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Posted: Mon Jul 30, 2018 12:30 pm Post subject: Using of manufactured sand in concrete
Dear Sir,á1.What is the significance of particleásize of sand for 300 n 150 microns size in manufactured sandá2. If any such sand used (particularly failed in above sieves and where as passed in 75╬╝ sieve during sieve analysis) in RCC M30 concrete (pumped) what are the consequences after hardening , remediesáplease if any?
Posted: Wed Aug 01, 2018 7:15 am Post subject: PARTICLE SIZE OF MANUFACTURED SAND
THE SIZES 300 MICRON PASSING AND 150 MICRON PASSING ARE EXTREMELY IMPORTANT FOR PUMPED CONCRETE. A mix meant for pumping must remain cohesive all along its journey from the mixer to the point of placement as it passes the pipeline under a high pressure. An ill-designed mix will easily segregate - the liquid slurry separating from the aggregates - leading to a choking of the pipe line. In order to have a cohesive mix you must have a minimum amount of fines (defined as matrl finer than 250 microns) in the mix. The generally accepted figure is about 425 - 475 kg - depending on the maximum size of aggregate used - 10mm or 20mm. These fines will include the Cement, Fly ash and the sand fraction finer than 250 microns. The rheology of the mix will further depend on whether the sand particles are rounded / angular etc. - best seen only from trial batches. A mix deficient of the fractions mentioned in your question may segregate. At the same time excessive amounts of matrl passing 75 micron will make the mix extremely sticky - difficult to handle in several situations. Hence the importance of the art of proper mix proportioning.
- T.P.Singh, Chf. consultant - Construction research technologies
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