Search

Unfired four-hole hollow brick (UFHB) is a type of environmental-friendly brick with low energy consumption. However, the using of ordinary Portland cement (OPC) in UFHB is costly and indirectly affects the environment. This paper focuses on an exploratory study on the use of blended fly ash (FA)-OPC in the production of the UFHB and proposes the application of FA-OPC mixtures as a timely solution for the reduction of OPC in UFHB. The 80×80×180 mm UFHB samples were produced using different proportions of FA and OPC under a constant coupled-static forming pressure. The report exhibited experimental characterizations on physical and mechanical properties of both starting materials and UFHB products. In addition, a scanning electron microscope (SEM) analysis was used to evaluate the microstructure of the final UFHB. Test results show that the inclusion of FA in the UFHB mixtures provided positive effects on brick properties. As a result, 10% FA was found as an optimal content, which resulted in the highest brick’s strength, the lowest water absorption rate, and a denser microstructure. Furthermore, properties of all of the UFHB samples produced for this study satisfied the requirements of the National Vietnamese standard for non-bearing building brick.

This paper presents the experimental results of an investigation on the engineering properties and durability of high loss on ignition-fly ash concrete fully immersed in 5% sodium sulfate solution. The fly ash used in this study is a raw material with the loss on ignition of 15.8%, which is much higher than the upper limitation of 6% as stipulated by ASTM C618. Eight concrete mixtures were designed with different water-to-binder ratios of 0.35 and 0.45. For each water-to-binder ratio, the fly ash was used to replace 0%, 10%, 20%, and 30% amount of cement. Test results show that the workability of fresh concrete increased, while its unit weight decreased with increasing the fly ash replacement level. In addition, the concrete mixtures with 10% and 20% fly ash content showed the higher compressive strength, especially at long-term ages, than that of the fly ash-free concrete mixture. Further, all of the fly ash concrete mixtures exhibited the good quality with ultrasonic pulse velocity values of higher than 4100 m/s.

This study investigates the feasibility of using raw fly ash with a high loss on ignition in concrete. The fly ash-free concrete samples were prepared with different water-to-binder (w/b) ratios of 0.35, 0.40, and 0.45, whereas the fly ash concrete samples were prepared with a constant w/b of 0.40 and with various fly ash contents (10%, 20%, and 30%) as a cement substitution. The physical properties and durability performance of the concretes were evaluated through fresh concrete properties, compressive strength, strength efficiency of cement, ultrasonic pulse velocity, and resistance to sulfate attack. Test results show that the w/b ratio affected the concrete properties significantly. The incorporation of fly ash increased the workability and reduced the unit weight of fresh concrete. In addition, the fly ash concrete samples containing up to 20% fly ash exhibited an improved strength at long-term ages. Further, all of the fly ash concrete samples showed a good durability performance with ultrasonic pulse velocity value of greater than 4100 m/s and a comparable sulfate resistance to the no-fly ash concrete.