bond behavior) in the performance of masonry components strengthened with this reinforcement technique. This study presents an experimental and analytical investigation on the bond performance of NSM-strengthened masonry bricks aiming at filling the existing gaps in the available experimental results in the literature. The main focus is on the effect of test setup and bond length, but attention has also been given to the groove size and loading regime effect on the bond performance. The accuracy of the existing bond strength prediction models is also assessed and the required modifications are proposed.
PDF
