Improving thermal conductivity and fluid loss properties of grouting materials: New mixed grout granules of bentonites and sands
Abstract
We propose new granule type grouting materials with optimized ratio of bentonites and sands for use in the ground source heat pump systems. The grouting materials could be prepared in various size of 1.18 to 4.75 mm. The granules consist of bentonite powders and sand particles inside and extra bentonite powders exists on the surface of granules. In different ratio (1:0-1:8) of bentonites and sands, the granules with 1:8 ratio show the best thermal conductivity (ca., 1.8 W/mK). In comparison to the existing powder type mixed grouting materials, the present granules show the lower values of fluid loss and the minimum values at 1:5 ratio of bentonites and sands. This might be due to the fact that the bentonites on the surface of granules strongly hold water, resulting in decrease of penetration of water into granules. We also investigated the effect of bentonites between the granules on fluid loss property by addition of them as slurry form. When only water is added, water channels were formed. When the slurry of bentonite and water is added, water channels were decreased, resulting from that the additional bentonites interacted with granules. According to aging time, the homogeneity of grouting layer is improved.