| dc.description.abstract | This research explores the influence of nano-calcium carbonate (CaCO₃) and sodium
carbonate (Na₂CO₃) as cement additives on the compressive strength of concrete,
aiming to enhance durability in the saline environments typical of coastal Bangladesh.
Three concrete mixes were tested: a control mix (Mix 1) with no additives, Mix 2 with
22 g Na₂CO₃ and 88 g nano-CaCO₃, and Mix 3 with 88 g Na₂CO₃ and 132 g nano
CaCO₃. A total of 18 cylindrical specimens (100 mm × 200 mm) were cast, with 9 cured
for 7 days and 9 for 28 days, and tested per ASTM C39. At 7 days, the control mix
achieved the highest strength at 3584 psi (24.72 MPa), while Mix 2 and Mix 3 showed
reduced strengths of 3079 psi (21.23 MPa) and 2650 psi (18.28 MPa), respectively,
indicating early hydration challenges due to the additives. However, by 28 days, Mix 2
exhibited a remarkable strength gain, reaching 5198 psi (30.34 MPa)—surpassing the
control’s 5120 psi (35.31 MPa)—while Mix 3 remained lower at 3785 psi (26.10 MPa).
These findings suggest that while high additive doses (Mix 3) consistently impair
strength, a moderate dosage (Mix 2) can enhance long-term performance, likely due to
improved hydration and microstructural refinement by nano-CaCO₃. This study
provides valuable insights for designing salt-tolerant concrete mixes, offering a
practical solution for coastal infrastructure in Bangladesh by balancing early-stage
limitations with significant 28-day strength gains. | en_US |
