The effect of glucose on the hydration kinetics of Ordinary Portland Cement
In this study, the application of fresh-wood-wool without any pre-treatment to produce wood-wool cement boards (WWCB) is investigated. The aim of this study is to create a binder which is less affected by the inhibitory substances of the wood-wool, without reducing the flexural strength properties of the boards. Moreover, the carbon footprint of WWCB is addressed by not using any waterglass and partly replace cement with limestone powder in the boards production. First, the hydration behavior of different binders is studied by means of an isothermal calorimeter, including e.g. different types of cement, addition of glucose as a retarder, reduction of anhydrite in OPC and the use of limestone powder as a partial cement replacement. Then, boards are produced with fresh wood-wool and a newly developed binder recipe that is resulted from the hydration behavior analysis. The results show that the retarding effect of glucose is highly dependent on the chemical composition of the cement. In general, high amounts of C3A and C3S in a binder are favorable. When available, glucose reacts first with C3A, hence, less glucose is available to retard the other cement compounds like C3S. In addition, when using the fresh wood-wool in boards, the strength of the produced boards is increased. Furthermore, the water absorption of the wood is significantly reduced (20%), since it is already physically and chemically bond within the wood-wool. This enables a lower water demand that results in a denser packing of the binder and a reduced ion migration, leading to a mechanical strength increase. Furthermore, without the use of waterglass and the incorporation of (36%) limestone powder as a partial cement replacement, the CO2 footprint of the developed board fulfills the stated requirements, while possessing a reduced CO2 footprint.