Investigation of Material Failure in Sanitary Sewer Tunnel

CTLGroup was retained by an attorney for a contractor to investigate failures of a repair mortar based on calcium aluminate cement (often called high-alumina cement). The high-alumina cement (HAC) mortar was being used to rehabilitate sanitary sewer manholes in Austin, Texas. The mechanisms of failure included early age cracking and debonding of the repair material.

CTLGroup's work included document and literature review, a site visit, observation and testing of mortar samples, as well as the development of opinions related to the possible causes of failure of the repair mortar.

CTLGroup used a number of techniques available in our laboratory facilities to determine the cause of the failure of the materials. CTLGroup performed Isothermal calorimetry, X-ray diffraction (XRD), X-ray fluorescence (XRF), petrographic examination of samples, scanning electron microscopy and temperature measurements of mockups made from the dry repair materials.

CTLGroup determined that the failures of the HAC mortar were caused, in part, by excessively high temperatures and temperature differentials. These high temperatures were caused by a poorly controlled and high rate of reaction of the material. Indications of phase changes were observed which correlated with these high temperatures.

CTLGroup's approach and capabilities, which helped our client determine the cause of the HAC mortar failure and reach a favorable settlement in the matter, can also assist in the investigation of failures of a wide variety of materials.