Abstract:
Hollow concrete blocks (HCBs) are widely used in Ethiopian housing developments. However,
the production of HCBs using traditional materials such as cement, river sand, water, and light
aggregates. They are made of concrete and moulded into moulds in order to obtain the necessary
physical strength and dimensions for the criteria and standards. The manufacturing of cement
releases carbon dioxide into the atmosphere, contributing to global warming. Construction
waste is also disposed of at landfill sites, causing environmental problems. Therefore, alternative
materials for HCB production are needed. This study aims to investigate the possibility of using
construction waste (CW) and scoria powder as alternative materials for river sand and cement,
respectively, in the production of class A HCBs. The objective was to partially substitute scoria
powder for cement and CW for sand in different proportions. Tests were conducted to determine
the appropriateness of the materials used and how well they performed in terms of engineering
qualities. Microstructural investigations were also carried out using XRD and SEM, while the
oxide content in scoria powder was determined using XRF. The compressive strength, density,
and water absorption of HCBs made from different proportions of scoria powder and CW were
measured. The compressive strength of HCBs decreased with increasing replacement rates,
except for CW (75%) and scoria (30%). However, the blocks still achieved the target strength
for class A blocks. The strength values of a mixture of 50% CW as sand and 30% scoria powder
as cement were either greater or comparable to the standard limit. The density and water
absorption of HCBs made from scoria powder and CW remain within Ethiopian standards. The
study concludes that construction waste and scoria powder can be used as alternative materials
for river sand and cement, respectively, in the production of class A HCBs. However, the
substitution rates should be carefully considered to ensure that the blocks meet the required
strength standards. The use of alternative materials can help reduce the environmental impact
of HCB production and waste disposal. Further research is recommended to investigate the
long-term durability and performance of HCBs made from alternative material
