Only comparatively small amounts of Moon rock have been transported to Earth, so in 1988 researchers at the University of North Dakota proposed simulating the construction of such a material by using lignite coal ash.Additionally, sulfur gains strength in a very short time and doesn't need any period of cooling, unlike hydraulic cement.The concrete doesn't have to be cured, instead it is simply heated to above the melting point of sulfur, 140 °C, and after cooling it reaches high strength immediately.[14] This sulfur concrete could be of especial value for dust minimization, for instance to create a launching pad for rockets leaving the Moon.By adding urea (byproduct in urine, sweat, and tears), the resultant material became substantially stronger than ordinary concrete, with 40 MPa of compressive strength.[15][16][17] As noted by the authors:[16] In essence, human serum albumin produced by astronauts in vivo could be extracted on a semi-continuous basis and combined with lunar or Martian regolith to ‘get stone from blood’, to rephrase the proverb.We believe that human serum albumin extraterrestrial regolith biocomposites could potentially have a significant role in a nascent Martian colony.Researchers also experimented with synthetic spider silk and bovine serum albumin as regolith binders, noting that these materials could also be produced on Mars after advancements in biomanufacturing technology.Tree resins, collagen from hooves, casein from cheese, and animal blood were all used as binders and additives for various applications".