Influence of Glass Microfibers on the Control of Autogenous Shrinkage in Very High Strength Self-Compacting Concretes (VHSSCC)

High-performance concrete (HPC) is widely used in infrastructure for its durability and sustainability benefits. However, it faces challenges like autogenous shrinkage, leading to potential cracking and reduced durability. Fiber reinforcement offers a solution by mitigating shrinkage-induced stresses and enhancing concrete durability. In this sense, this study investigates the use of glass microfibers to mitigate autogenous shrinkage and early-age cracking in high-strength self-compacting concrete. Samples were prepared with two water-to-binder ratios (w/b): 0.25 and 0.32; and three glass microfiber contents: 0.20%, 0.25%, and 0.30 vol.%. The concrete mixtures were characterized in the fresh state for slump flow and in the hardened state for compressive strength, static, and dynamic Young’s modulus. Unrestrained and restrained shrinkage tests were also conducted in the seven days-age. The findings revealed that glass microfibers reduced the workability in mixtures with lower slump flow values (w/b of 0.25), while less viscous mixtures (w/b of 0.32) exhibited a slight improvement. Compressive strength showed a proportional enhancement with increasing fiber contents in concretes with a w/b ratio of 0.32. A contrasting trend emerged in concretes with a w/b ratio of 0.25, wherein strength diminished as fiber additions increased. The modulus of elasticity improved with fiber additions only in the matrix with a w/b ratio of 0.25, showing no correlation with compressive strength results. In shrinkage tests, the addition of glass microfibers up to specific limits (0.20% for a w/b ratio of 0.25 and 0.25% for w/b of 0.32) demonstrated improvements in controlling concrete deformation in unrestrained shrinkage analyses. Concerning cracking reduction in restrained concrete specimens, the mixtures did not exhibit significant improvements in crack prevention.