Role of N-acetylcysteine in the management of COPD

The importance of the underlying local and systemic oxidative stress and inflammation in chronic obstructive pulmonary disease (COPD) has long been established. In view of the lack of therapy that might inhibit the progress of the disease, there is an urgent need for a successful therapeutic approach that, through affecting the pathological processes, will influence the subsequent issues in COPD management such as lung function, airway clearance, dyspnoea, exacerbation, and quality of life. N-acetylcysteine (NAC) is a mucolytic and antioxidant drug that may also influence several inflammatory pathways. It provides the sulfhydryl groups and acts both as a precursor of reduced glutathione and as a direct reactive oxygen species (ROS) scavenger, hence regulating the redox status in the cells. The changed redox status may, in turn, influence the inflammation-controlling pathways. Moreover, as a mucolytic drug, it may, by means of decreasing viscosity of the sputum, clean the bronchi leading to a decrease in dyspnoea and improved lung function. Nevertheless, as successful as it is in the in vitro studies and in vivo studies with high dosage, its actions at the dosages used in COPD management are debatable. It seems to influence exacerbation rate and limit the number of hospitalization days, however, with little or no influence on the lung function parameters. Despite these considerations and in view of the present lack of effective therapies to inhibit disease progression in COPD, NAC and its derivatives with their multiple molecular modes of action remain promising medication once doses and route of administration are optimized

Mineralogical evolution of cement pastes at early ages based on thermogravimetric analysis (TGA)

