Carbonic Acid Corrosion of Mortars Containing Fly Ash


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Title: Carbonic Acid Corrosion of Mortars Containing Fly Ash

Author(s): H. -P. Backes

Publication: Special publication

Volume: 91


Appears on pages(s): 621-636

Keywords: acid resistance; carbonation; cements; chemical attack; compressive strength; corrosion; durability; fly ash; mortars (material); nondestructive tests; porosity.

Date: 2/1/1986

The influence of fly ash addition - used as a concrete addition according to the German standard DIN 1045 in exchange for cement - on the resistance of mortar against carbonic acid attack has been investigated.The tests have been carried out with cements PZ 35 F (Portland cement) and HOZ 35 L (blast-furnace slag cement), two different fly ashes, three different water-cement ratios of the initial mortars without fly ash and the same flow value in each case. The fly ash(f)-cement(c)-proportion was varied from f/c = 0,25 to 1,OO. After certain periods of storing, values have been measured as follows: mass and volume of test specimen, bulk density, nal activation resonance frequency by longitude-respectively the dynamic modulus of elasticity, compressive strength, depth of carbonation and water absorption. The investigations on mortar prisms stored in water with a carbonic acid concentration of more than 60 mg C02/1 for 4 years showed that replacement of cement with fly ash can slow down the rate of attack. The loss of mass as a significant value essentially depends, under the same conditions, on the porosity of the hardened cement paste. It can be considerably influenced by using selected fly ashes.

Special publication, International Partner Access.

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