Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Recycled aggregate


Sustainable High-Performance Concrete Reinforced with Hybrid Steel Waste Fibers

Zainab A. Jabbar; Wassan I. Khalil

Engineering and Technology Journal, 2022, Volume 40, Issue 11, Pages 1-10
DOI: 10.30684/etj.2021.131833.1063

This research aims to study the benefit of using fibers made from waste materials in concrete and evaluate the ability to use these fibers as a substitute for commercial fibers. Different aspect ratios of alternative fibers formed from cut steel tied wire waste were utilized. This material is selected because of its low price and wide availability. Two concrete mixes with 15% waste crushed clay brick coarse aggregate reinforced with different volume fractions of 1.0 and 1.5% and an aspect ratio of 40 were prepared. Also, three concrete mixes reinforced with a hybrid aspect ratio of 40 and 65 of tied wire waste steel fibers (TWWSF) with different volume fractions of 1.0% and 1.5% were prepared. The compressive, splitting tensile, flexural strengths, and ultrasonic pulse velocity (UPV)  of all prepared concrete mixes were tested. The results illustrate that the inclusion of tied wire waste steel fibers significantly enhances the strength of concrete with 15% waste crushed clay brick coarse aggregate, and high-performance concrete with compressive strength of up to 85 MPa can be produced. The enhancement in compressive, splitting, and flexural strengths were 29%, 42.8%, and 38%, respectively, for concrete reinforced with a fiber aspect ratio of 40 and volume fraction of 1.5%. In comparison, for the same volume fraction, the percentage was 22%, 48%, and 44%, respectively, for equal content of hybrid aspect ratio of 40 and 65.

Effect of Recycled Aggregate on Behavior of Tied and Spiral Reinforced Fibrous Circular Short Columns

Eyad K. Sayhood; Mohammed A.E. Al-Hamdani; Jabbar K. Sahan

Engineering and Technology Journal, 2021, Volume 39, Issue 12, Pages 1945-1952
DOI: 10.30684/etj.v39i12.965

This study focuses on studying the behavior of fibrous circular short columns (tied and spirally reinforced) using recycled coarse aggregate (f'c, ft, Ec, and fr) by using recycled aggregates with comparison to normal aggregates with and without using steel fibers. For this purpose, ten (10) short columns were cast at five groups each of two circular columns(tied and spiral of 150 mm radius x 600mm height) with different percentages of recycled coarse aggregate (0%, 50%, and 100%) and different percentages of steel fiber (0%, 0.5% and 1%). The study showed that when adding the 50% normal aggregates with 50% recycled aggregates, decreases of (10%, 18%, 30% and 22%) for (compressive strength, splitting tensile strength, flexural strength and elasticity module), respectively were observed, and when replacing the 100% normal aggregates with 100% recycled aggregates, decreases of (30%, 35%, 58% and 63%) for (Compressive strength f'c, splitting tensile strength ft, flexural strength fr and elasticity module Ec), respectively were observed. The changes on the compressive strength of adding steel fibers to the RAC by a proportion of (0.5% and 1 %) resulted in a significant increase of about (14 % and 35 %), respectively.

Shear Strength of Reinforced Fibrous-self Compacted Concrete Box Girder using Recycled Concrete Aggregate

Mohammed A. Hadi; Eyad K. Sayhood; Ali S. Resheq

Engineering and Technology Journal, 2021, Volume 39, Issue 8, Pages 1307-1320
DOI: 10.30684/etj.v39i8.2100

Protection of environmental and conservation of natural resources is a fundamental issue in today’s world. In this research, the shear behavior of reinforced concrete box girders with recycled aggregate (RA), steel fiber, and internal diaphragms were investigated. Eleven reinforced concrete box girders with typical longitudinal and transverse reinforcement were tested under two point loading until failure. The RA was prepared by crushing the collected waste of concrete from the laboratory test cylinders and cubes. The experimental variables considered include; RA percent of 50%, 75%, and 100%(replacing from NA), steel fiber with volumetric ratios (Vf) of 0.5%, 1.0%, and 2%, diaphragm numbers (two and three).The test results revealed that the shear strength of the box girders affected by the RA content, the ultimate load was decreased by (32, 25, and 19) % for the (100, 75, and 50) %RA concrete, respectively in compared with the control specimen. In contrast the steel fiber was more effective in strengthening of the RA concrete specimen, for the (Vf) of 0.5%, 1.0%, and 2.0% with non-fibrous 100% RA concrete, the strengthening were (25, 40, and 77) % respectively. Moreover, when 1.0% steel fibers added to the 100%, 75%, and 50%RA concrete respectively, the strengthening were (40 ,45 ,and48 )% compared  each with its reference specimen.  On the other hand, when two and three diaphragms used, the strengthening for the non-fibrous 100% RA concrete was (6% and 9%) respectively. cracking load, ultimate load, load- deflection, and concrete surface strain has been taken into consideration in this research.

Influence of Incorporating Construction Building Demolition as Recycled Aggregate on Concrete Behavior

Shatha Sadiq Hussen

Engineering and Technology Journal, 2016, Volume 34, Issue 1, Pages 33-49

Because of increasing waste production and public concerns about the environment, it is desirable to recycle materials from construction and building demolition. This study aimed to find a technique for producing recycled aggregate concrete obtained from construction and building demolition waste. Laboratory trials were conducted to investigate the possibility of using recycled aggregate from different sources in Iraq, as a partial replacement of both coarse and fine natural aggregates or one of them. Recycled aggregate consists of crushed concrete (CC) or acombination of crushed brick (CB) and crushed concrete (CC). The aggregate in concrete was replaced with 10%, 20%, 30% and 50% by weight of crushedconcrete (CC) or crushed brick (CB) and crushed concrete CC. Some of mechanical properties of recycled aggregate concrete as compared to those of conventional normal aggregate concrete are studied. Compressive strength and the splitting tensile strength were determined after curing for 7, 28, and 90 days while density was determined after28 days.From these results, it is reasonable to assume that the use of recycled concrete aggregate does not jeopardize the mechanical properties of concretefor replacement ratios up to 50%. The concrete prepared with the crushed concrete only as a partial replacement of natural aggregate achieved the highest strength values at 7, 28and 90 days. The results suggested that an aggregate that contains 50% recycled aggregate is optimum for producing recycled aggregate concrete The test results showed that the replacement of coarse or fine natural aggregate by recycled brick aggregate at the levels of 10,20,30 and 50% had little effect on the compressive strength of the specimens.