[EN] Ordinary thermogravimetric analysis (TG) and high-resolution TG tests were carried out on three different Portland cement pastes to study the phases present during the first day of hydration. Tests were run at 1, 6, 12 and 24 h of hydration, in order to determine the phases at these ages. High-resolution TG tests were used to separate decompositions presented in the 100¿200 C interval. The non-evaporable water determined by TG was used to determine hydration degree for the different ages. The effect of particle size distribution (PSD) on mineralogical evolution was established, as well as the addition of calcite as mineralogical filler. Finer PSD and calcite addition accelerate the hydration process, increasing the hydration degree on the first day of eaction between water and cement. According to high-resolution TG results, it was demonstrated that ettringite was the only decomposed phase in the 100¿200 C interval during the first 6 h of hydration for all studied cements. C-S-H phase starts to appear in all cements after 12 h of hydration.Funding was provided by Colciencias (Grant No. Convocatoria 567-2012).Gaviria, X.; Borrachero Rosado, MV.; Paya Bernabeu, JJ.; Monzó Balbuena, JM.; Tobón, J. (2018). Mineralogical evolution of cement pastes at early ages based on thermogravimetric analysis (TGA). Journal of Thermal Analysis and Calorimetry. 132(1):39-46. https://doi.org/10.1007/s10973-017-6905-0S39461321Benboudjema F, Meftah JM, Torernti F. Interaction between drying, shrinkage, creep and cracking phenomena in concrete. Eng Struct. 2005;27:239–50.Holt E. Contribution of mixture design to chemical and autogenous shrinkage of concrete at early ages. Cem Concr Res. 2005;35:464–72.Darquennes A, Staquet S, Delplancke-Ogletree MP, Espion B. Effect of autogenous deformation on the cracking risk of slag cement concretes. Cem Concr Compos. 2011;33:368–79.Slowik V, Schmidt M, Fritzsch R. Capillary pressure in fresh cement-based materials and identification of the air entry value. Cem Concr Compos. 2008;30(7):557–65.Evju C, Hansen S. Expansive properties of ettringite in a mixture of calcium aluminate cement, Portland cement and ß-calcium sulfate hemihydrates. Cem Concr Res. 2001;31:257–61.Bentz DP, Jensen OM, Hansen KK. Olesen, Stang, H. Haecker, C.J. Influence of cement particle-size distribution on early age autogenous strain and stresses in cement-based materials. J Am Ceram Soc. 2001;84(1):129–35.Barcelo L, Moranville M, Clavaud B. Autogenous shrinkage of concrete: a balance between autogenous swelling and self-desiccation. Cem Concr Res. 2005;35(1):177–83.Bouasker M, Mounanga P, Turcry P, Loukili A, Khelidj A. Chemical shrinkage of cement pastes and mortars at very early age: effect of limestone filler and granular inclusions. Cem Concr Compos. 2008;30(1):13–22.Bentz DP. A review of early-age properties of cement-based materials. Cem Concr Res. 2008;38(2):196–204.Ozawa T. Controlled rate thermogravimetry. New usefulness of controlled rate thermogravimetry revealed by decomposition of polyimide. J Therm Anal Calorim. 2000;59:375–84.Ramachandran VS, Paroli RM, Beaudoin JJ, Delgado AH. Thermal analysis of construction materials. Building materials series. New York: Noyes Publications; 2003.Zanier A. High-resolution TG for the characterization of diesel fuel additives. J Therm Anal Calorim. 2001;64:377–84.Tobón JI, Payá J, Borrachero MV, Restrepo OJ. Mineralogical evolution of Portland cement blended with silica nanoparticles and its effect on mechanical strength. Constr Build Mater. 2012;36:736–42.Singh M, Waghmare S, Kumar V. Characterization of lime plasters used in 16th century Mughal Monument. J Archeol Sci. 2014;42:430–4.Majchrzak-Kuçeba I. Thermogravimetry applied to characterization of fly ash-based MCM-41 mesoporous materials. J Therm Anal Calorim. 2012;107:911–21.Silva ACM, Gálico DA, Guerra RB, Legendre AO, Rinaldo D, Galhiane MS, Bannach G. Study of some volatile compounds evolved from the thermal decomposition of atenolol. J Therm Anal Calorim. 2014;115:2517–20.Rios-Fachal M, Gracia-Fernández C, López-Beceiro J, Gómez-Barreiro S, Tarrío-Saavedra J, Ponton A, Artiaga R. Effect of nanotubes on the thermal stability of polystyrene. J Therm Anal Calorim. 2013;113:481–7.Yamarte L, Paxman D, Begum S, Sarkar P, Chambers A. TG measurement of reactivity of candidate oxygen carrier materials. J Therm Anal Calorim. 2014;116:1301–7.Borrachero MV, Payá J, Bonilla M, Monzó J. The use of thermogravimetric analysis technique for the characterization of construction materials. The gypsum case. J Therm Anal Calorim. 2008;91(2):503–9.Tobón JI, Payá J, Borrachero MV, Soriano L, Restrepo OJ. Determination of the optimum parameters in the high resolution thermogravimetric analysis (HRTG) for cementitious materials. J Therm Anal Calorim. 2012;107:233–9.Kuzielova E, Žemlička M, Másilko, J, Palou, M.T. Effect of additives on the performance of Dyckerhoff cement, Class G, submitted to simulated hydrothermal curing. J Therm Anal Calorim. Accepted 29 Oct 2017Genc M, Genc ZK. Microencapsulated myristic acid–fly ash with TiO2 shell as a novel phase change material for building application. J Therm Anal Calorim. Accepted 24 Oct 2017.Singh M, Kumar SV, Waghmare SA. The composition and technology of the 3–4th century CE decorative earthen plaster of Pithalkhora caves, India. J Archeol Sci. 2016;7:224–37.Liu L, Liu Q, Cao Y, Pan WP. The isothermal studies of char-CO2 gasification using the high-pressure thermo-gravimetric method. J Therm Anal Calorim. 2015;120:1877–82.Majchrzak-Kuce I, Bukalak-Gaik D. Regeneration performance of metal–organic frameworks TG-vacuum tests. J Therm Anal Calorim. 2016;125:1461–6.Ion RM, Radovici C, Fierascu RC, Fierascu I. Thermal and mineralogical investigations of iron archaeological Materials. J Therm Anal Calorim. 2015;121:1247–53.Rupasinghe M, San Nicolas R, Mendis P, Sofi M, Ngo T. Investigation of strength and hydration characteristics in nano-silica incorporated cement paste. Cem Concr Compos. 2017;80:17–30.Esteves PL. On the hydration of water-entrained cement–silica systems: combined SEM, XRD and thermal analysis in cement pastes. Thermochim Acta. 2011;518:27–35.Riesen R. Adjustment of heating rate for maximum resolution in TG and TMA (MaxRes). J Therm Anal. 1998;53:365–74.Lim S, Mondal P. Micro- and nano-scale characterization to study the thermal degradation of cement-based materials. Mater Charact. 2014;92:15–25.Gill PS, Sauerbrunn SR, Crowe BS. High resolution thermogravimetry. J Therm Anal. 1992;38:255–66.Mounanga P, Khelidj A, Loukili A, Baroghel-Bouny V. Predicting Ca(OH)2 content and chemical shrinkage of hydrating cement pastes using analytical approach. Cem Concr Res. 2004;34:255–65.Zeng Q, Li K, Fen-chong T, Dangla P. Determination of cement hydration and pozzolanic reaction extents for fly-ash cement pastes. Constr Build Mater. 2012;27:560–9.Parrott LP, Geiker M, Gutteridge WA, Killoh D. Monitoring Portland cement hydration: Comparison of methods. Cem Concr Res. 1990;20:919–26.Hewlett PC. Lea’s chemistry of cement and concrete. 4th ed. Oxford: Elsevier Science & Technology Books; 2004.ASTM C305 Standard practice for mechanical mixing of hydraulic cement pastes and mortars of plastic consistency. ASTM International, West Conshohocken, PA; 2012.Taylor HF. Cement chemistry. 2nd ed. Westminster: Thomas Telford; 1997.Nadelman EI, Freas DJ, Kurtis KE. Nano- and microstructural characterization of Portland limestone cement paste. In: Nanotechnology in construction. Proceedings of NICOM 5. 2015. p. 87–92

