Optimization of mix composition of cement-less wastepaper-based lightweight block (CWLB)

The development of cement-less wastepaper-based lightweight block (CWLB) is another important step towards the production of eco-friendly building materials from wastepaper. This block which was designed to be used for non-load bearing/non-structural application was developed without the use of hydraulic cement. This study was conducted to optimize the mix composition of CWLB for the purpose of maximizing its compressive strength. This aim was achieved by employing the Taguchi statistical optimization technique in conjunction with laboratory experimentation. The result indicated that water/binder ratio had the most significant effect on the compressive strength of CWLB. The analysis of result establishes the CWLB specimen with optimal parameter to be that which was made from; 2.5 WPA/Sand ratio, 0.75 Water/binder ratio, and 3.5 Metric ton (i.e. 13.7MPa) compacting force. Also, the optimal CWLB displayed; an average compressive strength of 2.71MPa which indicated an increase of 402% compared to the 0.50MPa displayed by the worst parameter combination and an average density of 901.5kg/m3. The compressive strength and the density of the optimal CWLB was found to maximally satisfy the requirements for non-load bearing lightweight blocks. Considering the high amount (typically, 75%) of waste content in the composition of CWLB, it was reckoned as a viable eco-friendly lightweight block suitable for non-load bearing application. Future work will investigate other relevant properties of CWLB which include; Elastic modulus, water absorption, thermal conductivity, and reaction to fire. Key-Words: - Taguchi method, compressiv

Strength and stiffness properties of the optimum mix composition of cement-less wastepaper-based lightweight block (CWLB)

The cement-less wastepaper-based lightweight block (CWLB) is a newly developed eco-friendly non-load bearing block manufactured from majorly cellulosic wastes without the use of cement. The main constituents of CWLB includes; wastepaper aggregate (WPA) produced from post-consumer wastepaper, waste additive and sand. This study was conducted to determine its optimum mix composition and the corresponding strength and stiffness properties. The experimentations carried out covered; the optimization of the mix composition of CWLB using the Taguchi statistical optimization technique (TSOT) and the determination of the compressive strength, density, elastic modulus and the ultrasonic pulse velocity (UPV) of the optimal CWLB specimen. The findings from the TSOT ascertains that the optimum mix composition of CWLB comprises of processing parameters including; 2.5 WPA/sand ratio, 0.75 water/binder ratio, and 3.5 Metric ton (i.e. 13.7 MPa) compacting force. Also, it was found that the optimal CWLB exhibited; an average compressive strength of 2.71 MPa, an average density of 901.5 kg/m3, an average UPV of 989.9 m/s and an estimated elastic modulus of 883.4 MPa. The comparison of these properties with the applicable standard requirements indicates the suitability of CWLB for non-load bearing application. In addition, the presence of 75% waste content in the mix composition of CWLB indicates its eco-friendliness and its potential to contribute to the sustainability in the construction industry through reduction in natural resources consumption. The innovation presented in this study includes; the development of a suitable optimum mix composition of constituent materials for the novel CWLB, the identification of factors that affects it strength properties and the determination of its engineering properties. Future work will investigate other relevant properties of CWLB which include; capillary water absorption, thermal conductivity, and the reaction to fire

