Effect of Recycled Iron Powder as Fine Aggregate on the Mechanical, Durability, and High Temperature Behavior of Mortars

Abstract

This study evaluates the mechanical, durability, and residual compressive strength (after being exposed to 20, 120, 250, 400 and 600 °C) of mortar that uses recycled iron powder (RIP) as a fine aggregate. Within this context, mechanical strength, shrinkage, durability, and residual strength tests were performed on mortar made with seven different percentages (0%, 5%, 10%, 15%, 20%, 30% and 50%) of replacement of natural sand (NS) by RIP. It was found that the mechanical strength of mortar increased when replaced with up to 30% NS by RIP. In addition, the increase was 30% for compressive, 18% for tensile, and 47% for flexural strength at 28 days, respectively, compared to the reference mortar (mortar made with 100% NS). Shrinkage was observed for the mortar made with 100% NS, while both shrinkage and expansion occurred in the mortar made with RIP, especially for RIP higher than 5%. Furthermore, significantly lower porosity and capillary water absorption were observed for mortar made with up to 30% RIP, compared to that made with 100% NS, which decreased by 36% for porosity and 48% for water absorption. As the temperature increased, the strength decreased for all mixes, and the drop was more pronounced for the temperatures above 250 °C and 50% RIP. This study demonstrates that up to 30% RIP can be utilized as a fine aggregate in mortar due to its better mechanical and durability performances.

Strength Properties of Sustainable Mortar Containing Waste Steel Slag and Waste Clay Brick: Effect of Temperature

“…These higher thermal cracks of the mortar made with WSS and WCB should be one of the main reasons for the lower strength than NS. This behavior is in agreement with the literature [ 22 , 32 , 36 ]. It was shown that a significantly higher permeability occurred when heated at a higher temperature (e.g., 300 °C) for the mix made with coarser particles (size of aggregate is around 5 mm) than the mix containing a small-sized aggregate of 0.6 mm [ 19 ].…”

“…Conversely, the particle shape of NS was uncrushed, smooth in surface and nearly well-rounded ( Figure 1 a,d), which provided a weak bond among the particles and weak ITZ between NS and cement paste, leading to lower tensile and flexural strength. Similar results were reported in the literature [ 32 ]. It is noted that a significantly higher amount of very fine particles (smaller than 74 µm) of WSS (12.38%) and WCB (21.41%) was found on the pan of the ASTM sieve.…”

“…It was shown that a significantly higher permeability occurred when heated at a higher temperature (e.g., 300 °C) for the mix made with coarser particles (size of aggregate is around 5 mm) than the mix containing a small-sized aggregate of 0.6 mm [ 19 ]. Miah et al [ 32 ] showed that the mortar containing NS exhibited lower strength loss at elevated temperatures (e.g., 600 °C) compared to the mortar made with recycled iron powder (RIP), which was coarser than NS (fineness modus of NS and RIP was 2.86 and 3.15, respectively). Roy et al [ 22 ] investigated the residual mechanical properties (compressive strength, elastic modulus, flexural strength and tensile fracture energy) of concrete containing EAF slag as a partial/complete replacement for natural sand at elevated temperatures (200–1000 °C).…”

“…The authors found a significant increase in permeability at temperatures from 80 to 120 • C. mortar made with 100% WCB. This behavior could be linked to the higher temperature, which accelerates water evaporation (more and rapid drying) and thermal damages (i.e., higher crack (Section 3.3), which allows the higher release of moisture from the specimens [31,32]). Compared with control specimens, the minimum mass loss was observed for the mortar made with 100% WSS, while a noticeable mass loss was found for 100% WCB for all thermal loads.…”

Sustainable Approach for Recycling Medical Waste Needles to Partially Replace Aggregate in Lightweight Concrete Production

“…The decrease of water absorption with time referred to a modification of total void space in concrete. In a related study, Miah et al [31] observed a similar trend using waste iron as fine aggregate. They reported that the water absorption decreased with the increasing the ratio of iron waste.…”