A Cement-Bitumen Emulsion Grout as Backfilling Material of Narrow Trenches on Road Pavements

Narrow trenching on road pavement has become a widespread practice for installing telecommunication infrastructures on road pavements. Although such technique guarantees a social and environmentally sustainable construction, the quality of the backfilling plays a crucial role in both the short- and long-term properties of the trench. In this context, the present research aims to assess the effectiveness of a cement-bitumen emulsion grout (CBEG) as unique backfilling material for narrow trenches. To this purpose, a real-scale field trial was constructed and monitored through visual inspection, coring activity, and permeability tests. Skid resistance tests, compressive and flexural strength tests were also carried out on specimens casted in the laboratory. Moreover, indirect tensile strength tests were performed to evaluate the adhesion properties at the existing pavement backfilling interface on both cored and laboratory moulded specimens. Results mainly show that the CBEG, due to its flowable nature, quick hardening, and great early strength, provides uniform backfilling and fast restoration of the pavement surface. The latter shows skid resistance values comparable to those of hot mix asphalt pavement. After long curing, the backfilling does not show any lowering phenomenon and ensures adhesion at the interface as testified by the absence of water penetration. Finally, a satisfactory adhesion at the interface is determined also in terms of indirect tensile strength.