1Progress in Concrete TechnologyChallenge: Compared to steel, normal concrete has a low strength/weight ratio. Concrete with a higher strength/weight ratio is needed for tall buildings and long-span bridges.Solution: To increase the strength/weight ratio, reduce the weight by using lightweight concreteor increase the strength by using high-strength concrete.Challenge: For placement of concrete in heavily reinforced structures, high workability is needed.Solution: Use high-workabilityorflowing concrete. Challenge: Drying shrinkage of normal concrete frequently leads to cracking.Solution: Use shrinkage compensating concrete.Challenge: Normal concrete has low toughness and low resistance to impact.Solution: Use fiber-reinforced concrete.Challenge: Low permeability and high chemical resistance are needed for durability of concrete.Solution: Use polymer concrete. Challenge: Control of temperature rise in mass concrete use for dams and other large structures is needed to reduce the chance of cracking of the concrete.Solution: Use techniques for precooling of concretematerials or roller-compacted concrete.Challenge: High density material is needed for use as radiation shielding in nuclear power plants.Solution: Use heavyweight concrete.
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