Durability of high belite cement as new technical solution for concrete

The study presents an investigation on the durability performance of concretes produced with an industrial scale high belite cement. This binder, thanks to the high amount of C-S-H gel and the lower C3S/C2S ratio, is characterized by high durability properties. Good resistance to freeze/thaw cycles, very low chloride migration and excellent resistance to sulfate attack were demonstrated. Theaccelerated carbonation test revealed that the belite cement, due to the high C2S phase amount, is able to increase its strength over time when exposed to high CO2 concentration. Durability and strength results were compared with those of CEM I, CEM II, and CEM III. In addition, a comparison of the performance of a self-compacting concrete produced with high belite cement and CEM I (as reference) is also presented. The results show that the self-compacting concrete with the high belite cement is able to reach sufficient strengths already after 1 day of hydration, with a low heat development and improved durability properties, compared to CEM I

Fingerprinting the Hydration Products of Hydraulic Binders Using Snapshots from Time-Resolved In Situ Multinuclear MAS NMR Spectroscopy

The very early hydration behavior of a hydraulic binder phase, ye'elimite, Ca4Al6O12SO4, in the absence and in the presence of calcium sulfate, has been investigated. A time-resolved in situ multin..

A Preliminary Study on Light Transmittance Properties of Translucent Concrete Panels with Coarse Waste Glass Inclusions

This paper investigates the potential reuse of coarse glass wastes as insert in a high performance cement matrix to produce translucent concrete panels for architectural applications such as interior walls. The effects of the addition of glass scraps on chemical and optical properties of concrete were studied. Alkali-silica reactivity resistance tests were carried out to evaluate the reactivity between amorphous waste glass and alkaline concrete pore solution. Light transmittance LT was evaluated through Radiance simulations and measurements on sample prototypes. The increase in the amount of daylight in a sample room and the reduction in the energy demand for lighting EDl were investigated through Daysim simulations. Compared to two opaque side walls, the use of two translucent concrete walls with a LT of 5% allowed a reduction in EDl up to 16% in Palermo (L=38.3°N)

Involvement of the Ubiquitin-Proteasome System in the Formation of Experimental Postsurgical Peritoneal Adhesions

We investigated the Ubiquitin-Proteasome System (UPS), major nonlysosomal intracellular protein degradation system, in the genesis of experimental postsurgical peritoneal adhesions. We assayed the levels of UPS within the adhered tissue along with the development of peritoneal adhesions and used the specific UPS inhibitor bortezomib in order to assess the effect of the UPS blockade on the peritoneal adhesions. We found a number of severe postsurgical peritoneal adhesions at day 5 after surgery increasing until day 10. In the adhered tissue an increased values of ubiquitin and the 20S proteasome subunit, NFkB, IL-6, TNF-α and decreased values of IkB-beta were found. In contrast, bortezomib-treated rats showed a decreased number of peritoneal adhesions, decreased values of ubiquitin and the 20S proteasome, NFkB, IL-6, TNF-α, and increased levels of IkB-beta in the adhered peritoneal tissue. The UPS system, therefore, is primarily involved in the formation of post-surgical peritoneal adhesions in rats

Limestone calcined clay binders based on a Belite-rich cement

Portland-based Limestone Calcined Clay Cements, LC3, are receiving considerable attention because the CO2 footprint can be reduced up to 40 %. Here, we report a related family: Belite-rich-LC3. These blends are expected to have very good durability performances. Selected properties for two members are reported including calorimetric data and mechanical strength developments. The phase evolutions are studied by Rietveld analysis backed by the thermal behaviour. Their microstructures are studied by mercury intrusion porosimetry. The hydration rates of these blends have been boosted by C-S-H seeding which led to an increase of mechanical strengths. At 28 days, seeded mortars with cement replacement degrees of 30 and 45 wt% displayed 74 and 61 MPa of compressive strengths, respectively. Moreover, overall porosities and pore entry threshold values decreased in the admixture-containing binders.Financial support from PID2020-114650RB-I00 research grant from the Spanish Government, which is co funded by FEDER, is gratefully acknowledged. The contribution of Mr. Iván González-Fernández to some parts of the experimental section is gratefully acknowledged. Funding for open access charge: Universidad de Málaga / CBUA

Processing and hydration activation of limestone calcined clay belite rich cements.