PROPERTIES OF CONCRETE CONTAINING CRUSHED LIMESTONE AS TOTAL REPLACEMENT OF NATURAL SAND AND RECYCLED ENGINE OIL

The rapid growth in the construction industry at the global level has made concrete the most widely used construction material throughout the world. Accordingly, the consumption of natural sand which is one the main raw material constituent of concrete is continuously growing. The demand for river sand is highly increasing due to its scarcity in the market. Manufactured sand produced by crushed rock is being considered as an appropriate alternative to replace river sand in concrete. In recent years, there is a growing interest in the use of crushed sand obtained from limestone quarries in some countries where river sand is not widely available”. The objective of this study is to investigate the effect of total replacement of the natural sand by fine aggregates obtained from crushed limestone. However, it needs more research on the crushed stone fine aggregates to reveal its engineering properties prior to utilization in concrete. Another objective of this study is to study the effect of using the waste engine oil as partial replacement of water reducing admixture. The use of waste engine oil in concrete is beneficial for the environment. It is to be noted that some countries are recycling this used oil but others are throwing it in the sea and harming the marine life. In this paper, different combinations and grading of fine lime stone and coarse aggregates were tried in order to attain the optimal proportion that provide an acceptable concrete performance in terms of workability and compressive strength. Also, different percentages of admixture replacement ranging from zero to one hundred percent of the used engine oil were tried in the selected optimal mixture proportion. The final selected proportion using engine oil and crushed limestone could be considered as an economical solution and friendly environmental concrete product

The effectiveness of using raw sewage sludge (RSS) as a water replacement in cement mortar mixes containing unprocessed fly ash (u-FA)

The performance of two groups of mortar mixes containing Unprocessed Fly Ash (u-FA) with either Raw Sewage Sludge (RSS) or water was examined. Both groups included four mortar mixes containing Portland cement, sand, u-FA. Group 1 used RSS as a water replacement and Group 2 used water. Cement was replaced with 0, 10, 20 and 30% u-FA of total binder weight and one Liquid/Binder ratio of 0.8 was used. Mortar mixes were tested for their flowability, Total Water Absorption (TWA), Ultrasonic Pulse Velocity (UPV), compressive strength and drying shrinkage. The outcomes of the investigation were encouraging in that cement-based materials containing RSS demonstrated good engineering properties in comparison to the control mixes. The inclusion of u-FA significantly reduced flowability; however improved long-term compressive strength for both groups. The greatest compressive strength was recorded for the mixes with 10–20% u-FA replacement

Structural behaviour of reinforced concrete beams containing a novel lightweight aggregate

This paper reports the results of an experimental investigation into the structural behaviour of reinforced concrete beams incorporating a novel EPS-based lightweight aggregate (LWA) called stabilised polystyrene (SPS) aggregate. Four concrete mixtures with water to cement (W/C) ratio of 0.8 were used. The replacement levels of natural aggregate by SPS were 0%, 30%, 60% and 100%. The volume ratio to manufacture SPS aggregate was 8:1:1 (80% waste EPS: 10% cement: 10% clay). A total of 24 beams were cast and tested at 28-day age. Three types of tension reinforcement were used: 2 bars, 3 bars and 2 bars + shear links. There were no compression bars at the top for all beams. Four point-loading flexural tests were conducted up to failure. In general, it can be observed that the structural behaviour of SPS concrete beams is similar to that of other types of lightweight aggregate concretes used around the world.Iraqi government-Kurdistan regio

Nanopore Sequencing SARS-CoV-2 genome in Qatar

Background: The current pandemic, COVID-19, is cause by an RNA coronavirus that was recently identified as SARS-CoV-2. RNA viruses tend to have a high mutation rate; the rate is around a million times greater than that of their hosts. The mutagenic potential of the virus depends on many factors, including the fidelity of nucleic acid-replicating viral enzymes, such as SARS-CoV-2 RNA dependent RNA polymerase (RdRp). The rate of mutation drives viral evolution and genome variability, consequently allowing viruses to escape the immunity of the host and develop resistance to drugs. Therefore, the characterization of SARS-CoV-2 variants might lead to implement better therapeutics treatments, vaccines design and identify new diagnostics approaches. Aim: The aim of this study was to establish a fast sequencing method to identify SARS-CoV-2 mutations in Qatar. This will help to assess if there are new viral variants that are spreading in country. Methods: RNA was isolated from samples collected from Qatar COVID-19 positive patients. The Artic Network V3 primer scheme and Oxford Nanopore ligation sequencing kit were used to prepare the sequencing libraries. Libraries were loaded on to R9.4.1 flow cells and ran on a GridION. Bioinformatics analysis was done following the Artic Network SARA-CoV-2 bioinformatics tools. Results: Genome coverage of sequenced samples was >80% and the depth was average at 200x. The coverage was highly dependable on sample viral load; samples of CT value lower than 30 resulted in better sequence coverage. The sequenced genomes were deposited in GISAID and were mainly clustering with genomes deposited from the UK. Sequences were compared to Illumina and sanger sequences and they showed compatible results. Conclusion: The use of ONT to sequence SARA-CoV-2 is a quick, affordable, and reliable technique to determine viral mutation. Using this technique, the first sequences from Qatar were deposited in to GISAID. Up to date, 700 genomes have been sequences from Qatari samples

