Effect of Synthetic and Natural Zeolite on ASR Expansion
Keywords:ASR, synthetic zeolite, natural zeolite, expansion, compressive strength.
The cation exchange capability (CEC), pozzolanic reaction, and filling effects are important keys of natural zeolite for mitigation of Alkali Silica Reaction (ASR), but variation of the zeolite's composition is a major problem when it is utilized. This may not be the case for synthetic zeolite. This paper presents the effects of natural and synthetic zeolite on Alkali Silica Reaction's expansion control. The percentage cement replacement of synthetic and ground natural zeolite-clinotilolite type (SZ and NZ) varied from 0 to 10 and 0 to 20, respectively. It was found that the large percentage replacement (10 - 20%) changed behaviors of fresh and hardened mixtures significantly. Large replacements of SZ (i.e., 7.5% and 10%) significantly reduced workability and compressive strength, and increased expansion. Slight reductions in expansion were even found for the use of small percentage replacement (SZ < 5.0%). Chemical analysis and strength reactivity index tests revealed the non-pozzolanic properties of synthetic zeolite, but not the ground natural zeolite (NZ). The NZ exhibited both pozzolanic reactivity and the capability to significantly reduce expansion. At 20% replacement of NZ, the expansion significantly reduced to none at 14 days of acceleration and less than 0.02% at the longer duration of 28 days. It was confirmed that the high CEC of the studied synthetic zeolite is not the key factor for the effective mitigation for ASR.
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