The preparation and axial compressive properties of 3D-printed polymer lattice-reinforced cementitious composite columns

In the most structural codes, deformation capacity of the unreinforced masonry shear walls is estimated based on their structural behavior(failure mode) and aspect ratio. In this paper, deformation capacity was determined for the Persian historic brick masonry walls by considering the effects of various parameters such as lateral constraints, aspect ratio and thickness. Also, to take into account the uncertainties in material and geometry of the walls in their deformation capacity, partial factor γdu was proposed, somehow, deformation capacity of shaer wall is determined by multiplying this factor in the computed deformation. Accordingly, the in-plane behavior of 48 different specimens of masonry walls with four lateral constraint configurations (contribution of transverse walls and also top slab), four distinct aspect ratios(height to length) of 0.5, 0.75, 1.0 and 1.5, three traditional wall thicknesses of 0.20, 0.35 and 0.50 m, under pre-compression load of 0.10 MPa were computed using nonlinear pushover analyses. Then, the obtained force-deformation curves were idealized by bilinear curves (linear elastic – perfectly plastic) to make them easier for comparison objectives as well as to be more adopted in practical purposes. The latter results indicated that deformation capacity of the shear walls decreases by stiffer lateral constraints, more thickening; and decrease in height-to-length aspect ratio. In addition, it was observed that the transverse walls (vertical constraints on two sides, and at two ends of the base shear walls) were more efficient in reducing deformation capacity than the top slab (horizontal constraint). As a result, according to the numerical calculations, the ultimate drift value for the Persian historic brick masonry walls determined between 1.3% and 2.7%. Eventually, the partial factor of γdu to consider uncertainty in modulus of elasticity and thickness assessment in deformation capacity of the Persian historic masonry shear walls achieved in the range of 1.3 to 1.7.

We invert time‐domain airborne electromagnetic data in such a way as to obtain a model that varies slowly along the profile. This is achieved by modifying a typical one‐dimensional inversion algorithm to include lateral constraints. The lateral constraints are included as a roughness matrix that is solved simultaneously with the Jacobian matrix in an iterative eigenparameter inversion. In this case, multiple soundings along a line are all solved simultaneously. The lateral constraints can be applied to the resistivities and the thicknesses, both separately and together. We apply these techniques in two situations where airborne geophysical data are applied to near‐surface exploration. The first case is in a resistive environment where we are interested in quantifying a superficial conductive overburden. In this case, lateral constraints improve the geological image compared with those images obtained using unconstrained layered‐earth inversion. In the second case, we want to map the thickness of a resistive aquifer covering a saline layer. In this case, we show how varying the weights on the lateral constraints can change the image of the thickness of the aquifer. The presence of numerous cultural artefacts makes the inversion problematic. Application of a first‐difference constraint did the best job at removing culture but resulted in oversmoothing of the hydrogeology. The use of a second‐difference lateral constraint gave a good rendition of the hydrogeology but did not suppress the culture as well as the first‐difference constraint.

Inversion of airborne transient electromagnetic data based on reference point lateral constraint

Review of models for restricted-path movements

<div class="section abstract"><div class="htmlview paragraph">The crash safety of lithium-ion batteries has received great attention in recent years because of their growing popularity in electric vehicles. However, the safety issues of prismatic batteries have not been thoroughly studied; in particular, the mechanical responses of prismatic battery cells with lateral constraints under varied loading conditions still remain unclear.</div><div class="htmlview paragraph">In this study, indentation tests are conducted to study the mechanical response of prismatic battery cells. Fixtures providing lateral constraint which simulates the real packing situation in battery module are designed. Firstly, the effects of lateral constraints on coupled mechanical and electrical responses of prismatic battery cells are analyzed and discussed. Secondly, dynamic indentation tests of prismatic cells with lateral constraints are carried out. The response of the stacked batteries under local loading is revealed. Thirdly, non-destructive X-ray computed tomography imaging technique is employed to detect the fracture patterns in battery cells caused by indentation.</div><div class="htmlview paragraph">The results of indentation tests indicate that the indentation depth and the peak force for the battery internal failure are affected by the side constraint conditions and the responses of battery cells vary under different loading speeds. Also, the XCT scanning results of the samples clearly show the different levels of internal damage and fracture patterns under varied conditions. The detailed mechanical responses of the prismatic battery cell disclosed in the present study can provide support for modeling and protection of batteries under side impact.</div></div>

