Effects Of Amorphous Siliceous Materialson Properties Of Dry-Mix/Steam-Injection Concrete

Scientists generally believe that establishing lunar base is of greatstrategic significance for exploiting the moon resources，and it is almostimpossible without concrete materials. Considering that there is anunfavorable lunar environment such as vacuum, weightless and perhaps nowater, the dry-mix/steam-injection method （DMSIM） was researched inAmerica in the1990s. The DMSIM is a novel technology developed forconcrete mixing on the moon. And amorphous siliceous materials arefound on the moon. Therefore, it is possible to reduce the cost ofestablishing lunar base.For the purpose of using the amorphous siliceous materials on themoon, the effects of the amorphous siliceous materials （such as tuff,volcanic and burnt clay） on the properties of hardened Portland cementpaste, mortar and concrete prepared by DMSIM were investigated by physical mechanics measurement and XRD analysis. To examine thedifferences between DMSIM and wet-mix/steam-injection method（WMSIM）, the effects of the amorphous siliceous materials （tuff andvolcanic） on the properties of hardened Portland cement paste prepared byWMSIM were also studied. The main conclusions are as follows:（1） The compressive strength of hardened cement paste, and mortarprepared by DMSIM increases at first and then decreases continually withthe increase in the amount of amorphous siliceous material （tuff andvolcanic）. For instance, when the optimal replacement percentage levels ofthe volcanic are20%by weight, the compressive strength of the hardenedpaste is135.4MPa, which increases by63.7%as compared with thehardened cement paste prepared by WMSIM with the same replacementpercentage levels of volcanic, and which remains almost unchanged ascompared with the hardened Portland cement paste prepared by DMSIM.（2） The compressive strength of concrete prepared by DMSIMappears a trend from ascent to descent with the increase in the amount ofamorphous siliceous material （tuff, volcanic and burnt clay）. For example,when the optimal replacement percentage levels of the volcanic are40%by weight, the compressive strength of the concrete is61.2MPa, whichincreases by18.0%as compared with the compressive strength ofhardened Portland cement concrete.（3） The DMSIM has advantages of reducing cement content and anincrease in compressive strength. For example, the compressive strengthsof mortar are118.6,100.7and80.1MPa with the incorporption of20%, 40%and60%volcanic, respectively.（4） The increase of amorphous siliceous material continuouslydecreases the chemically combined water content of hardened pasteprepared by DMSIM. For example, the contents are15.02%,12.56%,10.93%,8.68%and6.77%with the incorporption of0%,20%,40%and60%volcanic, respectively.（5） By using XRD analysis, there is a complete reaction betweenCa（OH）₂and volcanic in hardened paste prepared by DMSIM when thereplacement percentage levels of the volcanic are20%, and the content ofportlandite is few. Besides, when the replacement percentage levels of thevolcanic are40%, there are obvious quarz and oligoclase diffraction peakswhich the volcanic itself contains.In a word, the results suggest that hardened Portland cement paste,mortar and concrete with high volume amorphous siliceous materialscould be prepared by DMSIM. Besides, the DMSIM could save cement,and also be one of feasible methods to produce concrete on the earth.