*2.1. Materials*

Type-1 Ordinary Portland cement (OPC) from a Saudi cement factory was used as a primary binder in all concrete specimens [22]. The cement's specific gravity and maximum particle size were recorded as 3.14 and 0.072 mm, respectively, provided by the local

manufacturer. Biochar was produced using date palm fronds at 500 ◦C with a heating rate of 10 ◦C/min for 2 h. Industrially available sand was utilised as a finer aggregate (FA) in all concrete mixtures. A 0.49% absorption capacity and 2.6% specific gravity were recorded in FA [23]. The particle size distribution investigation showed that particles passed 100% from the ASTM sieve size #4 (2 mm), 100% from sieve size #8 (4 mm), 100% from sieve size #16 (600 μm), 74% from sieve size #30 (425 μm), 12% from sieve size #50 (212 μm), 6% from sieve size #100 (150 μm) and 5% from sieve size #200 (75 μm). Pulverised limestone was added as a coarser aggregate (CA) in all mixtures. Absorption, bulk specific gravity, and maximum particle size was recorded as 1.19%, 2.57, and 18.5 mm. Tap water is used as a mix of water in fabricating all concrete specimens.