Weakly cemented red sandstone is common in the construction of shaft engineering in western China. Based on the actual working conditions, the dynamic mechanical behavior of this kind of rock under the combined action of multiple variables was studied. Based on the freezing temperature of the freezing method for shaft construction, the experimental temperature gradient was set at 25°C to −25°C. Using an modified split Hopkinson pressure bar (SHPB) experimental system, the dynamic mechanical response of frozen weak-cemented red sandstone under lateral constraints was studied. Taking dynamic and static stress fields and temperature fields as the entry point, the relationship between dynamic load, confining pressure, temperature, and dynamic mechanical characteristics parameters of weakly cemented rock is established, and the strain rate effect, lateral constraint effect, and negative temperature effect of dynamic compressive strength are analyzed. The research results show that: 1) The confining pressure changes synchronously with the axial dynamic load, and undergoes three stages: rapid increase, slow increase, and unloading rebound. 2) Under the combined effects of multiple variables, the dynamic mechanical behavior of the rock shows obvious compaction and rebound characteristics. 3) The dynamic compressive strength of the rock is jointly affected by strain rate, confining pressure, and temperature. Among them, lateral constraints have a strengthening effect. The dynamic compressive strength increases exponentially with increasing strain rate, and increases first and then decreases with decreasing temperature. At the same time, the degree of rock fragmentation is consistent with its strength characteristics. The research results have certain reference significance for the engineering design and safe operation and maintenance of frozen rock structures under dynamic loading.

The botryoid hybrid nano-carbon materials were incorporated into cementitious materials to develop a new type of self-sensing cementitious composites, and then the mechanical, electrically conductive, and piezoresistive behaviors of the developed self-sensing cementitious composites with botryoid hybrid nano-carbon materials were comprehensively investigated. Moreover, the modification mechanisms of botryoid hybrid nano-carbon materials to cementitious materials were also explored. The experimental results show that the compressive strength and the elasticity modulus of the self-sensing cementitious composites botryoid hybrid nano-carbon materials decrease with the increase in the botryoid hybrid nano-carbon material content, while the Poisson’s ratio does the opposite. The percolation threshold zone of the self-sensing cementitious composites botryoid hybrid nano-carbon materials is from 2.28 to 3.85 vol.%. The optimal content of botryoid hybrid nano-carbon materials is 3.38 vol.% for piezoresistivity of the self-sensing cementitious composites botryoid hybrid nano-carbon materials. The amplitude of fractional change in resistivity goes up to 70.4% and 28.9%, respectively, under the monotonic compressive loading to failure and under the repeated compressive loading within elastic regime. The piezoresistive stress/strain sensitivity reaches (3.04%/MPa)/354.28 within elastic regime. The effective modification of botryoid hybrid nano-carbon materials to electrically conductive and piezoresistive properties of cementitious materials at such low content is attributed to their botryoid structures, which are beneficial for the dispersion of botryoid hybrid nano-carbon materials and the formation of conductive network in cementitious materials. The use of botryoid hybrid nano-carbon materials provides a new bottom–up design and fabrication approach for nano-engineering multifunctional cementitious composites.

Construction materials are at the forefront of global economic development as they provide the foundation for the infrastructure of other industries, with cementitious materials being predominantly used in construction projects. To promote sustainable development, alternative materials are added to cement mortar to increase durability and reduce emissions. In this regard, graphene oxide (GO) and fly ash (FA) are two alternative materials commonly used in cement mortar, which are readily available or are just the waste from other local material production. With different ratios, the amount of GO and FA can affect the properties of cement mortar positively or negatively. This study aims to determine the effects of GO and FA on cement mortar mixtures under material conditions. Research results show that 10 wt% FA and 0.036 wt% GO will give cement mortar the best physical and mechanical properties while ensuring other necessary properties, such as workability. When increasing FA to 30 wt% or GO to 0.05 wt%, the strength of the mortar mixture tends to decrease. Another issue is that the specific surface area of graphene is very high, which poses a significant challenge when uniform dispersion in the cement paste mixture is required. Polycarboxylate combined with a specific mixing sequence has demonstrated good dispersibility and high stability. Through this research, it is demonstrated that the addition of GO and FA has the potential for sustainable development of the construction industry by considering the contexts of the local recycled cementitious replacement materials.

