We were discussing about sand replacement with glass sand and its impact on concrete properties. Naik and Wu conducted extensive tests for determining effect of sand replacement with glass aggregate; these were a partial replacement. In this application alkali-silica reaction (ASR)is the controlling factor for concrete mix design and used some ASR suppressors like
a. Cement replacement by flyash. Class F flyash are used at a percentage of 15, 30, and 45 by weight.
b. Corresponding replacements of sand with glass aggregate were also 15%, 30% and 45% of concrete sand.
Under this combination of concrete mix alkali-silica reaction, compressive strength and tensile strength (splitting) as well of resulting concrete were evaluated. The following conclusions were drawn:
a. A little reduction of compressive strength was found when sand is replaced with crushed glass.
b. A linear relationship of expansion was observed corresponding to percentage of crushed glass when flyash is absent in concrete mix, the expansion was obviously for ASR.
c. Of these different percentage of cement replacements, up to 30% replacement with flyash didn’t stop expansion, only can delay expansion i.e. no influence on long term expansion.
d. A successful suppression of ASR expansion was observed when cement replacement reached 45% irrespective of percent replacement of sand with glass aggregates. It is established that a greater than 45% cement replacement with class F flyash can control deleterious expansion.
Dear reader we think, you will have better understanding about partial replacement of sand from the studies provided by Naik and Wu. In our next post we will discuss about other recycled materials as aggregates for concrete.