Failure reliability and damage detection of ferrocement composite slabs

This paper introduces suitable features and methods to define hazard rate function by acoustic emission parameters to develop robust damage statement index and reliability analysis. AE signal energy was first examined to find out relation between damage progress and AE signal energy so that a damage index based on AE signal energy was proposed to quantify progressive damage imposed to composite slabs. Moreover by using AE signal strength, historic index was utilized to develop a modified hazard rate function through integration bathtub curve and Weibull function

Fracture characterization of multi-layer wire mesh rubberized ferrocement composite slabs by means of acoustic emission

This study investigated the fracture behaviour of multi-layer ferrocement composite slabs with partial replacement of tire rubber powder as filler utilizing acoustic emission (AE) technique for characterization. Ferrocement slab specimens prepared using normal-compact cement mortar, self-compact cement mortar, fly ash, and rubberized self-compact cement mortar –with varying steel mesh reinforcement layers– were statically loaded to failure. The inclusion of 10% rubber powder (by weight) was found capable of altering the failure mode of composite slabs from brittle to ductile with a slight reduction in the ultimate flexural strength. Fracture development of the specimens was closely monitored using AE for enhanced characterization. It is seemingly evident that the measured AE parameters could be effectively processed to distinguish different modes of fracture. The collected AE data was utilized to quantify stiffness reduction in the specimens due to progressive damage.No Full Tex

Phase change materials incorporation into 3D printed geopolymer cement:A sustainable approach to enhance the comfort and energy efficiency of buildings

The advent of 3D printing has revolutionized conventional construction, offering cost-effective and fast construction of complex structures. Nevertheless, there remain challenges to be addressed regarding the effective integration of functional additives into 3D printing construction materials. Herein, we present a straightforward and environmentally friendly approach to promote sustainable buildings while reducing energy consumption. This is achieved by integrating Macroencapsulated Phase Change Materials (MEPCM) into a 3D printable geopolymer paste (GPP) derived from fly ashes. The research followed a systematic methodology, encompassing the assessment of fresh and hardened properties of geopolymer pastes with varying amounts of MEPCM, analyzing their thermal properties, and investigating the thermal performance by printing miniature houses without and with 20 vol% MEPCM. Notably, MEPCM demonstrated its dual functionality as a thermal energy management component and a viscosity modifier for 3D printable geopolymer paste. Overall, this study paves an innovative path toward sustainable construction, highlighting the significance of energy efficiency and waste reduction.</p

Fracture Evaluation of Multi-layered Precast Reinforced Geopolymer-Concrete Composite Beams by Incorporating Acoustic Emission into Mechanical Analysis

In this study, a multi-layered steel reinforced composite beams which are composed of geopolymer concrete section at tensile zone and Portland cement based concrete at compression are investigated. The beams were tested to failure to compare the toughness, post peak behaviour and failure mode based on the variation of the depth of layers. The mechanical analysis incorporated into acoustic emission technique showed that the geopolymer beam endured more deflection than the ordinary Portland cement based beams, however their ultimate load carrying capacities were quite similar. Further, the composite beams, resulted in transition of failure mode of shear to a flexural

Effects of Methadone on Liver Enzymes in Patients Undergoing Methadone Maintenance Treatment

Background: Methadone is currently the most frequently used substance in the treatment of short-term and particularly long-term opiate dependence. Patients' beliefs about the adverse effects of methadone on function of organs, especially liver, have widely affected the use of this substance. This study aimed to determine the effects of methadone on liver enzyme levels in patients on methadone maintenance treatment. Methods: In a retrospective study, a total of 94 patients undergoing methadone maintenance therapy were recruited from Shahid Beheshti Hospital (Kerman, Iran). Liver enzyme levels in all patients were tested every six months from the onset of treatment until 24 months. The relations between test results and age, gender, and methadone dose were then evaluated. Data was analyzed using logistic regression with random data plan. Findings: At the 24th month, alanine aminotransferase (ALT) levels in 4 patients (4.3%) and aspartate aminotransferase (AST) levels in 3 patients (3.2%) were above normal. Among 46 patients (50%) who had normal alkaline phosphatase (ALP) levels after 24 months, 26 subjects were younger than 40 and 20 subjects were over 40 years of age. The mean age of subjects with abnormal ALP levels and the mean methadone dose were 39.9 years and 19.55 cc, respectively.Conclusion: The results of this study indicated the significant effect of methadone on ALP levels. These effects can account for cholestatic pattern liver injury (obstruction). Further prospective studies including greater samples of patients with heart and liver complications and encompassing other drugs are required to confirm our findings.Keywords: Methadone, Substance abuse, Liver, Alanine aminotransferase, Aspartate aminotransferase, Alkaline phosphatas

