S. Hashim Mohseni, Sifatullah Bahij, Safiullah Omary*, Françoise Feugeas and Fahri Birinci
DOI: 10.37421/2165-784X.2022.12.449
Concrete is the commonly used building material. It has to be poured into the formwork to take the appropriate shape of a structural element. Therefore, the used formwork affects the surface parameters and final properties of cementitious materials. This paper aims to study the effect of formwork surface texture parameters and release agents on the surface of cementitious materials. Including a reference formwork (F17-Ref), mineral oil (F17-MO), vegetable oil (F17-VO), polyethylene terephthalate coated (PET), and polymeric coated (C20C27) formworks were prepared. For this purpose, pre-crack demolding tests on cement paste samples and pull-off demolding tests on concrete samples were conducted to analyze the adhesion between cement paste/concrete and formwork. The results highlight that the specimens with polymeric-coated plates had the lowest surface roughness values, but all of the coated formworks had almost similar surface energy. In addition, the experimental tests confirmed that samples subjected to PET and F17-VO formworks presented lower adhesive force. As a comparison vegetable oil showed better demolding behavior compared to mineral oil. On the other hand, the visual aspect reveals that the cementitious surfaces subjected to polymeric- coated formworks are shiny and smooth compared to the opaque surface of oil-coated formworks. Finally, based on the outcomes, the PET-coated formwork could be recommended as an alternative solution to release agentss.
Yahia M.S. Ali and Tarek Abdelaleem
Crushed Over-burnt Clay Bricks (COBB) is a promising alternative to the natural gravel aggregate in Light Weight Concrete (LWC) production because of its high strength-to-weight ratio. In addition, COBCB is considered a green aggregate by solving the problem of disposing of this solid waste. in this paper, a total of fifteen Reinforced Concrete (RC) beams were constructed and tested up to failure. The experimental program was classified to five groups, the first group was casted with Normal Weight Concrete (NWC) as control, and the remaining four groups were casted with LWC. The test parameters were concrete type; reinforcement ratio and silica fume (SF) content. The behavior of beams was evaluated in terms of crack patterns, failure mode, ultimate deflection, and ductility. Based on the experimental results, the resulting concrete showed that it satisfies the requirements of LWC in terms of unit weight and strength. In addition, increasing the reinforcement ratio and silica fume content increased overall beam performance. The results revealed that measurable enhancements to the majority of the performance characteristics of LWC beam by adding SF. Thus, using COBCB as a coarse aggregate has successfully been used to produce good quality lightweight concrete. Both ACI 318-14 and CSA-A23.3-14 give acceptable for predicting cracking moment, ultimate capacity and mid-span deflection.
Sanjaya Dahal
The term "geopolymer" was created and applied by Davidovits, a French scientist, in 1979 to represent a kind of inorganic polymer with SiO4 and A1O4 tetrahedral being the structural units. In general, geopolymers as a class of inorganic polymer are formed by reaction between an alkaline solution [e.g., sodium hydroxide and sodium silicate] and an aluminosilicate sources such as metakaolin, fly ash, and slag. Nowadays, geopolymer studies are receiving commendably increasing attention because they may be used as a viable economical alternative to organic polymers and inorganic cements in diverse applications, such as military, aircraft high-tech ceramics thermal insulating foams fire-proof building materials protective coatings refractory adhesives and hybrid inorganicorganic composites. This interest is due to their exceptionally high thermal and chemical stability, excellent mechanical strength, adhesive behavior and long-term durability. In addition, early researcher have demonstrated that geopolymers are cheap to produce and can be made from a great number of minerals and industrial by-products, including pozzolana, natural aluminosilicate minerals, metakaolin fly ash granulated blast furnace slag fly ash and kaolinite mixture fly ash and metakaolin mixture red mud and metakaolin mixture and red mud and fly ash mixture. Moreover, they are environmentally friendly materials from the point of view of reducing green house effects caused by CO2 emission from the manufacturing of Portland cement.
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