Effect of Expansive Agents and Shrinkage Reducing Admixtures on the Performance of Fiber-Reinforced Mortars

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Title: Effect of Expansive Agents and Shrinkage Reducing Admixtures on the Performance of Fiber-Reinforced Mortars

Author(s): M. Collepardi, V Corinaldesi, S. Monosi, and A. Nardinocchi

Publication: Special Publication

Volume: 302

Issue:

Appears on pages(s): 289-298

Keywords: expansive agent. SRA. fiber reinforced mortars. steel fibers. polyvinyl-alcohol fibers. glass fibers. compressive strength. flexural strength. restrained length-change. free length-change

Date: 6/1/2015

Abstract:
In this research several fiber-reinforced mortars (FRMs) were studied. The effectiveness of three different kinds of macro-fibers was tested: brass-coated steel fibers (SF), polyvinyl-alcohol fibers (PM and anti-crack HP glass fibers (GF) were separately added to superplasticized mortar mixtures, at the same rate of about 1,2% by volume of the mortar. Moreover, special FRMs were also manufactured combining a CaO-based expansive agent with a shrinkage reducing admixture (SRA) in order to reduce the risk of cracking induced by drying shrinkage and make more reliable mortars from the durability point of view. All the mortar mixtures were characterized by the same w/c ratio of 0.45, and the same sand/cement ratio of 3.0, as well as the same amount of a polycarboxylate-based superplasticizer (0.6% by weight of cement). A control superplasticized mixture (CM) with the same w/c, the same sand/cement ratio, but without fibers, expansive agent and SRA was also prepared and studied for comparison purpose. Moreover, an expansive mortar (EM) without fibers but with expansive agent and SRA was manufactured and studied. All the mortar mixtures were characterized for the workability in the fresh state (where they showed approximately the same plastic consistency), and in the hardened state by measuring compressive and flexural strength, as well as free or restrained length changes. The results obtained show the effectiveness in the restraint expansion of the combined use of macro-fibers, expansive agent and SRA when glass fibers and steel fibers were used.