Academic literature on the topic 'Experimental investigation, Fibre reinforcements, Masonry, Durability'

Masonry made with soft clay brick is commonly used in gravity load bearing of construction in India. The masonry piers and walls typically fail by vertical splitting. The purpose of this study is to improve the strength of masonry columns under compression using wrapping for additional confinement. The compressive load carrying performance and capacity of masonry columns wrapped with fiber reinforced composites in organic and inorganic matrixes are compared. For the purpose of overall improvements in cost and durability, glass and basalt fiber reinforcement is used. 30-40% improvement in the compressive performance of masonry prisms was achieved for both Organic and Inorganic matrixes. However, the specimens with inorganic matrixes were found to exhibit higher ductility compared to organic matrixes. Glass fibers were found to be more effective in wrapping masonry specimens compared to Basalt fiber specimens owing to its higher fiber count per unit length. Analytical models for predicting the compressive capacity of masonry columns with wrapping are verified against the experimental results.

Nowadays, the solution of durability problems of existing buildings has a key role in civil engineering, in which there is an ever-increasing need for building restorations. Over the past 50 years, there is a growing interest in a new composite material, fibre-reinforced polymer (FRP), suitable for increasing the resistance and the stability of existing buildings and, consequently, for extending their service life. In this context, the effectiveness of the strengthening system is related to the bond behaviour that is influenced by several parameters such as bond length, the stiffness of the reinforcement, the mechanical properties of the substrate, environmental conditions, etc. This paper aims to analyse the main experimental results from shear tests performed on two kinds of masonry substrates and different types of FRP reinforcements. The purpose is to highlight the role played by many parameters to the bond behaviour of these systems: the mechanical properties of substrates; the stiffness of reinforcements; the type of supports (i.e., unit or masonry unit). The obtained experimental results underlined that the specimens realised with masonry unit show an increase in debonding load and different stress transfer mechanisms along the bonded length with respect to the specimens with a unit substrate. The analysis of the data revealed that the presence of mortar joints cannot be neglected because it influences the interface global performance.

Fabric Reinforced Cementitious Matrix (FRCM) and Composite Reinforced Mortar (CRM) are used in structural strengthening of heritage masonry construction due to their high compatibility with the substrate. Due to the interaction between the reinforcement fibers, made by glass or basalt, and the alkaline matrix, durability problems may be met in the field. In this study a large experimental program is presented and discussed in a synthetic form, with reference to glass fibers reinforcements used in FRCM and CRM systems. Ageing conditions were reproduced in a laboratory environment by immersing the glass-fibre reinforcements into three different solutions. The artificial alkaline solutions used in this study simulated the chemical aggression of lime mortar matrix, Portland cement matrix and standard alkaline solutions (ASTM standard). Four conditioning periods were applied as ageing protocol: 500hrs, 1000hrs, 2000hrs and 3000hrs. Accelerating effects were produced by increasing the temperature during ageing, from 23°C to 40°C and 70°C. The residual mechanical properties and physical damage observed by using Scanning Electronic Microscopy (SEM) are discussed in the paper. The decay of the mechanical properties is highlighted in terms of tensile strength on the whole FRCM strengthening system and for each of the constituents.

Progress in engineering research has shifted the interest from traditional monolithic materials to modern materials such as fibre reinforced composites (FRC). This paradigm shift can be attributed to the unique mechanical characteristics of FRCs such as high strength to weight ratio, good flexural strength, and fracture toughness. At present, synthetic composites dominate the automotive, aerospace, sporting, and construction industries despite serious drawbacks such as costly raw materials, high manufacturing costs, non-recyclability, toxicity, and non-biodegradability. To address these issues, naturally occurring plant fibres (such as jute, hemp, sisal) are being increasingly researched as potential reinforcements for biodegradable or non-biodegradable polymer matrices to produce environmentally friendly composites. In this study, sisal fibres were selected owing to their low production costs, sustainability, recyclability, and biodegradability. The hydrothermal ageing and mechanical characteristics of sisal fibre-reinforced epoxy (SFRE) composites were determined and compared with glass fibre-reinforced epoxy (GFRE) synthetic composites. Moreover, a first-of-its-kind numerical model have been developed to study the hydrothermal ageing and mechanical characteristics of SFRE, along with GFRE, using ANSYS software. Moreover, microstructural analysis of flexural tested GFRE and SFRE samples were carried out to identify the microstructural properties of the composites. Both experimental and numerical results exhibited an influence of short- or long-term hydrothermal treatment on the flexural properties of glass and sisal fibre-based composites. In the case of GFRE, the moisture uptake and fibre-matrix de-bonding existed, but it is less severe as compared to the SFRE composites. It was found that the dosage of sisal fibres largely determines the ultimate mechanical performance of the composite. Nonetheless, the experimental and numerical flexural strengths of SFRE were comparable to GFRE composites. This exhibited that the SFRE composites possess the potentiality as a sustainable material for advanced applications.