Belite-rich limestone calcined clay cements, BR-LC3, could be an alternative for low carbon binders with potentially very good durability properties, given the high amount of C-S-H gel from the cement hydration with additional C-(A)-S-H from the pozzolanic reaction. Nevertheless, BR-LC3 phase hydration rates at early ages are slow and they must be enhanced, for instance by using C-S-H nucleation seeding admixtures. In this work, a BR-LC3 binder was prepared using a clinker-activated Belite-rich cement, BC (58 wt%), kaolinitic calcined clay (26 wt%), limestone (13 wt%) and gypsum (3 wt%). Pastes were prepared with a water-to-binder (w/b) ratio of 0.40 and superplasticizer. Mortars were prepared with the w/b=0.40 and having a target slump self-flow of 210±20 mm. Paste hydration characterization was carried out by thermal analysis, Rietveld quantitative phase analysis and mercury intrusion porosimetry. The compressive strengths of the mortars were also determined. Remarkable compressive strength improvements at 7 and 28 days are shown by using a C-S-H seeding admixture. The improvement of mechanical strengths is not related to belite phase hydration acceleration but mainly to lower porosity.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

LFA-1 antigen identifies immature stages of human NK cell differentiation

Background. Human Natural killer (NK) cells are characterized by NK cell receptors (NKRs) with inhibitory and activatory function that finely control their functional activities. In particular, they express inhibitory receptors for MHC class I molecules, named killer cell immunoglobulin (Ig)-like receptors (KIRs) and C-type lectin CD94-CD159a, and many triggering molecules like NKp30, NKp44, NKp46, (called natural cytotoxicity receptors, NCRs), NKG2D, CD161, and CD244. The majority of peripheral blood human NK cells are characterized by a phenotype with a low density expression of CD56 (CD56dim) and a high expression of CD16 (CD16bright), whereas a minority (approximately 5–10%) shows a bright expression of CD56 (CD56bright). This latter NK subset presents relatively high expression of some cytokine receptors (CD117 and CD25) and the CD94-CD159a heterodimeric inhibitory receptor. CD56bright NK cells are widely expressed in lymphoid tissues and can be generated from CD34+ cells when cultured with combinations of flt-3 ligand (FL) or stem cell factor plus IL-15 or IL-2. During their development, NK cells sequentially acquire many different antigens but there is still limited knowledge on differentiation antigens able to identify immature human NK cells and the specific sequence through which developing NK cells acquire the expression of NKR.Methods. NK cells obtained from human CD34+ hematopoietic progenitor cells after 30-day culture with FL plus IL-15, or from peripheral and umbilical cord blood samples were characterized.Results. Virtually, all CD56 NK cells differentiated in vitro expressed CD117, CD25, NCRs, NKG2D, CD161, and CD244, while only a subset expressed CD18-CD11a (LFA-1), and CD94 molecule, defining an immature CD56bright/NCRs+/NKG2D+/LFA-1-/CD94- subset. Another small subset of cells expressing CD94 but not LFA-1 integrin was also identified, suggesting that during NK differentiation LFA-1 might be upregulated later than CD94. To verify this hypothesis in vivo, we evaluated the NK cell expression of LFA-1 in both peripheral and umbilical cord blood samples. Interestingly, in these blood fluids, we have identified a lineage negative CD34-/LFA-1low/NKp46dim/NKG2Ddim/CD94- subset that resembled an immature stage of NK cells present in lymph nodes. Conclusions. Altogether, the results indicate that CD18-CD11a integrin, as well as CD11b in mice, may be a useful marker to identify immature stages of human NK cell differentiation

Portland and Belite Cement Hydration Acceleration by C-S-H Seeds with Variable w/c Ratios

The acceleration of very early age cement hydration by C-S-H seeding is getting attention from scholars and field applications because the enhanced early age features do not compromise later age performances. This acceleration could be beneficial for several low-CO2 cements as a general drawback is usually the low very early age mechanical strengths. However, the mechanistic understanding of this acceleration in commercial cements is not complete. Reported here is a contribution to this understanding from the study of the effects of C-S-H gel seeding in one Portland cement and two belite cements at two widely studied water–cement ratios, 0.50 and 0.40. Two commercially available C-S-H nano-seed-based admixtures, i.e., Master X-Seed 130 and Master X-Seed STE-53, were investigated. A multi-technique approach was adopted by employing calorimetry, thermal analysis, powder diffraction (data analysed by the Rietveld method), mercury intrusion porosimetry, and mechanical strength determination. For instance, the compressive strength at 1 day for the PC (w/c = 0.50) sample increased from 15 MPa for the unseeded mortar to 24 and 22 MPs for the mortars seeded with the XS130 and STE53, respectively. The evolution of the amorphous contents was determined by adding an internal standard before recording the powder patterns. In summary, alite and belite phase hydrations, from the crystalline phase content evolutions, are not significantly accelerated by C-S-H seedings at the studied ages of 1 and 28 d for these cements. Conversely, the hydration rates of tetracalcium alumino-ferrate and tricalcium aluminate were significantly enhanced. It is noted that the degrees of reaction of C4AF for the PC paste (w/c = 0.40) were 10, 30, and 40% at 1, 7, and 28 days. After C-S-H seeding, the values increased to 20, 45, and 60%, respectively. This resulted in larger ettringite contents at very early ages but not at 28 days. (...)This research has been partly supported by a P18-RT-720 research grant, co-funded by ERDF, from Junta de Andalucía, Spain. Partial funding for open access charge: Universidad de Málaga

