مقاله انگلیسی رایگان در مورد رفتار خوردگی بتن سبز طراحی شده برای تیر اصلی پل – الزویر 2018

Creep and shrinkage behaviors are critical factors in the precast/ prestressed concrete industry because these factors allow engineers to assess the long-term performance of concrete and to develop life-cycle estimates for concrete structures. The current study presents the results of an experimental work that addresses creep and shrinkage behaviors as well as the 20 development of compressive strength in ordinary Portland cement concrete (OPC), high performance concrete (HPC), and self-consolidating concrete (SCC). The concrete mixtures created for the present study were used to fabricate prestressed bridge girders. A conventional method (ACI) was used to design the mixture proportion for OPC and a densified mixture design algorithm (DMDA) was used to design the mixture proportions for HPC and SCC. All concrete mixtures had the same target strength of 69 MPa (10000 psi) at 56 days. Additionally, a comparative performance in terms of strength development and creep and shrinkage behaviors of ACI and DMDA concrete is performed in the present study. Test results show that all of the samples attained the target strength after 28 days of curing and that the strengths of each continued to increase afterward. Importantly, the incorporation of pozzolanic materials into concrete mixtures affected the propagation of creep strain and shrinkage positively. Furthermore, the DMDA concrete sample delivered better long-term performance than ACI concrete in terms of compressive strength, creep strain, and shrinkage.

Introduction

Today, the global construction industry consumes over 10 billion tons of concrete  annually [1]. Over the past decade, in order to meet the requirements of advanced construction activities, the demand specifications for concrete have expanded beyond the traditional considerations of durability, cost, and safety to include considerations of workability and ecology [2]. Traditional concrete uses a relatively high water-to-cement (w/c) ratio as a safety criterion. However, this practice increases the risks of early deterioration, corrosion, and cracks [2–5]. Thus, the water-to-binder (w/b) ratio influences the long-term performance of concrete. High w/b ratios have been associated with increased permeability and increased risks of bleeding and segregation, while the calcium hydroxide (Ca(OH)2) that results from the cement hydration process is a potential cause of sulfate attack, leaching, and precipitation [4–7]. Thus, these problems degrade concrete quality and deteriorate concrete durability. Partially replacing cement with pozzolanic materials such as fly ash (FA), ground granulated blast furnace slag (GGBFS), rice husk ash (RHA), silica fume (SF), and metakaolin (MK) holds the potential to enhance the long-term performance of concrete, as these materials reduce hydration-generated heat and the pozzolanic reaction of these materials turns soluble alkali into C-S-H gel, which is significantly more stable [4,8,9].