Rheological behavior of fresh inorganic polymer paste: Polymer bridging effect of the alkali silicate solution

Inorganic polymers (IP), produced by alkali activation of a glassy precursor, have been mainly investigated on their microstructure and mechanical strength properties. However, it is important to understand how the IP flow behaves under shear conditions, in particular when pumping is required. The activating solution is one of the main parameters influencing rheology. Therefore, the physical effect of the silicate structure on the rheology was investigated by varying the SiO2/Na2O molar ratio from 1.4 to 2.0 in the activator. The elastic and rheological properties of the IP were measured with a rheometer. In order to investigate the activator silicate structure and IP polymerisation development, Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance Spectroscopy (NMR) were performed. A decrease in elasticity was monitored for IP with a low SiO2/Na2O ratio as a result of the dissolved species, which can be correlated to NMR. The FTIR spectra implied that an activating solution with a higher SiO2/Na2O ratio resulted in the formation of a 3D silicate network with Q3 and Q4 crosslinks. The presence of a network modifier in the activating solution, such as Na, resulted in more Q1 and Q2 crosslinks. A higher stress, at a shear rate of 0.1 s-1; was observed in IP which consisted of a 3D silicate network as a result of the polymer bridging effect between the particles. A stronger shear thinning was observed in an IP with a higher SiO2/Na2O ratio, due to the steric hindrance from the entangled silicates. The rheological data of the IP can be fitted with the Herschel-Bulkley model

DEVELOPING A 3D PRINTABLE INORGANIC POLYMER, DERIVED FROM AN Fe-RICH SLAG

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Monitoring early-age crack formation in a Ca-Fe-Al-rich inorganic polymer

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Promoting the use of Fe-rich slag in construction: Development of a hybrid binder for 3D printing

The construction sector is responsible for significant CO2 emissions, especially due to the production of ordinary Portland cement (OPC). One option to decrease CO2 emissions is to print mortar made from an alternative binder. A precursor was used consisting of mainly non-ferrous metallurgy Fe-rich slag and a minor amount of OPC

Shrinkage and Mitigation Strategies to Improve the Dimensional Stability of CaO-FeOx-Al2O3-SiO2 Inorganic Polymers

Volumetric stability is an important aspect of the performance of building materials, and the shrinkage of CaO-FeOx-Al2O3-SiO2-rich inorganic polymers (IPs) has not been thoroughly investigated yet. Hence, this paper describes the outcome of a study conducted to investigate ways to minimize their shrinkage using different curing regimes. Two different slags were used as case studies to assess the robustness of the developed mitigation strategies. IP pastes and mortars were cured at (i) room condition, (ii) in slightly elevated temperature (60 °C for 2 d) and (iii) in a water-saturated environment. The reaction kinetics and formed products were examined on IP pastes, while mortars were made to characterize the 28 d pore structure, autogenous shrinkage, drying shrinkage, and strength development. The results showed that the precursors' reactivity and curing conditions severely affect shrinkage mechanisms and magnitude. Volumetric changes in the plastic stage can be related to the precursors' reactivity but drying shrinkage was the driving mechanism affecting the volumetric stability of all IP mortars. Understanding the effect of a precursor's composition and curing conditions on shrinkage is fundamental to develop proper mitigation strategies and to overcome one of IPs' main technical drawbacks.status: publishe

3D printing of an iron-rich slag based hybrid mortar:A durable, sustainable and cost-competitive product?

Automation through 3D printing can be a possible technological breakthrough in construction. However, the carbon footprint is not necessarily reduced as the print formulations consist of more ordinary Portland cement (OPC) compared to conventional high-performance mortar. In this study, a hybrid mortar with minor amount of OPC and mainly Fe-rich, low-Ca slag is used for printing several structures, followed by a profound study on the durability properties of the printed material. The hybrid mortar outperformed the benchmark with respect to its compressive strength (80.5 ± 4.3 MPa versus 52.4 ± 1.7 MPa) and drying shrinkage (0.8 mm/m versus 1.3 mm/m). The capillary pores present in the printed hybrid resulted in a lower freeze-thaw resistance. Leaching tests showed that the hybrid binder immobilized heavy metals. The hybrid mortar has a CO2 impact between 164 kg CO2/m3 and 548 kg CO2/m3, and costs range from 129 to 193 euro/m3. This study showed that the hybrid mortar can offer a suitable alternative to 3D-printable OPC-mortars