Q.: A stucco was intended to be white but is light tan in color. The stucco mix was made with one bag of white Portland cement, one bag of white masonry cement and three 5-gallon buckets of masonry grade sand mixed with torpedo sand. The white portland cement and white masonry cement have been checked for color and have been found to satisfy the color requirement. Subsequent efforts to reproduce the same tan color have failed. What could have caused the tan discolorations?
A.: It sounds very much as though the mix became misproportioned to the extent that the sand determined the color. There also might have been excess fines in the sand. We suggest that you determine the cement content of the stucco by chemical or petrographic analysis to see if it conformed to the mix design. If it did not conform, the sand content may have been high or may have contained an excess of fines.