The bond behaviour of anchors applied to masonry substrates is an important aspect to investigate, especially in case of buildings subjected to seismic actions. This topic has received a growing attention in the last decades, given the various applications that anchors can have in the strengthening of historical structures, such as connection of wall corners, anchorage of externally applied reinforcements or structural elements, stitching of masonry leaves, and others. This experimental research presents and discusses the outcomes of pull-out tests carried out on steel anchors installed on a three-wythe solid brick masonry wall, and having an embedment length of 300 mm. Two types of steel anchors, either solid threaded bars (with M10 and M14 diameters) or spikes made of 24 thin ultra-high strength steel cords, were considered. Moreover, two different embedding matrices were used: a Natural Hydraulic Lime (NHL) based mortar with a nominal strength class of M15, and a bicomponent structural epoxy adhesive. Six different types of installed anchors were tested, since M10 bars, M14 bars and 24-strand spikes were embedded with either the NHL based mortar or the epoxy adhesive. Each set envisaged 3 repetitions, for overall 18 tests. The experimentation extends a previous campaign that investigated the performance of steel cord spikes applied to existing clay brick masonry. The outcomes confirmed the boding efficiency of epoxy adhesives and also highlighted interesting outcomes when using a Natural Hydraulic Lime (NHL) based mortar as embedding material.

In modern prefabricated wooden buildings, CLT elements (Cross Laminated Timber, also known as Xlam, CrossLam or BSP) are assembled into macro elements (e.g., walls and slabs) and anchored by means of steel brackets and fasteners. A wide variety of such elements, in the shape of nails, screws and bolts, has been used in the construction market in recent years. Both the novelty of the construction technique and the wide number of fastener types imply that the knowledge about timber (CLT) joints is still limited. Under seismic shocks, steel-to-timber joints can prevent timber panels from overturning but, due to their high stiffness and low ductility, seismic energy dissipation occurs by damaging the timber elements over the fastening area. Hence, the sizing of such joints is a key factor in the design of a timber building. To improve the knowledge on the behavior of fastened steel-to-timber joints an experimental campaign was carried out. The paper discusses the testing of steel-to-CLT specimens, at changing of fasteners (i) type (i.e., 60 mm-length Anker nails and screws) and (ii) number (i.e., 2, 10, 18). The research aimed at characterizing the strength and stiffness of the compound element and at estimating the potential redistribution of loads at increasing number of fasteners (i.e., group effect).

One of the last scientific activities of Ermanno Grinzato was the research on radiant heating and cooling systems. In addition to providing a novel view for thermal and thermographic testing of these systems, he had foreseen the importance of using efficient and sustainable materials. Firstly, this work introduces the issue of testing radiant heating and cooling systems and the arising interest in geopolymers. Afterwards, the synergy between these two research fields is highlighted by the realisation and testing of a novel geopolymeric panel.

This study presents an assessment of externally bonded Fibre-Reinforced GeoPolymers (FRGPs) as strengthening material for masonry structures. Geopolymer matrices can also potentially fulfil the requirements of restoration criteria for historical buildings, with heat-resistant performances generally better than Fibre-Reinforced Polymers (FRPs). Four FRGPs, embedding either unidirectional steel or bidirectional carbon, basalt or glass mesh as reinforcement, were tested by means of local shear and bending tests on fired clay brick specimens, either alone or coupled with hydraulic lime mortar. In addition, the behaviour of each reinforcement exposed to alkaline environments was investigated through tensile tests on coupons. Results confirmed the interesting potential of FRGPs for strengthening masonry elements, highlighting a good performance of steel and carbon reinforcements.

Due to their intriguing properties, phosphate cement, also known as chemically bonded phosphate cement, have been developed for the past decade. The need for sustainable building material with low cost and easy availability has prompted research into the use of laterites, which are abundant in Cameroon. The purpose of this research was to synthesize laterite-based phosphate cement (LPCs) with phosphoric acid as the sole activator. The parameters taken into consideration were the molar concentration of phosphoric acid, liquid to solid ratio and the type of solid precursors. Early reactivity of the LPCs was assessed using a semi-adiabatic calorimeter and the results showed an increase in the heat of reaction proportionally to the concentration of phosphoric acid, except for 10 M solutions where early reactivity was inhibited. The results of the 14-day compressive strengths of the studied LPCs were in the range of 23-98 MPa for LPE and 31-105 MPa for LPN, respectively depending on the specific formulation. For both laterite phosphate cement, molar concentrations of 6 and 8 M resulted in the optimum strength. The phase composition was determined using X-ray powder diffraction, and the amorphous and crystalline phases of the raw materials and phosphate cement were quantified using Rietveld measurement. The X-ray pattern of the laterite-phosphate cement revealed that the intensity peak of hematite decreases in the presence of phosphoric acid and led to the formation of an amorphous product, which is supported by phase analysis quantification using Rietveld refinement. The micrographs of LPCs revealed a dense matrix.

