•Highly reactive ashes from bamboo leaves (BLA) were prepared by autocombustion.•BLA presented a high silica content (74.23%) most of it was amorphous silica.•Pozzolanic reactivity of BLA was ...characterized by different procedures.•Replacement of OPC by BLA (5–30%) was achieved, yielding good mechanical performance.•BLA is a suitable and sustainable alternative for partial OPC replacement.
In the context of world concern with the environment, this study aims to characterize an auto-combustion produced bamboo leaf ash (BLA) by its pozzolanic behaviour, reactivity and its influence in the total porosity, pore size distribution, tortuosity and mechanical behaviour of cementitious matrices. The chemical and physical characterization of the BLA was carried using X-ray fluorescence, determination of amorphous silica content, X-ray diffraction, Fourier Transform Infrared Spectrophotometry (FTIR), laser granulometry and field emission scanning electron microscopy (FESEM). The assessed BLA is a siliceous material (74.23%) with an amorphous nature due to the amorphous silica content, which represents 92.33% of the total silica. The BLA was classified as highly reactive by assessing its pH and conductivity in a saturated calcium hydroxide (CH) medium for different proportions and temperatures. Frattini analysis, the study of CH:BLA pastes (Thermogravimetric analysis and FTIR) and Portland cement (OPC)/pozzolan pastes (Thermogravimetric analysis and FESEM) are in agreement with this classification. The replacement of OPC by BLA improved the mechanical behaviour of the cementitious matrices, as well their durability. All the mortars containing BLA presented very similar compressive strength to a control mortar (100% OPC) after only 3 days of curing and at the following tested curing ages: 7, 28 and 90 days. In the mercury intrusion porosimetry analysis, the pastes with 20 and 30% BLA content presented higher tortuosity or fewer connected pores than the control paste. Thus, the auto-combustion method proved to be successful and BLA is a suitable alternative for sustainable high-performance matrices.
Carbon Nano Fibre Reinforcements In Concrete Awan, Maqbool S; Ali, Arshad; S, Perviz ...
Indonesian journal of science and technology,
03/2019, Volume:
4, Issue:
1
Journal Article
Peer reviewed
Graphite nanomaterials offer distinct advantages over micro-scale reinforcing fibers in terms of engineering properties and geometric attributes. Thorough dispersion and effective interfacial ...interactions through proper functionalization of carbon nanofibers are the prerequisites for their effective use in high performance cementitious matrices. Furthermore, use of nano- and micro-scale reinforcements together provides reinforcing effects at different scales, thus rendering balanced gains in engineering properties of the matrix. However, their use in coarser high-performance matrices has not been evaluated thoroughly. The results show improvements in all flexural attributes, impact and abrasion resistance of DSP concrete with addition of 0.16 vol.% of oxidized and poly-acrylic acid physisorbed carbon nanofibers, over the corresponding properties of plain matrix. The results also point to synergetic effect of hybrid reinforcements in improving the various engineering properties of DSP concrete matrix, especially with low modulus polypropylene microfibers.
In this article, we made a comprehensive discussion of the advantages and disadvantages of cementitious matrices for low-and intermediate-level nuclear waste conditioning, reviewed the effects of ...water type (i.e., adsorbed water, trapped water, pore water in the layered structure, and pore water in a three-dimensional network) on H2 production. This research aims to determine the influence of various parameters on the radiolytic H2 production of cement paste, in order to adjust the cement formula and ensure the safety of long-term storage and disposal of cement matrices for low-and intermediate -level nuclear waste conditioning.
•Extruded vegetable fiber-cement composites are treated by supercritical carbonation.•Carbonation parameters and age of the composites are defined for optimized curing.•The best parameters: 24h of ...initial hydration and 1h of supercritical carbonation.•The bleached cellulose pulp is a key point for the composite mechanical behavior.
This paper presents a study of cellulose pulp fiber-cement composites subjected to supercritical carbonation at a very early age. The raw materials used for the creation of cementitious composite mixes include: Portland cement, limestone filler, and cellulose pulp. Composites were produced by a slurry vacuum dewatering process and subjected to curing conditions which studied the effect of supercritical carbonation concentration (0% and close to 100% of CO2), the effect of cellulosic pulp (unbleached or bleached), and durability. All samples were subjected to mechanical, physical, and microstructural tests. The initial period of thermal curing (varying from 24h to 48h) and exposure time to carbonation (from 1h to 2h), did not have a statistically significant effect on the mechanical performance of the composites. However, the flexural test results of carbonated composites reinforced with bleached pulp showed a statistically significant improvement when compared to unbleached pulp reinforcement (24% increased average modulus of rupture). Thus, for cementitious composites cured with supercritical carbonation, the use of bleached cellulosic pulp, 24h of thermal hydration and 1h in an environmental chamber provided the optimal curing conditions and the most desirable properties in this study.
In recent years, FRCM systems have become a preferred strengthening system in reinforced concrete structures together with masonry structures. The most important factor in the choice of FRCM as a ...strengthening system is its compatibility with concrete or masonry substrates. In addition, high fire resistance is an important factor in their preference. The components of FRCM composites are known to have high durability separately. However, the durability of composites, composed of a combination of fabric and matrices is still a matter of no detailed reported knowledge. In this experimental study, the durability properties of FRCM composites with lime matrix reinforced with glass and glass-polypropylene hybrid fabrics were investigated. Composite samples were subjected to tensile and bending tests before and after freeze thaw cycles. Load-deformation relations were obtained. As a result of the experimental study, the following results can be drawn: Following freeze thaw cycles, reduction in the bending and tensile performances of the biaxial glass fabric reinforced composite samples as well as matrix samples were obtained. A significant decrease of deformation capability was determined for biaxial glass fabric reinforced matrices and plain matrix.
