FEASIBILITY STUDIES OF PRINTABLE SINGAPORE MARINE CLAY-LIMESTONE COMPOSITES IN COST EFFECTIVE FORMWORK FOR CASTING REINFORCED CONCRETE STRUCTURES

Abstract

Formwork is an essential and crucial component in construction processes. Its purpose is to act as a mould and hold the freshly poured concrete in place, whilst providing smooth finishes. Formwork materials often include, but are not limited to wood, metals, plastic, and fabric. In this study, concrete is explored as a material for formwork, with marine clay and limestone as additives in the mix. Since marine clay and limestone are widely available, they have the potential to act as partial substitutes for the high cement content in the concrete mixture where the production of cement results in adverse environmental impacts.

Furthermore, the construction of the formwork utilised 3D printing which encouraged an in-depth examination of marine clay-limestone concrete mix as a 3D printable material. This paper hypothesises that the ideal composition of concrete mixes with marine clay and limestone will produce a durable and cost-effective wall formwork for casting reinforced concrete structures during 3D concrete printing.

The ideal composition of the concrete mix is determined through numerous rheology tests. The tests discovered that the ideal printable concrete composition (Batch 37) contained 19% limestone and 1% marine clay, that is high in strength and adhesive properties, compared to the other mixes. The extrusion test supplemented Batch 37 as a printable material with its satisfactory buildability and flowability.

A complex-shaped wall formwork was then designed and printed in 4 sections, to maximise the flexibility of 3D printing. The printed formwork was then subjected to further design changes after printing due to its versatility of formwork sections. The printed formwork sections were dense and heavy, therefore requiring more manpower to relocate. After the formwork was left to cure for a week, regular concrete was casted into the formwork to discover that there was relative ease of removal. Besides, double-layered samples were printed for the purpose of mechanical tests. The tests revealed that Batch 37 was lower in compressive, tensile, flexural and shear strength after curing for 14 days, in comparison to the reference mix that was cured for 28 days. Even so, there is still a possibility of Batch 37 being a stronger material since the samples did not shatter into pieces during the tests.