The positive and negative influences of VMA's on the robustness of fresh self-compacting concrete

Over time, several mix design metliods liave been developed to obtain a selfcompacting concrete (SCC) with suitable fresh and hardened concrete properties. The very fluid concrete with no need for external compaction is achieved by using a higher powder content and the use of chemical admixtures. Segregation and bleeding are prevented by either...

The combined influence of paste volume and volumetric water-to- powder ratio on robustness of fresh self-compacting concrete

In order to avoid durability problems caused by an inadequate consolidation of concrete, self-compacting concrete (SCC) has been developed. The mix design of SCC aims at balancing a minimum flowability allowing air bubbles to escape and a maximum flowability in order to avoid segregation. Because of the higher demands on mix design and...

Experimental study on workability of alkali activated fly ash and slag-based geopolymer concretes

This paper presents an investigation on workability and strength of geopolymer concrete made of fly ash (FA), blast furnace slag (BFS) and a multicompound activator of Na2SiO3 and NaOH solutions. The FA/BFS ratios were 100:0, 70:30, 60:40, 50:50, 40:60, 30:70 and 0:100. The workability of geopolymer concretes was performed by using slump test...

Time- and load- dependent behaviour of flowable concrete: Progress report of fib task group 4.3

Stress and strain interaction is of vital importance for concrete structures as it has an influence on cracking, deflection and prestressing loss. With the increased range of compressive strengths and flow characteristics, the mixture composition of nowadays concretes often differs considerably from Vibrated Concrete (VC) with regard to paste...

Optimization of tensile strain-hardening cementhious composites for tensile strain capacity

The synergistic action of a cementitious matrix and fibres can result in strain hardening in tension. The accompanied tensile strain capacity can be an important design parameter for strain-hardening cementitious composites in order to prevent the localization in a single crack and to assure that the stress is at least the tensile strength o f...

Double-curved textile reinforced concrete panels with tensile strain-hardening characteristics

The construction of buildings with fi-ee-form surfaces can be accompanied with relatively high costs. An innovative method to produce free-form surfaces in concrete is the application of double-curved precast panels produced with a flexible re-usable mould technique. Traditional placing of reinforcing bars to strengthen such panels causes...

The production effect on the performance of panels: Cast with self-compacting fibre reinforced concrete

The strain-hardening behaviour of cementitious composites is the result of a synergistic behaviour of the cement matrix and fibres in a cracked cross-section. The distribution and orientation of the fibres are essential in order to obtain such favourable tensile behaviour. Strain-hardening composites can be applied and are especially useftil in...

Optimization of the flexible mould process for the production of double-curved concrete elements

Free-form buildings tend to be expensive. By optimizing the production process, economical and wellperforming concrete structures and elements can be manufactured. In this paper, an innovative method is presented that allows producing highly accurate double curved-elements without the need for milling two expensive mould surfaces per single...

Optimization of flowable concrete for structural design: Progress report of fib task group 8.8

With the tendency to apply concrete with a higher workability and the use of new concrete components more options are available to design concrete. New concrete types like self-compacting concrete (SCC), ultra-high performance fibre reinforced concrete (UHPFRC) and high performance fibre reinforced cementitious composite (HPFRCC) also require...

Self-compacting fibre reinforced concrete applied in thin plates

Floor panels produced with traditionally vibrated concrete are relatively thick due to the need to reinforce concrete and consequently, heavy. Without the need to place rebars in panels and by applying self-compacting fibre reinforced concrete (SCFRC) the production process becomes more efficient. Fibres improve the performance of concrete by...

UHPFRC in large span shell structures

Ultra-High Performance Fibre-Reinforced Concrete (UHPFRC) is an innovative concrete type with a high compressive strength and a far more durable character compared to conventional concrete. UHPFRC can be applied in structures with aesthetic appearance and high material efficiency. Shell structures are spatially curved surface structures of which...

Parkbridge: Optimization of a slender bridge in UHPFRC

Ultra High Performance Fibre Reinforced Concrete (UHPFRC) is a concrete type with superior characteristics concerning strength, ductility and durability compared to conventional concrete. In spite of extensive research efforts the number of applications is still limited. In order to promote UHPFRC in the Netherlands, Cement & Beton Centrum...

Rheological parameters used for deliberate deformation of a flexible mould after casting

This paper describes how curved precast concrete elements can be manufactured in an open and reusable flexible mould. The proposed method reduces formwork costs of architectural freeform elements in concrete. First, the method is described briefly, then a series of tests are discussed, demonstrating that by measuring the rheological parameters...

Influence of particle packing density on the rheology of low cement content concrete

Optimizing concrete mixtures with regard to cement content is one of the most important solutions in sustainable concrete design. Workability o f these low cement content or ecological mixtures is very important. Eleven mortar mixtures are presented, which show how a higher packing density can be used to obtain mixtures that require less water....

Deliberate deformation of concrete after casting

This paper discusses the effect of intentional deformation of a flexible formwork after casting of the concrete and the influence of the characteristics of concrete in the fresh state on the quality of a concrete element. This deformation is intended to bring the concrete element in its desired final shape; the deformation typically takes place...