سلوك الانحناء للبلاطات الخرسانية المسلحة الهجينة أحادية الاتجاه تحت تأثير هجوم الكبريتات

Flexural behavior of hybrid reinforced one way slabs under the effect of sulfate attack

Abstract
The current research includes an experimental analysis to examine the flexural behavior of hybrid reinforced one way slab under the effect of sulfate attack, as well as the mechanical and physical properties (compressive strength, splitting, flexure, absorption, void ratio, and density) under two types of environments for three months. Resistance to sulfate attack is one of the most important properties for maintaining the longevity of concrete.
The experiment included 13 simply supported one-way slab models. Three slabs were exposed to a concentrated sulfate environment, while the rest were kept in normal lab air conditions for 3 months. Most slabs measured (530×1700×50 mm), except two with depths of 75 mm and 100 mm, which were tested under two-line loads. After 28 days of water curing, the slabs were reinforced using different combinations of steel and CFRP bars: 100% steel, 100% CFRP, 75% steel + 25% CFRP, and 50% steel + 50% CFRP. Three slabs were fully submerged with a 5% H2SO4 solution, while the remaining ten stayed in normal lab air conditions. The concrete type used in the present work was normal concrete (M1=30, M2=28, M3=26, M4=31, M5=17). Four key factors were examined: crumb rubber used to substitute fine aggregate, the impact of the ratio of CFRP bars, the impact of slab depth, and the impact of concrete compressive strength.
The parameters for both conditions, obtained the following results:
The first parameter showed that, in normal lab conditions, the ultimate load of slabs decreased as crumb rubber (CR) content increased. However, in sewage conditions, the ultimate load increased with more CR. The second parameter examined different reinforcement types: 100% steel, 100% CFRP, and a mix of 75% steel + 25% CFRP. The slab with full CFRP had the highest load (54.91% more than steel), and the mixed slab also performed better than the steel-only one (23.64% higher). The third parameter studied slab depth. Increasing the depth from 50 mm to 100 mm significantly raised the ultimate load, showing depth plays a major role. The fourth parameter looked at compressive strength. The slab with higher strength concrete carried a higher load (27.33% more), confirming that stronger concrete improves performance.