Abstract

Background
The accumulation of polyethylene terephthalate (PET) plastic waste 
poses environmental and sustainability challenges due to its non
biodegradable nature and limited disposal options. Repurposing PET 
as aggregates in structural lightweight concrete (SLWC) offers a dual 
benefit of waste valorisation and conservation of natural resources, 
while supporting circular economy objectives.
Methods
Eight experimental mix proportions of SLWC were developed using a 
factorial design approach, with water–to–cement ratios ranging from 
0.40 to 0.45. PET aggregates were produced via thermal–mechanical 
processing and subjected to calcium hypochlorite treatment to 
improve surface bonding with cement paste. Standard tests were 
conducted to determine workability (Vebe time), fresh and dry 
densities, compressive strength, splitting tensile strength, and water 
absorption. Structural efficiency was also computed as a strength-to
weight performance indicator.
Results

The fresh and dry densities of the PET-based SLWC ranged from 
1455–1515 kg/m3 and 1490–1537 kg/m3, respectively, corresponding 
to category D1.6 lightweight concrete. Compressive strengths ranged 
between 14.1 and 16.5 MPa, fulfilling the LC13 classification for 
structural applications. Splitting tensile strengths were between 0.84 
and 1.4 MPa, with several mixes achieving minimum thresholds for 
structural performance. Water absorption values ranged from 4.66% 
to 10.16%, remaining within international standards for lightweight 
concrete durability. Workability was low (Vebe times 13–40 s), 
attributed to the angular and hydrophobic properties of PET 
aggregates. Structural efficiency values of 9.5–10.9 kPa·m3/kg 
exceeded minimum international requirements.
Conclusions
This study confirms that PET aggregates can be successfully utilised to 
produce structurally viable and durable lightweight concrete. 
Although workability is reduced, the compressive strength, tensile 
strength, density, and durability criteria align with international 
standards. These results demonstrate a sustainable strategy for PET 
waste valorisation in construction, contributing to resource 
conservation, reduced environmental burden, and advancement of 
circular economy goals.