Microstructure of alkali-silica reaction products in conventional standard and accelerated testing


Mortar bars with granite or chalcedonite aggregate were tested under conventional standard testing, based on storage  of specimens at 38 plus or minus 2 C, RH at least 95%. Aggregates of granite or chalcedonite and silica sand containing opal were used in mortar bars for expansion measurement under accelerated testing, based on storage of specimens in 1 N NaOH solution at 80 C. SEM equipped with EDX showed that specimens that expanded in the conventional standard mortar bar test (after 30 months) contained alkali-silicate products and secondary ettringite. Specimens  that expanded in the accelerated test (after 16 days) showed  the same morphological and compositional alkali-silica gel only. The reaction products in both methods appear to be the  same, indicating that reaction mechanisms are the same but differ only in rates. The results of the conducted test show  that the alkali content (especially potassium) in cement plays an important role in the process of expansion in the accelerated method. 21 refs.

Primary author(s): Owsiak Z

                            Kielce,Technical University

Source: Ceramics-Silikaty


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