# Concrete Waste and CDW Powders as Portland Cement Replacement in Mortar: A Preliminary Study

## TL;DR

This study explores using concrete and demolition waste powders as sustainable alternatives to replace part of the cement in mortar, reducing environmental impact while maintaining performance.

## Contribution

The novelty lies in demonstrating that CDW and CON powders can replace up to 10% of cement without compromising mortar strength.

## Key findings

- Replacing up to 10% of cement with CDW or CON powders maintained or slightly improved compressive strength.
- Higher replacement levels (15-20%) caused moderate strength reductions due to dilution effects.
- CDW and CON powders transformed 52.5 R Type I cement into a 42.5 R Type II equivalent, showing feasibility for sustainable binders.

## Abstract

The construction industry’s heavy reliance on Ordinary Portland Cement (OPC) significantly contributes to global CO2 emissions, prompting the search for sustainable alternatives. This study investigates the partial substitution of Portland cement with construction and demolition waste (CDW) powder and concrete waste (CON) powder in mortar mixes. Replacement levels of 5%, 10%, 15%, and 20% by weight were tested following EN 196-1 standards to evaluate the mechanical performance of the resulting materials. X-ray diffraction (XRD), X-ray fluorescence (XRF), and thermo-gravimetric analyses confirmed that CDW and CON powders consist mainly of quartz and calcite, with chemical compositions compatible with cementitious systems. Mechanical testing revealed that compressive strength was maintained or slightly improved at replacement levels up to 10%, while higher substitutions led to moderate reductions due to dilution effects. The use of CDW and CON powders effectively transformed a 52.5 R Type I cement into a 42.5 R Type II equivalent, demonstrating the feasibility of producing sustainable binders with acceptable performance.