Experimental Study, Characterisation, and Microstructural Analysis of Ultra-Strength Concrete (M80 to M120 Grade): Design, Durability, and Cost-Benefit Dynamics
Abstract
Ultra-Strength Concrete (USC), spanning the M80 to M120 grade range, represents a major advancement in structural materials engineering, offering exceptional load-carrying capacity, dimensional efficiency, and durability compared with conventional concrete (Aïtcin, 1998; Mehta & Monteiro, 2014). This paper presents an expanded experimental and literature-grounded investigation into the design, mechanical behaviour, durability, and cost-benefit dynamics of M80, M100, and M120 concrete relative to standard M40/M45 concrete. High-quality constituents OPC 53 Grade cement, densified silica fume, fly ash, Ground Granulated Blast-furnace Slag (GGBS), and Polycarboxylate Ether (PCE) superplasticisers were combined at ultra-low water-to-binder (w/b) ratios of 0.17 to 0.25, consistent with particle-packing optimisation principles established for reactive powder and ultra-high-performance concretes (Richard & Cheyrezy, 1995; de Larrard & Sedran, 1994). Mechanical properties were evaluated through compressive strength testing at 7, 14, 28, and 56 days, along with flexural and split tensile strength tests. Durability was assessed via Rapid Chloride Permeability Testing (RCPT), water absorption, and water penetration under pressure. Results confirm that M120 concrete reaches a 28-day compressive strength of 124 MPa and a flexural strength exceeding 12 MPa, with RCPT charge passed falling to 110 Coulombs within the “negligible” permeability class (Whiting, 1981; ASTM C1202). Volumetric material costs for M80, M100, and M120 are 89.7%, 158.6%, and 244.8% higher than M40 respectively; however, structural analysis shows that USC permits up to a 71.6% reduction in column cross-sectional area, a corresponding cut in dead load, a 15–25% reduction in foundation sizing, and measurable gains in rentable floor area, together justifying the material cost premium on a whole-project basis (Sreenivasulu & Srinivasa Rao, 2012).