Objective – This study aims to investigate the influence of polypropylene fiber addition on the mechanical and functional properties of permeable concretes containing 10% silica fume, assessing their potential for application in sustainable urban pavements. To this end, the effects of incorporating different fiber contents (1, 2, 3, and 4 kg/m³) on permeability, void content, and mechanical strengths (axial compression, splitting tensile strength, and flexural tensile strength) were evaluated. Furthermore, variations in the modulus of elasticity and post-peak deformation capacity were analyzed, comparing the results with a reference mixture to determine the feasibility of using these compositions in urban infrastructure. Methodology – The study was conducted in a laboratory setting following an experimental approach to assess the effects of polypropylene fiber addition in permeable concretes containing 10% silica fume. Initially, the constituent materials were selected, including Portland cement, aggregates, silica fume, and polypropylene fibers. The mixtures were prepared with varying fiber contents (1, 2, 3, and 4 kg/m³), along with a reference mixture without fibers for comparison. Specimens were cast and subjected to tests to determine their physical and mechanical properties. Bulk density, permeability, and void content were evaluated to characterize the porous structure of the concrete. Mechanical strength was analyzed through axial compression, splitting tensile, and flexural tensile strength tests. The modulus of elasticity and post-peak deformation capacity were also investigated to understand the structural behavior of the samples. The results were compared among the different mixtures, allowing an assessment of the influence of fiber incorporation on the mechanical strength and functionality of permeable concrete. The findings contribute to the development of more sustainable and durable urban pavements. Originality/Relevance – The rapid urbanization process has exacerbated issues such as soil impermeabilization, increased stormwater runoff, and the urban heat island effect, necessitating sustainable solutions for urban drainage. In Brazil, urban drainage prioritizes hydraulic efficiency, often at the expense of environmental impacts. Permeable concrete emerges as a viable alternative, as it reduces surface runoff and improves water quality. However, its high porosity compromises mechanical strength, limiting its application in traffic areas. Recent studies have explored modifications in cementitious composites to address this limitation, such as the use of silica fume and polymeric fibers. Nevertheless, there is a gap in the literature regarding the impact of polypropylene fiber incorporation in permeable concretes containing silica fume, particularly in relation to the balance between permeability, mechanical strength, and post-cracking behavior. This study contributes to advancing knowledge by investigating different dosages of polypropylene fibers (1, 2, 3, and 4 kg/m³) in permeable concretes with 10% cement replacement by silica fume, evaluating their influence on mechanical and functional performance. The results may support the development of stronger and more durable concretes, expanding their practical application in sustainable urban infrastructure. Results – The results demonstrated that the addition of polypropylene fibers significantly influenced the physical and mechanical properties of permeable concrete. The incorporation of fibers reduced bulk density while increasing permeability and void content, indicating greater pore connectivity. In mechanical tests, axial compressive strength and splitting tensile strength did not exhibit significant variations among different fiber dosages. However, flexural tensile strength increased with the addition of 1 kg/m³ of fibers, suggesting a positive effect on the concrete's ability to withstand bending stresses. For higher fiber dosages (2, 3, and 4 kg/m³), a slight reduction in flexural strength was observed, possibly due to increased porosity and difficulties in achieving homogeneous fiber dispersion within the cementitious matrix. Theoretical/Methodological Contributions – This study contributes to the scientific literature by deepening the understanding of the impact of polypropylene fiber addition in permeable concretes modified with silica fume. The detailed analysis of the material's physical and mechanical properties, particularly concerning permeability, flexural strength, and modulus of elasticity, fills a research gap regarding the structural viability of this type of concrete for urban infrastructure applications. From a methodological perspective, the research stands out for its systematic experimental approach, evaluating different fiber contents (1, 2, 3, and 4 kg/m³) and comparing their effects on the porous structure and mechanical behavior of permeable concrete. The combined use of strength tests, modulus of elasticity assessment, and post-peak deformation capacity analysis provides a more comprehensive understanding of fiber-matrix interactions, enabling a more precise determination of optimal reinforcement conditions. Additionally, the results of this study offer a methodological foundation for future research aimed at optimizing permeable concretes with polymeric reinforcements, contributing to the development of more efficient and sustainable materials for the construction sector. Social and Environmental Contributions – The use of permeable concrete with polypropylene fibers contributes to urban sustainability by reducing surface runoff, aiding in flood control, and enhancing groundwater recharge. Additionally, its application can mitigate the urban heat island effect, promoting improved thermal comfort. Socially, the adoption of this material supports the development of more resilient cities, reducing the need for conventional drainage infrastructure and its associated maintenance costs. This study fosters the advancement of sustainable construction technologies aligned with sustainability principles.

Considering that karst caves, underground rivers, and dissolution fractures in shallow carbonate formation in the Sichuan Basin are extremely developed, leakage, failure and plugging difficulties are easy to occur in the drilling process. The TDEM was used to carry out the exploration of hidden karst geological bodies in well QM2, and the quasi-three-dimensional inversion based on lateral constrain was used to invert the TDEM data. Three NW trending anomalous bands were identified in the lower Triassic Jialingjiang Formation within the range of drilling, consisting of seven relatively low-resistivity anomalous zones. Under the guidance of TDEM quasi-three-dimensional inversion resistivity data, the low-resistivity karst development area is avoided, and the specific drilling location of well QM2 is determined. No karst cave and underground river were drilled in the later drilling process of well QM2, as well as no instability phenomenon occurred. It indicates that the TDEM detection results are consistent with the actual drilling, and the quasi-three-dimensional TDEM inversion interpretation data based on lateral constraints is reliable and can accurately detect the buried karst in the wellsite.