The durability of Portland cement mortars is often affected by environmental factors, which can cause physicochemical and mechanical degradation processes. In this study, the performance of three products, calcium acetoacetate and calcium tetrahydrofurfuryloxide dissolved in two different solvents developed and tested as stone consolidants, was evaluated in terms of crack filling or sealing and consolidation. Realistic cracks were induced in quasibrittle cement mortar prisms using a custom-designed test rig. The effectiveness and the performance of the considered treatments, investigated on specimens, were evaluated by optical and scanning electron microscopy, colourimetry, water absorption rate, ultrasonic pulse velocity, and surface hardness measurements. Results revealed that, in the examined conditions, the products were more suitable as surface consolidants than as crack fillers.

Modeling the postpeak behavior of brittle materials like concrete remains a challenge from the point of view of computational mechanics due to the strong nonlinearities arising in the material behavior during softening and the complexity of the yield criterion that may describe their deformation capacity under generic triaxial stress states. A numerical model for plain concrete in compression is formulated within the framework of the coupled elastoplastic damage theory. The aim is to simulate, via the finite-element (FE) method, the stress-strain behavior of concrete at the mesoscale, where local confinement effects generally characterize the cement paste under the action of the surrounding aggregates. The mechanical characterization of the components are accomplished through a specific experimental campaign. With the subsequent validation study, it is shown that a few calibration parameters give a good prediction of the material strength and deformation capacity encountered in real uniaxial compression tests. (C) 2022 American Society of Civil Engineers.

Low-CO2, Portland-free cement binders can be produced by reaction of calcined clays in alkaline solutions, although the environmental footprint associated with alkaline activators may represent a point of concern. The amount of alkaline activator, and its embodied CO2, can be reduced by partial replacement of calcined clay with waste marble. Fresh and hardened state properties, as well as compositional and microstructural evolution of alkali-activated blends of calcined clay and waste marble, were investigated by combining experimental methods with thermodynamic modelling. It was shown that substitution of calcined clay with 30% waste marble was beneficial to the workability and mechanical properties of alkali-activated binders and can mitigate drying shrinkage. The physical and chemical role of calcium carbonate and the composition of the reaction products were discussed, along with the role of carbonation reactions occurring by uptake of atmospheric CO2. This approach can contribute to both reducing the CO2 footprint of cement and upcycling potentially hazardous waste from the dimension stone industry.

Modeling the post-peak behaviour of brittle materials like concrete is still a challenge from the point of view of computational mechanics, due to the strong nonlinearities arising in the material behaviour during softening and the complexity of the yield criterion that may describe their deformation capacity in generic triaxial stress states. A numerical model for plain concrete in compression is formulated within the framework of the coupled elasto-plastic-damage theory. The aim is to simulate via the Finite Element (FE) method the stress-strain behaviour of concrete at the meso-scale, where local confinement effects generally characterize the cement paste under the action of the surrounding aggregates. The mechanical characterization of the components are accomplished through a specific experimental campaign. With the subsequent validation study, it is shown that a few calibration parameters give a good prediction of load strength and deformation capacity coming from real uniaxial compression tests.

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This paper reports on the effect of cellulose nanofibrils (CNFs) on the fresh-state properties of alkali activated ground granulated blast-furnace slag (GGBS). Surface functionalized (oxidized) CNFs were added to alkali activated GGBS water suspensions (hydraulic pastes). The rheological behaviour of the pastes was compared with OPC and interpreted based on the CNF-mineral surface interaction, and on the CNF-water interaction and swelling. The water dispersion of CNFs with different surface functionalization degrees resulted in gels of different viscosity and yield stress, due to their different hydrophilicity and water adsorption properties. On increasing the CNFs surface oxidation degree, the viscosity of the CNF water dispersion decreases and the CNF water adsorption increases, while the viscosity of fresh pastes increases because of the reduced amount of available mixing water. In the hardened state, the hydraulic pastes show differences in mechanical strength related to the type and the amount of CNF influencing the porosity of the matrix as evidenced by the microstructural investigation performed by X-ray microtomography. The presence of higher amounts of CNFs induces the formation of porous agglomerates that may act as stress concentrators due to the swelling ability of nanofibrils.

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.

A main aspect of the geothermal well design is the selection of grouts backfilling the space between a geothermal probe and the surrounding ground, taking into consideration the mineralogical, thermo-physical, mechanical and flowability properties. The EU GEO4CIVHIC project aimed at developing efficient and cost-effective geothermal systems suitable for the air-conditioning refurbishment of urban buildings. A selection of different grouts was performed to ensure the whole efficiency of shallow geothermal heat exchangers designed within the project. Experimental tests were executed to identify flowable grouts with the best possible combination of different material properties, while also fulfilling a competitive cost target set forth in the preliminary project cost analysis. Grout acceptance criteria were defined: a working time of at least 4 h, a water bleeding target of 2% and a volumetric shrinkage upper bound of 4%, a thermal conductivity in water saturated conditions of at least 1.4 to 1.5 Wmxfffd; 1K-1, a compressive strength range of 1 to 2.1 MPa, a flow time range of 60 +/- 15 s. Two out of six commercial grouts were selected for installations onsite.

