Characterisation of crushed fine aggregate for use in concrete based on methylene blue test
  M.C. Nataraja, S. Karthik and A.N. Madhusudan
  Different types of fine aggregates are being used for the production of mortar and concrete. The natural river sand is becoming scare and this sand many times is contaminated with large amount of clay as it is extracted from the bottom of the deposit. IS 383:2016 has recommended different types of manufactured sand in addition to natural and crushed sands for use in concrete. However this code is salient about some of the durability tests when compared to international codes of practices. In practice aggregates are mixed with clay particles due to improper storage and handing in the site leading to clay contamination. As these particles are deleterious in nature, it is essential to know their harmful effects, which can be determined by the Methylene blue absorption (MBA) test. In this investigation, the MBA value is determined for 3 samples of river sand and 5 samples of crushed sand by both titration and the spectrophotometer methods to determine the level of harmful particles present in the form of fines. The specific surface area and the cation exchange capacity of all the samples are also determined and a measure of good aggregate in terms of durability is proclaimed. EDS analysis is carried out to indicate the harmful elements in the fine aggregates which is detrimental to the mortar and concrete when used.