1 Experimental Investigation of the Effect of Microfibers on the Tensile and Flexural Strengths of Low-Viscosity Grouts S. Vaidya 1 , Md. A. Alam 2 , E. N. Allouche 3 1 Research Associate, Trenchless Technology Center, Louisiana Tech University, Ruston, LA, USA, PH (318)257- 4072. Email: svaidya@latech.edu . 2 Research Assistant, Trenchless Technology Center, Louisiana Tech University, Ruston, LA, USA, PH (318)257- 4072. Email: maa029@latech.edu . 3 Technical Director, Trenchless Technology Center, Louisiana Tech University, Ruston, LA, USA, PH (318)257-4072, FAX (318)257-2777. Email: allouche@latech.edu . Abstract The on-set and propagation of tensile cracks are the limiting factors in designing grout-in-place liners which utilize cementitious grouts. To improve the strength of the grout and postponed the on-set and delay the propagation of tensile cracking, micro-fibers were added to a low viscosity commercial grout. Four fiber types were utilized in this experimental study (polypropylene, poly-vinyl alcohol, glass fiber and carbon fiber) to determine the best performing fiber that maximizes the tensile and flexural strengths of the grout with little or no reduction in flowability. Micro-fibers were added at predetermined weight percentage fraction with respect to the cementitious material. The addition fiber percentage was controlled by the need to maintain the viscosity of the grout within a fixed range. The effect of fiber addition on the grout strength was studied by performing standard tensile and bending tests (ASTM C 307 and ASTM C 580) on the fiber reinforced grout specimens. Results from the tensile and flexural tests suggest that the addition of micro-fibers could significantly enhance the tensile strength of low viscosity cementitious grouts without hindering their flowability. Introduction Grout-in-place pipelining (GIPP) is a family of methods used for pipeline rehabilitation. A thermoplastic (PVC or HDPE) liner with anchors/studs on its outer surface is pulled through the host pipe. These anchors serve as spacers and form an annular space throughout the length of the pipe between the host pipe and the liner. The annular space is then filled with a cementitious grout under pressure which upon curing, acts as a bond, connecting the host pipe and the liner (ASCE, 2009). GIPP liners can be used to rehabilitate any pipe and/or culvert with any material, shape and the condition (corroded/partially corroded, deformed and near collapse). According to Paterson (2000), GIPP lining with HDPE can be done in three different systems, such as, basic system, preliner system and double system. In basic system a single HDPE liner with studs on its outer surface is grouted in place with the 61 Pipelines 2010: Climbing New Peaks to Infrastructure Reliability—Renew, Rehab, and Reinvest © 2010 ASCE Downloaded 28 Jan 2011 to 134.121.64.253. Redistribution subject to ASCE license or copyright. Visit http://www.ascelibrary.org