Performance of magnesia-modified sodium carbonate-activated slag/fly ash concrete

Abstract

Various innovative research in the cement industry is looking into improving its environmental sustainability. Sodium carbonate-activated slag/fly ash (NC-SF) binders has recently evolved as a potentially more sustainable binding materials than both Portland cement and conventional alkali activated materials such as sodium silicate and sodium hydroxide activated materials. The reaction mechanism and some microstructural properties of NC-SF cements have been a major area of research recently. However, very few studies have scaled up the investigation of these binders into concrete specimens. This paper, therefore, provides new insight into the strength development and the durability performance of NC-SF concrete and MgO-modified NC-SF concrete. Concrete testing included measurements of compressive strength, split tensile strength, water absorption, depth of carbonation, sulphate exposure, acid exposure and elevated-temperature exposure. Microstructure studies were conducted using Powder X-Ray diffraction (PXRD), Thermogravimetric analysis (TGA) and Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR). It is concluded that NC-SF concrete mixes develop acceptable mechanical strength and demonstrate high resistance to sulphate attack. They also showed higher resistance to acid attack than the control mix based on sodium silicate-activated slag concrete. Here, emphasis is placed on the potential of developing NC-SF concrete with excellent performance and less complicated production methods as well as a low carbon footprint. It is also found that the use of reactive MgO enhanced the strength development of NC-SF concrete as well as its resistance to acid and carbonation.

Characteristics of Preplaced Aggregate Concrete Fabricated with Alkali-Activated Slag/Fly Ash Cements

“…The better compaction and higher flowability of the alkali-activated grout compared to those of the conventional cement grout may have resulted in a dense structure. Specimens with more fly ash showed lower water absorption, contrary to the results obtained in previous studies of traditionally placed alkali-activated concrete [ 45 , 46 , 47 ]. This difference can be explained by the type of placement used and the preconditioning of the specimen.…”

Improvement of the performance and microstructural development of alkali-activated slag blends

“…6 presents the XRD patterns of all samples after 14 days of curing. The broad hump located at around 25-35° 2 observed in sample GA0H0 was attributed to the presence of amorphous phases [48], whereas with the introduction of activator in samples GA10H0 and GA10H2 led to the appearance of C-(A)-S-H at 30-31° 2 (PDF #00-033-0306) as the major hydrate phase, which was in line with the findings of previous studies [49]. The XRD pattern of sample GA10H2 also demonstrated the presence of hydrotalcite (Mg6Al2(OH)16CO3•4H2O; PDF #01-070-2151), however at a lower intensity when compared with C-(A)-S-H.…”

“…(i) 30-220°C: Mass loss due to the dehydration of C-(A)-S-H, with an endothermic peak at ~80°C [49].…”

Dolomitic filler in self-compacting concrete: a review

“…[3]. One interesting product is MgO-based expansive agent added to cement/concrete to reduce their shrinkage [36][37][38][39]. Dolomite is effective also as a parent-sorbent for high temperature CO 2 capture [40].…”