Prefabricerade sandwichelement kommer att produceras till Linnéskolan i Älmhult av Torps Byggelement AB. Ett sandwichelement består av två lager betong (fasad och bärande skikt) med isolering mellan de två skikten. Dessa sandwichelement hade till en början förankringssystemet Thermopin tillverkade av B.T. Innovation, men på grund av produktion- och leveransproblem så ersattes detta förankringssystem mot Isolink som tillverkas av Schöck. Isolink och Thermopin är två förankringssystem tillverkade av glasfiberarmerade plaststänger (GFRP). Sandwichelementen som kommer att användas i Linnéskolan använder sig av isoleringen Kooltherm tillverkad av Kingspan. I detta arbete jämförs förankringssystemens bärförmågor i form av utdragskapacitet. Beräkningar för kapacitet mot vidhäftningsbrott, utdragsbrott och brott i stångmaterial görs för de båda systemen. Utöver detta testas även bärförmågan i form av utdragskapacitet för isolering Kooltherm. 12 testprover, som tillverkades och levererades av Torps Byggelement AB, utsätts för utdragslaster till brott uppstod. Endast de förankringssystem som bär vinkelrät mot skikten testades. De 12 testproverna var uppdelade på följande vis: Fyra tester med Thermopin, fyra tester med Isolink samt fyra tester med endast isoleringen Kooltherm. De testprover med Isolink-systemet gav ett utdragsbrott vid 18.9 kN. Thermopin gav ett spjälkningsbrott vid 14.9 kN. Kooltherm gav brott i isoleringen vid 1.3 kN. Då Isolink fick ett vidhäftningsbrott är det viktigt med en god vidhäftning mellan förankringssystemet och omkringliggande betong. Vibrering av betongen i flera steg vid användning av Isolink kan därför anses vara viktig. Thermopin fick ett spjälkningsbrott då tillverkarens minsta avstånd till kant inte uppfylldes med testproverna. Det går med stor sannolikhet att säga att Thermopin inte hade fått ett utdragsbrott även om minsta avstånd till kant uppfylldes, mest troligt är att ett konbrott hade uppstått. / Prefabricated sandwich elements will be produced to Linnéskolan in Älmhult by Torps Byggelement AB. A sandwich element is built up by two layers of concrete (facade- and load bearing layer) with insulation separating the two layers. These sandwich elements were intended to have the anchors Thermopin produced by B.T. Innovation but due to delivery problems, this connection system was replaced with Isolink made by Schöck. Isolink and Thermopin are two anchors consisting of glass fiber reinforced plastic bars (GFRP). The sandwich elements that will be used in Linnéskolan will have the insulation Kooltherm made by Kingspan. This work is comparing the two connection systems in load bearing capacity by pull-out load tests. Calculations for pull-out failure, concrete failure and anchor failure were done for both of the connection systems. The load bearing capacity was also to be checked for the Kooltherm insulation by pull-out load tests. 12 test specimens were manufactured and delivered by Torps Byggelement AB. Only the anchors perpendicular to the concrete layers were tested. The 12 test specimens were divided as follows: four tests with Thermopin, four tests with Isolink and four tests without a connection system with only the Kooltherm insulation. The test specimens with Isolink gave a pull-out load at 18.9 kN. Thermopin gave a splitting failure at 14.9 kN. Kooltherm insulation gave a failure in the insulation at 1.3 kN. Due to Isolink getting a pull-out load failure, it is important that the bond between the anchor and the surrounding concrete is strong. Compacting of the concrete in multiple steps when using the Isolink-system can be considered important. The test specimens with the Thermopin-system got a splitting failure due to the manufacturers requirement on minimum edge distance not being achieved in the test specimens. It is proper to state that it is very unlikely that a pull-out failure would occur in the Thermopin test specimens even if the minimum edge distance was achieved. Most likely a concrete-cone failure would have occurred.

As part of the work in this project, a literature review is conducted to determine the optimal thickness of the outer concrete layer in prefabricated concrete sandwich elements. These elements are used as exterior walls in buildings and consist of a load-bearing inner concrete layer, an intermediate insulation layer, and an outer concrete layer that forms the building's facade. The focus is on optimizing the sandwich wall in precast concrete by reducing the thickness of the outer skin compared to the current standard thickness of 80 mm. This could potentially reduce the weight of the elements by approximately 1.5-2 tons by reducing the thickness from 80 mm to 30 mm. This weight reduction can have a significant impact, for instance, on the crane capacity in large construction projects, allowing a crane to handle all the elements on a construction site without the need for relocation. Additionally, this optimization of the sandwich wall will result in cost savings by using less material in the elements, as well as impacting other aspects of the construction process, such as energy consumption and transportation costs. In this project, test specimens of size 400mm x 400mm have been used, and to draw comprehensive conclusions, full-scale experiments are required to account for factors such as temperature variations and shrinkage in the outer skin. In this work, compressive strength tests have also been conducted to determine the strength of the concrete used in the outer skin of the tested sandwich walls. The concrete used in the tests was a fiber-reinforced concrete from Finja, and the reinforcing mesh was a hot-dip galvanized plaster mesh. Initially, samples were cast to test the laboratory equipment and evaluate the testing methods. Subsequently, the remaining samples were cast and tested according to a predetermined schedule to ensure relevant testing conditions. Samples on the wall elements were made with both diagonal and straight anchoring and were tested under tensile load parallel to the outer layer as well as tensile load perpendicular to the outer layer. In total, 20 samples were conducted in the study, testing various combinations of anchoring systems, loads, reinforcement, and recesses. Samples 1-10 were tested with diagonal anchoring and parallel load, while samples 11-20 were tested with perpendicular anchoring and perpendicular in combination with parallel load. The samples exhibited a variation in failure types, such as grain failure in the outer layer, anchor pull-out, adhesion, and outer layer failure. The highest load values were observed in sample 2 (8.7 kN) and 6 (7.6 kN) for samples 1 to 10, and sample 12 (10.6 kN) and 15 (9 kN) for samples 11 to 20. In summary, it can be stated that the trials have yielded initially positive results regarding the practical use of a thinner outer panel for prefabricated concrete sandwich elements.