Strengthening and Repair of a Precast Reinforced Concrete Residential Building

The deterioration or ageing of the existing infrastructures coupled with increased safety requirements necessitate immediate strengthening. Developing long lasting and cost effective repair techniques and materials continue to capture the attention of concrete professionals worldwide. The main purpose of this investigation was to extend the life span of a multi-storey precast reinforced concrete structure built in Riyadh 40 years ago. The condition assessments relied on analytical tools, visual, field and laboratory experiments for core samples collected from the building. The analytical checks of the building revealed considerable deflections of some slabs because of design error. The field and chemical analysis tests performed, confirmed the occurrence of durability defects as a result of poor workmanship during the construction stage. Several state-of-the-art repair techniques and materials were used for enhancing the service life of the structure at a minimum cost. The Repair strategy implemented included, removal of the deteriorated concrete, pouring a bonding agent on the surface of the damage, followed by injecting high strength cementitious grouts, supporting the deflected slabs using I-section steel beams, using cathodic protection to prevent corrosion, strengthening the columns and beams using carbon fiber reinforced polymer (CFRP) sheets, and steel jackets. Doi: 10.28991/cej-2020-03091630 Full Text: PD

Performance of Jordanian Masonry Cement for Construction Purposes

Laboratory tests were conducted to evaluate the performance of a newly produced Jordanian masonry cement by Jordan Cement Factories Company (Lafarge), and to identify the optimum mortar mixes best suited to different masonry applications. Tests conducted include air content, water retention and workability in the fresh state, compressive, flexural and tensile strengths, and capillary water absorption in the hardened state. Test results indicated that masonry mortar mixtures proposed in this investigation met the European and American standard requirements for water retention and air content. The use of hydrated lime in these mixtures resulted in reducing the compressive and flexural strengths without enhancing the workability. The strength test results also indicated that masonry mortars, prepared at an aggregate to cement ratio equal to or less than 4 on loose volume basis, can be successfully used for different masonry applications in Jordan

Attityder till cannabis – Intervjuer med unga vuxna

Syftet med denna studie är att undersöka en grupp unga vuxnas attityder till cannabis. Att undersöka och förstå attityder till cannabis är värdefullt för att effektivisera strategier att bemöta olika problem menar experter. Studien ämnar undersöka deltagarnas uppfattning om cannabis, deltagarnas uppfattning om olika lagstiftningars betydelse i relation till cannabis samt deltagarnas uppfattning om omgivningens attityder till cannabis. I Sverige är det främst unga killar/men i åldern 16-29 som använder cannabis och uppskattningsvis är det omkring 9 procent. Den valda metoden var kvalitativ ansats med en fokusgrupp som bestod av fem unga vuxna killar i åldern 20-25. Ur fokusgruppen framkom det att erfarenhet, media, samhälle och olika lagstiftningar är några av de viktiga faktorer som har en direkt koppling till attityderna till cannabis. Tidigare forskning påvisar dessa samband men denna korrelation kan även bero på många andra bakomliggande komplexa förklaringar och faktorer vad det gäller attityder till cannabis

The Efficiency of the PQ4R Strategy in Understanding the Mathematical Proof among the Primary School Female Students

The purpose of the study is to examine the efficiency of the PQ4R strategy in understanding the mathematical proof among primary school female students. To achieve the purpose of the study, the analytical approach is used. The sample of the study consists of 40 female students divided into two groups, one is experimental and the other is control, with each group consisting of (20) students. As for the validity and reliability of the study instrument, they are validated as required by a group of highly respective validators. The results of the study show that there is an efficiency of the teaching strategy using (PQ4R) in improving the understanding of mathematical proof for female primary school students. DOI: 10.7176/JEP/11-16-09 Publication date:June 30th 202

Recycled Plastic Fibers for Minimizing Plastic Shrinkage Cracking of Cement Based Mortar

The development of new construction materials using recycled plastic is important to both the construction and the plastic recycling industries. Manufacturing of fibers from industrial or post-consumer plastic waste is an attractive approach with such benefits as concrete performance enhancement, and reduced needs for land filling. The main objective of this study is to investigate the effect of plastic fibers obtained locally from recycled waste on plastic shrinkage cracking of ordinary cement based mortar. Parameters investigated include: Fiber length ranging from 20 to 50 mm, and fiber volume fraction ranging from 0% to 1.5% by volume. The test results showed significant improvement in crack arresting mechanism and substantial reduction in the surface area of cracks for the mortar reinforced with recycled plastic fibers compared to plain mortar. Furthermore, test results indicated that there was a slight decrease in compressive strength of mortar reinforced with different lengths and contents of recycled fibers compared to plain mortar. This study suggests that adding more than 1% of RP fibers to mortar, can be used effectively for controlling plastic shrinkage cracking of cement based mortar, and thus results in waste reduction and resources conservation

Optimal conditions for olive mill wastewater treatment using ultrasound and advanced oxidation processes

