Enhancing the hardened properties of blended cement paste cured at 0 °C by using alkali-treated ground granulated blast furnace slag

Abstract The use of high-volume ground granulated blast furnace slag (GGBFS) in cement-based materials significantly reduces CO2 emissions. Nevertheless, low curing temperatures are barriers to using environmentally friendly materials in winter construction works. This is mainly attributed to slow GGBFS’s reactivity and blends’ strength development due to the low alkalinity offered by the slow hydration rate of Portland cement (PC) at low temperatures. In this study, sodium hydroxide was employed to produce dry reactive pre-alkali-activated GGBFS (A-GGBFS), with an intention to increase the system’s alkalinity and reactivity. The blended cement paste was prepared with 50% PC replacement with untreated and treated GGBFS, and cured constantly at 0 °C for 28 days. The A-GGBFS accelerated the hydration rate and enhanced the precipitation of hydration products. By adding an optimal NaOH content during the pre-alkali-activation process, the 3 and 28 days compressive strengths of paste increased by 41% and 37%, respectively, gaining a comparable 28 days compressive strength to that measured in a 100% PC-based binder. The microstructural assessments are consistent with compressive strength measurements

A comparative study of the thermal behaviour of phosphate washing sludge from Tunisia and Morocco

International audienc

Properties of a new material based on a gypsum matrix incorporating waste brick

Many rehabilitation operations of historic buildings have not succeeded to utilize appropriate material for purpose of the project. Currently, the use of construction waste, especially the waste brick, is largely expanded in the world due to construction and rehabilitation of buildings. For efficient and sustainable use of such material in the rehabilitation of the architectural ornaments, an experimental study was conducted to examine the influence of the waste brick content on the physical and mechanical properties of the gypsum mortar. The materials used to prepare the gypsum mortar were gypsum, natural sand, waste brick, water and superplasticizer. The main variable in this study were the waste brick content (0% to 100%) and the type of the substrate (limestone and brick). The W/B ratio of all the mixtures was kept constant to maintain a similar level of the workability. Several tests were performed to assess the physical and the mechanical behaviour of the gypsum mortars including the adhesion test, XRD and the SEM analysis. The results found show that the adhesion strengths in the mortars are more important when the substrate is made from limestone with the regard to the substrate made with brick. However, excessive percentage of waste brick in the mortar can lead to adverse effects and reduce the adhesive strength. Gypsum mortars made with 75% of waste brick should be recommended for the rehabilitation of the architectural ornaments.(undefined