An Innovative Method for Sustainable Utilization of Blast-Furnace Slag in the Cleaner Production of One-Part Hybrid Cement Mortar

Abstract

Hybrid cement (HC) can be defined as alkali activated-blended-Portland cement (PC). It is prepared by the addition of an alkaline solution to high-volume aluminosilicate-blended-PC. Although this cement exhibits higher mechanical performance compared to conventional blended one (aluminosilicate–PC blend), it represents lower commercial viability because of the corrosive nature of alkaline solution. Therefore, this study focuses on the preparing one-part HC using dry activator–based BFS (DAS). DAS was prepared by mixing sodium hydroxide (NaOH) with BFS at low water to BFS ratio, followed by drying and grinding to yield DAS-powder. Different contents of DAS (equivalent to 70 wt.% BFS and 1, 2, and 3 wt.% NaOH) were blended with 30 wt.% PC. A mixture containing 70 wt.% BFS and 30 wt.% PC was used as a reference sample. The mortar was adjusted at a sand–powder (BFS-PC and/or DAS-PC) weight ratio of 3:1. The microstructural analysis proved that DAS-powder is mainly composed of sodium calcium aluminosilicate–activated species and unreacted BFS. These species can interact again with water to form calcium aluminum silicate hydrate (C-A-S-H) and NaOH, suggesting that the DAS acts as a NaOH-carrier. One-part HC mortars having 1, 2, and 3 wt.% NaOH recorded 7th day compressive strength values of 82%, 44%, and 27%, respectively, higher than that of the control sample. At 180 days of curing, a significant reduction in compressive strength was observed within the HC mortar having 3 wt.% NaOH. This could be attributed to the increase of Ca (within C-S-H) replacement by Na, forming a Na-rich phase with lower binding capacity. The main hydration products within HC are C-S-H, C-A-S-H, and chabazite as part of the zeolite family.

Recycling of Precast Concrete Waste Sludge With Paper Mill and Biomass Ashes for Lightweight Granulated Aggregate Production

“…As: sodium calcium aluminum silicate (00-019-1183), Ph: phlogopite (01-070-2125), Gy: gypsum (04-009-3817), Q: quartz (04-014-7568), A l : albite (04-017-1022), C: calcite (04-008-0198), P: portlandite (04-014-8866), G: gehlenite (01-079-2421), T: thermonatrite (sodium carbonate hydrate) (00-008-0448), L: lime (04-011-9020), and Na Cl : sodium chloride (04-002-1178). (Fayed et al, 2021). The formation of thermonatrite (sodium carbonate hydrate) and portlandite phases has been detected for all the samples with a higher intensity for the samples with high ashes content.…”

An Experimental Study of the Mechanical Properties of Partially Rehabilitated Cable Tunnels

“…Bae [ 8 ] studied the characteristics of mortars with blast furnace slag powder and mixed fine aggregates containing ferronickel-slag aggregate. Cobos [ 9 ] studied the influence of crystalline admixtures at early age performance of cement-based mortar by electrical resistance monitoring, and Fayed [ 10 ] proposed an innovative method for sustainable utilization of blast-furnace slag in the cleaner production of one-part hybrid cement mortar. On the other hand, many researchers have studied the high-performance cement mortar materials: Li [ 11 ] studied the mechanical properties of aramid/carbon hybrid fiber-reinforced concrete; Haroon [ 12 ] studied the performance of reinforced concrete beams strengthened with carbon fiber reinforced polymer strips; and Shi [ 13 ] studied the effect of desert sand on the pore structure of fiber reinforced mortar.…”