Effect of curing time on selected properties of soil stabilized with fly ash, marble dust and waste sand for road sub-base materials

The properties of sub-base filling materials in highway construction are essential, as they can determine the performance of the road in service. Normally, the existing materials are removed and replaced with new materials that have adequate load-bearing capacity. Rising environmental concern and new environmental legislations have made construction professionals consider other methods. These methods include stabilizing the existing materials with other additives to improve their performance. Additives can be waste materials generated by different industries. In this work, the existing excavated soil is stabilized with waste materials. The wastes consisted of fly ash, marble dust and waste sand. The percentage addition of waste materials was 5%, 10%, 15% and 20% (by mass) of the existing soil. The soil/waste specimens were cured for 1, 7, 28, 56, 90 and 112 days before testing. Testing included the dry unit weight and unconfined compressive strength ( qu) as well as X-ray diffraction analysis and scanning electron microscopy observation. Also, the California Bearing Ratio values were obtained and are reported in this investigation. The results showed that the qu values increased with the increase in waste materials content. Also, there is tendency for the dry unit weight to increase with the increase in waste materials

Development and assessment of cement and concrete made of the burning of quinary by-product

The aim of this study is to evaluate the usability of new cement (NC) made by the burning of quinary by-product to make commercial binders. Chemical analysis of the by-products and NC as well as X-ray diffraction (XRD) analysis of NC, fineness, density, consistency, and setting time of NC paste, and slump in addition to compressive strength (CS) and splitting tensile strength (STS) of NC concrete (NCC) were conducted. The results suggested that chemical composition of by-products is suitable to make NC binder. The NC contains Ca3SiO5, Ca2SiO5, Ca3Al2O6, and Ca3Al2FeO10. The particles passing through the 200 um Sieve were 56% compared with 52% for Portland cement (PC). The density of the of NC was similar to that of PC. The NC needed 48% more water than PC for normal consistency. The initial and final setting-time of NC was 105 min and 225 min respectively which is much higher than that of PC (15 and 45 min). The slump, compressive strength and splitting tensile strength were slightly lower for concrete containing NC compared with that pf PC concrete. Although the CS and STS of NCC are the lowest, the rate of the CS and STS gain of NCC is greater than that of PCC. It was concluded that NC is a viable alternative to PC for the production of greener concrete

Effect of synthesis parameters on the performance of alkali-activated non-conformant EN 450 pulverised fuel ash

The fly ash reported in this paper is coarser than conventional pulverised fuel ash (PFA), with loss on ignition (LOI) exceeding 10.8%. Consequently, it is precluded from being used as a supplementary cementitious material (SCM) according to EN 450 and disposed in landfills. Alkali-activation of such PFAs is considered here. Three concentrations of sodium hydroxide (NaOH) were separately blended with water glass at different ratios to modify the silica modulus. Heat of reaction, setting time, compressive strength and drying shrinkage were investigated as a function of activator composition. Specimens were either cured at room temperature or hydro-thermally treated at 75 °C for five hours. The results show that by optimizing the activator composition, a binder with a 28 day compressive strength of 25 MPa can be synthesised from such PFAs even at room temperature. Among the activator parameters, the alkali content was observed to be most influential

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London