Shear study on the interface between ultra-high durability concrete and low-cement-lightweight concrete for precast composite walls

Abstract

Precast wall system is one of the solutions with great potential, as it makes it possible to build structures in a simple and quick way, without using columns and beams. Considering the advantages of this system, an innovative composite structural precast wall has been developed, using a layer of ultra-high durability concrete (UHDC) on the outside and another layer of low cement lightweight concrete (LCLWAC) on the inside. This provides a triple benefit: (a) a reduction in dead weight, (b) an increase in durability and therefore a higher life of the structure, and (c) a reduction in cement dosage and consequently a reduction of the carbon footprint of the product. The main topic of this research is the study of the interface shear strength between a low cement lightweight aggregate concrete (LCLWAC) and an eco-efficient ultra-high durability concrete (UHDC). An experimental program was carried out to evaluate this shear strength, considering two parameters: i) the roughness interface and (ii) the transversal reinforcement crossing the interface; and using two types of tests, push-off and flexural tests. Results were compared with the predictions of Eurocode 2 and fib Model Code 2010, including the new versions of both codes, to assess how suitable are the models and coefficients for this situation. The shear strength between LCLWAC-UHDC is quite effective, and the predictions are conservative for this combination, at least 2 times lower than the experimental results and close to 7 times in some cases.