Development of near-zero water consumption cement materials via the geopolymerization of tektites and its implication for lunar construction

Abstract

The environment on the lunar surface poses some difficult challenges to building long-term lunar bases; therefore, scientists and engineers have proposed the creation of habitats using lunar building materials. These materials must meet the following conditions: be resistant to severe lunar temperature cycles, be stable in a vacuum environment, have minimal water requirements, and be sourced from local Moon materials. Therefore, the preparation of lunar building materials that use lunar resources is preferred. Here, we present a potential lunar cement material that was fabricated using tektite powder and a sodium hydroxide activator and is based on geopolymer technology. Geopolymer materials have the following properties: approximately zero water consumption, resistance to high- and low-temperature cycling, vacuum stability and good mechanical properties. Although the tektite powder is not equivalent to lunar soil, we speculate that the alkali activated activity of lunar soil will be higher than that of tektite because of its low Si/Al composition ratio. This assumption is based on the tektite geopolymerization research and associated references. In summary, this study provides a feasible approach for developing lunar cement materials using a possible water recycling system based on geopolymer technology.

The effect of microencapsulated phase change materials on the rheology of geopolymer and Portland cement mortars

“…In order to explore the time evolution of the viscosities during the geopolymer and condensation reactions, the samples were measured as a function of time at two different shear rates (1 s −1 and 10 s −1 ). When looking at the time‐dependent viscosities, it can be helpful to keep in mind that the geopolymerization process consists of two steps: geopolymer precursors are first formed, after which the 3D geopolymer network is developed from these precursors 56,57 . Portland cement normally undergoes a stage of early cement hydration, followed by a relatively dormant induction period before the main hydration process at later times 58,59 .…”

“…First, the aluminosilicates react with the alkaline activator, forming geopolymer precursors. Second, these monomers also react with the alkaline activator forming the 3D geopolymer structure 56,57 . The first step only causes a moderate viscosity increase, while the second step causes a significantly steeper growth of the viscosities 35 .…”

“…When looking at the time-dependent viscosities, it can be helpful to keep in mind that the geopolymerization process consists of two steps: geopolymer precursors are first formed, after which the 3D geopolymer network is developed from these precursors. 56,57 Portland cement normally undergoes a stage of early cement hydration, followed by a relatively dormant induction period before the main hydration process at later times. 58,59 Accordingly, as can be seen from Figure 8, the time-dependent viscosities of GM and PM behaves very differently.…”

“…Second, these monomers also react with the alkaline activator forming the 3D geopolymer structure. 56,57 The first step only causes a moderate viscosity increase, while the second step causes a significantly steeper growth of the viscosities. 35 Interestingly, it seems that the much higher viscosities for the samples containing high amounts of St-DVB-PCM at 1 s −1 is mainly due to a faster reaction rate during the first step of the process (increasing Γ 1 in Figure 10A), since the onset of the second stage (τ GM in Figure 11A) and how steeply the viscosity is raising during the second stage (β in Figure 11C) is changing very little with the addition of St-DVB-PCM.…”

Extra-terrestrial construction processes – Advancements, opportunities and challenges

“…Excess evaporation of water can cause formation of severe porosity in the concrete, leading to weakening of the strength and structural failure of the hardened material. Recent works have tried to further extend the potential of lunar concrete by developing a water-less concrete (Toutanji et al 2005, Koh et al 2010, Wang et al 2016, including a sulphur-based concrete (Leonard and Johnson 1988, Omar 1993, Casanova and Gracia 1998, Grugel and Toutanji 2008, phosphoric acid-based concrete (ESA 2017), a new lunar simulant with a special binder to be used with a direct manufacturing technique (Cesaretti et al 2014), and a glassfibre based reinforcement for lunar concrete (Tucker et al 2006). However, ESA's test of lunar simulant printing with a liquid binder (Cesaretti 2012) indicated the potential freezing of the binder and the related operation with a wet-mix based printing process under the lunar environment's extreme temperature changes.…”