Influence of Activation Parameters on the Mechanical and Microstructure Properties of an Alkali-Activated BOF Steel Slag

ABSTRACT: Steel slag (SS) is a secondary material from steelmaking production with little commercial value. Its volumetric expansion and low reactivity limit the use of SS in Portland cement (PC)- based materials. This study investigated the potential use of basic oxygen furnace (BOF) slag as a single precursor in alkali-activated matrices (AAMs). Six AAM pastes were assessed by changing the silica modulus (0.75, 1.50 and 2.22) and the sodium concentration (4% or 6% Na2O?wt. SS). The early hydration was assessed using isothermal calorimetry (IC), followed by the assessment of the mechanical performance (compressive strength), apparent porosity, and structure and microstructure characterization (X-ray diffraction, thermogravimetric analysis and scanning electron microscopy). The results indicated that although the BOF slag may be considered a low-reactivity material, the alkaline environment effectively dissolved important crystalline phases to produce hydrates (reaction products). An optimized combination of activator sources was achieved with 4% Na2O and a silica modulus of 1.50?2.22, with a compressive strength up to 20 MPa, a significant amount of reaction products (C-S-H/C-A-S-H gels), and low initial and cumulative heat release. Those properties will help to promote SS recycling use in future engineering projects that do not require high-strength materials.This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES)—finance code 001, grant PPM-00709-18 (FAPEMIG) and grant 316882/2021-6 (CNPq

A direct role for SNX9 in the biogenesis of filopodia.

Filopodia are finger-like actin-rich protrusions that extend from the cell surface and are important for cell-cell communication and pathogen internalization. The small size and transient nature of filopodia combined with shared usage of actin regulators within cells confounds attempts to identify filopodial proteins. Here, we used phage display phenotypic screening to isolate antibodies that alter the actin morphology of filopodia-like structures (FLS) in vitro. We found that all of the antibodies that cause shorter FLS interact with SNX9, an actin regulator that binds phosphoinositides during endocytosis and at invadopodia. In cells, we discover SNX9 at specialized filopodia in Xenopus development and that SNX9 is an endogenous component of filopodia that are hijacked by Chlamydia entry. We show the use of antibody technology to identify proteins used in filopodia-like structures, and a role for SNX9 in filopodia

Reactivity tests for supplementary cementitious materials: RILEM TC 267-TRM phase 1

A primary aim of RILEM TC 267-TRM: “Tests for Reactivity of Supplementary Cementitious Materials (SCMs)” is to compare and evaluate the performance of conventional and novel SCM reactivity test methods across a wide range of SCMs. To this purpose, a round robin campaign was organized to investigate 10 different tests for reactivity and 11 SCMs covering the main classes of materials in use, such as granulated blast furnace slag, fly ash, natural pozzolan and calcined clays. The methods were evaluated based on the correlation to the 28 days relative compressive strength of standard mortar bars containing 30% of SCM as cement replacement and the interlaboratory reproducibility of the test results. It was found that only a few test methods showed acceptable correlation to the 28 days relative strength over the whole range of SCMs. The methods that showed the best reproducibility and gave good correlations used the R3 model system of the SCM and Ca(OH)2, supplemented with alkali sulfate/carbonate. The use of this simplified model system isolates the reaction of the SCM and the reactivity can be easily quantified from the heat release or bound water content. Later age (90 days) strength results also correlated well with the results of the IS 1727 (Indian standard) reactivity test, an accelerated strength test using an SCM/Ca(OH)2-based model system. The current standardized tests did not show acceptable correlations across all SCMs, although they performed better when latently hydraulic materials (blast furnace slag) were excluded. However, the Frattini test, Chapelle and modified Chapelle test showed poor interlaboratory reproducibility, demonstrating experimental difficulties. The TC 267-TRM will pursue the development of test protocols based on the R3 model systems. Acceleration and improvement of the reproducibility of the IS 1727 test will be attempted as well

Kinetochore-Independent Chromosome Poleward Movement during Anaphase of Meiosis II in Mouse Eggs

Kinetochores are considered to be the key structures that physically connect spindle microtubules to the chromosomes and play an important role in chromosome segregation during mitosis. Due to different mechanisms of spindle assembly between centrosome-containing mitotic cells and acentrosomal meiotic oocytes, it is unclear how a meiotic spindle generates the poleward forces to drive two rounds of meiotic chromosome segregation to achieve genome haploidization. We took advantage of the fact that DNA beads are able to induce bipolar spindle formation without kinetochores and studied the behavior of DNA beads in the induced spindle in mouse eggs during meiosis II. Interestingly, DNA beads underwent poleward movements that were similar in timing and speed to the meiotic chromosomes, although all the beads moved together to the same spindle pole. Disruption of dynein function abolished the poleward movements of DNA beads but not of the meiotic chromosomes, suggesting the existence of different dynein-dependent and dynein-independent force generation mechanisms for the chromosome poleward movement, and the latter may be dependent on the presence of kinetochores. Consistent with the observed DNA bead poleward movement, sperm haploid chromatin (which also induced bipolar spindle formation after injection to a metaphase egg without forming detectable kinetochore structures) also underwent similar poleward movement at anaphase as DNA beads. The results suggest that in the chromatin-induced meiotic spindles, kinetochore attachments to spindle microtubules are not absolutely required for chromatin poleward movements at anaphase

Diversified actin protrusions promote environmental exploration but are dispensable for locomotion of leukocytes