Graphene materials have been extensively explored and successfully used to improve performances of cement composites. These formulations were mainly optimized based on different dosages of graphene additives, but with lack of understanding of how other parameters such as surface chemistry, size, charge, and defects of graphene structures could impact the physiochemical and mechanical properties of the final material. This paper presents the first experimental study to evaluate the influence of oxygen functional groups of graphene and defectiveness of graphene structures on the axial tension and compression properties of graphene-cement mortar composites. A series of reduced graphene oxide (rGO) samples with different levels of oxygen groups (high, mild, and low) were prepared by the reduction of graphene oxide (GO) using different concentrations of hydrazine (wt %, 0.1, 0.15, 0.2, 0.3, and 0.4%) and different reduction times (5, 10, 15, 30, and 60 min) and were added to cement mortar composites at an optimal dosage of 0.1%. A series of characterization methods including scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetric analysis, and Fourier transform infrared spectroscopy were performed to determine the distribution and mixing of the prepared rGO in the cement matrix and were correlated with the observed mechanical properties of rGO-cement mortar composites. The measurement of the axial tension and compression properties revealed that the oxygen level of rGO additives has a significant influence on the mechanical properties of cement composites. An addition of 0.1% rGO prepared by 15 min reduction and 0.2% (wt %) hydrazine with mild level of oxygen groups resulted in a maximum enhancement of 45.0 and 83.7%, respectively, in the 28-day tensile and compressive strengths in comparison with the plain cement mortar and were higher compared to the composite prepared with GO (37.5 and 77.7%, respectively). These results indicate that there is a strong influence of the level of oxygen groups and crystallinity of graphene structures on the physiochemical and mechanical properties. The influence of these two parameters are interconnected and their careful balancing is required to provide an optimum level of oxygen groups on rGO sheets to ensure that there is sufficient bonding between the calcium silicate hydrate (C-S-H) components in the cement matrix and minimum level of defects and higher crystallinity of graphene structures, which will improve the mechanical properties of the composite. Finding the optimized balance between these two parameters is required to formulate graphene cement composites with the highest performance.

Assessing the mechanical and thermal stability of heat storage media is vital in the design and wellbeing of sensible heat storage systems, which are typically designed below ground level or as part of the sub-structure of buildings with load bearing capabilities. Nevertheless, considering the importance that a mechanically sound heat storage media (especially at elevated temperatures) has on the efficiency and performance of heat storage systems, it has not been given adequate attention in past studies. On this basis, the mechanical performance of two commercial cemented heat storage materials at different curing periods, pressure and temperature is studied in this research. The influence of curing period on the mechanical strength of the materials was studied by performing unconfined compression tests, where as to study the effects of pressure and temperature on seismic velocities, and hence mechanical properties of the materials, laboratory tests on P- and S-wave velocities were performed. Ultrasonic wave velocity studies can be used to estimate many geomechanical properties of materials such as density, elastic modulus, Poisson’s ratio etc., thus providing an accurate and reliable estimate of the mechanical properties of rocks and cemented materials. The results presented in this study show a considerable dependence of the mechanical behavior of the investigated materials on curing period, pressure and temperature, which when unaccounted for can result in the inaccurate planning and design of heat storage systems.

Agro-industrial waste from corn straw fiber: Perspectives of application in mortars for coating and laying blocks based on Ordinary Portland cement and hydrated lime

The aim of the study was to design a cementitious material that is prepared with the synergistic addition of sodium silicate and granite fine aggregate in order to obtain low capillary suction. For this purpose, three different classes of cement mortar (M15, M10, M5), one type of granite fine aggregate and two different proportions of additive in the form of sodium silicate (0.002 kg, 0.005 kg) were analysed. Firstly, the capillary suction of the granite aggregates was analysed and compared with traditional sand. Afterwards, nine cementitious material bars were made, which were then used to examine the capillary suction. It was proved that the M15 cementitious material with the granite fine aggregate and a higher proportion of the additive had the lowest capillary suction. In turn, the M5 cementitious material without the additive had the highest index of capillary suction, which shows that adding sodium silicate to cement mortar can significantly reduce its capillary suction. Finally, the results of this study were compared with the previous authors’ studies concerning basalt and quartz fine aggregates. As a result of the research, it was found that the cementitious material with the fine quartz aggregate had a lower rate of capillary suction index than the cementitious material with the fine basalt aggregate.KeywordsDesignCementitious materialsCapillary suctionGranite fine aggregateMortar

Prediction model for elastic modulus of recycled concrete based on properties of recycled coarse aggregate and cementitious materials