The compressive behaviour of mortar under varying stress confinement

The confinement of mortar in masonry under compression is one of the key processes influencing the compressive strength of the composite material. It is triggered by the mismatch of elastic properties between units and mortar, coupled with deformation conformity between the two material phases. In cases where the mortar is particularly deformable compared to the units, this confinement results in a peak stress many times the uniaxial compressive strength of the mortar. Therefore, a careful examination of this effect is critical in understanding the failure mechanisms of masonry in compression.Mortar under compression can be modelled in a damage mechanics context, following the establishment of a) a constitutive stress-strain relation, b) a model for the increase of the compressive failure stress under lateral confinement and c) a model for the development (increase) of the Poisson’s ratio of mortar under different stress levels. The first aspect is approached using established hardening-softening curves used for quasi-brittle materials, such as concrete. The second aspect is dealt with through the adoption of a suitable and sufficiently flexible failure criterion. The third aspect is addressed through fitting against experimental data.The above aspects are expressed in a damage mechanics context, resulting in fast calculations of the compressive stress-strain curves for confined mortar. This approach allows the quantification of the development of damage in compression, the development of the apparent compressive strength and the relation between orthogonal strains in the mortar, leading to a full characterization of the stress, deformation and damage of the material. The analysis results are compared to experimental findings on different mortar types and are used for their interpretation and evaluation. The complexity of the behaviour of confined mortar is demonstrated, motivating the use of advanced numerical models for its accurate simulation and assessment.Peer ReviewedPostprint (author's final draft

The confinement of mortar in masonry under compression: experimental data and micro-mechanical analysis

The present paper deals with the behavior of several types of mortar in masonry under compression. The quantification of the response of mortar to triaxial confinement afforded by the masonry units in the composite subjected to compressive stresses is paramount in the determination of the peak stress of wallettes and pillars under compression. This behavior is greatly affected by the behavior of the mortar micro-structure and is manifested by the constrained lateral expansion of the mortar in the joint. A series of experimental results is presented, carried out on different assemblages of masonry composites (couplets and wallettes) with different types of masonry units and mortar, ranging in type from pure lime to cement based mortars. These experiments are subsequently simulated numerically using micro-mechanical techniques accounting for the shifting behavior of the Poisson's ratio of the mortar for varying levels of applied compression. Masonry is treated in a micro-mechanical framework as a composite material composed of two macroscopically distinct material phases: units and mortar. The experiments and their simulation provide insight into the complexities of masonry under compression that need to be accounted for in numerical analysis, including a discussion on the progression of damage in each material phase. The results and their analysis are further enriched through a comparative parametric study. A clear difference emerges between the assigned and the apparent Poisson's ratio for the material components.Funding for this work was procured through the GEPATAR project (“GEotechnical and Patrimonial Archives Toolbox for ARchitectural conservation in Belgium” BR/132/A6/GEPATAR), which is financially supported by BRAIN-be, BELSPO (Belgian Research Action through Interdisciplinary Networks, Federal Public Planning Service Science Policy Belgium).Peer ReviewedPostprint (author's final draft

Scalar dispersion in strongly curved open-channel flows

River hydrodynamicsTurbulent open channel flow and transport phenomen

Crack monitoring in historical masonry with distributed strain and acoustic emission sensing techniques

The analysis of crack patterns and crack growth is one of the most important steps in the assessment of structural damage in historical masonry. In a search for integrated and accurate monitoring techniques for crack measurements in masonry, several novel techniques based on distributed strain monitoring and acoustic emission (AE) sensing have been investigated in an experimental test campaign. Aim of the test program was to develop integration procedures for the strain and AE sensors, analyse their use for crack monitoring specifically in historical masonry and assess their robustness and efficiency with respect to the experimentally observed crack pattern.This work is performed within the framework of the GEPATAR project (“GEotechnical and Patrimonial Archives Toolbox for ARchitectural conservation in Belgium” BR/132/A6/GEPATAR), which is financially supported by BRAIN-be, Belspo.Postprint (updated version

Scalar dispersion in strongly curved open-channel flows

Large-eddy simulations (LES) and Reynolds-averaged numerical simulations (RANS) are performed for the flow and scalar dispersion through a strongly curved open-channel bend. The aim of the study is to investigate the performance of both LES and RANS as regards the reproduction of the key bend flow features and the associated prediction of scalar spreading along the flume. In this respect, three different issues are addressed. Firstly, the influence of the water depth on the flow behavior as computed by LES and RANS is considered. Secondly, the plume statistics of the case with a continuous vertical line source is investigated. And thirdly, the dispersion behavior of a scalar tracer is studied by means of the case in which a blob of the scalar tracer is instantaneously injected. It is found that the LES computations fairly well reproduce the main flow features, whereas RANS computations experience severe difficulties in predicting the flow field. Moreover, it was found that the gradient-hypothesis of diffusion is only limitedly valid; even counter-gradient diffusion is observed. In addition, the residence time characteristics of the instantaneously injected blob of the scalar tracer in the bend are addressed as well

