His field of study is durability and strengthening of concrete structures. Dr. Ekasit Limsuwan, born in 1947, received his Ph.D. from the University of Texas at Austin 1977. He has experienced in structural design, construction supervision and research work in high performance concrete, structural concrete, formwork technology and concrete durability. Concrete is classified as durable materials compared to other building materials. Permeability characteristics and tensile strength are

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... ly affect to the concrete durable properties. Aggressive anions and gas can penetrate to the concrete pores by diffusion process. This leads to the deterioration process beneath the concrete surface by physical, chemical or both actions. Concrete can also be damaged by physical process such as frost attack, abrasion, and etc. Strength, serviceability, or structural performance of concrete structures can be reduced with time by these deterioration mechanisms and processes. Such deterioration process can be predicted by mathematical function described the loss of material properties and performance with time by considering the environmental factors and concrete properties. The deterioration models can be utilized in durability design or service life prediction of concrete structures that are the useful information to impose the maintenance policies. This paper presents the basic concept of degradation modeling and mathematical models of deterioration of concrete bridge girders in Bangkok area considering the environmental factors and concrete properties. 1.