Evaluation of Industrial Ashes in Cement Replacement in Mortars

Abstract

It is well known that cement production has a high negative impact on the environment. This fact, in conjunction with the high demand for this product worldwide, has created concern over how to reduce its use. Various materials have been tested as partial or total replacements for cement, one of which is biomass ash. In this article we report the preparation of test samples of mortar using two types of biomass ash, the first of forest origin and the second agricultural; both were used to replace cement in proportions of 10%, 20% and 30%. The test samples were assayed for compression and flexion after 7, 14, 28 and 90 days. After 28 days the apparent density, open porosity, absorption, capillarity and ultrasound velocity were measured. All the results of the series were compared with a control mortar. In the compression and flexion assay, a higher resistance than the control mortar was obtained with 10% replacement of both types of ash after 90 days, however with 20% and 30% ash the results were inferior to traditional mortar. There was an increase in the absorption percentage and porosity as the percentage of cement replacement increased; this increase was smaller for ash from agricultural biomass than ash from forest biomass. The density diminished as the percentage of replacement material increased, but the change was smaller with ash from agricultural biomass; this may be attributed to a filler effect produced by its granulometric distribution.