Mechanical Strengths of Modified PET Mortar Composites in Aggressive MgSO4 Medium: ACI & B.S Predictions

Composites mortars based on plastic aggregates are often considered as an innovative materials of the future because of their potential and the advantages they present. In this paper, a comparative study was carried out on the effect of magnesium sulfate MgSO4 (5%) attack on the durability of composite mortars modified by recycled polyethylene terephthalate (PET). Laboratory tests were accomplished on limestone sand and cement mortars where the blended Portland cement was partially replaced by various volume fractions of PET plastic aggregates. Mechanical properties measured on specimens were used to assess the changes in the compressive strengths of PET-mortar composites exposed to MgSO4 attack at different ages, mainly the Young modulus of elasticity. Based on experimental compressive tests on selected specimens and there densities, the evolution of static Young modulus of elasticity has been discussed in accordance to predicted models proposed by (ACI-318) and (BS-8110) codes of practice. In addition, a comparative analysis has been carried out for corrosion resistance coefficients K of referenced mortar to those modified with plastic aggregates. It can be noted that, the corrosion resistance coefficients decrease as much as composite specimens are exposed to MgSO4 corrosive medium. For the case of modified composites, the values of K based on predicted Young modulus before and after immersion are better than the ones calculated for the unmodified mortar. Therefore, ACI 318 prediction model is recommended code for design and investigation works related to reparation mortars, screeds, pavements…etc. Also, it can be concluded that adding PET plastic aggregates by volume to blend Portland cement act to improve the corrosive resistance of this cement against MgSO4 aggressive medium

The thermal properties of mortars modified by the effect of combining polymers and SCMs

The thermal performance of the building materials is relevant to any use of composite materials, especially in relation to constructions where it is desirable to have high specific heat, low thermal conductivity and slight or no decrease of stiffness upon heating. The thermal coefficients of composite mortars made up of mixtures of combining styrene polyacrylic SPA Latex and supplementary cementitious materials SCMs were measured at different ages (7, 14, 28, 60, 90 and 120 days). So, in order to determine the thermal conductivity, the calorific capacity and thermal diffusivity of SCM-modified mortars, it seemed interesting to evaluate the influence of adding the SPA Latex (0.5%, 1% and 2%w) on the properties of these mortars when exposed to a quick thermal conductivity meter based on standard ISO 8302-91. The highest thermal conductivity of 1.51 W.m-1.K-1 was observed with the samples containing only plain cement. It decreased with the increase of SPA latex percentages. The lowest values of thermal coefficients were obtained with the samples prepared with SPA polymer at 2% and SCMs. In this way, the results obtained highlight the beneficial effect of combining SPA polymer and SCM materials as thermal insulation in comparison with other insulation materials. In fact, using SCMs as cement substitutes reduces the energy consumption. These composite mortars address problems related to environmental pollution by CO2 emissions, and can be recommended as materials for energy efficiency in buildings

Structural Characteristics of Composite Mortars and their Evolution with PET Substitution Level for Several Specimens’ Ages

This present study aims to investigate the evolution of structural response of PET-Mortar composite test with a short-beam specimen in three-point bending tests, with composite mortar ages and volumetric polymer rate and this, based on compression strength tests. The ultimate PET-mortar composite structural responses are calculated at the mid span of the short-beam by the mean of mechanics-of-materials theory basis. According to this theory, the distribution of bending moments and shear forces at any point of the composite short-beam specimen doesn’t depend on material mechanical properties especially the young modulus of modified mortar composite; so, the structural response analysis has been limited to investigate the evolution of ultimate deflection with several volumetric PET rates and composite mortar ages. In the other hand, we present a comparative study between experimental test results of splitting tensile and compressive strengths with the ones predicted by codale previsions (ACI-363 and B.S) codes in terms of PET mortar ages and volumetric PET rates in order to recommend the most suitable design code for PET-mortar composite applications in construction industries

Association of maternal prenatal copper concentration with gestational duration and preterm birth: a multicountry meta-analysis

