Micro-filler from crushed concrete waste influence on properties of new concrete made from concrete waste

Abstract

The micro-filler researched in the work was gotten by crushing concrete and reinforced concrete waste and sieving gotten particles. Researched crushed particle size was smaller than 0.125 mm. Main micro-filler characteristics were determined. After doing research according to the special research method and according to the gotten results it can be stated that additive (micro-filler) made from crushed concrete waste is active. It was determined that when using concrete waste for concrete mixture mixing a higher amount of water is needed since part of the water is absorbed by used waste filler moistening. Big amount of this excess water is probably absorbed by smaller mixture particles gotten during the crushing process. Due to this reason W/C ratio changes. Research was done that showed how the requirement of water is changed with smaller mixture particles of which size is 00.125 mm. 5 %, 10 %, 15 %, 20 %, 25 % and 30 % MFA was put in and mixed with water up to normal thickness paste. Research results showed that by changing the cement part with micro-fillers W/C ratio rises, normal thickness cement paste gotten when W/C is 0.27, and when gradually rising micro-filler amount the requirement for water rises proportionally. Wanting to evaluate micro-filler additive effect to self-binding material’s hydration process calorimetry research was carried out. Cement and cement with micro-filler compositions’ (85% CEM II+15% MFA) calorimetry curves were compared. When researching the hydration process electrical conductivity research was also carried out as well micro-filler influence on concrete strength properties. According to cement composition strength property results it can be stated that micro-fillers lower cement strength properties. After conducting research it was determined that used filler from crushed concrete waste has to be sieved and separated from very small particles, which are smaller than 0.125 mm, since micro-particles that appear between large (4/16) and small (0.125/4) fraction in the mixture change the hardened concrete structure by rising the distance between fillers. Due to this even a small amount can significantly change gotten sample physical and mechanical characteristics (compression strength is lowered 38-42%, bending strength is lower 15 %) when comparing with mixture made using natural fillers.