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Smart cement : development, testing, modeling and real-time monitoring
\"Smart cement is a chemo-thermo-piezoresistive material that functions as a highly sensing 3-dimensional bulk sensor. It can be used for monitoring changes oflectrical resistivity in concrete by the addition of 0.03% of selected conductive or semi-conductive fibers are added to the bulk cement\"-- Provided by publisher.
BOOK
Optimization of Fresh and Mechanical Characteristics of Carbon Fiber-Reinforced Concrete Composites Using Response Surface Technique
As a top construction material worldwide, concrete has core weakness relating to low tensile resistance without reinforcement. It is the reason that a variety of innovative materials are being used on concrete to overcome its weaknesses and make it more reliable and sustainable. Further, the embodied carbon of concrete is high because of cement being used as the integral binder. Latest research trends indicate significant potential for carbon fiber as an innovative material for improving concrete mechanical strength. Although significant literature is available on the use of carbon fiber in concrete, a limited number of studies have focused on the utilization of carbon fiber for concrete mechanical strength improvement and the reduction of embodied carbon. Following the gap in research, this study aimed to investigate and optimize the use of carbon fiber for its mechanical characteristics and embodied carbon improvements. The use of carbon fiber in self-compacting concrete lowers sagging. The greatest quantity of carbon fiber is that it reduces the blockage ratio, forcing the concrete to solidify as clumps develop. With time, carbon fiber improves the durability of concrete. Self-compacting concrete with no carbon fiber has a poor tensile strength. Experiments were conducted by adding carbon fiber at 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% by weight. Fresh concrete tests including slump test and L-box test, hardened concrete tests involving compressive strength and splitting tensile strength, and durability tests involving water absorption and acid attack test were conducted. Embodied carbon ratios were calculated for all of the mix ratios and decreasing impact, in the form of eco-strength efficiency, is observed with changes in the addition of carbon fiber in concrete. From the testing results, it is evident that 0.6% carbon fiber is the ideal proportion for increasing compressive strength and split tensile strength by 20.93% and 59%, respectively, over the control mix. Response Surface Methodology (RSM) is then applied to develop a model based on results of extensive experimentation. Optimization of the model is performed and final modelled equations are provided in terms of calculating the impact of addition of carbon fiber in concrete. Positive implications are devised for the development of concrete in the future involving carbon fiber.
Journal Article
Metagenomics of Parkinson’s disease implicates the gut microbiome in multiple disease mechanisms
Parkinson’s disease (PD) may start in the gut and spread to the brain. To investigate the role of gut microbiome, we conducted a large-scale study, at high taxonomic resolution, using uniform standardized methods from start to end. We enrolled 490 PD and 234 control individuals, conducted deep shotgun sequencing of fecal DNA, followed by metagenome-wide association studies requiring significance by two methods (ANCOM-BC and MaAsLin2) to declare disease association, network analysis to identify polymicrobial clusters, and functional profiling. Here we show that over 30% of species, genes and pathways tested have altered abundances in PD, depicting a widespread dysbiosis. PD-associated species form polymicrobial clusters that grow or shrink together, and some compete. PD microbiome is disease permissive, evidenced by overabundance of pathogens and immunogenic components, dysregulated neuroactive signaling, preponderance of molecules that induce alpha-synuclein pathology, and over-production of toxicants; with the reduction in anti-inflammatory and neuroprotective factors limiting the capacity to recover. We validate, in human PD, findings that were observed in experimental models; reconcile and resolve human PD microbiome literature; and provide a broad foundation with a wealth of concrete testable hypotheses to discern the role of the gut microbiome in PD.
Here, the authors perform large-scale high-resolution Parkinson’s disease metagenomics analyses, revealing widespread dysbiosis characterized by overabundance of pathogens, immunogens, toxicants, and curli, reduction in neuroprotective and antiinflammatory molecules, and dysregulated neuroactive signaling.
Journal Article
Shear Test on Concrete Corbels: ACI 318-19 Formulas Evaluation
The reinforced concrete corbel is widely used in assembled concrete structures as a convenient cantilever support member. In this paper, eight double-corbel specimens with the same design load capacity were obtained according to the strut-and-tie method (STM) in ACI 318-19. Corbels with different dimensional parameters were produced by varying the concrete compressive strength or shear span separately. The differences in actual bearing capacity and mechanical performance among the corbels were then compared to assess the accuracy and safety of the STM under the two variables. In addition, as the horizontal stirrups are not taken into consideration in the nominal design capacity of the STM, three non-stirrup corbel specimens were designed to investigate the effect of stirrups on the load-bearing capacity under different shear spandepth ratios. The results show that changing the concrete strength or shear span significantly affects the actual bearing capacity of the corbels, despite the design load capacity remaining constant. Increased compressive strength of the concrete or decreased shear span at the design stage results in a higher level of safety for the STM. The larger the shear span-depth ratio, the greater the strengthening effect of the stirrups on the corbels' bearing capacity. Keywords: concrete compressive strength; horizontal stirrups; reinforced concrete corbel; shear span-depth ratio; strut-and-tie method (STM).
