Effect of nanosilica on properties of porcelanite aggregate concrete

Lightweight concrete has been used in buildings for centuries, due to its longevity and durability. In recent years, new studies have shed light on additives capable of reducing concrete weight while increasing strength. Nanosilica is one of these additives, which regulate the fundamental calcium-silicate-hydrate (C-S-H) process in water. The addition of nanosilica (NS) particles to concrete improves its density and strength. In this work, we started by creating a reference mixture without additives and another mixture containing a different ratio of nanosilica. Porcelanite was used as a lightweight aggregate. First, the porcelanite aggregate was crushed into pieces of different sizes (6 and 9.5 mm). The results of testing under compression showed that mixes containing 1 wt. %, 1.5 wt. %, and 2 wt. % of nanosilica gave the best results when compared to a reference mix without nanosilica. Porcelanite (rich in SiO₂) and nanosilica were utilized to partially substitute cement. A comparison was made with the reference mix (without nanosilica) to figure out the efficiency of using nanosilica in lightweight porcelanite concrete. The highest average compressive strength at a particle size of porcelanite (6 mm) of 18.1 MPa and 15.3 MPa can be obtained at 28 days using 1.5 wt. % and 2 wt. % of nanosilica, with 40.3 % and 18.6 %, respectively. The addition of 1 wt. % of NS, on the other hand, has a negative effect on the compressive strength of 6 mm grain size porcelanite by a factor of not more than 2.3 % at 28 days. Flexural strength of 3.04 MPa can be obtained at 28 days using 1.5 wt. % of NS at a particle size of 6 mm of porcelanite, with percentages of 424.1 %. The flexural strength of porcelanite aggregate concrete increases with a low percentage of various NS. The bulk density decreases when using porcelanite aggregate concrete at 6 mm and 9.5 mm particle sizes with 2 % of nanosilica by 4.84 % and 8.86 %, respectively. Field emission scanning electron microscope (FESEM) test was carried out to study the structure of the fractured nature of the highest compressive strength samples and reference.