Workability Behaviour of Cement Mortar with Pond Ash as Fine Aggregates–Partial to Full Replacement

Abstract

AbstractRapid urbanization has led to high consumption of natural river sand as an aggregate as well as higher generation of pond ash due to the high demand for energy. Pond ash, a waste generated in thermal power plants during the coal combustion process, is detrimental to the environment, directly or indirectly demanding a large area of land for disposal. The properties of pond ash, however, also make it suitable to serve as an alternative to river sand as fine aggregates in concretes and mortar. The use of pond ash as fine aggregates in mortar helps to solve two pressing problems at the same time without much risk. This paper focuses on investigation on fresh and hardened mortar with varied percentages of pond ash as natural aggregate in different cement: sand proportions. The properties are assessed as per the standard test procedures. Flow table test is conducted to assess the workability characteristics, while compressive strength test is conducted for its strength behaviour. The results show that the workability and compressive strength of the mixes are lesser for higher percentage of replacement and for leaner mix. This can be attributed to the shape of pond ash and higher fine aggregate content. The investigation showed that higher water content was necessary at higher replacement percentages of sand with pond ash, to contribute to increased workability, which may be the reason for decreased compressive strength. The bleeding of water on the flow table may be due to the higher water absorption of pond ash particles and lesser water retentivity at later point of time. The compressive strength, even after reduction is still in the range of requirements as per the standard set by the BIS. The flowability of mortar shows that the mortar mixes are workable at all levels of replacements of sand with pond ash. The investigation recommends using mortar for masonry works without compromise in its wet properties and also compressive strength. However, the study highlights the scope of future research to address the water absorption properties of porous particles of pond ash so as to use the pond ash in large scale for sustainable construction activities, solving problems of sand deficiency and problem of disposal of pond ash.KeywordsSustainabilityNatural river sandPond ashWorkabilityCompressive strength