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The accelerated carbonation of steel slag can improve its subsequent application as construction materials and can also store CO 2 as stable minerals. Due to the differences in the production process, electric arc furnace slag (EAFS) and basic oxygen furnace slag (BOFS) acquire diverse physical and chemical properties, which expected to perform differently upon accelerated carbonation . Especially considering the potential use as green building material, thereby may be subject to fire risk. This research aims at comparing the influence of carbonation temperature, CO 2 pressure, and carbonation time on mechanical properties and carbonation efficiencies of EAFS and BOFS pressed blocks, and emphasizing on their performances under elevated high temperatures. Results show that BOFS block has a much better performance than EAFS block, with about twice the compressive strength and CO 2 uptake, owing to the higher calcium content and more reactive calcium mineral (portlandite) existed. The strengths of both two types of steel slag pressed blocks were found to increase with the increase of high temperature exposure up to 400 °C due to subsequent hydration reaction induced by elevated temperature. Although a slight decrease of compressive strength can be found after further heating at 600 °C, the residual strength was still comparably higher than that at 20 °C. However, with further increase of heating temperature up to 800 °C, a significant reduction in strength was noticed for both EAFS and BOFS blocks, associated to the decomposition of carbonates phases as the main contributor of bearing-strength within the blocks.

Managing and dredging of ultra-fine sediment (UFS) in river estuaries becomes an environmental challenge due to its threat to the ecosystem. However, upcycling of UFS for the production of self-compacting mortar (SCM) could be a step toward sustainable waste management and yield the special rheological properties that required for SCM. This paper used UFS to replace cement at ratios of 0%, 5%, 10%, 15%, 20%, 25% and 30% to evaluate the packing density, hydration heat, rheological, fresh and hardened properties of SCM. The microstructure of SCM samples was also characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that all the SCM mixtures met the self-compacting characteristics requirement in accordance to EFNARC. The packing density and fluidity (mini-slump flow and V-funnel flow time) improved with 5% of UFS replacement but decreased at a higher replacement level. Furthermore, SCM mixtures containing UFS behaved like a pseudoplastic fluid , while apparent viscosity of SCM with UFS (up to 20%) during 60 min almost remained a constant value. The incorporation of 5%–15% UFS in SCM decreased the 60-min static yield stress. Based on the calorimetry and mechanical results, the presence of UFS decelerated the hydration, and SCM prepared with 5%–15% of UFS was able to retain 90% and 85% of its original flexural and compressive strengths at 91 days, respectively, with a 28-day strength of mortar grade M. SEM images also revealed that the bond between the UFS particles and the C–S–H gel matrix (interfacial transition zone) was weaker compared with that between the standard sand (NS) particles and the C–S–H gel matrix at higher replacement ratios of cement. Overall, based on the mechanical properties and the microstructure observation , it can be concluded that UFS can be effectively utilized at a replacement level of 5%–15% to produce self-compacting mortar with a lower carbon footprint .

Concrete, known as the second most consumed material in the world after water, is a versatile, inexpensive and durable construction material. Due to its high density, concrete is usually employed as rigid walls in buildings and also as sound barrier in highway. Researchers have proposed several methods to treat the concrete to also be capable of absorbing sound and thus improving the sound quality in a room. However, there exists limited information regarding the sound absorbing capability of concrete or more generally the cement-based materials. This paper reviews the sound absorption properties of various modified concrete materials from the existing published works. The influence of aggregate types and alteration of concrete ingredients on the acoustic properties of modified concrete materials are discussed. From the review, it is concluded that the sound absorption of the concrete or cement-based material can be improved by creating porous structures in the materials through different methods, namely incorporating lightweight aggregate, creating physical voids, such as in pervious concrete or by inducing voids with the inclusion of foam in cellular concrete. Another proposed method is also to incorporate large amount of hemp shiv to produce hemp concrete. A linear relationship is found to generally estimate the noise reduction coefficient as the function of the density of the materials using the data available from the published works.

As with all industrial processes, concrete production comes with environmental costs that are proportionate to its use. As such, approximately 8% of all, global carbon dioxide (CO2) emissions are related to cement and concrete. Combining new technology with the mass production of concrete offers one of the few feasible pathways to improve global air quality by reducing concentrations of CO2 and other airborne pollutants. Carbonation of concrete waste and concrete blocks not only improves the performance of these products, the transformation of calcium or magnesium-rich minerals into thermochemically stable carbonates also offers a path to sequestering CO2 on a large scale, creating products with commercial value. Carbonation seems to have the largest potential to reduce concrete-related emissions of CO2 of any current technology and offers the potential of carbon negative concretes, thereby harnessing the potential of the cement industry and turning it into the world's greatest carbon sink rather than its largest CO2 emitter.

This research strives to develop a high-temperature resistant lightweight aggregate (LWA) mortar skin layer for use in sandwich concrete composite. The first phase of the research was focused on the development of the LWA mortar while the subsequent phase of work dealt with assessing the performance of the resulting sandwich concrete composite. In phase 1 of the investigation, it was found that mortar incorporating calcium aluminate cement (CAC) as binder and lightweight expanded clay aggregate (LECA) as fine aggregate had the best resistance towards high temperature of 1000 °C. The developed mortar along with basalt fibre mesh were used to form textile reinforced concrete (TRC) as skin layer which could still exhibit residual strength upon heated to high temperature. Furthermore, sandwich composite beam made of the TRC skin and aerated concrete as core had better flexural strength/weight ratio compared to that using conventional EPS foam as the core material. There was also no significant damage found on the sandwich concrete composite upon exposure to direct flame. The findings suggest that the development of the sandwich concrete composite is promising and further works can be explored to improve the performance.