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Concrete microstructure homogenization technique with application to model concrete serviceability


Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/20818

Concrete microstructure homogenization technique with application to model concrete serviceability

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dc.contributor.author Fan, Tai
dc.date.accessioned 2012-07-03T18:28:17Z
dc.date.available 2012-07-03T18:28:17Z
dc.date.issued 2012-07-03
dc.date.submitted May 2012
dc.identifier.uri http://hdl.handle.net/1928/20818
dc.description.abstract Conventionally, mechanical properties of concrete are attained through experiment by leaving microstructural phases interaction in a black box. To fully understand concrete, it is necessary to bridge the gap between microstructure and macro properties. In this dissertation, with several models being given progressively, an innovative homogenization model of concrete is proposed in which concrete is regarded as cement and aggregate particles connected by interfacial transition zone (ITZ). Defined on a representative volume element (RVE), the relationship between microstructure and macro properties is established. The proposed model is validated by experimental results and then applied in the study of concrete serviceability. The concrete homogenization model includes RVE in two scale levels: cement paste RVE in microscale and concrete RVE in mesoscale. Cement paste RVE is composed by microstructural phases (water, unhydrated cement, calcium hydroxide, calcium silicate hydrate, etc.), which are determined by the validated three-dimensional (3D) cement hydration and microstructural development model HYMOSTRUC® or CEMHYD3D. The developed cement paste RVE at different hydration ages is transferred to a finite element method (FEM) model and upscaled by homogenization as inputs for concrete RVE in the mesoscale. Cement paste homogenization model is validated by the experimental study of nanosilica effects on the mechanical properties of cement paste. Concrete RVE can be generated by converting realistic or (re)constructed concrete material image into finite element environment. In this dissertation, cell operation method is presented to (re)construct concrete. The similarity between (re)constructed image and target image is verified by low-order correlation functions. In the discrete model of concrete, each cement paste element or each aggregate is treated as a discrete particle; and these particles are bonded together by equivalent ITZ. To simulate cracking and particle interaction, ITZ is represented by cohesive zone model (CZM) and contact mechanism. This dissertation will demonstrate that the concrete homogenization technique can capture the relationship between structure and material, and enable us to study concrete serviceability in view of microstructure evolution. As the applications of the proposed homogenization model of concrete, the following studies on concrete serviceability are carried out: deflection variation in reinforced concrete (RC) beams propagated from concrete microstructural variability, and mechanical consequences of concrete subjected to alkali-silica reaction (ASR). Due to the inherent uncertainty in concrete microstructure, variation of RC beam deflection is inevitable. For satisfactory use of RC members, it is necessary to incorporate uncertainty of concrete properties in deflection prediction. With the help of homogenization modeling, microstructural variability in concrete is projected to the deflection variation in RC beams. Alkali-silica reaction (ASR) is a kind of chemical reaction in concrete. Alkali in cement meets with reactive silica in aggregate and expanding gels are produced if there is enough water. The swelling of gels will induce stress and alter concrete microstructure. In some cases, this alteration includes cracking and expansion in concrete member. The condition becomes more complicated when the expansion caused by swelling gels is confined by reinforcement and prestress in concrete. Using the proposed homogenization technique, the mechanical consequence of ASR on concrete is simulated. ASR gels expansion is achieved by aggregate volume increase, which causes internal stress and deteriorates ITZ in concrete RVE model. The proposed mechanical model of concrete subjected to ASR is demonstrated on plain concrete specimens (prism and cylinder). The simulated cases are validated by experimental work by others. It is proved that the proposed ASR model by using concrete microstructure homogenization can stand with ASR chemical and diffusional models given by other researchers to predict the serviceability of concrete structure subjected to ASR. en_US
dc.description.sponsorship The Defence Threat Reduction Agency (DTRA) en_US
dc.language.iso en_US en_US
dc.subject CONCRETE en_US
dc.subject.lcsh Concrete--Mathematical models.
dc.subject.lcsh Concrete--Testing.
dc.subject.lcsh Concrete--Microstructure.
dc.subject.lcsh Concrete--Chemical resistance.
dc.subject.lcsh Concrete beams--Testing.
dc.title Concrete microstructure homogenization technique with application to model concrete serviceability en_US
dc.type Dissertation en_US
dc.description.degree Engineering en_US
dc.description.level Doctoral en_US
dc.description.department University of New Mexico. Dept. of Civil Engineering en_US
dc.description.advisor Taha, Mahmoud Reda
dc.description.committee-member Taha, Mahmoud Reda
dc.description.committee-member Gerstle, Walter
dc.description.committee-member Maji, Arup K.
dc.description.committee-member Shen, Yu-Lin

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