Properties of crumb rubber hollow concrete block Mohammed, Bashar S.; Anwar Hossain, Khandaker M.; Eng Swee, Jackson Ting ...
Journal of cleaner production,
03/2012, Letnik:
23, Številka:
1
Journal Article
Recenzirano
Several researches have been conducted to determine the fresh and hardened properties of crumb rubber concrete (CRC), concrete containing crumb rubber as partial replacement to fine aggregate. The ...benefits of outlined from these works include low density, good thermal resistivity, better sound absorption, increase slump values and toughness, and better impact resistivity of the resulting concrete. Reduction in strength, increase in water absorption and are some of the adverse effect of utilizing crumb rubber in concrete. The study reported in this paper is a development of crumb rubber hollow concrete block (CRHCB). For the purpose of this work, sixty-four trial mixes were prepared to produce hollow concrete blocks of dimension 390 mm × 190 mm × 190 mm using 0%, 10%, 25% and 50% crumb rubber (CR) as replacement of fine aggregate. Tests conducted on the hardened concrete include compressive strength, thermal conductivity, electrical resistivity, acoustic absorption and transmission loss, and electrical resistivity. It has been found that CRHCB can be produced as load-bearing hollow blocks as well as lightweight hollow blocks. The CRHCB also has better thermal, acoustic and electrical properties in comparison with conventional hollow block.
Ambient cured alkali-activated mortars (AAMs) are developed through the activation of supplementary cementitious materials (SCMs) by powder form reagents with silica sand using a novel dry-mixing ...method. The fresh state, rheological, compressive strength and microstructural characteristics of eight AAM mixes are comprehensively investigated. The effects of binary/ternary combinations/proportions of SCMs, different combinations/dosages of powder form reagents and the fundamental chemical ratios (SiO2/Al2O3, Na2O/SiO2, CaO/SiO2 and Na2O/Al2O3) present in the precursors and the reagents are investigated. The AAM mixes obtained compressive strengths ranging from 34 to 42.6 MPa with initial and final setting times between 122 and 458 min and 215 and 483 min, respectively. The yield stress and viscosity of the mixes decreased with the increase in the slump flow spread. All the mixes demonstrated pseudoplastic behavior. The microstructural analysis revealed the formation of more longer polymeric chains comprising Si-Al linkages in N-C-A-S-H/N-A-S-H gels for reagent one (calcium hydroxide:sodium metasilicate = 1:2.5) mixes, which resulted in a lower slump flow, higher yield stress, higher plastic viscosity and quicker setting times compared to their reagent two (calcium hydroxide:sodium sulfate = 2.5:1) counterparts.
The results of investigations on the suitability of using volcanic pumice (VP) as cement replacement material and as coarse aggregate in lightweight concrete production are reported. Tests were ...conducted on cement by replacing 0% to 25% of cement by weight and on concrete by replacing 0% to 100% of coarse aggregate by volume. The physical and chemical properties of VP are critically reviewed to evaluate the possible influence on both fresh and hardened state of cement and concrete. The standard tests on different Portland cement–volcanic pumice powder (VPP) mixes provided encouraging results and showed good potential of manufacturing Portland volcanic pumice cement (PVPC) with higher setting time using up to 15% of VPP. The properties of volcanic pumice concrete (VPC) using different percentages of volcanic pumice aggregate (VPA) were evaluated by conducting comprehensive series of tests on workability, strength, drying shrinkage, surface absorption and water permeability. It is concluded that the VPC has sufficient strength and adequate density to be accepted as structural lightweight concrete. However, compared to control concrete, the VPC has lower modulus of elasticity and has more permeability and initial surface absorption.
Schizophrenia is characterised by hallucinations, delusions, depression-like so-called negative symptoms, cognitive dysfunction, impaired neurodevelopment and neurodegeneration. Epidemiological and ...genetic studies strongly indicate a role of inflammation and immunity in the pathogenesis of symptoms of schizophrenia. Evidence accrued over the last two decades has demonstrated that there are a number of pathways through which systemic inflammation can exert profound influence on the brain leading to changes in mood, cognition and behaviour. The peripheral immune system-to-brain communication pathways have been studied extensively in the context of depression where inflammatory cytokines are thought to play a key role. In this review, we highlight novel evidence suggesting an important role of peripheral immune-to-brain communication pathways in schizophrenia. We discuss recent population-based longitudinal studies that report an association between elevated levels of circulating inflammatory cytokines and subsequent risk of psychosis. We discuss emerging evidence indicating potentially important role of blood–brain barrier endothelial cells in peripheral immune-to-brain communication, which may be also relevant for schizophrenia. Drawing on clinical and preclinical studies, we discuss whether immune-mediated mechanisms could help to explain some of the clinical and pathophysiological features of schizophrenia. We discuss implication of these findings for approaches to diagnosis, treatment and research in future. Finally, pointing towards links with early-life adversity, we consider whether persistent low-grade activation of the innate immune response, as a result of impaired foetal or childhood development, could be a common mechanism underlying the high comorbidity between certain neuropsychiatric and physical illnesses, such as schizophrenia, depression, heart disease and type-two diabetes.
