Effect of Ornamental Stone Waste Incorporation on the Rheology, Hydration, Microstructure, and CO2 Emissions of Ordinary Portland Cement

Abstract

The ornamental stone industry generates large amounts of waste thus creating environmental and human health hazards. Thus, pastes with 0–30 wt.% ornamental stone waste (OSW) incorporated into ordinary Portland cement (OPC) were produced and their rheological properties, hydration kinetics, and mechanical properties were evaluated. The CO2 equivalent emissions related to the pastes production were estimated for each composition. The results showed that the paste with 10 wt.% of OSW exhibited similar yield stress compared to the plain OPC paste, while pastes with 20 and 30 wt.% displayed reduced yield stresses up to 15%. OSW slightly enhanced the hydration kinetics compared to plain OPC, increasing the main heat flow peak and 90-h cumulative heat values. The incorporation of OSW reduced the 1-, 3-, and 28-days compressive strength of the pastes. Water absorption results agreed with the 28 days compressive strength results, indicating that OSW increased the volume of permeable voids. Finally, OSW incorporation progressively reduced the CO2 emission per m3 of OPC paste, reaching a 31% reduction for the highest 30 wt.% OSW content. Overall, incorporating up to 10 wt.% with OSW led to pastes with comparable fresh and hardened properties as comported to plain OPC paste.

Assessing the Rheological, Mechanical, and Photocatalytic Properties of Niobium Oxide-Incorporated White Cement Pastes

“…The four main stages of the Portland cement hydration process can be identified in Figure 5, namely: (i) initial, (ii) induction, (iii) acceleration, and (iv) deceleration periods [56]. The main heat flow peak of WC pastes occurred at approximately 7.3 h. Note that this induction period is typically shorter compared to grey cement pastes, as indicated by the results reported by Scolaro et al [57]. The authors observed that the main heat flow peak for a grey PC paste with a water-to-cement ratio (w/c) of 0.45 and a superplasticizer (SP) content of 0.025 wt.% is around 10 h. Similarly, the results reported by de Matos et al [58] showed that the main heat flow peak of a cement paste with a w/c of 0.4 and grey Portland cement without SP occurred approximately at 12 h. The isothermal calorimetry results also indicate that the partial replacement of WC with Nb 2 O 5 percentages up to 2.0 wt.% does not affect the heat flow and the cumulative heat of the pastes.…”

Reuse of Oil Refining Sludge Residue Ash via Alkaline Activation in Matrices of Chamotte or Rice Husk Ash

“…The global cement industry is looking for experimental ways to develop cements that require less energy in their manufacture, degrade the environment less due to the high consumption of mineral resources and emit less polluting gases into the atmosphere, which contribute almost 7% of global CO 2 emissions (2.5 Gt/year), aggravating global warming and its consequences [ 1 , 2 , 3 ]. In addition, the industry is facing challenges such as increasing demand for cement and, at the same time, limited limestone reserves and increasing carbon taxes [ 4 ]. The so-called circular economy is emerging as an environmental and economic concept that aims to keep the value of products, materials and resources (water, energy, etc.)…”