|M.Sc Student||Pavel Larianovsky|
|Subject||Internal Curing of Concrete Using Super Absorbent Polymers|
|Department||Department of Civil and Environmental Engineering||Supervisor||Professor Kovler Konstantin|
|Full Thesis text - in Hebrew|
High-Strength Concrete (HSC) has become an object of intensive research due to its growing use in the construction practice.
However, the low water-cement (w/c) ratio (below ~0.4) of HSC, which is necessary for the enhancement of strength and durability, leads to a so-called self-desiccation of concrete, as a result of the cement hydration process. This causes considerable volume changes known as autogenous shrinkage, which in turn lead to concrete cracking. The internal curing of concrete using small, well distributed water reservoirs seems to be able to solve this problem.
In this study, the effect of super-absorbent polymer (SAP) as agent for internal curing on free autogenous shrinkage and compressive strength of concrete with low w/c ratios is investigated. Water entrainment by means of SAP leads to the controlled formation of water-filled macropore inclusions in the fresh concrete, which prevent self-desiccation shrinkage of the hardening concrete.
The SAP used in this study was Cabloc C96 - suspension-polymerized covalently cross-linked acrylamide/acrylic acid copolymer. Low w/c concretes were prepared with and without addition of SAP.
The research shows that the water entrainment by SAP addition has a critical effect on the autogenous strain. Without SAP addition, the concrete develops a considerable shrinkage. The effectiveness of the SAP is inversely proportional to w/c ratio. This implies that the SAP is effective mainly at low w/c ratios. Additionally, it is found, that using of SAP in a wet condition is preferable.
The effects of adding polymer on compressive strength of concrete are studied experimentally and discussed. No pronounced differences in autogenous shrinkage and compressive strength are observed between different dosages of SAP at the same content of internal curing water.
Finally, the effectiveness of this internal curing method in mitigation of autogenous shrinkage in HSC is compared to that of more popular method of using pre-saturated lightweight aggregates.