Carbonation of fly ash concrete

Abstract

The carbonation of fly ash concrete is reported, with particular emphasis on the role of curing. Concretes with nominal strength grades C25, C35 and C45 and a range of fly ash levels (0–50%) were exposed to various treatments during the first 28 days; i.e. different moist curing periods anda range of ambient temperatures and relative humidities after curing. After28 days the concretes were stored either internally or externally (sheltered) and the rate of carbonation was monitored. The results emphasize the importance of adequate curing for concrete durability, irrespective of the presence of fly ash. In some cases increasing the initial curing period from 1to 7 days had the effect of reducing carbonation by 50%. Concretes with up to 30% fly ash carbonated to a similar or slightly greater degree compared with OPC concretes of the same strength grade. However, concretes containing 50% fly ash carbonated at significantly greater rates. A graphical model is presented which allows prediction of the carbonation rate to be made from a knowledge of the concrete mix (strength grade and fly ash content), degree of curing, ambient conditions during and after casting, and type of exposure.

Relation between carbonation resistance, mix design and exposure of mortar and concrete

“…However, a wide range of CO 2 concentrations, different relative humidity conditions and temperatures are used in such accelerated tests [8,10,[12][13][14]. Therefore it is not clear, whether the results obtained with one specific accelerated test are transferable to another one and, even more important, to natural carbonation [15][16][17][18][19][20]. Another important point is the curing of the samples before they are exposed to carbonation.…”

Strength, Water Absorption and Carbonation Depth of Micro Fine Quarry Dust Concrete Grade 60

“…Study by Hewlet [38] stated that concrete with pozzolanic material is less capable of resisting carbonation than OPC concrete. The extended of chemical interaction which bind the CO 2 will be reduced compared to CONTROL concrete [39]. From Fig.…”

A natural cement analogue study to understand the long-term behaviour of cements in nuclear waste repositories: Maqarin (Jordan)

“…The ingress of the carbonation front into mortar and concrete slows down following a square root of time relation. After an exposure to sheltered outdoor conditions for 10 years, a concrete of the strength class C25 produced with ordinary Portland cement may display a depth of carbonation of 15e20 mm (Thomas et al, 1992). C-A-S-H is more sensitive to carbonation than ettringite and thaumasite due to its low degree of crystallinity.…”