Abstract
High volume fly ash (FA) binders are characterized by long setting times and low early strength. By applying mechanical and/or chemical activation methods, it is possible to increase the reactivity of FA and improve the properties of the binder. In this paper, influence of mechanical activation of FA on the properties of binders prepared with 70% FA and 30% Portland cement was investigated. Additionally, effect of chemical activation of the binder by using sodium sulfate as activator was evaluated. The binder obtained by combining mechanical and chemical activation had the highest early strength (up to 7 days) and the shortest setting times. However, the highest strength of the binder after 90 days was obtained by applying only mechanical activation of FA.
Highlights
binders are characterized by long setting times
possible to increase the reactivity of fly ash (FA)
influence of mechanical activation of FA on the properties of binders prepared with 70% FA
Summary
U ovom istraživanju korišćen je uzorak EFP iz termoelektrane „Nikola Tesla B“ (Srbija), portland cement oznake CEM I 52,5 N (NašiceCement, Hrvatska) i natrijum-sulfat (Sigma-Aldrich, čistoće > 99,0%). Mehanička aktivacija EFP je izvršena mlevenjem u planetarnom mlinu (Fritch Pulverisette 05 102) pri brzini od 380 rpm, u trajanju od 15 min [22]. Hemijska aktivacija je izvršena dodavanjem 2% natrijum-sulfata u odnosu na ukupnu masu vezivnog materijala (EFP + PC), pri homogenizaciji. Kontrolni uzorci na bazi 100% PC pripremljeni su i negovani pod istim uslovima kao paste i malteri sa EFP. Specifična površina uzoraka EFP i MAEFP je određena metodom adsorpcije-desorpcije N2 pomoću uređaja Micromeritics ASAP 2020 (Micromeritics) korišćenjem BET (Brunauer, Emmett, Teller) jednačine. Ispitivanje morfologije uzoraka EFP i MAEFP izvršeno je metodom skenirajuće elektronske mikroskopije (SEM). Uzorci su ispitivani u opsegu 5 - 55 o2 , pri brzini od 1°/min. Određivanje vremena vezivanja izvršeno je prema standardu SRPS EN 196-3 [23], pomoću Vikat aparata, a ispitivanje čvrstoće pri pritisku maltera prema standardu SRPS EN 196-1 [24] pomoću uređaja Advantest 9 (Controls)
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