An accelerated test method was used to predict the compressive creep of Recycled Polymeric Piling (RPP) made of a recycled High Density Polyethylene (HDPE) matrix and reinforced with Fiber Reinforced Polymer (FRP, aka. fiberglass or E-glass). The method is based on the equivalence of the Strain Energy Density (SED) between conventional constant-stress creep tests and stress-strain tests conducted at different strain rates. The methodology has been validated using specimens of virgin HDPE. SED also compared favorably with thermal creep acceleration methods such as the stepped isothermal method and time temperature superposition. Results indicate that the tested recycled HDPE exhibited a pronounced viscoelastic-viscoplastic response when loaded in compression. SED predicts that recycled HDPE will creep by 1.1 % over 100 years when loaded at an ultimate stress of 8.3 MPa (1200 psi). FRP exhibits a small viscoelastic tendency (Fig. 1). SED predicts that the FRP loaded in compression will creep by less than 0.5 % over 100 years when loaded at an ultimate stress of 88 MPa (128,000 psi).
Fig. 1- Creep of recycled polymeric piling components: FRP and HDPE
The stress-strain behavior of RPP depends on the strain-compatibility of both HDPE and FRP. The creep of RPP depends on the percentage of FRP reinforcement in the cross section. The creep of RPP is estimated to be on the order of 0.4 to 0.8 % over 100 years when typical RPP geometries and reinforcement ratios are considered (Fig. 2).
Fig. 2- Creep of recycled polymeric piling at different composite creep stresses.
Primary References
- Bozorg-Haddad, A. and M. Iskander (2012). “Creep of reinforced polymeric piling,” Journal of ASTM International, Vol. 9, No. 2, doi: 10.1520/JAI103668
- Bozorg-Haddad, A., M. Iskander, and Y. Chen (2011). “Compressive strength and creep of recycled HDPE used to manufacture polymeric piling,” Construction & Building Materials Journal, Vol. 26, pp. 505-515, doi: 10.1016/j.conbuildmat.2011.06.051, Elsevier
- Bozorg-Haddad A. and M. Iskander (2011). “Predicting compressive creep behavior of virgin HDPE using thermal acceleration,” Journal of Materials in Civil Engineering, Vol. 23, No. 8, pp. 1154-1162, doi:10.1061/(ASCE)MT.1943-5533.0000278, ASCE
- Bozorg-Haddad A. and M. Iskander (2011). “Comparison of accelerated compressive creep behavior of virgin hdpe using thermal and energy approaches,” Journal of Materials Engineering and Performance, Vol. 20, No. 7, 1219-1229, DOI: 10.1007/s11665-010-9743-9, Springer
- Bozorg-Haddad, A., M. Iskander and H. Wang, (2010). “Compressive creep behavior of virgin HDPE using equivalent strain energy density method,” Journal of Materials in Civil Engineering, Vol. 22, No. 12, pp. 1270-1281, doi: 10.1061/(ASCE)MT.1943-5533.0000136, ASCE.
