Term composite material or composite signifies material that consists of several materials with different structures in order to improve characteristics. One of the best known composites, that surounds us, is reinforced concrete. Concrete gives form and takes over compressive forces while steel bars take over tensile ones. Same part take epoxy resin and carbon fibres where resin takes concrete role and carbon fibres take steel role.
Object is wraped into carbon fibres fabric and paints over with epoxy resin in several layers. Each layer is sanded in order to get perfectly flat and smooth surface. At the end, object is polished or varnished.
Carbon plates, of unidirectional type, strengthen building construction. Exceptional carbon fibres strength, light weight, resistance to fatigue and favourable mechanical characteristics enable simple and elegant solutions.
Carbon plates are composites made of carbon fibres and polimer binding with minimum fiber content of 65-70%. All carbon fibers inside plate have longitudinal direction and they are uninterrupted.
Application of carbon plates and binding against sub grade is realised through epoxy resins.
Chapel belfry with scaffold
Consolidations 618 GRADEVINAR 63 (2011) 6
Because of earthquake activities during last century cracks appeared on the belfry. During last 400 years original binding lost its characteristics and it had to be replaced with adequate material. Prior to injecting sub grade was prepared in the manner where bigger gaps and crack foreheads were filled with two component mortar whose pozzolan composition match existing binder. After filling, 8 mm wide bores were made, each 20 cm. Boring depth depended on wall structure its self. Injecting was performed using compressor that pumped low viscosity mass, with no cement, into bores. Holes were pluged using two component cementitious mortar. Construction consolidation had goal to increase compactness and ductility of belfry. In this case strong points were nave walls, more compact than belfry ones. Static calculations quoted that load capacity had to be improved by carbon fibre sheet application every 300 cm. In order to secure good connection with sub grade, layer of repair mortar was applied wide as carbon sheet. Calculation proved that carbon sheet, characterized with high strength and elasticity modulus, would create satisfying horizontal frame that minimises need for longitudinal anchoring. Carbon sheet application was performed using dry procedure where epoxy resin was used to impregnate sheet. Connection with repair mortar was ensured using basic epoxy coating and epoxy putty. Consolidation through low viscosity mass injection and carbon sheet application was finished with anchoring. Anchors were made of carbon tie. Tie was soaked with low viscosity epoxy resin, sprayed with quartz sand and left 7 hours to dry. In this way anchors were created with free carbon fibres on one side in order to overlap carbon sheets. Carbon anchors were built in by epoxy resin injected into holes on both sides of sheets under angle of 30 on sheet axis. Consolidation of construction saved belfry from further cracking and has connected it for building. So this is the way how protected monument was saved.
Dejan Šomoši, Mapei Croatia