Optimizing the concrete strength of lightweight concrete containing nano palm oil fuel ash and palm oil clinker using response surface method

Lightweight aggregate concrete (LWAC) has gradually gained popularity as a significant material in the concrete industry worldwide. One of the important lightweight aggregates is palm oil clinker (POC). Moreover, palm oil fuel ash (POFA) can be used as a partial cement replacement in concrete. This paper presents a study in which POFA of Nano-particle size was used to enhance the lower performance of LWAC made with POC aggregate. The Nano-POFA (NPOFA) was used as cement replacement of 0%, 10%, 20%, and 30% and POC aggregate was used as coarse aggregate at replacement levels of 0%, 50%, and 100%. Flexural and split tensile strengths and ultrasonic pulse velocity (UPV) were investigated for different concrete mixtures. For optimizing the parameters of the mix design, the response surface method (RSM) was adopted, and within it, a central composite design (CCD) approach was used. The results show that the interaction of POC and NPOFA affects the responses (UPV, flexural and tensile strengths). However, the POC tends to decrease all the responses. Whereas, the NPOFA tends to increase it especially at later ages. The highest UPV, flexural and split tensile strengths were observed for mixture (M7) that were 4375 m/s, 8.53 MPa, and 5.38 MPa, respectively. It can be concluded that the optimization method by RSM is an active way to enhance the mix design of LWAC

Exploring engineering properties of waste tire rubber for construction applications - a review of recent advances

A sizeable amount of tire rubber waste is generated due to the increasing number of road automobile users all over the world. The accumulation of this waste in the open area poses environmental threats and therefore requires suitable treatments. The use of waste obtained from tire rubber as a construction material could contribute to a circular economy, while at the same time be an eco-friendly method of minimizing the depletion of raw materials used for the development of building materials. This study aims to show the impact of crumb rubber (CR) on the properties of concrete. This review covers the environmental consideration of fresh and hardened properties of composites developed using waste tires. The results show that the plastic nature of CR with suitable admixture led to increasing slump value and consequently enhanced the CR concrete workability

Exploring engineering properties of waste tire rubber for construction applications-a review of recent advances

A sizeable amount of tire rubber waste is generated due to the increasing number of road automobile users all over the world. The accumulation of this waste in the open area poses environmental threats and therefore requires suitable treatments. The use of waste obtained from tire rubber as a construction material could contribute to a circular economy, while at the same time be an eco-friendly method of minimizing the depletion of raw materials used for the development of building materials. This study aims to show the impact of crumb rubber (CR) on the properties of concrete. This review covers the environmental consideration of fresh and hardened properties of composites developed using waste tires. The results show that the plastic nature of CR with suitable admixture led to increasing slump value and consequently enhanced the CR concrete workabilit

Exploring engineering properties of waste tire rubber for construction applications

A sizeable amount of tire rubber waste is generated due to the increasing number of road automobile users all over the world. The accumulation of this waste in the open area poses environmental threats and therefore requires suitable treatments. The use of waste obtained from tire rubber as a construction material could contribute to a circular economy, while at the same time be an eco-friendly method of minimizing the depletion of raw materials used for the development of building materials. This study aims to show the impact of crumb rubber (CR) on the properties of concrete. This review covers the environmental consideration of fresh and hardened properties of composites developed using waste tires. The results show that the plastic nature of CR with suitable admixture led to increasing slump value and consequently enhanced the CR concrete workability

Effects of nano-palm oil fuel ash and nano-eggshell powder on concrete

Palm oil fuel ash (POFA) is a by-product from palm oil manufacturing and is currently disposed to open areas and landfills without treatment, thereby causing environment pollution. Grinding POFA to nanoparticles called NPOFA results in increased pozzolanic activity. Meanwhile, eggshells (ESs) are a biowaste from restaurants. They are disposed to landfills, thus generating undesirable gases and causing environmental damages. ES powder (ESP) has a large amount of calcium oxide, which is essential for hydration in concrete production. In this study, ESP was used to induce low calcium content in NPOFA. Cement was replaced with NPOFA at ratios of 0%, 10%, 20%, and 30% to produce green concrete, and the ESP proportions constituted 2.5% and 5% of the total binders. The curing ages were 7, 14, and 28 days. The results showed that NPOFA exhibited a significant improvement in strength of developed green concrete. ESP improved concrete durability by reducing water absorption. Therefore, this concrete may have high resistance to environmental attacks, such as those involving sulfates and acids

Optimising concrete containing palm oil clinker and palm oil fuel ash using response surface method

Cement production led to the consumption of high energy and generated harmful gases, such as CO2. Therefore, the use of alternative materials becomes necessary. The research attempts to use palm oil clinker (POC) and ultrafine palm oil fuel ash (UPOFA) as a full replacement of coarse aggregate and partial cement replacement, respectively. This study aims to use the response surface method (RSM) to optimise the properties of concrete, namely, density and water absorption. The study investigated the density and water absorption of concrete using RSM. Results showed that the density reduced sharply owing to the full replacement coarse aggregate by POC aggregate. Meanwhile, water absorption increased significantly due to the rise in the POC aggregate replacement. However, water absorption decreased because of the use of UPOFA as cement replacement. The study recommended the use of more UPOFA as cement replacement because of its high pozzolanic property

The present state of the use of eggshell powder in concrete: a review

Eggshell (ES) is a bio-waste material obtained from bakers and fast-food restaurants. This waste material is generally disposed of in landfills, causing health hazards and polluting the environment. Eggshell powder (ESP) has high amounts of calcium and can be combined with pozzolanic materials, such as fly ash, which have low calcium content. This paper presents the results of the latest studies on the utilization of ESP as a filler, cement and fine aggregate. The chemical composition, physical properties and fresh and hardened properties of ESP concrete at different proportions are also presented. Results indicate the potential of using ESP with other pozzolanic materials to improve concrete properties and reduce cement production, thereby minimizing environmental pollution. The compressive, flexural and tensile strengths have also been improved with the use of some materials with ESP as cement replacement. However, some studies reported a reduction when cement is replaced with high percentages of ESP, particularly those larger than 10%. Furthermore, the modulus of elasticity decreases with high levels of replacement. The specific gravity of ESP was found to be lower than that of cement. The durability and water absorption of concrete were reduced with the addition of ESP

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