Anti-blast windows are critical in ensuring the safety of structures exposed to explosive threats, such as terrorist attacks or accidental explosions. These windows consist of blast-resistant glass ...and a structural framing system that must be able to withstand the high-pressure shock of an explosion. The present study presents a novel structural framing system for anti-explosion windows that adheres to the standards set forth by the American Institute of Steel Construction (AISC) 360-16 Specifications and the Aluminum Design Manual (ADM) 2020. The system encompasses a distinct combination of aluminum 6063-T6 angles and ASTM A36 steel embed plates that are connected by spaced bolts and augmented by the addition of a carbon nanotube-reinforced polymer CNT/polymer gasket. A numerical investigation utilizing ABAQUS software was performed to evaluate the mechanical behavior of the window assembly under intense blast loads, taking into account the effect of incorporating the CNT/polymer gasket and the impact of the gasket weight fraction on the performance of the structure. The results of the study demonstrate that the use of the CNT/polymer gasket and increasing the wight fraction ratio resulted in improvement of the blast performance of the window frame structure in terms of the significant reduction in stress, deformation and rotation, as well as the increasing of the energy dissipation during the blast event compared to when the gasket was not utilized. These findings offer crucial benchmarks for the proposed structure and offer recommendations for its implementation in industry practice, with the ultimate goal of developing more efficient and effective designs for anti-explosion windows that meet industry standards.
•Design aspects of novel blast resistance windows using reinforced polymer gaskets.•Numerical modeling of windows against blast loading.•Analysis of stress and strain development due to blast impact.•Effect of carbon nanotube volume fraction in polymer gasket on energy absorption.
This paper presents the results of an investigation on the influence of aggregate type and size on the mechanical and ductility properties of engineered cementitious composites (ECC). ECC is a ...micromechanically-based designed high-performance fiber-reinforced cementitious composite with high ductility and improved durability due to tight crack width. Standard ECC mixtures are typically produced with microsilica sand (200 µm 0.008 in. maximum aggregate size). In this study, ECC mixtures containing either crushed dolomitic limestone sand or gravel sand with maximum sizes of 1.19 or 2.38 mm (0.047 or 0.094 in.) were investigated. For each aggregate type and maximum aggregate size, three different ECC mixtures with fly ash/portland cement (FA/C) ratios of 1.2, 2.2, and 4.2 were cast. Specifically, the effects of maximum aggregate size, aggregate type, and FA/C on the uniaxial tensile, flexure, and compressive properties, as well as crack development and drying shrinkage behavior, were experimentally determined. The experimental results show that the ECC mixtures produced with crushed dolomitic limestone sand and gravel sand with higher maximum aggregate sizes exhibit strain-hardening behavior with strain capacities comparable with the standard microsilica sand ECC mixtures, provided that a high FA content is employed in the matrix. For these mixtures, the tensile ductility can maintain 1.96 to 3.23% at 28 days of age, with tensile strengths of 3.57 to 5.13 MPa (0.52 to 0.74 ksi). The use of crushed dolomitic limestone sand and gravel sand can also play the role of drying-shrinkage arrestors in the paste, further improving the material behavior. PUBLICATION ABSTRACT
Individuals with a diagnosis of schizophrenia are known to be at high risk of premature mortality due to poor physical health, especially cardiovascular disease, diabetes, and obesity. The reasons ...for these physical health outcomes within this patient population are complex. Despite well-documented cardiometabolic adverse effects of certain antipsychotic drugs and lifestyle factors, schizophrenia may have an independent effect.
To investigate if there is evidence that schizophrenia is causally related to cardiometabolic traits (blood lipids, anthropometric traits, glycaemic traits, blood pressure) and
using bi-directional two-sample Mendelian randomization (MR) analysis.
We used 185 genetic variants associated with schizophrenia from the latest Psychiatric Genomics Consortium GWAS (
= 130,644) in the forward analysis (schizophrenia to cardiometabolic traits) and genetic variants associated with the cardiometabolic traits from various consortia in the reverse analysis (cardiometabolic traits to schizophrenia), both at genome-wide significance (5 × 10
). The primary method was inverse-variance weighted MR, supported by supplementary methods such as MR-Egger, as well as median and mode-based methods.
In the forward analysis, schizophrenia was associated with slightly higher low-density lipoprotein (LDL) cholesterol levels (0.013 SD change in LDL per log odds increase in schizophrenia risk, 95% CI, 0.001-0.024 SD;
= 0.027) and total cholesterol levels (0.013 SD change in total cholesterol per log odds increase in schizophrenia risk, 95% CI, 0.002-0.025 SD;
= 0.023). However, these associations did not survive multiple testing corrections. There was no evidence of a causal effect of cardiometabolic traits on schizophrenia in the reverse analysis.
Dyslipidemia and obesity in schizophrenia patients are unlikely to be driven primarily by schizophrenia itself. Therefore, lifestyle, diet, antipsychotic drugs side effects, as well as shared mechanisms for metabolic dysfunction and schizophrenia such as low-grade systemic inflammation could be possible reasons for the apparent increased risk of metabolic disease in people with schizophrenia. Further research is needed to examine the shared immune mechanism hypothesis.
