Production Technologies of Ancient Bricks from Padua, Italy: Changing Colors and Resistance over Time

Representative and very uneven texturally bricks having yellow/beige or pale or dark red colors from the Renaissance walls (16th century) of Padua, Northeast Italy, were studied by means of colorimetric, petrographic (MOP), chemical (XRF), mineralogical (PXRD) and microstructural analysis (FESEM-EDS). Starting from the color measurements of the ceramic bodies, the manufacturing technologies and their influence on the physical behavior and durability of the bricks were established. The porous system was characterized by means of hygric tests and mercury intrusion porosimetry; the compactness and structural anisotropy were defined through ultrasound velocity; the uniaxial compressive strength was determined; and durability to salt crystallization and frost action of the bricks was assessed. Mg- and Ca-rich illitic clays fired at temperatures ≥900 ◦C were used to manufacture the beige hue bodies, while the pale red bricks were made out with Ca- and Fe-rich illitic clays fired at 850–900 ◦C. A lower carbonate content on the base clays and a lower firing temperature were the main causes responsible for the changing colors from beige to red hue. The increase of the red color was associated to higher silicate inclusions content and lower development of reaction rims around grains. The low sintering degree achieved yielded highly porous bodies with diverse porous systems, leading to differential physical performance and durability of the bricks that may turn out beneficial for the conservation of the historic walls.Marie Sklodowska-Curie grant agreement No 836122CLAYONRISK ProjectResearch Group of the Junta de Andalucía RNM179MSC Actio

Strengthening of three-leaf stone masonry walls: an experimental research

The paper summarizes the results of an experimental research carried out on three-leaf masonry walls of typical granite stone constructions from the North of Portugal. The research aimed at studying the behaviour under compression of this wall typology, as well as the improvements introduced by common strengthening techniques applied for the structural rehabilitation of masonry heritage buildings. Ten masonry specimens were tested, plain or strengthened by transversal tying of the external leaves, with GFRP bars, or/and by injection of the inner leaf, with a lime-based grout. The results obtained showed that these strengthening techniques were successful in increasing the compressive strength of the walls and in improving their behaviour under compressive loads.The authors would like to thank the technical staff of the Structural Laboratory of University of Minho for the help provided. Acknowledgements are also due to the companies Fradical, Mapei and Augusto de Oliveira Ferreira for providing raw materials and workmanship. Finally, the funding provided by the Portuguese Science and Technology Foundation, through the POCI/ECM/58987/2004 project, is gratefully acknowledged

FAKI: Soldiers of God

This short documentary film follows the urban path of a London-based Congolese brass band, FAKI, part of the Kimbanguist church, a transnational Afro-Christian movement. FAKI brass band members meet and worship in converted warehouses, anonymous within the urban fabric of the post-industrial metropolis. However, through their religious practice, territorial and sonic presence Kimbanguists have carved out ‘third spaces’ of re-enchanchment within the urban moral landscape. Focusing on the discourses, embodiment, spatiality and aurality of the spiritual warfare, the film explores how contemporary African diasporic churches are, in their own terms, reconfigurating dialectics of margin/centrality, invisibility/visibility in a ‘global city’ like London

Optimization and mechanical-physical characterization of geopolymers with construction and demolition waste (CDW) aggregates for construction products

The paper presents the mechanical and physical characterization of a metakaolin-slag-fly ash-potassium silicate geopolymer mortar embedding inorganic recycled aggregates from Construction and Demolition Waste (CDW). The binder was holistically optimized to comply with the pilot plant requirements for producing architectural panels of satisfactory quality, among them: reduced viscosity, minimum open time of 1 h, use of commercial reagents, sufficient strength and limited shrinkage. Size and aspect ratio of small scale cylindrical specimens were investigated in compression, comparing the performance of tested geopolymers to available provisions for natural rocks, cement concrete and mortars. Empirical correlations between compressive and splitting tensile strength were calibrated through the results of about 130 geopolymer mixtures produced in former and current activities. Lastly, the suitability of reusing geopolymers at their end-of-life as recycled aggregates in a new geopolymer production was preliminarily assessed to explore the feasibility of a closed-loop process

