CIGMAT Report: Update From This Unique, Industry-Specific Ongoing Research Program

By C. Vipulanadan, PhD, P.E., professor of Civil Engineering, director of CIGMAT and the Texas Hurricane Center for THC-IT | September 2010 Vol. 65 No. 9
1) Macro-cells 2) Macro-holes in the Macro-cell walls 3) Macro-cell walls. Fig. 1: Microstructure of a polyurethane grout.

CIGMAT CT-3 or ASTM C 321: In this test, the coating was sandwiched between two rectangular concrete specimens and then tested for bonding strength. Both dry and wet concrete specimens were used to stimulate the extreme coating conditions. The bonded specimens were cured under water up to the point of testing. Tests are performed over a period of several years. The test configuration is in Fig. 9. Since sample preparation and testing in CIGMAT CT-3 (ASTM C 321) is easier, this test was selected for comparison purposes with CIGMAT CT-2.

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(a) Test specimen configuration (b) Load frame test setup

Fig. 9: Bonding test arrangement for sandwich test.

Pipe-joint infiltration test facility
While many small and large older cities are undergoing repairs and maintenance, several newer cities are planning to install wastewater systems. Infiltration due to leaking pipes, manholes, laterals and other components of a wastewater system will add to the problem of overflow and substantially load the treatment facilities. Frequent overflows not only lead to regulatory problems but also increase treatment cost. Leaking systems will result in the erosion of soils through the leaking joints leading to the settlement of the ground surface, formation of sinkholes and damage to surrounding pavements and structures. Erosion of soil materials around the pipes and manholes can lead to formation of void and settlement of pipes, accelerating the damage. Eroding soils entering the wastewater system through the leaking joints can cause problems within the wastewater system.

Literature review clearly indicates that each type of pipe is tested differently in determining the infiltration rate at the pipe joint. Therefore a testing method must be developed to better quantify the infiltration at pipe joints under various joint-loading conditions. Based on literature review and ASTM testing standards, a testing protocol to determine infiltration at the pipe joint must be developed.

The primary purpose of the test protocol was to establish a comprehensive procedure for testing pipe joints for infiltration. The model tests will verify the performance of the joints up to an applied external hydrostatic pressure of 48 kPa (7 psi) (Figure 10).

A test protocol was developed to test the pipe joint under the following conditions:
a. Straight joint (Method A)
b. Angular deflection (Method B)
c. Shear load (Method C)

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Fig. 10: Configuration of a pipe-joint infiltration test

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