This paper presents the mass transport properties and some durability aspects of lightweight self-consolidating concrete (LWSCC) using three types of lightweight aggregates having different ...densities--namely furnace slag (FS), expanded clay (EC), and expanded shale (ESH). The properties of developed LWSCC mixtures were evaluated through comprehensive investigations on porosity and water absorption, sorptivity, rapid chloride permeability (RCP), corrosion resistance (in terms of loss of bond strength and reinforcing bar mass), and drying shrinkage. EC-LWSCC mixtures showed highest water absorption, sorptivity, and porosity when compared with FS/ESH-LWSCCs, where a reduction in sorptivity was observed with age. Consequently, EC-LWSCC mixtures experienced highest relative RCP values; however, all mixtures exhibited improved performance with age to satisfy the "low" permeability criterion by 91 days. Corrosion resistance of LWSCC mixtures was found to be primarily determined by the type, quality, and properties of aggregates. LWSCC made with EC aggregates showed the highest bond strength loss due to reinforcing bar corrosion. All LWSCC mixtures exhibited drying shrinkage of greater than or equal to600 microstrain at 112 days; a substantial increase of the drying shrinkage values were reported for mixtures made of aggregates with higher absorption capacity (such as ESH) and lower coarse-to-fine aggregate ratio. Keywords: bond strength loss; corrosion; drying shrinkage; lightweight aggregate; mass transport properties; porosity; self-consolidating concrete; sorptivity.
Poor mental health is associated with obesity, but existing studies are either cross-sectional or have long time periods between measurements of mental health and weight. It is, therefore, unclear ...how small fluctuations in mental wellbeing within individuals predict bodyweight over short time periods, e.g. within the next month. Studying this could identify modifiable determinants of weight changes and highlight opportunities for early intervention.
2,133 UK adults from a population-based cohort completed monthly mental health and weight measurements using a mobile app over a period of 6-9 months. We used random intercept regression models to examine longitudinal associations of depressive symptoms, anxiety symptoms and stress with subsequent weight. In sub-group analyses, we included interaction terms of mental health variables with baseline characteristics. Mental health variables were split into "between-individual" measurements (= the participant's median score across all timepoints) and "within-individual" measurements (at each timepoint, the difference between the participant's current score and their median).
Within-individual variation in depressive symptoms predicted subsequent weight (0.045kg per unit of depressive symptom severity, 95% CI 0.021-0.069). We found evidence of a moderation effect of baseline BMI on the association between within-individual fluctuation in depressive symptoms and subsequent weight: The association was only apparent in those with overweight/obesity, and it was stronger in those with obesity than those with overweight (BMI<25kg/m2: 0.011kg per unit of depressive symptom severity 95% CI -0.017 to 0.039; BMI 25-29.9kg/m2: 0.052kg per unit of depressive symptom severity 95%CI 0.010-0.094kg; BMI≥30kg/m2: 0.071kg per unit of depressive symptom severity 95%CI 0.013-0.129kg). We found no evidence for other interactions, associations of stress and anxiety with weight, or for a reverse direction of association.
In this exploratory study, individuals with overweight or obesity were more vulnerable to weight gain following higher-than-usual (for that individual) depressive symptoms than individuals with a BMI<25kg/m2.
•Using CRP data from age 9, 15 and 18 we identified four population subgroups.•The subgroups represent persistently low, persistently high; decreasing; increasing CRP levels.•Increasing CRP levels ...were associated with moderate/severe depression at age 18.
Meta-analyses confirm increased circulating C-reactive protein (CRP) levels in depression. Longitudinal studies have linked one-off measurements of CRP at baseline with increased risk of developing depressive symptoms subsequently at follow-up, but studies with repeat CRP measures from the same individuals are scarce.
We have examined whether longitudinal patterns of inflammation, based on three CRP measurements from childhood to early-adulthood, are associated with the risk of depression in early-adulthood in the Avon Longitudinal Study of Parents and Children, a prospective birth cohort.
Using Gaussian mixture modelling of available CRP data from age 9, 15 and 18 years, we identified four population clusters/sub-groups reflecting different longitudinal patterns of CRP: persistently low (N=463, 29.5%); persistently high (N=371, 24%); decreasing (N=360, 23%); increasing (N=367, 23.5%). The increasing group showed a steep increase in CRP levels between adolescence and early-adulthood. Participants in this group had a higher risk of moderate/severe depression at age 18 years, compared with those with persistently low CRP; adjusted odds ratio (OR)=3.78 (95% Confidence Interval (CI), 1.46–9.81; p=0.006). The odds of moderate/severe depression were also increased for the persistently high CRP group, but this was not statistically significant; OR=2.54 (95% CI, 0.90–7.16).
Repeat CRP measures were available for a subset, who may not be representative of all cohort participants.
The results suggest that an increasing pattern of inflammation from adolescence to early-adulthood is associated with risk of depression in early-adulthood.
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