Title: Carbonic Acid Corrosion of Mortars Containing Fly Ash

Author(s): H. -P. Backes

Publication: Symposium Paper

Volume: 91

Issue:

Appears on pages(s): 621-636

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

DOI: 10.14359/10091

Date: 2/1/1986

Abstract:
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.