This dissertation is the product of a research project which focused on the behaviour of Fibre Reinforced Cementitous Matrix (FRCM) for the reinforcement of masonry structures in service conditions and its latest applications. The research was conducted both experimentally and analytically, first considering the results from a preliminary state of the art investigation and then providing an original contribution regarding the durability and new applications of FRCM. Based on the literature and existing regulations on fibre reinforcements for masonry structures and their durability in service conditions, it appears clear that although in the past two decades much work has been done on this subject, still very little is known. Specific conversion factors are provided in a Bulletin on Technical Recommendations for Constructions composed by the Italian National Research Council pertaining to service conditions and Fibre Reinforced Polymers (FRP). Although there are currently no specific guidelines regarding the environmental effects on FRCM, these are to be carefully considered and evaluated before designing these systems. The first step towards a better understanding of the physical behaviour of such systems is through experimentation, but experimental investigations on FRCM systems when subjected to environmental conditions are virtually non-existent. Hence the original contributions of this work, as resulting from four experimental campaigns. The methodology of the procedure for durability testing on FRCM analysed in the present dissertation was derived from the literature review of the testing performed on FRP systems. The first two campaigns are directed toward investigating the behaviour of fibres combined with cementitious matrices after they have been subjected to artificial ageing. In the first campaign freeze/thaw cycles are carried out whereas in the second campaign specimens are subjected to wet/dry cycles in sodium chloride solutions. The third and the fourth campaigns regard durability testing on masonry reinforced FRCM subjected to wet/dry cycles, specifically on small pilasters reinforced through glass and steel fibres, and masonry panels reinforced with a new FRCM technique known as Reticolatus. For the numerical analysis of masonry panels with the reticolatus technique a non-linear procedure has been proposed, which implements the non-linearity of the material in an iterative numerical technique correcting the elastic-linear solution after having evaluated it, step by step, pursuing the final goal of respecting congruence. Every mortar joint is represented in discrete form as a curtain of trusses positioned perpendicularly to the interface of the block and one truss placed in a tangential direction. The trusses perpendicular to the interface of the blocks are able to transmit only compressive strength and therefore the deformations are comparable to elastic cushions interposed between the masonry blocks. The reinforcement is constituted by a mesh made by a steel wire of limited section (ca 1mm) in such a way that it can pass through the scraped mortar joints and the clutch in the steel bars inserted in the panel. Since the section of the wire is limited it can sustain only tensile strength, and therefore the reinforcement is modelled as a sequence of trusses connected to each other and fixed at the ends on the nodes. FEM modelling was used and an iterative calculus process was proposed for the numerical analysis of this specific type of FRCM. Three model panels were calculated with the proposed iteration model, with random positioning of the reinforcement wire, in order to check the method of the analysis. All model panels were subjected to a diagonal compression impressed only on the upper right corner and then tested. The second step of the numerical analysis was to recalculate the panels using the modified strength values found from the experimental campaigns described above. The conclusions drawn about FRCM reinforcing systems for masonry in this dissertation are able to answer questions about these reinforcements that are important in the renovation and restoration of historical structures, such as how long the reinforcement will be able to function effectively and how much time passes between onset of the degradation of the system and the need for replacement.