Effect of medium-density fiberboard wastes ash on calcium silicate hydrate crystal of concrete.

Due to the high consumption of Medium-density fiberboard (MDF), waste products of this material are growing worldwide. In this research, the feasibility of using Medium-density fiberboard waste ash (MDFWA) as part of cement in concrete was investigated. For this purpose, 0, 5, 10, 15, 20, and 25% of the cement in concrete was substituted with MDFWA. For all design mixes, the water/blind ratio and the volume of aggregates were same. The slump, compressive strengths, SEM, EDX, TGA, DSC, and FTIR tests were conducted on the samples. At 28 days, the results demonstrated that the compressive strength of the sample containing 20% MDFWA increased by 13.6% compared to the control sample. Furthermore, the microstructure of the concrete show that the voids of the sample containing 20% MDFWA reduced compared to the control sample and also more calcium silicate hydrate (C-S-H) crystal formed.Implications: The significance of the present paper is to solve the environmental issue caused by large amount of Medium-density fiberboard waste ash (MDFWA) and produce also sustainable concrete. In addition, the replacement of cement with MDFWA increases the compressive strength and enhancement of the microstructure of concrete due to extra C-S-H products. Therefore, the findings confirm that by using 20% MDFWA, a more eco-friendly production, denser, sustainable, economical, and stronger concrete would be achieved.

Flexural strengthening of beams using post-tensioned metal straps fully wrapped around steel channels anchored to normal steel reinforced concrete beams.

The efficacy of post-tensioned metal straps PTMS, wrapped around steel channels anchored to normal reinforced concrete (R.C) beams is tested in increasing the flexural capacity of the beams. For this purpose, nine normal R.C beams with dimensions of 160 mm x 240 mm x 2100 mm are constructed to fail in bending. The location and the number of the straps are considered as the main variable. It is found that using PTMS can enhance the load-carrying capacity of the beam by 29% to 63%. The decisive factors affecting the increase are the location of the straps (at the bottom or sides), shape of the flange and web edges (squared or rounded) and alignment of the flanges (vertical or inclined). A complete guide can be found in the paper as it is a novel method of strengthening beams which can be applied to the beams cast in place with integral slabs.