ume of relatively low modulus synthetic fibers.Higher volume percentages (0.4 to 0.7 percent) of fibers havebeen found to offer significant property enhancements to theSNFRC, mainly increased toughness after cracking and bettercrack distribution with reductions in crack width. Chapter 4 de-tails the current technological advancements in SNFRC in sep-arate sections that discuss each specific fiber material.As described in Chapter 5, natural fiber reinforced con-cretes vary enormously in the sophistication by which theyare manufactured. Treatment of the fibers also varies consid-erably. In less developed countries, fibers are used in a min-imally treated state. In more advanced countries, wood pulpfibers are used. These fibers have been extracted by an ad-vanced industrial process which significantly alters the char-acter of the fibers and makes them suitable for their end uses.1.6—ApplicationsAs more experience is gained with SFRC, more applica-tions are accepted by the engineering community. ACI Com-mittee 318 “Building Code Requirements for ReinforcedConcrete” does not yet recognize the enhancements thatSFRC makes available to structural elements. As more expe-rience is gained and reported, more data will be available tocontribute to the recognition of enhanced SFRC properties inthis and other codes. The most significant properties ofSFRC are the improved flexural toughness (such as the abil-ity to absorb energy after cracking), impact resistance, andflexural fatigue endurance. For this reason, SFRC has foundmany applications in flat slabs on grade where it is subject tohigh loads and impact. SFRC has also been used for numer-ous shotcrete applications for ground support, rock slope sta-bilization, tunneling, and repairs. It has also foundapplications in plant-produced products including concretemasonry crib elements for roof support in mines (to replacewood cribbing). SIFCON is being developed for military ap-plications such as hardened missile silos, and may be prom-ising in many public sector applications such as energyabsorbing tanker docks. SFRC applications are further sum-marized in Chapter 2.GFRC has been used extensively for architectural clad-ding panels due to its light weight, economy, and ability tobe formed against vertical returns on mold surfaces withoutback forms. It has also been used for many plant manufac-tured products. Pre-packaged surface bonding products areused for dry stacked concrete masonry walls in housing ap-plications and for air-stoppage walls in mines. Chapter 3 dis-cusses the full range of GFRC applications.SNFRC has found its largest commercial uses to date in slabson grade, floor slabs, and stay-in-place forms in multi-storybuildings. Recent research in fibers and composites has openedup new possibilities for the use of synthetic fibers in construc-tion elements. Thin products produced with synthetic fibers candemonstrate high ductility while retaining integrity. Chapter 4discusses applications of SNFRC for various fiber types.