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Shallow concealed reinforced concrete (RC) beams (wide beams) make parts of a structure and are used in the construction industry, especially in ribbed and waffle slab systems. They are designed based on the requirements and provisions of structural codes of practice, which are applicable for shallow dropped RC beams (narrow beams). The main concern in regard to the behavior of these shallow concealed RC beams is transversal-spacing of stirrup-legs across their width. This paper aims to investigate the transversal-spacing of stirrups-legs (Sw) for two shallow concealed RC beams, namely, WB-SC and WB-EC.

The beams are tested under a three point-loading system. Their design has been performed to the SBC304 for beam WB-SC (Saudi Building Code for concrete structures) and comparison to EC2 for beam WB-EC (Eurocode-2 for concrete structures) is addressed in terms of flexural and shear strength design requirements. Experimental behavior and results of both beams are analyzed and conclusions are provided; also, a comparison of these codes is performed. Both beams had dimensions of 3,400 mm length, 700 mm width and 350 mm height.

Experimentally, beam WB-SC failed in flexure while beam WB-EC failed shear. The investigation concludes in favor of a safer design for SBC304 Code compared to EC2 Code for designing shallow concealed RC beams.

This study recommends that the transversal-spacing of stirrups-legs of these beams has an influence on their strength and behavior and should not exceed the lesser of 0.56(d) or 170 mm (6.7 in.).

This study aims to enhance the resilience of foamed concrete (FC) against carbonation and water absorption (WA) by integrating microorganisms, specifically Aspergillus iizukae EAN605.

The focus was on understanding how variables such as microorganism concentration, concrete density and water-to-cement (w/c) ratio affect these properties. Optimal results were observed under specific conditions—FC density set at 1800 kg/m³, a w/c ratio of 0.5 and an Aspergillus iizukae EAN605 concentration of 0.5 g/L—resulting in significant reductions in carbonation and WA compared to standard FC.

It is observed that fungi not only fill pores with calcium oxalate but also limit carbonation by consuming CO₂ and block water penetration through their mycelial network. A central composite design within response surface methodology was employed for the experimental design, resulting in mathematical models that align closely with the empirical data. The models identified the most effective parameters for minimizing carbonation depth: FC density at 1970 kg/m³, fungal concentration at 0.585 g/L and w/c ratio at 0.470. Further regression analysis showed a high correlation between the experimental data and the predicted outcomes, with a coefficient of determination (R²) of 92.29 and a model F-value of 16.45.

Statistical analysis highlighted the significant roles of density and fungal concentration in these reductions. Besides, scanning electron microscopy provided visual evidence of fungal-mediated mineral formation in FC, supporting the empirical findings. Overall, the study demonstrated the effective use of Aspergillus iizukae EAN605 in enhancing the durability of FC, marking an innovative stride in sustainable construction materials.