Flexural strengthening of timber beams by CFRP laminates

In this contribution, experimental analyses for the validation of some strengthening techniques for historic timber floors using traditional and/or innovative materials (FRP, fibre reinforced polymer) are presented. The traditional proposed method consists in placing reinforcing planks above the existing floor beams and in fixing them with a \u2018dry\u2019 connection by means of hardwood dowels. The FRP strengthening was evaluated first as separate technique on timber beams and then in combination with the traditional jointed beams. The characterization of the connections between the materials (\u2018dry\u2019 wooden dowels and FRP bond behaviour) and the flexural tests on simple and mechanically jointed beams with or without carbon FRP (CFRP) reinforcement are presented. The main execution phases of the strengthening techniques, and their limits and advantages, are described

Characterization of a dovetail joint for timber roofs

In this paper experimental and numerical analyses on dovetail joints for timber roofs are presented. These joints have a ordinary shape and are an old efficient type of connection, but they have become economically advantageous in the last years because the progress on machine tools. In literature there are few information and no design rules for the dovetail joint, as well as in Eurocode 5 and in other design guidelines. The results of shear tests on the joints are presented. Several variables were taken into account in order to characterize the connection, in particular: the angle of the tail, the wood fibre configuration of the tenons and the geometry of the groove. Different failure modes were observed depending on the groove geometry. Based on the experimental results an empirical model was developed in order to describe and design the behaviour of the dovetail joints. Finally, the behaviour of the dovetail joints were analyzed by means of finite element models

Flexural strengthening of timber beams by traditional and innovative techniques

This work presents experimental analyses for validating various strengthening techniques applied to historic timber floors using traditional and/or innovative materials (FRP, fibre reinforced polymer). The traditional method proposed here consists of placing reinforcing planks above the existing floor beams and fixing them with 'dry' connections by means of wooden dowels. As an innovative technique, strengthening with wet lay-up carbon FRP laminates (CFRP) applied at the underside of the beams is examined, both as unique strengthening for floor beams and in combination with the above-mentioned traditional method on the composite structure. Results on the characterisation of the connections between materials ('dry' wooden dowels and FRP bond behaviour) and flexural tests on simple and mechanically jointed beams with or without CFRP strengthening are discussed. The main execution phases of the strengthening technique, and their limits and advantages, are also described

Testing and numerical modelling of the structural behaviour of brick masonry strengthened by the bed joints reinforcement technique

In the paper, the main experimental and numerical results, regarding the compressive behaviour of brick masonry panels reinforced with CFRP strips and the local bond behaviour of CFRP reinforcement, are presented. The experimental program on masonry panels consisted in monotonic compression tests on brick masonry panels in plain, strengthened and repaired conditions after pre-damage according to four reinforcement configurations. Whereas, the experimental program on local bond behaviour consisted of several pull-out tests performed on specimens made of a single CFRP strip inserted in a mortar joint between two solid clay bricks. In order to reproduce realistic in situ conditions, 2 a confining pressure, normal to the mortar joint, was applied while applying the pull-out load. Different anchorage lengths and confining pressures were investigated. Numerical finite element models were developed for the identification of the local bond slip law. This local law was then used for the implementation of the numerical models of the symmetrically strengthened brick masonry panels. These last models, together with the experimental data, were finally used to obtain practical design information for the application of the investigated intervention technique

Experimental Characterization of Solid Clay Bricks: Correlations Among Mechanical Properties

Strengthening interventions on existing structures, especially in the case of Architectural Heritage, require an in-depth knowledge of construction techniques, geometry and materials for an optimal design aiming at the minimum intervention approach ideal. Nonetheless, conservative values of material properties, often derived from codes or literature, might hinder the effectiveness of the design approach. Non-Destructive Tests (NDT) and Minor Destructive Tests (MDT) are fundamental tools for the characterization of existing materials with a minimum or no impact. The paper presents an experimental study that investigated the possibility of defining empirical correlations among the main mechanical properties of solid clay bricks, which are one of the most common unit for masonry load-bearing members. Extruded bricks, typical of modern constructions, and soft-mud bricks, resembling historical units, were tested to cover for the ample variability of solid clay bricks. The examined mechanical properties were compressive, bending, splitting and pull-off strengths. The dataset of mechanical properties allowed calibrating linear correlations expressing one property as a function of another, thus giving the possibility of estimating a set of strengths based on the results of the MDT pull-off test. An innovative aspect consisted in performing the four tests on the same unit, so that the calibrated linear correlations are based on punctual data instead of average values. A practical application can consist in the on-site execution of pull-off tests, which are minor destructive and can be easily performed on a wall surface, for estimating the compressive strength of clay units