Title:
Sulfate Attack of Mortars Containing Recycled Fine Aggregates
Author(s):
S. T. Lee, H. Y. Moon, R. N. Swamy, S. S. Kim, and J. P. Kim
Publication:
Materials Journal
Volume:
102
Issue:
4
Appears on pages(s):
224-230
Keywords:
compressive strength; expansion; fine aggregate; sulfate attack
DOI:
10.14359/14614
Date:
7/1/2005
Abstract:
This paper presents a detailed experimental study on the durability of mortar specimens made with recycled fine aggregate exposed to external sulfate attack. The replacement level and the type of the recycled fine aggregate were the main test variables. The mortar specimens were immersed in a 5% sodium sulfate solution for 360 days and regularly monitored for visual damage, variation of expansion, and compressive strength. In addition, at the end of 360 days, the products of sulfate attack and the mechanism of attack were investigated through x-ray diffraction and scanning electron microscopy. To evaluate the strength loss further, some mortar specimens were cured in tap water. The experimental data indicate that the use of recycled fine aggregates up to a maximum of 50% replacement level had a beneficial effect on durability against sulfate attack both in terms of strength loss and expansion. Mortar specimens incorporating 100% replacement level, regardless of type of recycled aggregate, suffered severe deterioration. The test results indicated that the water absorption of the recycled fine aggregate was a major factor controlling expansion, strength loss, and the intensity of damage due to sulfate attack. The microstructural studies indicated that the primary cause of deterioration of the mortar specimens with recycled aggregate was the formation of thaumasite and gypsum due to sulfate attack.