Cementation Processes of Naturally Aged Hawaiian Calcarerous Sands

Abstract

Researchers have studied cementation of calcareous sands for decades. While cementation increases static and cyclic strengths, it also reduces skin friction on piles. Cementation of sands in their own environment varies widely with many different factors. Obtaining undisturbed samples can be difficult and costly, and laboratory reproduction of samples has become an accepted method for testing calcareous materials. The focus of this research is on understanding the processes and effects of early cementation in calcareous sand. Understanding of these processes will allow researchers the ability to better estimate light cementation effects for various types of calcareous sands. The project compared results of cyclic and static triaxial tests, cone penetrometer tests, and Scanning Electron Microscope (SEM) photographs to show the differences between two distinctly varied calcareous sands at similar densities and aged for relatively short periods of time. "Natural aging" was the baseline used for this project. All samples were saturated with distilled water and aged under a confining pressure of one atmosphere. Although not truly representative of the "natural" environment, it provides a relative baseline of how calcareous sands react in the absence of any additional cementing agent. The results of the project bring about many conclusions, as well as raising additional questions. The SEM pictures provide critical information to the project. The photographs provide a visual sense of the bonds caused from the cementation and give a visual picture of the mechanisms causing increases in static and cyclic strength. The SEM photos show two distinctly different types of bonding between the two types of sands investigated, and generally show an increase in bonding as aging time is increased. Data from all laboratory tests also show related strength increases, which can be attributed to the increase in cementation shown in the SEM photographs.