Properties of Alkali Activated Lightweight Aggregate Generated from Sidoarjo Volcanic Mud (Lusi), Fly Ash, and Municipal Solid Waste Incineration Bottom Ash

Abstract

Production of artificial lightweight aggregate (LWA) from industrial by-products or abundant volcanic mud is a promising solution to prevent damaging the environment due to the mining of natural aggregate. However, improvements are still needed in order to control the high water absorption of LWA and strength reduction in resulting concrete or mortar. Hence in this research, fly ash, municipal solid waste incineration bottom ash (MSWI BA), and Sidoarjo volcanic mud (Lusi) were employed as a precursor and activated using NaOH 6 M and Na2SiO3 in producing LWA. The influence of the type of the precursors on the physical properties of resulting LWA was investigated. The effect of replacing natural fine aggregate with the resulting LWA on the compressive strength and volume density of mortar was also determined. Finer particles, a high amount of amorphous phase, and low loss on ignition (LOI) of the raw material improved the properties of resulting LWA. Mortar compressive strength was decreased by 6% when replacing 16% by volume of natural fine aggregate with fly ash based LWA. Compared to the expanded clay LWA, the properties of alternative LWAs in this study were slightly, but not significantly, inferior. Alternative LWA becomes attractive when considering that expanded clay LWA requires more energy during the sintering process.

Eco-Friendly Materials Obtained by Fly Ash Sulphuric Activation for Cadmium Ions Removal

“…As a result of coal combustion, fly ash is found in large quantities and it has been reported that this fact causes serious environmental problems [10,11]; therefore, it must be addressed [12,13]. Fly ash is rich in aluminosilicate and includes polymeric minerals and inorganic oxide material [14,15].…”

An Evaluation of the Physical and Chemical Stability of Dry Bottom Ash as a Concrete Light Weight Aggregate

“…Soluble SiO 2 in coal ash combines with Ca(OH) 2 generated during cement hydration at room temperature to form insoluble calcium silicate (CaO·SiO 2 ·nH 2 O) that is stable in form, thereby causing a pozzolanic reaction that increases the long-term compressive strength of concrete. Moreover, when fly ash is used as a subsidiary material in cement, it behaves as a fusing agent (Al 2 O 3 , Fe 2 O 3 ) that lowers the melting point during the clinker reaction, which is why it is a crucial raw material in the manufacturing process of cement [ 22 , 23 , 24 , 25 ].…”

Synthesis of artificial aggregates and their impact on performance of concrete: a review

“…Aggregates produced using only FA led to lower strength and higher water absorption than aggregates produced by blending GGBS and OPC separately with FA [2,22]. It is also noted that the FA of higher fineness and GGBS improved the pelletization process, while FA of lower fineness decreased the pelletization [23,37,[43][44][45].…”

“…For the manufacture of pelletized aggregates, an alkaline solution with a minimum of 6 M concentration was suggested as a lower concentration of NaOH will avoid workability issues during the pelletization process. As the NaOH concentration rises, a higher temperature is required to start and accelerate the polymerization reaction [37]. Aggregates produced using K-Si, and KOH were stronger than aggregates produced using NaAlO 2 and NaOH [10].…”