Experimental Study on Freeze-Thaw Damage Mechanism of Lightweight Aggregate Concrete


Book Description

In order to clarify the deterioration process and damage mechanism of lightweight aggregate concrete when subjected to freezing and thawing, it is necessary to investigate the effects of lightweight aggregate on the concrete performance and analyze the relationship of freeze-thaw resistance between them. In this study, rapid freezing and thawing tests were conducted on lightweight concrete and lightweight coarse aggregate, respectively. The results of the concrete tests showed that the freeze-thaw resistance of lightweight concrete was mainly controlled by the water content of the lightweight aggregate. The tests of lightweight aggregate produced similar results: The higher the water content of the aggregate, the higher the weight loss and grain ratio passing 10 mm sieve; the lower the crushing strength, the larger the pore volume after freezing and thawing. When the lightweight aggregate with high water content was subjected to freezing and thawing, the pore volume grew larger since the aggregate structure suffered damage from frost expansion inside the structure. Micro-cracks began to form in the lightweight aggregate, then enlarged and spread to the adjacent mortar, and finally caused expansion and damage of lightweight concrete.




Freeze-Thaw Durability of Concrete


Book Description

Concrete durability in climates where freezing and thawing occurs is a continuing problem. It is particularly acute for highway and bridge structures, where de-icing salts are used to combat the effects of frost, snow and ice. These salts can cause damage to concrete and accelerate corrosion of reinforcements. This book presents the latest international research on this area, with contributions from North America and Europe which were presented at an international RILEM workshop.




Lightweight Aggregate Concrete


Book Description

In spite of the increasing use and demand for lightweight aggregate concrete (LWAC), there is still a lack of adequate explanations to understand the mechanisms responsible for the strength and durability properties of LWAC. This book is written to give an overall picture of LWAC, from the historical background, aggregate production, proportioning and production of concrete, to applications in structures. Physical properties and chemical durability are described in detail. The physical properties include density, strength, shrinkage, and elasticity. Chemical durability includes resistance to acids, chloride ingress, carbonation, and freeze-thaw resistance. Fire resistance is also included, which is seldom considered, but is a very important aspect of the safety of the structure. Microstructure development and its relation to the durability properties of LWAC generally are not highlighted in the literature. The development of bonds, the microstructure with different binder systems, and different types of lightweight aggregates are explained. They show how lightweight aggregate concrete differs from normal weight concrete. The chapters on chloride ingress and freeze-thaw resistance are detailed because of the use of LWAC in offshore construction. The economical aspects of using LWAC are also reviewed. Emphasis is placed on the fact that although the cost of LWAC is high, the total cost of construction has to be considered, including the cost of transport, reinforcement, etc. When these are considered then LWAC becomes cheaper and attractive. The life cycle cost of the concrete is another consideration for calculating long-term savings on maintenance costs.







Freeze-thaw Durability of High-strength Concrete


Book Description

This report presents freeze-thaw durability results of an investigation regarding the application of high performance concrete (HPC) to prestressed bridge girders. This study included a total of 30 concrete mixes and more than 130 specimens, with the following variables: aggregate type: round river gravel, partially-crushed gravel, granite, high-absorption limestone, and low-absorption limestone; cementitious material composition: Type III portland cement only, 20% fly ash, 7.5% silica fume, and combination of 20% fly ash with 7.5% silica fume replacement by weight of cement; and curing condition: heat-cured or seven-day moist-cured.