טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentSouslikov Andrew
SubjectOptimization of Using Pre-Saturated Lightweight Aggregate
to Counteract Autogenous Shrinkage of
High Strength Concrete
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Kovler Konstantin


Abstract

Self desiccation and autogenous shrinkage of high strength concretes is one of their drawbacks which can not be readily accommodated by conventional curing. The concept of internal curing using lightweight soaked aggregates has been advanced by several groups, to provide internal reservoirs of water which enable uniform curing of the whole cross-section. The present study is intended to develop this approach further, by optimizing the porosity and size of the aggregates to enable successful internal curing with only a small amount of aggregates, which could be viewed as additives rather than bulk replacement of conventional aggregates. The approach taken was to increase the porosity of the aggregates and reduce their size, to obtain a system with numerous internal reservoirs of sufficiently small spacing to allow water to be readily discharged from the aggregate and transported over the whole range of the matrix. It was shown that aggregates with porosities of about 50% by volume, size of few millimeters and contents of less than 50 kg/m3 could provide full elimination of autogenous shrinkage in concretes having w/c as low as 0.25, with only a small effect on strength. The parameters controlling the efficiency of the aggregates were assessed, indicating that their pore structure and paste-aggregate proximity are the most important ones, and that water from within the aggregates can be readily transported into the matrix to a range of few millimeters.