Hilal El-Hassan

Reaction Products in Carbonation-Cured Lightweight Concrete

The effect of early-age carbonation curing on the microstructure and properties of lightweight concrete with expanded slag aggregates was examined. Carbonation was performed on concretes either immediately after casting or after 18-h air curing. Their corresponding carbon uptake was 8 and 23%, respectively, based on cement content. A process involving initial air curing, carbonation curing, water compensation, and subsequent hydration was developed to maximize the degree of carbonation and hydration. Reaction products of carbonation-cured concretes at early and late age were characterized by using thermogravimetrical (TG) analysis, X-ray diffraction analysis, and scanning electron microscopy. Although the presence of calcium carbonates was evident, the microstructure was nevertheless typical of amorphous. It was believed that early carbonation of concrete consumed calcium hydroxide, calcium silicate hydrates, and anhydrous calcium silicates while producing calcium carbonates of different polymorphs and amorphous calcium silicate hydrocarbonates.

Pervious concrete pavement incorporating GGBS to alleviate pavement runoff and improve urban sustainability

The increasing use of pervious concrete as sustainable and environment-friendly paving materials is primarily owed to its ability to reduce pavement runoff. The mechanical and transport properties of pervious concrete with 50% ground-granulated blast furnace slag (GGBS) replacement were examined. Open-graded 10 and 20 mm aggregates were used to attain porosity of 10%, 15%, and 20%. Polypropylene short-cut fibres were added to the mix. The clogging potential of pervious concrete exposed to dust was investigated. The results indicated that increasing the porosity led to a decrease in compressive and tensile strength. The fibre addition was effective in low-porosity concrete. Permeability was proportional to porosity and inversely proportional to aggregate size. After 40-year simulated dust exposure, the concrete permeability could be restored with the water flushing maintenance process. In comparison to Ordinary Portland cement concrete, pervious concrete incorporating GGBS is a more sustainable paving solution, offering a decrease in cost, heat island effect, and embodied energy, while also reducing carbon emissions by 54%.

Effect of process parameters on the performance of fly ash/GGBS blended geopolymer composites

Alkali activation of fly ash and ground-granulated blast-furnace slag (GGBS) is a sustainable technology that promotes recycling of industrial by-products in the form of geopolymer composites. In this study, geopolymers are prepared with fly ash, GGBS, and desert dune sand (fines). The alkaline activator solution is formulated using sodium silicate and 14 M sodium hydroxide solutions. The effect of mixture proportioning and curing conditions on the workability, setting time, and compressive strength of geopolymers was examined. The investigated process parameters included percentage of fly ash replacement by GGBS, superplasticizer dosage, amount of fines, alkaline activator solution content, and sodium silicate to sodium hydroxide ratio. The final geopolymeric product could be enhanced by employing subsequent continuous and intermittent water curing techniques. Based on the experimental results, analytical models correlating mixture proportions with workability and 28-day compressive strength were developed for geopolymers made with 100% GGBS and equal proportions of fly ash and GGBS.