Influence of silica fume and water content on the microstructure and diffusion parameters of cement pastes

International audienceDurability of silica fume cement based materials is of great importance for radioactive wastestorage. This study investigates the durability in the aspect of tritiated water (HTO) diffusion inrelation with the porosity and the microstructure within silica fume cement pastes. A silica fume(SF) replacement varying from 0 to 20% by weight of cement was used to prepare cement pastesat water-to-binder ratios (w/b) ranging from 0.3 to 0.5. The manufactured pastes were tested bythrough-out diffusion and their microstructure characterized by water and mercury porosimetry(MIP), thermogravimetric analysis (TGA) and by scanning electron microscopy (SEM)associated to (EDS) analysis.It was observed that the addition of silica fume as a slurry –a liquid mixture of undensifiedpowder and water- offers a better dispersion and improves diffusion properties of SF pastescompared to the use of a densified powder, often studied in literature.Test results also showed that despite an increase in total porosity, the addition of silica fume hasa positive impact on pore refinement and on reducing the effective diffusion coefficients.Finally, HTO diffusion coefficients seem to increase linearly with w/b ratio especially forPortland cement pastes where the increase is more important compared to SF pastes

Prediction of cracking in massive concrete structures by numerical simulations

cited By 0International audienc

EFFECT OF SELF-HEALING ON THE CHLORIDE DIFFUSIVITY AT EARLY AGE

International audienceThe chloride diffusivity of cementitious materials significantly affects the durability of civil engineering structures (e.g. reinforced concrete buildings) and the waste containment matrices (e.g. sediments, radioactive waste). Its influence becomes greater when cracks appear due to restrained shrinkage. The results of an experimental campaign on the chloride diffusion characteristics of uncracked, cracked and self-healed mortar specimens are presented at several ages. The mortar compositions are characterized by several contents of blast-furnace slag. The diffusion characteristics are measured by means of accelerated migration tests and solutions titration with silver nitrate to determine the steady state stage and the effective diffusion coefficient. The cracking size is monitored using optical microscopy. Results clearly show that self-healing is a positive phenomenon that limits and reduces the crack size, therefore leading to a decrease of the diffusion coefficient. Moreover, the addition of blast-furnace slag intensifies this trend due to the slow hydration kinetics of this type of hydraulic binder

EFFECT OF SELF-HEALING ON THE CHLORIDE DIFFUSIVITY AT EARLY AGE

International audienceThe chloride diffusivity of cementitious materials significantly affects the durability of civil engineering structures (e.g. reinforced concrete buildings) and the waste containment matrices (e.g. sediments, radioactive waste). Its influence becomes greater when cracks appear due to restrained shrinkage. The results of an experimental campaign on the chloride diffusion characteristics of uncracked, cracked and self-healed mortar specimens are presented at several ages. The mortar compositions are characterized by several contents of blast-furnace slag. The diffusion characteristics are measured by means of accelerated migration tests and solutions titration with silver nitrate to determine the steady state stage and the effective diffusion coefficient. The cracking size is monitored using optical microscopy. Results clearly show that self-healing is a positive phenomenon that limits and reduces the crack size, therefore leading to a decrease of the diffusion coefficient. Moreover, the addition of blast-furnace slag intensifies this trend due to the slow hydration kinetics of this type of hydraulic binder

