Performance of self-compacting repair mortar including metakaolin and glass fibers

Abstract

Introduction: Self compacting mortar is known as a highly fluid mortar that can flow and fill all spaces under its own weight without vibration or compaction. This experimental work aims to produce a self-compacting mortar (SCM) that can be used to repair damaged structural concrete by replacing a proportion of ordinary Portland cement with metakaolin (MK) and adding glass fibers (GF). Methods: Mixtures including various percentages of MK and GF were prepared and tested. All mixtures were tested in the fresh state to assess fluidity and viscosity through mini-slump flow and mini V-funnel flow time tests, respectively. Physical and mechanical properties of all mixtures were measured, such as compressive strength, flexural strength and water absorption. In order to check the performance of prepared SCM in structural repair two experiments were conducted on damaged reinforced concrete beam and cylindrical specimens. Results: The results showed that the addition of GF and MK needs an increase in SP dosage to reduce their negative effect on the fluidity and the viscosity of SCM mixtures. The use of MK up to 10% of cement as replacement resulted in a compressive strength gain of 11 MPa at 28 days and 13 MPa at 56 days. Similar behavior was observed in the mixture containing 0.4% of GF and 10% of MK. Adding GF with 0.2, 0.4, and 0.6% led to flexural strength gains of 4, 6, and 15%, respectively. Water absorption was reduced by 29% when 15% of MK was incorporated. Using MK improves the bond between the repair mortar and the concrete substrate. Conclusion: Following a rigorous analysis of the obtained results, it can be concluded that MK and GF can be used to improve mechanical properties and reduce water absorption of SCM mixtures. The mixture including 0.4% of GF and 10% of MK exhibited the best performance and was considered more suitable for repairing damaged SCC beams.