Cement Pastes (IMAGE) NASA/Johnson Space Center Caption These images compare cement pastes mixed in space (above) and on the ground (below). The sample from space shows more porosity, or open spaces in the material, which affects concrete strength. Crystals in the Earth sample also are more segregated. Credit Penn State Materials Characterization Lab Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.