Mechanical Properties and Microstructure of High-Strength Alkali-Activated Concrete Including High-Volumes of Waste Brick Powder Using Response Surface Methodology

Abstract

The current study aims to produce and design high-strength alkali-activated concrete (AAC), containing carbon fiber (CF) and the optimum content of waste brick powder (WBP) as source materials. A response surface method (RSM) was empolyed to design and optimize the properties of AAC. Three main parameters selected for this study were WBP content, Na2SiO3/KOH ratio, and CF content. Seventeen AAC mixtures were generated by activating the source materials with an alkaline-activation solution of KOH and Na2SiO3. The fresh properties, compressive, flexural strengths and density of the AACs were evaluated. The fresh AAC mixtures containing less than 40% WBP were highly workable with a diameter of 195-215 mm. The compressive, flexural strengths and density responses ranged from 22 and 121.22MPa, from 2.10 and 9.6MPa and from 2116 to 2366 kg/m 3 . From expermental work, the optimum mix of WBP (5%), Na2SiO3/KOH ratio (1.90), and CF (1.0%) was found to develop the AAC with the optimum of WBP. According to microscopic investigation, the optimum mixture had a nonporous and dense microstructure compared other mixtures incorporated with WBP, which had best mechanical properties (111.15MPa, 8.3MPa and 2316kg/m 3 ). Finaly, it is possible to produce high strength AAC (70 MPa) with 40% waste brick powder content.