© 2019 Elsevier B.V. The treatment of olive mill wastewater (OMW) in Jordan was investigated in this work using ultrasound oxidation (sonolysis) combined with other advanced oxidation processes such as ultraviolet radiation, hydrogen peroxide (H2O2) and titanium oxide (TiO2) catalyst. The efficiency of the combined oxidation process was evaluated based on the changes in the chemical oxygen demand (COD). The results showed that 59% COD removal was achieved within 90 min in the ultrasound /UV/TiO2 system. A more significant synergistic effect was observed on the COD removal efficiency when a combination of US/UV/TiO2 (sonophotocatalytic) processes was used at low ultrasound frequency. The results were then compared with the COD values obtained when each of these processes was used individually. The effects of different operating conditions such as, ultrasound power, initial COD concentration, the concentration of TiO2, frequency of ultrasound, and temperature on the OMW oxidation efficiency were studied and evaluated. The effect of adding a radical scavenger (sodium carbonate) on the OMW oxidation efficiency was investigated. The results showed that the sonophotocatalytic oxidation of OMW was affected by the initial COD, acoustic power, temperature and TiO2 concentration. The sonophotocatalytic oxidation of OMW increased with increasing the ultrasound power, temperature and H2O2 concentration. Sonolysis at frequency of 40 kHz combined with photocatalysis was not observed to have a significant effect on the OMW oxidation compared to sonication at frequency of 20 kHz. It was also found that the OMW oxidation was suppressed by the presence of the radical scavenger. The COD removal efficiency increased slightly with the increase of TiO2 concentration up to certain point due to the formation of oxidizing species. At ultrasound frequency of 20 kHz, considerable COD reduction of OMW was reported, indicating the effectiveness of the combined US/UV/TiO2 process for the OMW treatment

Testing of a Potentially Used Antiseptic Consists of Povidon Iodine, Hydrogen Peroxide and Aloe Vera

In this study a new antiseptic was formulated and tested to match the effectiveness against microorganisms. The formulation consisted of Povidone - Iodine (PVP-I) (10%), H2O2 (3%) and Aloe Vera gel (pure). Different ratios of these materials were prepared within the acceptable range of pH for an antiseptic (3-6). The prepared samples were tested. The In Vitro test was performed by using four bacteria, two were Gram-Positive (Staphylococcus aureus and Bacillus cereus) and two were Gram-Negative (Escherichia coli and Pseudomonas aeruginosa). The new antiseptic showed 100% killing rate for E. coli, Ps. aeruginosa and S. aureus and 96.4667% killing rate for B. cereus. When the new antiseptic was compared with two common antiseptics (chloroxylenol (Dettol) and alcohol-based antiseptic), it was superior because the alcoholic antiseptic showed 100% killing rate for E. coli, Ps. aeruginosa and S. aureus and 89.8000% for B. cereus. The Dettol did not show killing rate against bacteria. Ex vivo test was carried out using the sample that showed the highest effectiveness in the In Vitro test. This was performed by applying the formulation on the skin of lab mice after wounding and contaminating the wounds with two bacteria (Staphylococcus aureus and Escherichia coli). After applying the antiseptic on the wounds, swabs from the wounds were taken for testing. The new antiseptic showed amazing efficacy against bacteria by leaving agar dish completely empty from bacteria. In vivo test was also conducted using the polymerase chain reaction (PCR) test for COVID-19. The new antiseptic did not show effectiveness against Coronavirus because the virus could not be isolated like bacteria

Impact of a Sand Filtration Pretreatment Step on High-Loaded Greywater Treatment by an Electrocoagulation Technique

Greywater (GW) treatment by the electrocoagulation (EC) technique alone might not meet the required standards in terms of pollutant removal, specifically when GW contains high loads of pollutants. In this preliminary study, a sand filtration (SF) unit was integrated with the EC technique as a pretreatment step to enhance the EC process for treating high-loaded GW. Three different voltage gradients were investigated (5 V/cm, 10 V/cm, and 15 V/cm) in the EC unit. The results demonstrated that the pretreatment SF step can contribute significantly to reducing pollutant concentrations in the greywater to be treated by EC. In terms of physical impurities, the results showed that the SF pretreatment step reduced the turbidity and the color of the treated GW by 28.4%, and 9.4%, respectively. The COD concentration was reduced by 25.5% by the SF step, which allowed a reduction of EC steady state time in the EC unit from 45 min to 30 min at an applied voltage of 15 V/cm. In addition, a high COD removal rate of 87.8% from high-load greywater was achieved with an energy consumption of only 4.11 kWh/m3 in comparison with 6.21 kWh/m3 without the SF step, which is equivalent to a 34% saving in energy consumption.This research was funded by the Scientific Research and Innovation Support Fund in Jordan; Grant Reference WE/1/19/2015

Textile-to-mortar bond behaviour in lime-based textile reinforced mortars

Lime-based textile-reinforced mortars (TRM) have recently found a growing interest for repair and strengthening of masonry and historical structures. Despite extensive experimental and numerical investigations performed in the last years on the performance of these composites, there is still a lack of fundamental understanding of the fabric-to-mortar bond behaviour (as one of the main mechanisms affecting the cracking and nonlinear response of these composites) and the parameters affecting that. This paper, aimed at addressing this gap, presents a comprehensive experimental and analytical investigation on how the test setup, embedded length, load rate, mortar age and fabric configuration affect the bond behaviour in lime-based TRMs. In total 160 pull-out tests are performed on a glass-based and a steel-based TRM commonly used for strengthening of masonry structures. The results contribute to standardization of the test procedures for characterization of the fabric-to-mortar bond behaviour, to fundamental understanding of this mechanism and to optimization of the design of these composites for enhancing their mechanical response.This work was partly financed by FEDER funds through the Competitivity Factors Operational Programme (COMPETE) and by national funds through the Foundation for Science and Technology (FCT) within the scope of project POCI-01-0145-FEDER-007633. The support to the first author through grant SFRH/BD/131282/2017 is acknowledged