The use of soy methyl ester-polystyrene sealants and internal curing to enhance concrete durability

Michael Ryan Golias, Purdue University

Abstract

The US infrastructure is dominated by concrete structures. As it ages, these structures are beginning to deteriorate. Although concrete is typically assumed to be a very durable material, exposure to the environment and time is leading to cracking, spalling, and other deterioration of concrete elements. In order to continue maintaining and expanding the current infrastructure steps must be taken to improve durability. This thesis explores the use of Soy Methyl Ester-Polystyrene and internal curing (IC) as methods to enhance concrete durability. Soy Methyl Ester (SME) is a non-toxic, biodegradable, and renewable concrete sealant. As it is derived from soy bean oil, this product is highly hydrophobic making it ideal for use as a water sealant. This thesis explores the use of Soy Methyl Ester-Polystyrene (SME-PS) blends as a topical sealant to increase the durability of concrete. Experimental results show that SME-PS reduces water absorption (up to 75%), protects from damage caused by freezing and thawing (reduces damage by 66%), reduces chloride ingress depth by up to 50%, and slows the rate of the alkali-silica reaction by 50%. Internal curing is a technique in which cement hydration is enhanced by internal water which is not part of the mixing water. This process is accomplished by providing curing water throughout the concrete matrix through the use of pre-wetted inclusions such as lightweight aggregate (LWA). The use of this technique improves concrete durability by increasing compressive strengths, reducing shrinkage and cracking potential, and reducing fluid transport. This thesis investigates the role of initial LWA moisture content and explored utilizing LWA with different levels of initial moisture. Although typically pre-wetted for a minimum of 24 hours prior to mixing, it was possible to achieve internal curing benefits (improved mechanical and fluid transport properties) with either initially dry or vacuum saturated LWA. When proper external curing is not provided concrete can experience significant moisture loss to evaporation leading to long term durability problems including cracking and increased fluid ingress. Despite typically being used to compensate for self-desiccation (internal drying) in low water-to-cement ratio systems, it should be possible to use IC to compensate for water lost to evaporation (external drying). While experimental results confirm the hypothesis that the use of internal curing can help mitigate the negative effects of drying, it is not recommended that IC be used as a substitute for good curing practices.

Degree

M.S.C.E.

Advisors

Weiss, Purdue University.

Subject Area

Civil engineering

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