Most migrating cells extrude their front by the force of actin polymerization. Polymerization requires an initial nucleation step, which is mediated by factors establishing either parallel filaments in the case of filopodia or branched filaments that form the branched lamellipodial network. Branches are considered essential for regular cell motility and are initiated by the Arp2/3 complex, which in turn is activated by nucleation-promoting factors of the WASP and WAVE families. Here we employed rapid amoeboid crawling leukocytes and found that deletion of the WAVE complex eliminated actin branching and thus lamellipodia formation. The cells were left with parallel filaments at the leading edge, which translated, depending on the differentiation status of the cell, into a unipolar pointed cell shape or cells with multiple filopodia. Remarkably, unipolar cells migrated with increased speed and enormous directional persistence, while they were unable to turn towards chemotactic gradients. Cells with multiple filopodia retained chemotactic activity but their migration was progressively impaired with increasing geometrical complexity of the extracellular environment. These findings establish that diversified leading edge protrusions serve as explorative structures while they slow down actual locomotion

Mutations in KEOPS-Complex Genes Cause Nephrotic Syndrome with Primary Microcephaly

Galloway-Mowat syndrome (GAMOS) is an autosomal-recessive disease characterized by the combination of early-onset nephrotic syndrome (SRNS) and microcephaly with brain anomalies. Here we identified recessive mutations in OSGEP, TP53RK, TPRKB, and LAGE3, genes encoding the four subunits of the KEOPS complex, in 37 individuals from 32 families with GAMOS. CRISPR-Cas9 knockout in zebrafish and mice recapitulated the human phenotype of primary microcephaly and resulted in early lethality. Knockdown of OSGEP, TP53RK, or TPRKB inhibited cell proliferation, which human mutations did not rescue. Furthermore, knockdown of these genes impaired protein translation, caused endoplasmic reticulum stress, activated DNA-damage-response signaling, and ultimately induced apoptosis. Knockdown of OSGEP or TP53RK induced defects in the actin cytoskeleton and decreased the migration rate of human podocytes, an established intermediate phenotype of SRNS. We thus identified four new monogenic causes of GAMOS, describe a link between KEOPS function and human disease, and delineate potential pathogenic mechanisms

Combining Reactivity Test, Isothermal Calorimetry, and Compressive Strength Measurements to Study Conventional and Alternative Supplementary Cementitious Materials

In this study, we show the results of reactivity testing for a large variety of supplementary cementitious materials (SCMs) and fillers. The reactivity test is performed by measuring the heat release (using isothermal calorimetry) and calcium hydroxide consumption (using thermogravimetric analysis) of SCMs mixed with calcium hydroxide (3:1 ratio of calcium hydroxide and SCM) at 50 °C in a 0.5 M KOH environment. Based on the response in the test, SCMs may be classified into inert, pozzolanic, and latent hydraulic; the pozzolanic and latent hydraulic materials may be further classified into less reactive and more reactive materials. Reactivity test results are compared with isothermal calorimetry and compressive strength measurements on cementitious pastes made with a subset of SCMs. Good correlations are obtained between isothermal calorimetry and compressive strength. Clear correlations between reactivity test results and compressive strength were not seen

Evaluation of probabilistic and deterministic life-cycle cost analyses for concrete bridges exposed to chlorides

Owners and designers are increasingly dealing with infrastructure maintenance to ensure adequate level of performance and functioning required by current standards. Corrosion of reinforcement is one of the major factors that reduces the durability of concrete structures. Fiber reinforced polymers (FRP) have emerged as an effective non-corrosive alternative to traditional steel reinforcement (CS), especially for bridges located in chloride-laden environments. This paper aims to undertake probabilistic and deterministic Life-Cycle Costs (LCC) analyses for: a) an entirely FRP-reinforced concrete bridge; and, b) a conventional reinforced concrete (RC)/prestressed concrete (PC) bridge; assumed to be located in different corrosion intensity locations of Florida. The deterministic LCC analysis is investigated as a function of varying chloride concentrations for different locations in Florida. A probabilistic analysis is then performed to account for uncertainties in the deterministic model based on a selected coefficient of variation value. For each maintenance intervention, the probabilistic model yields a range of potential effects produced on the LCC by the same cause, ultimately producing more realistic results. The probabilistic model is validated through the input of maintenance and repair cost data from actual in-service bridges. In the probabilistic model, the repair cost is evaluated as a smooth curve, and the results are sensitive to the selection of the coefficient of variation adopted. The probabilistic model allows for better estimation and prediction of the range of long-term LCC behavior of both bridge alternatives. The CS-RC/PC alternative is found to be a high-risk design alternative with higher range (cost spread) and increased LCC. Data available to validate the probabilistic model show a promising match and revealed that the CS-RC/PC alternatives may become costlier earlier in time with a higher degree of probability

Pretreatment of corn stover ash to improve its effectiveness as a supplementary cementitious material in concrete

This paper investigates the feasibility of using corn stover ash (CSA) as supplementary cementitious material to replace cement in concrete. Three types of CSA -- water-washed, acid-washed, and untreated burned corn stover -- were produced, and the influence of the pretreatment regimens on the physical and chemical properties of the produced ashes are evaluated. Moreover, the influence of CSA on the hydration kinetics of cement pastes, and compressive strength and bulk electrical resistivity of concrete specimens is discussed. The results of this study show that pretreating the corn stover before combustion increases the SiO2 content of the ash, and reduces the Cl and K2O contents, the loss on ignition, and the median particle size. The results also show that the pretreated CSA is more reactive and can accelerate the cement hydration process. Both acid- and water-washed CSA increase the strength and bulk electrical resistivity of concrete at later ages. Incorporating untreated CSA in the concrete mixture, on the other hand, reduces the compressive strength and bulk electrical resistivity of the concrete, due to the negative impacts of deleterious agents (such as high ash alkali contents) on the cement hydration process. While further work is needed, pretreated CSA could potentially be used as a novel supplementary cementitious material in concrete