Development of fiber reinforced self-consolidating concrete for marine structures in hot environments.

摘要

Concrete marine structures such as coastal berthing and mooring facilities, breakwaters, jetties, container terminals, and drilling platforms, are typically exposed to harsh environments and are usually expected to require a minimum level of repair or maintenance during their service life. Although these structures are typically made of relatively impermeable concrete, many will deteriorate prematurely before the end of their design service life. Such early deterioration is not typically caused by poor concrete quality but it is mostly due to poor construction practices or construction factors. Construction factors such as improper casting, concrete placement, and consolidation techniques and an inadequate curing regime can lead to surface cracking, poor compaction, and high concrete permeability. Such factors have been known to significantly reduce concretes resistance to the ingress of aggressive agents (chloride ions, moisture, oxygen, etc) and ultimately lead to the corrosion of the reinforcing steel. The corrosion of structural steel reinforcement can lead to serviceability issues and in extreme cases, it can cause large reductions in overall structural capacity, or even failure.; The ultimate goal of this thesis was to develop a commercially viable fiber reinforced self-consolidating concrete (FRSCC) mixture having adequate flow characteristics and a high cracking resistance and low permeability. To achieve this goal, 18 non-air entrained self-consolidating concrete mixtures made with w/c ratios of 0.40, 0.42, and 0.45 and reinforced with 38 mm long monofilament macro-synthetic self-fibrillating fibers at dosages ranging from 0.20% to 0.40% by volume, were developed, optimized and evaluated. The flow characteristics of all mixtures were evaluated using the four typical SCC workability test methods which included: slump flow, filling capacity, L-box, and V-funnel flow time tests. The cracking resistance of each mixture was evaluated by conducting plastic shrinkage testing. The suitability of FRSCC mixtures for exposure to marine environments was determined based on the compressive strength, chloride penetration resistance impact resistance, flexural strength and flexural toughness tests results. A typical Normal Concrete (NC) mixture, normally used for marine structures in hot environments, was also evaluated and used for comparison purpose.; The results demonstrated that all FRSCC mixtures developed had a satisfactory slump flow, filling capacity, and V-funnel flow time. However, L-box test results have shown to be unsatisfactory in many cases. The plastic shrinkage test results showed that the addition of 0.40% fibers by volume led to as much as a 70% reduction in total crack area and up to 50% reduction in maximum crack width compared to SCC without fibers. FRSCC mixtures had considerable higher cracking resistance, lower permeability, higher impact and flexural toughness than the reference plain SCC and NC mixtures of equal strength grade. The characteristics of the FRSCC developed in this thesis will eliminate the need for vibration, improve the quality of construction, increase the resistance to cracking and ultimately increase the service life of marine structures.