Fresh and Hardened Properties of 3D-Printed Concrete Made with Dune Sand

摘要

This paper examines the performance of 3D-printed concrete made with locally abundant desert dune sand.Cement was replaced by up to 10% silica fume and 30% fly ash to reduce its detrimental environmental footprint.The water-to-binder ratio used in the mix ranged between 0.35 and 0.40.Also,a superplasticizer was added in the range of 1 to 3%,by binder mass.Concrete mixes were proportioned to attain optimum fresh and hardened properties.A control mix with crushed dolomitic limestone aggregates served as a reference.The performance of 3D-printed concrete mixes was assessed based on slump flow,pumpability,and compressive strength.Experimental results showed a reduction in slump flow and pumpability with an increase in dune sand content.In turn,the compressive strength increased by 3% when 20% dune sand was utilized,but decreased by an average of 3% for every additional 10% subsequently.Concrete mixes incorporating a superplasticizer and higher water-to-binder ratio exhibited improved workability.While the former caused limited change to compressive strength,the latter resulted in a notable decrease.Upon replacing cement with silica fume and fly ash,the slump flow and pumpability increased.In fact,3D-printed concrete made with 3% superplasticizer,20% fly ash,and 10% silica fume experienced a 230 and 79% increase in slump flow and pumpability,respectively.Compressive strength increased by an average of 4% for every 10% fly ash replacement.The incorporation of 10% silica fume improved the strength by an additional 14%.Analytical models were developed to correlate slump flow to pumpability and 3D-printed concrete compressive strength to that of typical concrete cubes,serving as guidelines to produce optimal concrete mixes for large-scale concrete 3D printers.