Sustainable construction through eco-efficient ultra-high performance concrete

An innovative type of steel-fibre reinforced ultra-high performance concrete (UHPC), including its constituent materials and its mixing procedure, is reviewed in this paper. Furthermore, an energy-efficient curing method for developing precast UHPC members is presented as the main goal of the current study. It was found that just with 24 hours of curing in tempered water or steam with 67°C, 95% of 28-day compressive strength in normal curing method, 145 MPa, could be achieved which would be of great interest for prefabrication industry regarding their energy consumption. It also would be beneficial for any project in which early load-bearing capacity is expected. Self-compactness, compressive strength higher than 150 MPa, improved durability and finally low curing energy in precasting phase of the material all offer variety of slim interior and exterior architectural and structural applications even in high-rise structures and aggressive environments where higher strength, ductility and durability is required.(undefined

Effect of pozzolanic industrial wastes on durability of engineered cementitious composites (ECC)

In this research 26 different compositions of an engineered cementitious composite with different percentages of Fly ash and Silica fume, as two pozzolanic industrial waste and by-product, were mixed. The effect of different percentage of the pozzolans on durability of ECC was studied. To evaluate the durability of the material, two tests, namely water absorption by immersion and water absorption by capillary, were performed. The results from both tests demonstrated the same trend regarding the influence of the wastes on durability. In other words, by increasing the amount of pozzolans, the water absorption after immersion and boiling, decreased more than 50% besides the significant reduction in the rate of absorption by capillary (sorptivity). The results also indicated that silica fume has a higher influence on the water-absorption reduction compared to fly ash however, in the case of absence of silica fume, fly ash plays a significant role on the improvement of durability of the material.info:eu-repo/semantics/publishedVersio

Effective low-energy mixing procedure to develop high-fluidity cementitious pastes

Preparing a high fluidity paste is a major step in ultra-high performance concrete (UHPC) development with respect to its self-compacting ability as well as its ultra-high strength. In this regard, some experiments have been carried out in order to study various superplasticizer (SP) addition methods and times. Among these procedures, stepwise and delayed methods seem to be more efficient compared to direct addition of SP with or immediately after water addition. However, few studies regarding water addition time and method have been conducted since now. In this research work, the effects of water and SP addition methods on the fluidity of paste were investigated. The results demonstrated that stepwise and delayed water beside delayed SP addition remarkably reduce the flow time. This maximum fluidity was achieved after totally 15 minutes of mixing including 3 minutes after 70% of water addition to powder, as first-part water, 6 minutes after SP addition and finally an extra 6 minutes after second-part water which is 30% of the total water. Based on this procedure, the opportunity for developing self-compacting and durable UHPC could be accessible. Furthermore, using higher content of aggregates and supplementary cementitious materials would be possible due to higher fluidity of the paste which finally results in an eco-efficient UHPC