Effect of Water-Cement Ratio and Superplasticizer Dosages on Autogenous Deformation of Mortar Containing Burnt Clay Waste

Authors: *Fashanu, A.A., Olorunfunmi, T.C. And Abdulrahmon, I.O.

DOI Info: http://doi.org/10.5281/zenodo.21046736

ABSTRACT

This study examines the effects of water–cement ratio (0.4 and 0.6), superplasticizer dosage (1% and 2%), and partial replacement of cement with burnt clay waste powder (BCWP) at 5%, 10%, and 25% on autogenous deformation, compressive strength, and setting time of cement mortar. Experimental procedures followed relevant ASTM and BS EN standards. Results indicate that autogenous deformation increases rapidly within the first seven days before stabilizing. Lower water–cement ratio (0.4) produced higher shrinkage due to self-desiccation, while 0.6 reduced shrinkage but also lowered strength. BCWP showed a dual effect: 5–10% replacement slightly increased shrinkage, whereas 25% reduced it due to cement dilution and slower hydration. Superplasticizer dosage had a moderate influence, with 2% slightly increasing autogenous deformation while improving workability and strength development. Compressive strength increased with lower water–cement ratio, while higher BCWP content reduced strength. Optimal performance was achieved at 0.4 water–cement ratio, 2% superplasticizer, and up to 10% BCWP, yielding 28-day strengths above 15 N/mm2, suitable for structural masonry applications. Setting time results showed that BCWP accelerated both initial and final setting, whereas superplasticizer slightly delayed setting due to improved workability retention. The study concludes that BCWP can be effectively utilized as a partial cement replacement up to 10% for sustainable mortar production without significantly compromising performance. Optimization of water–cement ratio, superplasticizer dosage, and BCWP content provides a balanced approach to improving strength, shrinkage behavior, and setting characteristics.

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