“…A consensus exists upon the increased capacity of slag blended cements to bind chlorides, compared to pure OPC. This phenomenon has been attributed to the higher alumina content of slag [7], or to the [OH À ]/[Cl À ] ratio [5] and the negative role of sulphates has been highlighted [9]. In this study, only data obtained by the intrusion of external chloride ions into the sample [6] were employed, as opposed to internallymixed chlorides [5,8].…”
h i g h l i g h t sThe composition of the slag is crucial to the chloride binding capacity of a paste. The interaction between the slag and OPC components is taken into account. The C-S-A-H phase binds approximately two thirds of the total bound chlorides. The remaining third is attributed to AFm phases. The results of the model are highly improved from a previous model from literature.
a r t i c l e i n f o
a b s t r a c tAn improved hydration model of slag-blended cements, taking into account new insights, is used to estimate and quantify the hydration products of slag-blended cements. Individual chloride binding isotherms are used to correlate these amounts of hydration products with the amount of bound chlorides. A number of parameters are directly or indirectly taken into account when estimating the chloride binding ability of a slag-blended cement paste: cement composition, slag content, water/binder ratio, curing age, and free chloride concentration. The model allows the study of the breakdown of bound chlorides by hydration products and their source -either the OPC or the slag.
“…A consensus exists upon the increased capacity of slag blended cements to bind chlorides, compared to pure OPC. This phenomenon has been attributed to the higher alumina content of slag [7], or to the [OH À ]/[Cl À ] ratio [5] and the negative role of sulphates has been highlighted [9]. In this study, only data obtained by the intrusion of external chloride ions into the sample [6] were employed, as opposed to internallymixed chlorides [5,8].…”
h i g h l i g h t sThe composition of the slag is crucial to the chloride binding capacity of a paste. The interaction between the slag and OPC components is taken into account. The C-S-A-H phase binds approximately two thirds of the total bound chlorides. The remaining third is attributed to AFm phases. The results of the model are highly improved from a previous model from literature.
a r t i c l e i n f o
a b s t r a c tAn improved hydration model of slag-blended cements, taking into account new insights, is used to estimate and quantify the hydration products of slag-blended cements. Individual chloride binding isotherms are used to correlate these amounts of hydration products with the amount of bound chlorides. A number of parameters are directly or indirectly taken into account when estimating the chloride binding ability of a slag-blended cement paste: cement composition, slag content, water/binder ratio, curing age, and free chloride concentration. The model allows the study of the breakdown of bound chlorides by hydration products and their source -either the OPC or the slag.
“…The increase of sulfate content in cement was found to reduce the chloride binding capacity since sulfates were more strongly bound with C3A than were chlorides [8,9]. The contents of C3A, C4AF and sulfate in cement were found to be significant parameters influencing the chemical binding of chloride [10].…”
Section: L'article Prosente Un Module Capable De Provoir La Capacito mentioning
A model for predicting time-dependent chloride binding capacity of cement-fly ash cementitious systems was proposed. The proposed model took into account both chemical binding and physical binding. Chemical binding was considered to depend on the amount of unhydrated aluminate and aluminoferrite phases while physical binding depended upon the quantity of hydrated and pozzolanic products. The concept of time-dependent chloride binding capacity was introduced in the model with the consideration of curing time and chloride exposure period. The chloride binding of cement pastes and cement-fly ash pastes under different curing times and chloride exposure periods were tested. Three types of cement and two types of fly ash were used.From the experimental results, time-dependent behavior of chloride binding capacity was observed. At the same chloride exposure period, pastes with longer curing time prior to chloride exposure bound less chloride than those exposed with shorter curing time. Longer exposure period of paste resulted in larger chloride binding capacity. The analytical results from the model were verified with the experimental results from the authors mad other researchers. The verification showed that the proposed model was satisfactory for predicting the chloride binding capacity of various cement and cement-fly ash cementitious systems.
RI~SUMI~
“…Όμως, πιστεύεται ότι ο ρυθμός διάχυσης των χλωριόντων, για το σκυρόδεμα του σύνθετου τσιμέντου με σκωρία, θα μειώνεται με την ηλικία του σκυροδέματος [165]. Έχει δειχθεί ότι η αντικατάσταση αμιγούς τσιμέντου Portland με σκωρία υψικαμίνων αυξάνει σημαντικά την ικανότητα δέσμευσης χλωριόντων [166]. Λεπτομερέστερα, η ικανότητα δέσμευσης των χλωριόντων από πάστες με σκωρία βρέθηκε να αυξάνεται με την αύξηση των επιπέδων αντικατάστασης με σκωρία και με τη συγκέντρωση έκθεσης στα χλωριόντα.…”
Section: δέσμευση των χλωριόντων από τα σύνθετα τσιμένταunclassified
“…Αναφέρεται ότι η ικανότητα δέσμευσης των χλωριόντων από το τσιμέντο μειώνεται ταχέως με την αύξηση της συγκέντρωσης των θειικών ιόντων, ανεξαρτήτως του συνδεδεμένου κατιόντος με τα θειικά ιόντα [166]. Άλλες μελέτες έδειξαν, επιπροσθέτως, ότι η συγκέντρωση των υδροξυλιόντων αυξήθηκε σημαντικά λόγω της ύπαρξης των θειικών ιόντων σε σύγκριση με την αλκαλικότητα του διαλύματος των πόρων παστών τσιμέντου, που επιμολύνθηκαν με όμοιες ποσότητες χλωριούχων αλάτων.…”
Section: επίδραση των θειικών ιόντων στη δράση και στη δέσμευση των χunclassified
“…Αυτό αποδεικνύει ότι, ενώ η διάχυση των χλωριόντων είναι μεγαλύτερη στα σκυροδέματα που συντηρούνται στα σύνθετα διαλύματα, το μεγαλύτερο μέρος τους παραμένει αδέσμευτο. Ο λόγος είναι η περιορισμένη ικανότητα δέσμευσης χλωριόντων από τα χρησιμοποιούμενα υλικά και η προνομιακή δράση των θειικών ιόντων έναντι των χλωριόντων με τις ασβεσταργιλικές φάσεις του σκυροδέματος [92,93,166]. Τέλος, από το Σχήμα 7-2 γίνεται αντιληπτό ότι η διάχυση των χλωριόντων είναι μεγαλύτερη, καθώς αυξάνεται η περιεκτικότητα του τσιμέντου σε ασβεστόλιθο.…”
Section: συσχετισμός ελεύθερων και συνολικών χλωριόντωνunclassified
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