Heterogeneous distribution of lightweight porous ceramic sands in a high strength cement grout

Abstract

Material heterogeneity may occur to cement grouts especially when lightweight fine inclusions are used, however, the quantitative assessment still remains a challenging task. In this work, a lightweight ceramic sand (LCS) was adopted to partially replace a quartz sand (QS) for fabricating two grouts, namely LCS-GM and O-GM. The impacts of LCS on the flowability, expansion and compressive strength were first measured in laboratory tests. To approach the real construction conditions, the grouting materials were cast in 6-meter-long tubes, and the compressive strength and microstructure of the specimens at different depths were measured. X-ray computed tomography (XCT) was employed to nondestructively quantify the structure and distribution of the pores and LCS particles. Results demonstrated that the partial replacement of QS with LCS can decrease compressive strength, reduce expansion, but increase flowability. Both density and compressive strength increased linearly with depth. The long-tube casting entrapped more air voids for O-GM. Less air voids and LCS particles were detected for a deeper LCS-GM specimen. Tight interactions between the cement matrix and LCS particles were observed. The regimes of water release and air void accommodation by the porous LCS particles may account for the experimental observations. The findings provide a reliable way to fabricate lightweight and high strength grouting materials and deepen the understandings of material heterogeneity in cement-based materials.