Background Copper (Cu), an essential trace mineral regulating multiple actions of inflammation and oxidative stress, has been implicated in risk for preterm birth (PTB). Objectives This study aimed to determine the association of maternal Cu concentration during pregnancy with PTB risk and gestational duration in a large multicohort study including diverse populations. Methods Maternal plasma or serum samples of 10,449 singleton live births were obtained from 18 geographically diverse study cohorts. Maternal Cu concentrations were determined using inductively coupled plasma mass spectrometry. The associations of maternal Cu with PTB and gestational duration were analyzed using logistic and linear regressions for each cohort. The estimates were then combined using meta-analysis. Associations between maternal Cu and acute-phase reactants (APRs) and infection status were analyzed in 1239 samples from the Malawi cohort. Results The maternal prenatal Cu concentration in our study samples followed normal distribution with mean of 1.92 μg/mL and standard deviation of 0.43 μg/mL, and Cu concentrations increased with gestational age up to 20 wk. The random-effect meta-analysis across 18 cohorts revealed that 1 μg/mL increase in maternal Cu concentration was associated with higher risk of PTB with odds ratio of 1.30 (95% confidence interval [CI]: 1.08, 1.57) and shorter gestational duration of 1.64 d (95% CI: 0.56, 2.73). In the Malawi cohort, higher maternal Cu concentration, concentrations of multiple APRs, and infections (malaria and HIV) were correlated and associated with greater risk of PTB and shorter gestational duration. Conclusions Our study supports robust negative association between maternal Cu and gestational duration and positive association with risk for PTB. Cu concentration was strongly correlated with APRs and infection status suggesting its potential role in inflammation, a pathway implicated in the mechanisms of PTB. Therefore, maternal Cu could be used as potential marker of integrated inflammatory pathways during pregnancy and risk for PTB

Convalescent plasma in patients admitted to hospital with COVID-19 (RECOVERY): a randomised controlled, open-label, platform trial

SummaryBackground Azithromycin has been proposed as a treatment for COVID-19 on the basis of its immunomodulatoryactions. We aimed to evaluate the safety and efficacy of azithromycin in patients admitted to hospital with COVID-19.Methods In this randomised, controlled, open-label, adaptive platform trial (Randomised Evaluation of COVID-19Therapy [RECOVERY]), several possible treatments were compared with usual care in patients admitted to hospitalwith COVID-19 in the UK. The trial is underway at 176 hospitals in the UK. Eligible and consenting patients wererandomly allocated to either usual standard of care alone or usual standard of care plus azithromycin 500 mg once perday by mouth or intravenously for 10 days or until discharge (or allocation to one of the other RECOVERY treatmentgroups). Patients were assigned via web-based simple (unstratified) randomisation with allocation concealment andwere twice as likely to be randomly assigned to usual care than to any of the active treatment groups. Participants andlocal study staff were not masked to the allocated treatment, but all others involved in the trial were masked to theoutcome data during the trial. The primary outcome was 28-day all-cause mortality, assessed in the intention-to-treatpopulation. The trial is registered with ISRCTN, 50189673, and ClinicalTrials.gov, NCT04381936.Findings Between April 7 and Nov 27, 2020, of 16 442 patients enrolled in the RECOVERY trial, 9433 (57%) wereeligible and 7763 were included in the assessment of azithromycin. The mean age of these study participants was65·3 years (SD 15·7) and approximately a third were women (2944 [38%] of 7763). 2582 patients were randomlyallocated to receive azithromycin and 5181 patients were randomly allocated to usual care alone. Overall,561 (22%) patients allocated to azithromycin and 1162 (22%) patients allocated to usual care died within 28 days(rate ratio 0·97, 95% CI 0·87–1·07; p=0·50). No significant difference was seen in duration of hospital stay (median10 days [IQR 5 to >28] vs 11 days [5 to >28]) or the proportion of patients discharged from hospital alive within 28 days(rate ratio 1·04, 95% CI 0·98–1·10; p=0·19). Among those not on invasive mechanical ventilation at baseline, nosignificant difference was seen in the proportion meeting the composite endpoint of invasive mechanical ventilationor death (risk ratio 0·95, 95% CI 0·87–1·03; p=0·24).Interpretation In patients admitted to hospital with COVID-19, azithromycin did not improve survival or otherprespecified clinical outcomes. Azithromycin use in patients admitted to hospital with COVID-19 should be restrictedto patients in whom there is a clear antimicrobial indication

Properties of lightweight concrete made with crushed natural pozzolana as coarse aggregate