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In shallow geothermal systems, especially ground source heat pumps (GSHP), cementitious grouts play a decisive role in guaranteeing an efficient heat transfer between the probe and the surrounding ground. Several studies have been devoted to understand the effect of different additives (silica sand, graphite, fluorspar, glass and fly ash …) in improving especially the thermal conductivity of such mixtures, maintaining at the same time physical properties as viscosity and workability suitable for in situ application. In fact, when continuous operation mode is running, thermal conductivity shows a positive effect on the mean heat exchange rate of vertical borehole heat exchangers (BHE). However, when an intermittent operation mode is selected, the BHE performance improves when a high thermal conductivity is coupled with a high specific heat capacity. This research focus on assessing the contribution of two specific thermal additives (silica sand and molybdenum disulphide powder) to the thermal properties’ improvements of a specific commercial cementitious grout. These components are added in different proportion to the grout, up to the creation of 6 different mixtures. For each mixture 3 specimens are prepared, in order to perform the thermo-physical analyses. In addition, other 3 commercial grouts are considered. A total of 10 mixtures, leading to the creation of 30 specimens, have been analyzed. Then, thermal conductivity, thermal diffusivity and specific heat capacity of each specimen measured in anhydrous and saturated conditions are considered. The commercial grouts prepared as stated by the producers show, as expected, a minimum variation of their thermal properties in wet and anhydrous conditions. Instead, when the additives are used, a noticeable improvement of the thermal properties is observed in saturated conditions, where the effect of silica sand seems dominant. The best thermal properties improvement obtained by combining the two additives is also considered. However, the grouts suitability to be easily managed on site must be considered because, even if the new mixtures show a general gain of the thermal properties, these can be difficult to apply going from laboratory to full scale. Anyway, the characterization of the grouts thermal properties based on composition and saturation variations is important not only in numerical simulations, but also in analytical approaches, typical of the heat exchange probe fields sizing processes. In fact, the cementitious grouts play a key role in determining the shallow geothermal systems efficiency in transient mode operation, often neglected by sizing programs. In fact, those characterized by better thermal performances will contribute to the reduction of the borehole thermal resistances, interposed in the heat exchange processes between the heat transfer fluid and the ground. Finally, this research contributes to fill the gap between numerical simulation and experimental data, providing real data to be used as database for further numerical modelling analysis improvement. GEO4CIVHIC project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 792355.

The increasing attention to numerical issues related to material modeling is still a strong incentive to develop sound mechanical models that can explain material behavior up to failure. A procedure to handle a robust geometric meso-scale reconstruction of concrete materials is here proposed, based on X-ray Computed Tomography (CT-scan or X-ray CT). This study applies X-ray CT on ordinary concrete made with limestone aggregates. In this case the technique allows to acquire the overall inner geometry and distribution of the aggregates and also voids, thanks to the difference in material density of the compo-nents. Solid models have been generated with such technique and discretized in space to be numerically studied via the Finite Element (FE) method. The numerical results are compared with uniaxial compres-sion tests on the same scanned specimens. For the numerical analyses a specific non-associated elasto-plastic constitutive behavior, coupled with damage, is developed for the cement matrix, whereas the coarse aggregates are treated as elastic. The mechanical characteristics of the components are gathered through a specific experimental campaign. The study confirms that a predictive simulation of damage triggering and evolution in concrete under generic 3D stress states requires the characterization of the continuum at a meso-scale level. Comparisons between numerical and experimental results proves the soundness of the proposed constitutive description to evaluate the brittle behaviour of cementitious materials and to satisfactorily simulate damage triggering under generic 3D stress states. (c) 2021 Elsevier Ltd. All rights reserved.

The aim of this study was to help drive the Tunisian construction industry towards a more sustainable approach given the existence of abundant local raw material deposits that could be exploited for the production of low-CO2 binders. Various clay sediments from the Kebili region (southern Tunisia) were characterized by chemical analysis, X-ray diffraction, thermal analysis and geotechnical tests to determine their suitability for the preparation of geopolymer binders. The clays consist of illite and kaolinite with other accessory minerals. To test the possibility of using these materials as precursors for the production of low-CO2 and low-cost geopolymers, the raw samples were calcined and activated by addition of solid sodium silicate. Compressive strength tests performed on four alkali-activated clays show that promising mechanical performance may be achieved, with mechanical strength values as high as 25 MPa after 7 days, depending on the clay composition. The mechanical strength is related to the SiO2:Al2O3 and Al2O3:(NaO2 + K2O) ratios. Careful selection of the raw materials is, therefore, an essential step in the exploitation of clay deposits to be used for the production of ecological materials such as geopolymers.