Experimental investigation of sandy soil stabilization using chitosan biopolymer

The performance of an environmentally friendly biopolymer synthesised from secondary resources to overcome the wind erosion of sandy soil was investigated in this study. The study employed a multi-scale approach to investigate the mechanical, erosional, and hydraulic properties of sandy soil. At the macroscale, experimental techniques such as unconfined and triaxial compression tests, permeability measurements, contact angle assessments, and wind tunnel experiments were utilized to characterize the bulk behavior of the soil. Concurrently, molecular dynamics (MD) simulations were conducted at the nanoscale to predict surface mechanical characteristics and elucidate chemical interactions at the molecular level. Results show that when the outer surface of the sandy particles is coated with a sparse concentration of biopolymer, the sandy aerosol inhibitory performance is significant even under extreme storm conditions reaching speeds of 140 km/h of storms. The study on the impact of biopolymer content, curing time, and curing conditions revealed that the addition of chitosan biopolymer has the ability to enhance the bonding between particles and significantly enhance the mechanical properties of sandy soil. The atomic insight from molecular dynamics reveals huge entanglement between sandy particles and biopolymer by Van der Waals interaction. The results of the Unconfined Compressive Strength test indicate that chitosan enhances the compressive strength of sand by up to 320 kPa. Additionally, the triaxial test demonstrated that the application of chitosan led to a 34.2 kPa improvement in the cohesion of sand. Furthermore, analysis of the permeability test results revealed a decrease in the hydraulic conductivity coefficient from 1.6 × 10^-6 m/s to 5.7 × 10^-7 m/s, representing a reduction of approximately 35 %

The effects of elevated temperature and fiber reinforcement on fly ash based geopolymer concrete / Navid Ranjbar

Geopolymers are formed through the hydrothermal synthesis of aluminosilicate sources in the presence of alkali activators such as sodium hydroxide (NaOH) or sodium silicate (Na2SiO3) which cure and harden at near ambient temperatures. Due to ceramic-like characteristics, geopolymers show high quasi-brittle behaviour and are much less resistant to tensile load than compressive; however, it shows higher degree of resistance to elevated temperatures. This research investigates the fundamental material properties and structural response of geopolymer concrete developed using the two types of locally available materials in Malaysia to produce a new constructional binder as a replacement of the conventional Portland cement based products. This research is composed of four major aspects of the research findings that are reported in the form of six articles. In the first section, the fundamental differences between low and high Si/Al ratio geopolymers developed using fly ash (FA) and Palm Oil fuel ash (POFA) precursors is discussed. In the second part, the response of the proposed geopolymers is determined under elevated temperatures of 300C, 500C, 800C and 1000C to characterize the mechanical properties enhancement by heat treatment and their thermal resistance. Overcoming the brittleness of the FA based geopolymer by incorporation of fibers with different scales and material properties is the next phase of the research. And finally, structural application of the geopolymer material using novel multi-layer composite beams was done and verified by elastic theories and ACI 318-14. Based on the results obtained, it is observed that the particle shapes and surface area of POFA and FA as well as chemical composition affects the density and compressive strength of the mortars. The increment in the percentages of POFA increased the SiO2/Al2O3 ratio and that resulted in reduction of the early compressive strength of the geopolymer and delayed the geopolymerization process. Moreover, replacement of the v POFA in FA based geopolymer mortar expedited the start of micro-pore formation when the corresponding geopolymer specimens were exposed to high temperatures and shifted the ultimate strength peak from 300 °C to 500 °C. The addition of 1% graphene nanoplatelets (GNP) enhanced the compressive and flexural strength of the fly ash based geopolymer by 1.44 and 2.16 times, respectively. The point of interest is that introduction of GNP filler even at low filler weight fractions increased the toughness, stress and strain at the first crack and rigidity. Moreover, the wettability decreased with the increase of GNP content. It is observed that the degree of shrinkage of the polypropylene fiber reinforced geopolymer composite is minimized by addition of 3% of fiber into the geopolymer matrix; meanwhile, the presence of polypropylene fiber in fly ash based geopolymer matrix did not increase the flexural and compressive strength but did lead to enhanced post-peak load carrying capacity and energy absorption. On the other hand, micro steel fiber has the potential to minimize dry shrinkage of fly ash based geopolymer matrix in addition to significant increase in flexural strength and flexural toughness of the composites; it also enabled transformation of the brittle behaviour to ductile mode without an adverse effect on ultimate compressive strength. However, like other fibers, incorporation of micro steel fiber led to reduction in flow and workability of the composite in fresh state. Based on experimental results obtained from beam specimen tests, it was observed that the geopolymer beam showed about double deflection relative to the ordinary Portland cement based beams; however the ultimate load capacity was quite similar. Results showed that by increasing the geopolymer layer thickness in composite beams, ductility and energy absorption of the beams were increased and mode of damage was shifted from shear to flexural. Moreover, formation of horizontal shear cracks in composite beams at the interface of the layers limited the crack propagation to the geopolymers section causing a larger damage zone and corresponding toughness enhancement. The experimental results were also compared to elastic theory and ACI 318-14

Fiber-reinforced geopolymer composites: A review

There is a burgeoning interest in the development of geopolymers as sustainable construction materials and incombustible inorganic polymers. However, geopolymers show quasi-brittle behavior. To overcome this weakness, hundreds of research have been focused on development, characterization, and implementation of fiber-reinforced geopolymers for a wide range of applications. This paper discusses the rapidly developing state-of-the-art of fiber-reinforced geopolymer composites, focusing on material and geometrical properties of construction fibers, and underlying mechanisms on fiber-binder interaction at fresh and hardened states, mechanical properties, toughening mechanisms, thermal characteristics, and environmental durability. It is intended to build a strong conceptual and technical background for what is currently understood on fiber-reinforced geopolymers by tying the subject together with knowns for other similar cementitious composites rather than a historical report of literature