Cement, Energy and Environment

Suitability of Manufactured Sand as fine aggregates for Concrete& Mortars – A Case Study A study was conducted at Indian Ins tute of Science, Bangalore, to ascertain the suitability of Manufactured Sand as fine aggregate in Concrete (grades of M20, M30) and Cement mortars (ra o 1:4 and 1:6).Tests were conducted to study fresh and hardened proper es of the Concrete and Mortars made with river and Manufactured Sand. It was found that: 1. Grading limits of Manufactured Sand fell within the grading Zone-II of fine aggregates as specified in IS 383. 2. Shape of the Manufactured Sand par cles resembled the shape of river sand par cles. 3. Bulk density and specific gravity of Manufactured Sand were comparable to those of river sand. Concrete The details of the tests on concrete, comparison of results tabulated in Table 2 and inferences drawn are given below. Consistency of concrete This was measured by conduc ng slump test. Keeping the water- cement ra o at 0.50 and using super plas cizer (at 15 ml per kg of cement as specified by the manufacturer), the slump values were determined for both M20 and M30 mixes using river sand and Manufactured Sand as fine aggregate. Concrete with river sand gave higher slump value. IS 456 code specifies a minimum slump of 50 mm for medium workability. Both the concrete mixes met this requirement irrespec ve of the type of sand. Compressive and flexure strength of concrete Compressive strength was determined by tes ng the 28 days cured cube specimens. The mean compressive strength values of 5 cube specimens are reported in Table 2. Compressive strength of M20 and M30 grade concretes with Manufactured Sand as fine aggregate is 6 – 9% 3 Proper es River Sand Manufactured Sand Advantages of Manufactured. Sand Shape Spherical par cle Cubical par cle Higher Cohesion and Compressive Strength Grada on Cannot be controlled Can be controlled Reduc on in Voids and Higher strength Par cle passing 75micron Up to 3%(IS:383-2016) Up to 10% (IS:383-2016 Refer Note below Clay and Organic impuri es Likely to be present (retard the se ng &comp. strength) Absent Be er Concrete Quality Grading zone (IS-383) Mostly conforms to Zone II and III Manufactured to conform to Zone II Zone II ideal for Concrete Comparison of River Sand and Manufactured Sand Table 1: Comparison of Proper es of River Sand and Manufactured Sand Note:When par cles below75µ are nearer to the limit of 10%, it is advisable tomake suitable adjustment of water to cement ra o and ensure early curing to avoid problems of plas c shrinkage cracking