Increasing the strength of alkali activated mortars prepared without cement by adding lime and crushed brick

Abstract

Alkali-activated concretes, which aim to reduce cement, have received the most attention in recent years. By activating cementless geopolymer mortar samples with lime, blast furnace slag [BFS], fly ash [FA], crushed brick, sodium hydroxide, and sodium silicate, the study aims to produce more affordable and environmentally materials. Hydrated lime and crushed brick mortars, which have been utilized in ancient structures for thousands of years, have endured to the present day because of their toughness and appropriate construction techniques. However, the biggest disadvantage of ancient mortars is that their setting time is long due to the lime they contain and therefore their strength properties cannot be developed at an early age. In order to improve these properties of the mortars, 7.5 mole NaOH was used in fixed ratios and Na2SiO3 in variable ratios. On the mortar’s characteristics, the impacts of lime, crushed brick, BFA, and FA were examined. Tests on the generated samples included flow-table, setting-time, density, water absorption, porosity, flexural and compressive strength tests, as well as SEM, XRD, and FTIR studies. The reference ancient mortar sample has the lowest compressive strength value at 1.47 MPa, while the Y4 sample, which has a high BFS content at 22.5 MPa, has the highest compressive strength value. The YS4 sample comprising BFS, NaOH, and Na2SiO3 had the fastest setting time, at 20 minutes. In comparison to the reference samples, the samples’ workability was also enhanced. The reference sample had the highest water absorption value, 26.8%, while the other samples’ values stayed below 2%. In this case, activators contributed to the improvement of the mechanical qualities of traditional lime mortars.