International Concrete Abstracts Portal

Title: AN EXPERIMENTAL STUDY OF SPRAYED MORTAR FOR REPAIRING APPLICATION

Author(s): Siriporn Thongjaeng, Dr.Thanakorn Pheeraphan

Publication: TCA

Volume: 3

Issue: 2

Appears on pages(s): 24-29

Keywords: Mortar, Sprayed Mortar, Wet-mix Sprayed Mortar, Repair Applications, Column repair

DOI:

Date: 6/1/2015

Abstract:
This study is to develop mix proportions of sprayed mortar and to investigate the performance of sprayed mortar regarding fresh and hardened properties, including mini slump flow, setting time, sagging resistance, build-up thickness, compressive strength, bond (pull-off) strength, drying shrinkage and age at cracking for repairing application. The research focuses on the maximum size of aggregate of 0.6 mm. with the addition of admixtures and the percentage of fly ash used for cement replacement. The results have shown that sprayed mortar with 0.01% starch ether, 0.5% water reducing agent and 8% shrinkage compensating admixture is the optimum mix proportion for use with cement and fly ash. The maximum build-up thickness of each layer is 50 mm. that can be applied without sagging. The cement replacement of 40% fly ash also produces satisfactory performance including workability, pumpability and sprayability. The compressive strength, bond strength, drying shrinkage and age at cracking of this mix are 38 MPa, 1.81 MPa, 145 millionths (expansion) at 28 days and no cracking after 60 days, respectively. The hardened performance is higher when mortar is sprayed compared with hand application. For demonstration, this sprayed mortar is applied to repair a damaged column. After repairing, ultrasonic pulse velocity (UPV) is used to check the quality of concrete. The result shows that the quality of concrete is good. Additionally, the cost of this sprayed mortar is much lower than the commercial product with similar properties and application. Therefore, the development of sprayed mortar with fly ash used for cement replacement has been satisfied with high performance and low cost for repairing application.