Numerical analysis of settlement-induced damage to a masonry church nave wall

Differential soil settlements can induce structural damage to heritage buildings, causing not only economic but also cultural value losses. In 1963, the Saint Jacob’s church in Leuven was permanently closed to the public because of severe settlement-induced damage caused by insufficient bearing capacity of the founda- tion. Currently, the church is stabilized using a temporary shoring system. This work aims at implementing a practical modelling approach to predict damage on church nave walls subjected to differential settlements. For that purpose, a finite element model of the Saint Jacob’s church nave was generated and validated through on- site monitoring data including levelling, damage survey and laser scanningThis work was done within the framework of the GEPATAR project (“GEotechnical and Patrimonial Archives Toolbox for ARchitectural conservation in Belgium” BR/132/A6/Gepatar), supported by BRAIN.be, Belspo.Postprint (published version

Numerical Modeling of a Church Nave Wall Subjected to Differential Settlements::Soil-Structure Interaction, Time-Dependence and Sensitivity Analysis

Historic masonry structures are particularly sensitive to differential soil settlements. These settlements may be caused by deformable soil, shallow or inadequate foundation, structural additions in the building and changes in the underground water table due to the large-scale land use change in urban areas. This paper deals with the numerical modeling of a church nave wall subjected to differential settlement caused by a combination of the above factors. The building in question, the church of Saint Jacob in Leuven, has suffered extensive damage caused by centuries-long settlement. A numerical simulation campaign is carried out in order to reproduce and interpret the cracking damage observed in the building. The numerical analyses are based on material and soil property determination, the monitoring of settlement in the church over an extended period of time and soil-structure interaction. A sensitivity study is carried out, focused on the effect of material parameters on the response in terms of settlement magnitude and crack width and extent. Soil consolidation over time is considered through an analytical approach. The numerical results are compared with the in-situ observed damage and with an analytical damage prediction model.The authors acknowledge the funding received by BRAIN.be, Belspo in support of the GEPATAR research project (“GEotechnical and Patrimonial Archives Toolbox for ARchitectural conservation in Belgium” BR/132/A6/Gepatar).Peer ReviewedPostprint (author's final draft

Effect of Accelerated Carbonation on AOD Stainless Steel Slag for Its Valorisation as a CO2-sequestering Construction Material

Non-stabilized Argon Oxygen Decarburisation (AODNS) slag in powdered form was examined for its carbon dioxide sequestration capacity and for its potential utilization in the fabrication of high value building materials. The curing of the sample was carried out in two accelerated carbonation environments: i) in a carbonation chamber, maintained at atmospheric pressure, 22 °C, 5 vol.% CO2 and 80% RH; and ii) in a carbonation reactor, where the CO2 partial pressure (pCO2) and temperature could be further increased. In the carbonation chamber, an average compressive strength of over 20 MPa, on a 64 cm3 cubic specimen, was obtained after one week of curing, which is sufficient for many construction applications. Further carbonation resulted in a linear increase of strength up ~30 MPa after three weeks. The CO2 uptake followed a similar trend, reaching a maximum of 4.3 wt.%. In the reactor, the compressive strength improved with an increase in pCO2 up to 8 bar, temperature up to 80 °C, and duration up to 15 h where the maximum CO2 uptake was 8.1 wt%. The reduction in porosity in the carbonated specimens was approximately in line with the strength gain in the samples. Phase analysis by X-ray powder diffraction and inspection by scanning electron microscopy showed the precipitation of calcite and formation of significant amounts of amorphous material after carbonation. Infrared spectroscopy also pointed to the presence of aragonite and vaterite. In the carbonation chamber, the calcite morphology was uniform throughout the specimen. In the reactor, however, the calcite crystals near the outer edges of the cubes had different morphology than those near the core. Carbonation of the slag resulted in the reduction of basicity by up to one pH unit, and contributed to controlling the leaching of several heavy metals and metalloids

Soil settlement and uplift damage to architectural heritage structures in Belgium: country-scale results from an InSAR-based analysis

Soil movement may be induced by a wide variety of natural and anthropogenic causes, which are detectable in the local scale, but may influence the movement of the soil over vast geographical expanses. Space borne interferometric synthetic aperture radar (InSAR) measurements of ground movement provide a method for the remote sensing of soil settlement and uplift over wide geographic areas. Based on this settlement and uplift evaluation, the assessment of the potential damage to architectural heritage structures is possible. In this paper an interdisciplinary monitoring and analysis method is presented that processes satellite, cadastral, patrimonial and building geometry data, used for the calculation of settlement and uplift damage to architectural heritage structures in Belgium. It uses processed InSAR data for the determination of the soil movement profile around each case study, of which the typology is determined from patrimonial information databases and the geometry is calculated from digital elevation models. The impact on the historic structures is calculated from the determined soil movement profile based on various soil-structure interaction models for buildings. The Declercqresulting damage is presented in terms of a numerical index illustrating its severity according to different criteria. In this way the potential soil movement damage is quantified in a large number of buildings in an easily interpretable and user-friendly fashion. The processing of InSAR data collected over the previous 3 decades allows the determination of the progress of settlement- and uplift-induced damage in this time period. With the integration of newly acquired and more accurate data, the methodology will continue to produce results in the coming years, both for the evaluation of soil settlement and uplift in Belgium as for introducing related damage risk data for existing architectural heritage buildings. Results of the analysis chain are presented in terms of potential current damage for selected areas and buildings.The authors wish to acknowledge the funding received by BRAIN.be, BelSPO in support of the GEPATAR research project (“GEotechnical and Patrimonial Archives Toolbox for ARchitectural conservation in Belgium” BR/132/A6/Gepatar)Peer ReviewedPostprint (published version