Preparation And Performance Study On Cement And Concrete For The Lunar Environment

The establishment of the lunar base will be a magnificent andenormous space engineering. It takes a great financial, human andmaterial resources. Only if develop low-cost construction methods is itpossible to establish lunar base. The studies of many researchers on lunarcement and concrete have shown that concrete materials can be adaptedto the lunar environment. According to the research and analysis of lunarrock samples and informations, it can be sure that there are siliceousmaterials that is powder, sand or rocks containing more silicon dioxide onthe moon. Lunar cement and concrete can be prepared bydry-mix/steam-injection method (DMSIM), using siliceous materials onthe moon and cementing materials brought by ourselves such as Portlandcement and lime in order to reduce lunar base cost and serveestablishment of the lunar base in future. So it has great significance to investigate on preparation and properties of lunar cement and concrete.In this paper, dry-mix/steam-injection method (DMSIM) wasadopted which was a novel technology developed for mixing on the moon.In DMSIM, cement and aggregate were mixed first. The dry mixture wasplaced in a steam boiler or autoclave. Then saturated steam of105-200°Cwas introduced to induce hydration of concrete which completed in24hours. The influence of DMSIM on properties of lunar cement andconcrete were studied. The hydration-hardening and strength mechanismswere also investigated by determining the mechancial propertites ofcompressive strength and physical propertites of bulk density andpore structure and analyzing XRD. The results show that:(1) Under autoclave conditions at140~216℃for6~12h, thecompressive strength，apparent density，ratio of non-evaporable water tocement，ratio of water to cement, calcium hydroxide content andhydration degree of the hardened ordinary Portland cement pastes allincrease with both increasing temperature and prolonging time inautoclave.(2) Under autoclave conditions at140℃in the first step for3h andat213℃in the second step for9h, the paste possesses compressivestrength of120.5MPa which is increased by139%from contrastsample, dry apparent density of1.98g/cm~3which is lower than contrastsample, ratio of water to cement or ratio of non-evaporable water to cement of0.176or0.134which is far away from that cementcompletely hydrated，calcium hydroxide content of23.9%(by mass)and hydration degree of60%.(3) The compressive strength of the hardened ordinary Portlandcement pastes produced by DMSIM increases at first and then decreaseswith the increase of the mixing amount of crystalline siliceous materials.For example, the optimum mix amount of ground fine quartz sand is20%and the paste possesses the highest compressive strength of152.1MPawhich is increased by9.3%from sample without ground fine quartz sandand increased by116.7%from sample produced by thenormal-temperature wet-mix/steam-injection method (NTWMM).(4) In the same admixture types and replacement rate of admixture,the compressive strength of hardened Portland cement pastesprepared by DMSIM is the highest and the cement mortars take thesecond followed by the cement concrete. DMSIM can obviouslyincrease compressive strength of hardened Portland cement pastes.