This paper discusses the results of an experimental campaign on Composite-Reinforced Mortar (CRM) and Fabric-Reinforced Cementitious Matrix (FRCM) jacketing for the retrofit of stone masonry ...structures. Two double-leaf natural stone masonry piers were built with the same materials and geometry, including portions of adjoining spandrels above and below. Then CRM was applied to both faces of one of the specimens, using a natural hydraulic-lime mortar, glass-fiber-reinforced polymer meshes, and helicoidal steel connectors. The other pier, instead, was retrofitted with FRCM on both sides, combining a glass-fiber-reinforced cementitious mortar, bidirectional PBO textiles, and PBO connectors. Both specimens were subjected to the same vertical overburden load and to a quasi-static cyclic shear-compression test in double-curvature conditions, up to failure conditions. Different collapse mechanisms were triggered by the two retrofit systems, with flexure dominating the CRM specimen and shear controlling the FRCM one. The displacement capacity was enhanced by factors of about 2.5 in flexure and 3.0 in shear, compared to typical values for unstrengthened piers.
The problems generated by the ornamental stone extraction and processing industry caused by the inadequate disposal of this waste can negatively affect rivers, lakes, streams, and even natural water ...reservoirs. This study discusses and evaluates the potentiality and challenges of dimension stone waste (DSW) recycling generated from a Brazilian dimension stone processing industry in Portland cement formulations. Cement pastes with different amounts of DSW (10–30 wt.%), quartz (10 wt.%), and calcium carbonate (10 wt.%) were prepared and characterized in the fresh and hardened states. The results showed that DSW can be used in cement formulations, and its reactivity is governed by the size of the particles. With up to 10% DSW in place of cement, the samples had greater workability and compressive strength at 28 days compared with the reference mix. However, the strength was lower at early ages (3 and 7 days). When DSW is milled, the strength of the samples containing the waste matched the reference values at all ages, and the recommended replacement limit rose to 20%. On the other hand, the particle size reduction significantly decreased the workability. The use of DSW in cement-based formulations is encouraged due to the strong presence of stone processing and cement companies in Brazil and worldwide.
A cement-based matrix incorporating conductive materials such as carbon nanotubes and carbon nanofibers can have self-sensing capability. Both nanomaterials are characterized by excellent physical, ...mechanical and electrical properties. A disadvantage is that due to their hydrophobic nature it is very difficult to ensure uniform dispersion throughout the cementitious matrix. To overcome this problem a new nanomodified cement containing in-situ attached CNFs was developed leading to a very homogenous and conductive binder matrix. This study aimed to compare the piezoresistive responses of two types of matrixes, one based on the nanomodified cement and the second containing multi-walled carbon nanotubes. Several mortars were prepared containing either MWCNTs or the nanomodified cement, which partially replaced the untreated cement. The effective amount of the carbon nanomaterials was the same for both types of mixes and ranged from 0 wt.% to 0.271 wt.%, calculated by the all binder weight. Changes in the electrical properties were determined while applying compressive load. The results showed that the binders based on the nanomodified cement have significantly better load sensing capabilities and are suitable for applications in monitoring systems.
Retrofitting of structures has become an inevitable in the construction activity. It is necessary to improve the load carrying capacity of the damaged structural members and it could be achieved by ...strengthening externally, through a jacketing technique. Ferrocement Jacketing is preferred as one of the acceptable and viable way for strengthening of structural members. A laboratory experimental investigation was carried out to develop a rich and flowable nano silica based cementitious matrices which could be employed for repair and retrofit the structures. An investigation on nano based cement composite was conducted to obtain the strength and durability properties. Results indicated that the flowable nano silica cementitious mortar showed a significant increase in compressive strength in the range of 7.5–50% than that of the control cement mortar. The splitting tensile strength of cementitious matrices increased from 2.28 to 3.98 MPa. Nano silica with 3% showed a lowest rate of water absorption as compared to all other mortar specimens. From the obtained results, it is revealed that 3% of nano silica could be used as a flowable nano SiO2 based mortar, as it showed a better performance both in strength and durability aspects. Ferrocement jacketed columns has a higher load carrying capacity of about 40% with a higher axial displacement of 95% as compared to the control column. A ductile mode of failure was observed in all the ferrocement jacketed columns.
Nowadays the Laboratory research became assumed to enlarge high rich cementitious matrices for casting thin ferrocement laminates perfectly fitted for structural restore retrofit. The developed high ...rich mortar matrices contain diverse combos of silica fume and Metakaolin, and offer a great balance among flowability and rich. The matrices evolved have a 28-days compressive rich variety from 48 to 64 MPa with an equivalent float range from 129% to 138%. The different high rich mortar turned into used in generating ferrocement jackets for cylindrical stubs look at its performance of the stubs are subjected to axial stresses. The progressive excessive rich ferrocement laminates seem to provide the considerable increase and increasing in the load carrying potential, lateral and ductility. In positions of ferrocement efficiency, the stubs enveloped with the laminates containing 2 and 4 layers of welded wire meshes (WWM), presented approximately 61% and 31% increase in axial stress respectively, with a corresponding increase in axial stress of about 33% and 71% respectively. Based on the outcomes of the present research, high rich ferrocement laminates containing a particular variety of welded wire meshes may be taken into consideration as a promising material for maintenance and recovery of concrete structures, particularly when using flowable high rich mortar with WWM complying with ferrocement specifications.
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