Monitoring internal sulphate reactions by X-ray tomography

International audienceFor certain cement chemical compositions and under specific temperature and humidity conditions, concrete deterioration can be attributed to internal sulphate reactions. This pathology mainly affects massive structures (e.g. bridge piers, dams, nuclear power plants) or precast concrete structures that undergo specific heat treatments. Without an external sulphate source, sulphate reaction is characterized by delayed ettringite formation leading to swelling of the cementitious matrix and cracking. Nevertheless, the mechanisms and the impact of this pathology on the microscopic and structural scales are still today not thoroughly understood. A performance based approach (accelerated treatment) was recently proposed by IFSTTAR (test method n 66) in order to determine the sensitivity of a cementitious mixture to the delayed etttringite formation. It consists in longitudinal swelling measurements on cylindrical specimens submitted to drying and wet cycles followed by a water curing at 20 C. In this work, the internal sulphate reaction in a concrete specimen that has followed an accelerated treatment is monitored by means of X-ray tomography. X-ray tomography is a non-destructive test that provides information on the 3D mesostructural evolutions. Using a post-treatment method implemented in Matlab, the evolution of several parameters (porosity, cracking) is quantified. The interfacial zone between aggregate and paste matrix is also studied. Supplementary observations performed by means of optical and scanning electron microscopy confirm that the delayed ettringite is principally formed in the large pores and in the interfacial transition zone of the cementitious matrix. Finally, using a 3D numerical reconstruction method aggregates can be seperated from the cementitious matrix to create a finite element mesh of the specimen at the mesoscale level that can be used for numerical simulations

Monitoring internal sulphate reactions by X-ray tomography

International audienceFor certain cement chemical compositions and under specific temperature and humidity conditions, concrete deterioration can be attributed to internal sulphate reactions. This pathology mainly affects massive structures (e.g. bridge piers, dams, nuclear power plants) or precast concrete structures that undergo specific heat treatments. Without an external sulphate source, sulphate reaction is characterized by delayed ettringite formation leading to swelling of the cementitious matrix and cracking. Nevertheless, the mechanisms and the impact of this pathology on the microscopic and structural scales are still today not thoroughly understood. A performance based approach (accelerated treatment) was recently proposed by IFSTTAR (test method n 66) in order to determine the sensitivity of a cementitious mixture to the delayed etttringite formation. It consists in longitudinal swelling measurements on cylindrical specimens submitted to drying and wet cycles followed by a water curing at 20 C. In this work, the internal sulphate reaction in a concrete specimen that has followed an accelerated treatment is monitored by means of X-ray tomography. X-ray tomography is a non-destructive test that provides information on the 3D mesostructural evolutions. Using a post-treatment method implemented in Matlab, the evolution of several parameters (porosity, cracking) is quantified. The interfacial zone between aggregate and paste matrix is also studied. Supplementary observations performed by means of optical and scanning electron microscopy confirm that the delayed ettringite is principally formed in the large pores and in the interfacial transition zone of the cementitious matrix. Finally, using a 3D numerical reconstruction method aggregates can be seperated from the cementitious matrix to create a finite element mesh of the specimen at the mesoscale level that can be used for numerical simulations

Behaviour of slag cement concrete under restraint conditions

Some constructions built with slag cement concrete exhibit cracking at early age due to restrained shrinkage. To determine the slag effect on cracking, this study focuses on the autogenous deformation evolution of concretes characterized by different percentages of slag (0 and 42% of the binder mass) under free and restraint conditions by means of the TSTM device (Temperature Stress Testing Machine). Despite the fast kinetics of its autogenous deformation, the cracking appears later for the slag cement concrete than for the Portland cement concrete. This behaviour is related to the swelling of its cementitious matrix at early age and its large capacity for relaxing the stresses. © 2011 Lavoisier, Paris.SCOPUS: ar.jSCOPUS: ar.jinfo:eu-repo/semantics/publishe

9th International Conference on Fracture Mechanics of Concrete and Concrete Structures STUDY OF SHRINKAGE RESTRAINT EFFECTS AT EARLY-AGE IN ALKALI- ACTIVATED SLAG MORTARS

Abstract: Alkali-activated materials are being increasingly studied nowadays as hydraulic binders. In order to be enrolled in different civil engineering applications, several properties must be characterized. This study focuses on their cracking risk by shrinkage restraints. The current paper summarizes the experimental and numerical results of a project assessing the development of early age properties of an alkali-activated slag mortar. First, an experimental campaign was held in order to quantify hydration heat release and hydration kinetics, to determine the time evolution of the Young modulus and the tensile strength and to measure free shrinkage strains, all in autogenous conditions. Second, two modelling approaches for mechanical properties and shrinkage development were compared. The results showed that the classical approach to characterize the hydration kinetics based on semi-adiabatic calorimetry results isn't suitable for the studied binder because of slow hydration and low heat release. Numerical work was finally conducted in order to predict stress development of a massive structure of alkali-activated slag mortar subjected to internal (self) and external strains' restraints (at mesoscopic and macroscopic scales)