A Preliminary Investigation of Polymer Modified Hydrated Cement Paste Prisms and the Fracture Analysis of Tested Specimens


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Title: A Preliminary Investigation of Polymer Modified Hydrated Cement Paste Prisms and the Fracture Analysis of Tested Specimens

Author(s): J. Belkowitz, M. Best, M. Nilsen, F. Fisher and D. Armentrout

Publication: Special Publication

Volume: 278


Appears on pages(s): 1-14

Keywords: acrylic polymer; compressive and flexural strengths; hydrated cement; scanning electron microscopy

Date: 3/1/2011

The following paper documents the preliminary experimentation and analysis of a polymer fortified hydrated cement sample. Concrete is a brittle construction material. When compared to other construction materials, concrete can offer competitive structural resistance under compressive loads. But due to the brittle nature of the hydrated cement matrix, C-S-H network, concrete is poor when resisting flexural loads. The brittle C-S-H structures cannot absorb the flexural energy like a ductile material. The properties of concrete fracture are analyzed at the microscopic level to understand the method of failure. By including the acrylic polymer into the hydrated specimens it was the belief of the authors that the acrylic polymer would enhance the fracture behaviour of the concrete in flexure. The C-S-H hydrates precipitate from a saturated solution. The acrylic polymer, after being mixed into the cement paste while still fresh, becomes secured in the C-S-H structure as said structure hardens. Samples were cast, cured, and tested in order to determine if the acrylic polymer cause the C-S-H structure to behave in a ductile manner. The testing included compressive and flexural stress tests with microstructure observation via Scanning Electron Microscope (SEM). The compressive and flexural tests were used to discern a measured value of gain when using an acrylic polymer compared to a control mix. The SEM images were used to determine crack origin, type of failure, and acrylic polymer benefit. The tests and SEM images revealed that there was a negative reaction between the admixtures to cause an excessive air generation. Despite the setback, the SEM images revealed evidence of energy absorbing of the acrylic polymer mix.