Journal Article
Real-time concrete strength monitoring using piezoelectric sensors and deep learning
This study presents a transformative advancement in civil engineering by integrating artificial intelligence with infrastructure sensing to redefine concrete structures testing and monitoring. Traditional methods for evaluating concrete performance, largely unchanged for over a century, rely on labor-intensive, proxy-based techniques that are both time-consuming and limited in reliability. Our approach combines using piezoelectric sensors with AI-driven data analysis to enable real-time, in situ monitoring of structural conditions with enhanced accuracy and automation. By employing deep learning models to interpret electromechanical impedance signals, the system eliminates the need for destructive testing or human intervention, offering a scalable solution suitable for real-world deployment. Successfully validated across four large-scale highway construction projects, the system demonstrates prediction errors within approximately 15% when benchmarked against standard compression tests conforming to ASTM C39. Aspects of this technology, such as the underlying sensing principle have been incorporated into a new standard by the American Association of State Highway and Transportation Officials (AASHTO T412), representing a significant step toward the national standardization of this non-destructive testing method. Our findings propose a scalable method to integrate intelligent sensing into civil infrastructure system. This will enable the development of resilient and sustainable infrastructure, moving beyond traditional infrastructure monitoring.
Traditional concrete testing can be labour-intensive and limited in accuracy, consistency, and real-time applicability. The study uses piezoelectric sensors and deep learning for real-time monitoring of concrete strength, interpreting signals to achieve accurate predictions. This is further validated in highway projects.
Journal Article
Experimental investigation of the shear behavior at the pervious concrete-sand interface under monotonic loading
Interaction between soil and structural materials plays a critical role in the overall stability of geotechnical systems such as piles, retaining walls, soil nails, and soil anchors. Pervious concrete is increasingly being used as an alternative for conventional concrete in applications such as evaporative or wet cooling, ground improvement using microbial-induced carbonate precipitation (MICP) biogrouting, or possibly geothermal foundations (energy piles). The motivation and the aim of the present experimental study is to improve the understanding of shear behavior at the interface between pervious concrete and cohesionless soil under mechanical loading. This paper presents results from a series of interface direct shear tests performed on smooth, conventional concrete, pervious concrete of variable surface roughness sheared against fine and medium sands. It was found that the surface roughness of tested surfaces has a remarkable influence on the shear strength and volume change responses at sand-concrete interfaces. In the sand-pervious concrete tests, the interface shear strength and soil dilation increase as the surface roughness increases, which was significantly influenced by the porosity of concrete specimens. The smooth (untextured) interface exhibited a soil contractive behavior and yielded lower interface shear resistance among all surfaces, which is considered as the lower bound of strength. The results presented show that pervious concrete mobilizes interface shear strength and volume change increases with specimen porosity (i.e., 15% vs. 30%) and confining (normal) stress, which yielded a value ranges between 2.82 and 3.46 times of sand-smooth (untextured) surface strength in medium and fine sands, respectively.
Journal Article
Handbook of alkali-activated cements, mortars and concretes
This book provides an updated state-of-the-art review on new developments in alkali-activation.The main binder of concrete, Portland cement, represents almost 80% of the total CO2 emissions of concrete which are about 6 to 7% of the Planet's total CO2 emissions.
eBook
Drop-Weight Testing on Concrete Beams and ACI Design Equations for Maximum and Residual Deflections under Low-Velocity Impact
A thorough review was performed to outline the general procedures used for performing drop-weight testing on concrete beam members. Highlights of this review include the problems associated with early tests and the methods used to overcome them, which have now become standard practice. The findings of various types of concrete beams under low-velocity impact have also been examined. These include the impact behavior of conventionally reinforced, fiber-reinforced, and prestressed concrete beams. Next, a database of various concrete beam types has been carefully built for the development and discussion of observed trends. When applicable, comparison of the recorded drop-weight behavior of conventional reinforced concrete (RC) beams was aggregated to its ACI design capacity. Finally, empirical relations for both flexuraland shear-critical members are suggested, with applicability to the ACI design standard. Keywords: ACI design equation; drop-weight testing; fiber-reinforced concrete beams; prestressed concrete beams; reinforced concrete beams.
Journal Article
Experimental study on shear mechanical properties of concrete joints under different unloading stress paths
In order to study the shear mechanical properties of rock joint under different unloading stress paths, the RDS-200 rock joint shear test system was used to carry out direct shear tests on concrete joint specimens with five different morphologies under the CNL path and different unloading stress paths. The unloading stress paths include unloading normal load and maintaining constant shear load (UNLCSL), unloading normal load and unloading shear load (UNLUSL), unloading normal load and increasing shear load (UNLISL). The results show that the peak shear strength, cohesion, internal friction angle, pre-peak shear stiffness and residual shear strength of concrete joints under CNL path increases with the increasing JRC and normal stress. Under the UNLCSL path, under the same initial shear stress τ 1 , instability normal stress σ i decreases with the increasing JRC , and normal stress unloading amount Δσ n increases with the increasing JRC . Under the same JRC , σ i increases with the increase of τ 1 , and Δσ n decreases with the increasing τ 1 . Under the same JRC and σ i , τ i is significantly smaller under the UNLCSL path than the CNL path. Under the same JRC , the cohesion under the UNLCSL path is less than the CNL path, and the internal friction angle is higher than that the CNL path. Under the same JRC and σ i , τ i is the largest under the path of CNL and UNLISL, followed by the UNLCSL path, and τ i under the UNLUSL path is the smallest. Compared with the CNL path, the variation range of the specimen internal friction angle is within 3% while the average decrease percentage of the specimen cohesion reaches 37.6% under the UNLCSL path, UNLISL, and UNLUSL. Therefore, it can be inferred that the decrease in cohesion caused by normal unloading is the main reason for the decrease in joint instability shear strength. After introducing the correction coefficient k of cohesion to modify the Mohr-Coulomb criterion, the maximum average relative error after correction is only 3.5%, which is significantly improved compared with the maximum average relative error of 56.9% before correction. The research conclusions can provide some reference for the accurate estimation of shear bearing capacity of rock joints under different unloading stress paths, which is of great significance to the stability evaluation and disaster prevention of rock mass engineering.
Journal Article