This paper describes a laboratory‐based study examinig the use of natural pozzolana as an aggregate component in lightweight concrete (LWC). A range of conditioning variables, including cement and moisture content, storage period up to one year, was investigated. In order to explore these effects, a series of five concrete mixes using the same Portland cement was prepared. Three mixes (LWC1, LWC2, LWC3) were designed with cement content of 400 kg/m3 and three different W/C ratios leading to three different workability expressed with of a measured slumps of (3±1, 5±1 and 7±1) cm. Further two mixes (LWC4, LWC5) were also made with cement dosage of 300 and 350 kg/m3 and a constant workability with a slump of 3±1cm. The investigated properties included density, compressive strength, tensile strength and elastic modulus. The results were obtained for ages up to 365 days under different curing conditions (wet and dry). It is concluded that LWC with pozzolana, as coarse aggregate, has sufficient strength and adequate density to be accepted as structural lightweight concrete. Lengvojo betono, gaminto iš gamtinio pucolano ir naudojamo kaip stambusis užpildas, savybės Santrauka Aprašomi laboratoriniai tyrimai, kurie buvo atliekami siekiant nustatyti gamtinio pucolano naudojimo užpildu lengvajam betonui (LB) gaminti. Buvo tiriama daug kintamųjų, kaip antai cemento kiekis, drėgnumas, laikymo trukmė iki vienerių metų. Minėtų kintamųjų poveikiui nustatyti buvo pagaminti penki betono mišiniai, naudojant tą patį portlandcementį. Trys mišiniai LB1, LB2 ir LB3 buvo pagaminti iš cemento, kurio tūrio masė lygi 400 kg/m3, tačiau su trimis skirtingais V/C santykiais, lemiančiais betono technologiškumą, o kartu turinčiais skirtingą slankį, atitinkamai: 3 ± 1 cm, 5 ± 1 cm ir 7 ± 1 cm. Du likę mišiniai LB4 ir LB5 buvo pagaminti iš 300 kg/m3 ir 350 kg/m3 tūrio masės cemento, kurių technologiškumas ir slankumas toks pats – 3 ± 1 cm. Buvo tiriamos šios medžiagų savybės: tankis, gniuždomasis ir tempiamasis stipris, elastingumo modulis. Tyrimo rezultatai buvo gauti laikant medžiagas skirtingomis sąlygomis (sausoje ir drėgnoje aplinkoje) iki 365 dienų. Daroma išvada, jog lengvasis betonas, pagamintas naudojant pucolaną kaip stambųjį užpildą, turi pakankamą stiprumą ir tankį, kad būtų naudojamas konstrukcijoms betonuoti. First Published Online: 21 Oct 2010 Reikšminiai žodžiai: lengvasis betonas, lengvasis užpildas, pucolanas, mechanines savybes, gniuždomasis, tempiamasis stipris, gamtines medžiago

Co-valorization of Tuff and Sandy Residues in Roads Construction

In recent years, the use of local materials in pavements has developed to compensate for the lack of normalized standard materials in the Algerian arid regions. The main objective of this research is to assess the co-valorization of two local materials to design a road material with satisfactory characteristics. In this context, the use of tuff in combination with sand residues is explored. The evolution of the characteristics of tuffs mixed with sand residues according to percentages ranging from 0% to 50% is highlighted. The used materials were subjected to physical and mechanical tests. Then, a series of mechanical tests were carried out on mixed samples compacted at the optimal characteristics that were deduced from the modified Proctor test. The obtained results highlight the existence of an optimal formulation composed of 70% tuff and 30% sandy residues, which presented an unconfined compressive strength (UCS) of 5.16 MPs and a CBR index (CBRI) of 42.6 %. Moreover, the results show clearly the evolution of the measured characteristics with time (drying) and without the addition of binders. The possibility of the use of studied mixtures in pavements has been verified regarding the recommendations in use (CTTP 2001) and the Saharan Road Technique (SRT). Doi: 10.28991/CEJ-2022-08-05-013 Full Text: PD

Chemical, mechanical and thermal properties of mortar composites containing waste PET

International audienceThe main objective of this study was to investigate the potential utilization of polyethylene terephthalate PET waste incementitious matrix, as substituent to cement, to develop lightweight construction materials and for preventing chemical attacksor repairing various reinforced concrete structures. Composites containing different amounts of PET particles, as partialreplacement to cement by weight, were characterized by destructive and non-destructive testing. So, the thermal conductivity,ultrasonic pulse velocity (UPV) and sorptivity coefficients of composite made up of mixtures of PET polymer were measured;the adverse environmental conditions are simulated by using various acid solutions. The corrosion process was monitored bymeasuring the mass loss and compressive strength for different periods. The experimental investigation revealed that the additionof PET particles reduces the UPV; furthermore, thermal conductivity and sorptivity of the composites have been decreased. So,the decrease of the sorptivity-value is favorable to the durability of the specimen structures. On behalf of the resistance toaggressive environments, it was found that the course of action of acid attack is dependent on the type of acid and solubility ofthe calcium salt formed. The presence of PET was found to lower the detrimental effect of acids on composite. Scanning electronmicroscope (SEM), X-ray diffraction and FT-IR analyses were used to better understand the cement hydration products of thedeteriorated mortars. In this way, the obtained PET-mortar composites would appear to be low-cost materials which wouldcontribute to resolving some of the solid waste problems in addition to conserving energy

Evaluation of natural pozzolan for use as supplementary cementitious material

International audienc