Hydration of Secar 71 aluminous cement in presence of granulated blast furnace slag

Microstructural Evolution of Calcium Aluminate Cements Hydration with Silica Fume and Fly Ash Additions by Scanning Electron Microscopy, and Mid and Near‐Infrared Spectroscopy

“…Majumdar (1990) showed that with concrete based on equal amounts of CAC and BFS cured at either 20° or 38°C, the compressive strength increased continuously over a period of 1 year, in contrast to control samples made without BFS, which showed decreases in strength associated with conversion. Those concretes containing CAC+BFS have also shown good chemical resistance and reduced temperature rise during hardening 10,11 …”

“…[1][2][3][4][5] The conversion reactions of CAC are shown schematically below: 12 , AH 3 :Al(OH) 3 , and H:H 2 O. Some authors [6][7][8][9] have found that an interesting way to reduce hydrate conversion and decrease the strength is to replace some of the CAC by blast furnace slag (BFS) or a pozzolan such as microsilica and metakaolin. showed that with concrete based on equal amounts of CAC and BFS cured at either 201 or 381C, the compressive strength increased continuously over a period of 1 year, in contrast to control samples made without BFS, which showed decreases in strength associated with conversion.…”

“…Those concretes containing CAC1BFS have also shown good chemical resistance and reduced temperature rise during hardening. 10,11 The reaction that avoids the conversion of CAC hexagonalhydrated phases could take place in the following way 5,[11][12][13] : the silica content of the mineral addition would react with calcium aluminates, initially avoiding the formation of the hexagonal form C 2 AH 8 and subsequently, the conversion in the cubic form C 3 AH 6 . Therefore, instead of this cubic phase, a hexagonal aluminate hydrate-containing silica, called gehlenite (Ca 2 Al 2 SiO 7 Á 8H 2 O or C 2 ASH 8 ), is proposed to be formed.…”

Physico-mechanical characteristics and durability of calcium aluminate blended cement subject to different aggressive media

“…Presence of WCS or ACS decreases the rate of conversion process, through the formation of C 2 ASH 8 instead of C 3 AH 6 , which will increase both of the strength and resistivity against aggressive solutions [12][13][14]. CAC and CAC-WCS and CAC-ACS have good resistivity against aggressive media due to the decreasing amount of Ca(OH) 2 in their hydration medium, the low porosity of CAC pastes due to the precipitation of colloidal aluminum hydroxide (AH 3 ), which fills up the open pores which formed due to the conversion process [13][14][15]17,19,31]. The increase in the strength values of pastes immersed in 5% NaCl solution, this is attributed to the continuation of hydration reaction of the anhydrous particles present in the cement paste especially the slag portions (WCS or ACS) and also to the reaction that may be happened between the hydrated calcium aluminate and the sodium chloride solution to form the Friedal salt (calcium chloroaluminate phase-C 3 A.CaCl 2 .10H 2 O) (Fig.…”

“…One interesting way to reduce the conversion of hexagonal hydrates and the decreasing of strength, this is due to replace some of the CAC by pozzolans cured at either 20-60°C, the compressive strength increased continuously, whereas the compressive strength of neat CAC decreased, due to the conversion reaction. Stratlingite (C 2 ASH 8 or SF [11][12][13][14][15][16]. Initially, silica inhibits the formation of C 2 AH 8 , and C 3 AH 6 after conversion reaction as well as reflecting the role of WCS and ACS, preventing the conversion reaction occurring during hydration of CAC [13].…”