Characterization of an ultra-high performance concrete

DuctalRTM is a proprietary ultra-high performance concrete (UHPFRC) cooperatively developed by three companies Lafarge, Bouygues, and Rhodia in France. Ductal is claimed to be a technological breakthrough UHPFRC, offering very high compressive strength exceeding 200 MPa and flexural tensile strength exceeding 30 MPa, ductility like plastic or wood, durability like stone, and the aesthetic like ceramics. This new technology offers the possibility to build structural elements without passive reinforcements and to combine innovative applications, lightness, and excellent durability.;Ductal concrete is produced using materials commonly found in concrete: cement, silica fume, sand, superplasticizer and water, as well as some materials unique to Ductal: ground quartz and fibers. The various Ductal formulations are all based on an optimized proportioning, combining homogeneity and granular compacted density to satisfy rheological criteria (excellent workability and self-placing capability), mechanical criteria (very high compressive strength and non-brittle tensile behavior) and durability criteria (near-total invulnerability to all conventional aggressions).;In the light of this new development in concrete, an exploratory work was undertaken to study this material and examine its potential use as a construction and repair material in Saudi Arabia. An experimental program was planned to prepare Ductal concrete using imported Ductal materials and measure its basic mechanical properties and durability. The findings of this study are presented in this thesis work, which covers in detail all aspects of work carried out.;The experimental work focused on measuring properties and performance on two fronts: (a) physical and mechanical properties and (b) properties and performance related to durability. With regard to physical and mechanical properties, the following were obtained: • Compressive strength: 28-day strength exceeds 160 MPa. Strength increases in heat-cool cycles. • Flexural tensile strength determined from four-point bend tests shows a value of about 31 MPa. • Splitting tensile strength shows a value of 12.6 MPa after 28 days of water curing • Modulus of elasticity is about 57 GPa. • Stress intensity factor, Kic = 16.8 MPa m and fracture energy = 31.6 kN/m. • Drying shrinkage = 300*10 -6 after 28-day water curing. • Water absorption is almost negligible at about 0.1%. • Water permeability measured using DIN test showed virtually no depth of water penetration. • Rapid chloride permeability tests showed negligible readings.;Durability of Ductal was examined by using three exposure conditions for a period of 6 months: (a) exposure to laboratory conditions, (b) exposure to alternate heat-cool cycles (heating at 60°C for 2 days and then cooling at room temperature for 2 days), and (c) exposure to alternate wet-dry cycles (wetting for 2 days in sabkha type solution and then drying at 30°C for 2 days).;The tests conducted on the cycled specimens showed the following results: • There is a slight gain in compressive strength for specimens subjected to heat-cool cycles. • Heat-cool cycles also increased stress intensity factor (Kic) and fracture energy, and reduced water absorption. • Cyclic exposure did not show any noticeable change in water permeability and rapid chloride permeability.;The study affirms the claim by the manufacturers that Ductal has excellent physical and mechanical properties and it is a highly durable material in aggressive environment. The drawbacks for this material for a widespread application are its relatively much higher cost, controlled mixing and difficulty in finishing the surface by conventional trowelling and floating operation. The product can be utilized in special construction where weight and durability are major concerns.