Date of Award
Level of Access Assigned by Author
Master of Science (MS)
Second Committee Member
Third Committee Member
The researchers in the concrete field have to obtain a concrete with high durability; the goal is to prolong the service life and reduce maintenance costs. Shrinkage cracks due to losing the moisture, or due to self-desiccation is a leading in reducing durability. Cellulose Nano-Fibrils (CNF) is a natural material. It is produced by isolating from a cellulosic material. CNF show high tensile strength, low density, low cost. Furthermore, CNF has the ability to absorb the water. These properties give CNF potential to improve the properties and solve the problems of the conventional cement paste, for instance, shrinkage. Different (CNF) ratios were added, to evaluate the effects of CNF on drying shrinkage and autogenous shrinkage of cement paste.
Two cement paste prisms were cast and tested in accordance with ASTM C157 for each batch, with some modifications of the at curing method. The work of this study was organized into two phases. Phase one focused on free shrinkage while phase two focused on autogenous shrinkage.
In phase one, thirty-two batches were prepared. These batches were divided into four groups with water to cement ratio 35%, 40%, 45% and 50 %. Each group was further divided into CNF fraction of 0%, 0.05%, 0.1%, 0.2%, 0.5%, 1%, 1.5%, and 3%. Two cement paste prisms were cast and tested in accordance with ASTM C157 for each batch, with some modifying at curing method
In Phase two, four batches were prepared in the Concrete laboratory. Water to cement ratio was 30% for all the batches. Four different CNF ratios were used to assess the effect of the CNF on the autogenous shrinkage, the ratios of the CNF were 0 as the reference, 0.1%, 0.2% and 0.5%. Two sealed specimens were cast and were tested in according to of ASTM C157 for each batch. The flow table test was tested for all the batches in these phases.
The results of the free shrinkage (phase one) test for each batch were collected up to 90
days. When the w/c % were 40%, 45%, and 50%, the results of these groups at age 28
days showed that, the addition of the CNF with different ratios that led to increasing the
free shrinkage, with the exception that at law W/C ratio and law CNF dosage, shrinkage was reduced.
The results for phase two showed that CNF had little or no effect on autogenous shrinkage. However, it must be noted that extra water not considered in this study and early age effects not considered in this analysis,
Ahmed, Mohammed Akram, "Effect of CNF On Drying Shrinkage and Autogenous Shrinkage of Cement Paste" (2017). Electronic Theses and Dissertations. 2794.