Portland and belite cement hydration acceleration by C-S-H seeds with variable w/c ratios

The acceleration of very early age cement hydration by C-S-H seeding is getting attention from scholars and field applications because the enhanced early age features do not compromise later age performances. This acceleration could be beneficial for several low-CO2 cements as a general drawback is usually the low very early age mechanical strengths. However, the mechanistic understanding of this acceleration in commercial cements is not complete. Reported here is a contribution to this understanding from the study of the effects of C-S-H gel seeding in one Portland cement and two belite cements at two widely studied water–cement ratios, 0.50 and 0.40. Two commercially available C-S-H nano-seed-based admixtures, i.e., Master X-Seed 130 and Master X-Seed STE-53, were investigated. A multi-technique approach was adopted by employing calorimetry, thermal analysis, powder diffraction (data analysed by the Rietveld method), mercury intrusion porosimetry, and mechanical strength determination. For instance, the compressive strength at 1 day for the PC (w/c = 0.50) sample increased from 15 MPa for the unseeded mortar to 24 and 22 MPs for the mortars seeded with the XS130 and STE53, respectively. The evolution of the amorphous contents was determined by adding an internal standard before recording the powder patterns. In summary, alite and belite phase hydrations, from the crystalline phase content evolutions, are not significantly accelerated by C-S-H seedings at the studied ages of 1 and 28 d for these cements. Conversely, the hydration rates of tetracalcium alumino-ferrate and tricalcium aluminate were significantly enhanced. It is noted that the degrees of reaction of C4AF for the PC paste (w/c = 0.40) were 10, 30, and 40% at 1, 7, and 28 days. After C-S-H seeding, the values increased to 20, 45, and 60%, respectively...This research has been partly supported by a P18-RT-720 research grant, co-funded by ERDF, from Junta de Andalucía, Spain

C-S-H seeding activation of Portland and Belite cements: An enlightening in situ synchrotron powder diffraction study

C-S-H seeding in Portland cements is well known from basic scientific works and field applications. Moreover, this activation approach could be beneficial for low-CO2 cements under development where a general drawback is poor mechanical strengths during the first week of hydration. However, a mechanistic understanding of the different processes taking place when seeding is still not developed. Here, we contribute to this knowledge gap by studying one commercial Portland cement and two industrial-trial belite cements. Three different admixtures are employed, viz. two types of commercial C-S-H seeding and triisopropanolamine as a typical alkanolamine. A multitechnique approach is employed including calorimetry, ultrasonic pulse velocity, thermal analysis and Rietveld analysis of laboratory X-ray powder diffraction data. Chiefly, an in situ X-ray synchrotron diffraction study has allowed mapping out the evolution of every crystalline phase. Furthermore, the use of an internal standard permitted to measure the changes in the overall amorphous content. In a nutshell, alite and belite (phases) hydrations are not significantly accelerated by C-S-H seeding for the three studied cements. Conversely, sulphate and aluminate phase dissolutions are enhanced. Faster ettringite crystallisation contributes to the observed improved mechanical properties at early ages. Moreover, a synergistic effect between C-S-H seeding and alkanolamine addition is proved. The importance of these findings for the possible acceleration of low-CO2 cement hydration is discussed.This research has been partly supported by two research grants PID2020-114650RB-I00 (from Spanish Government) and P18-RT-720 (from Junta de Andalucía, Spain), which are co-funded by ERDF. ALBA synchrotron is thanked for granting beamtime at BL04-MSPD beamline. We also thank the assistance of Dr. Oriol Vallcorba during the synchrotron experiment and thorough discussion of this work with Peter Schwesig (Master Builders Solutions). Funding for open access charge: Universidad de Malaga/CBUA