Abstract:Shape memory polymer (SMP) products have been developed for application as crack closure devices in concrete. They have been made from PET in the form of both fibres and hollow tubes. Here, manufacturing methods using die-drawing and mandrel-drawing to induce shape memory are reported. The fibre-based devices are incorporated into concrete and, upon triggering, exert shrinkage restraint forces that close cracks in the concrete. The evolution of shrinkage restraint force in the fibres as manufactured was measured as a function of temperature, showing stresses in excess of 35 MPa. Tendons consisting of fibre bundles are incorporated into concreate beams subjected to controlled cracking. When activated, the tendons reduce the crack widths by 80%. The same fibres are used to produce another class of device known as knotted fibres, which have knotted ends that act as anchor points when they incorporated directly into concrete. Upon activation within the cracked concrete, these devices are shown to completely close cracks. The tubes are used to enclose and restrain prestressed Kevlar fibres. When the tubes are triggered, they shrink and release the prestress force in the Kevlar, which is transferred to the surrounding concrete in the form of a compressive force, thereby closing cracks. The Kevlar fibres also provide substantial reinforcement after activation. The devices are shown to be able to partially and fully close cracks that have been opened to 0.3 mm and achieve post-activation flexural strengths comparable to those of conventional reinforced and prestressed structural elements. Finally, a preliminary life cycle assessment study was used to assess the carbon footprint a nominal unit of concrete made with SMPs fibres compared to conventional concrete.Keywords: PET; shape memory polymer; crack closure; self-healing; civil engineering; crack width; LCA
get_appDownload get_appMirrorVersion 188.8.131.52 (18/1/2021)Fixed Bugs-You cannot use the Server Lobby feature in online building.-Keys are reset after the player dies or restarts from checkpoint.-Fuse Crawler doesn't bounce correctly on a Bouncy Ball on the ceiling in a certain pattern.-Fire Wall Modifier options have unused arrows.-Super Arm blocks and fragments do not crack or break Ice Blocks.-Centaur Flash can make you permanently invincible.-Soccer Ball Jet can't be hit by a Punch Block after flying once.-A crash can occur if you return to editor at the same moment Mega Man dies with Fuse Rail on your level.-When time is stopped, Splash Woman doesn't freeze completely if set to weakness.-When falling on the corner of a Conveyor Belt, it pushes you to the edge.-Push Block pushed by another moving platform can clip inside another Push Block.-Battan can get stuck in ladders and Jumpthrough Platforms while jumping.-Enemies and bosses can fall off moving platforms going up and down.-Enemies and bosses fall of Crash Lifts moving horizontally.
get_appDownload get_appMirrorVersion 1.0.3 (20/7/2017)Fixed Bugs-Enemies sometimes don't spawn properly.-Sometimes the screen randomly stops scrolling, preventing you from progressing until you restart the stage. 1e1e36bf2d