Materials characterization of superplasticized cement-sand grout

Selected material properties were determined for a superplasticized cement-sand grout formulation designed for sealing boreholes used with geothermal heat pumps (GHPs). The grout was investigated as an alternative to bentonite and near cements. Hydraulic conductivities (permeability coefficients) of grouts when cast around high density polyethylene (HDPE) pipes to represent a heat exchanger were measured over a range of typical operating temperatures. It was determined that the cement-sand grout had hydraulic conductivity up to two orders of magnitude lower than neat cements depending on test temperature. Infiltration tests performed on grouted tubes containing HDPE pipes also indicated better sealing capability with the cement-sand grout. Mechanical properties measured included bond strength to HDPE, compressive and splitting tensile strength, dynamic and static elastic moduli, shear modulus and Poisson's ratio. (C) 2000 Elsevier Science Ltd. All rights reserved.