Rice Husk Ash and Waste Marble Powder as Alternative Materials for Cement

Concrete, a cornerstone of modern construction, owes its widespread adoption to global industrialization and urbanization, with mortar being an essential component. However, the cement production process is energy-intensive and generates significant CO2 emissions. This study explores the use of agricultural (rice husk ash, RHA) and industrial (waste marble powder, WMP) waste materials as partial cement replacements in mortar. Despite extensive research on RHA and WMP individually, studies examining their combined effects remain scarce. This research assessed cement replacement levels from 0% to 30% in 5% increments, evaluating the fresh, mechanical, durability, and microstructural properties of the mortar. The findings showed that replacing 20% of cement with RHA and WMP increased compressive strength by 20.65% after 28 days, attributed to improved homogeneity and pozzolanic reactions that produced more calcium silicate hydrate. Water absorption decreased from 8.3% to 6.34%, indicating lower porosity and enhanced uniformity. Microstructural analyzes showed a denser mortar with 13% less mass loss at 20% replacement level. However, higher replacement levels reduced workability due to the increased surface area of RHA and WMP. Generally, using RHA and WMP as partial replacements of up to 20% significantly enhances mortar properties and supports sustainability.