A Study on the Performance Evaluation Of Precast Concrete Without Steam Curing by use of Calcium Based Hardening Accelerator

Abstract

ABSTRACT

A Study on the Performance Evaluation of precast concrete without steam curing by use of calcium based hardening accelerator

Min, Tae Beom Dept. of Frontier Architectural and Urban Environmental Engineering The Graduate School Hanyang University

Researches have been mainly focused on aspects of structures and construction like improvement of structure performance of connectors, prestress introduction, Half PC and efficiency of lifting, but has shortage on concrete material. Especially, for precast concrete, steam curing is widely used in construction site and this method in particular is mainly used to speed up the curing process to achieve early strength of concrete in the production of precast concrete and is done for 12 h per days. Thus the problem that a large amount of energy is consumed is raised. Additionally, the production of precast concrete member needs expensive steel forms to use in an efficient and fast procedure so as to reduce the initial cost of production generally. Under this background, this study focused on the development of compressive strength of concrete without steam curing. Various experiments were conducted to produce more than 10 MPa as early-stage strength at age of 6 h curing at room temperature without steam curing using hardening accelerator and high early strength cement that containing high C3S. This thesis is composed of 6 chapters with the purpose of development of precast concrete without steam curing, contents of each chapter is given below.

Chapter 1 covers background, necessity, purpose and method.

Chapter 2 covers production process of process and existing research about early compressive strength of concrete.

Chapter 3 deals with suggestion of experimental analysis on performance evaluation of hardening accelerator, its mechanism with high early portland cement and provned cement hydration mechanism.

Chapter 4 covers mixing technology and application of site performing mock-up test with precast concrete satisfying 10 MPa within 6 hours based on concrete quality required in its plant to develop precast concrete without steam curing.

Chapter 5 deals with economic and CO2 evaluation of precast concrete.

Chapter 6 contains summary of results of this study as follows. 1. Suggestion for hydration mechanism of hardening accelerator and high early portland cement

1) Hardening accelerator enhances development of compressive strength by stimulating C3A, C4AF initially, and stimulating C3S from 2 hours age.

2) Increasement of initial compressive strength by using calcium hardening accelerator is been measured because main component of hardening accelerator, Ca2+ ion, is dissolved, makes faster reaching on supersaturation and then stimulates C3S initially.