Development of low-shrinkage rapid set composite and simulation of shrinkage cracking distribution in repaired concrete members
Creators: name: Mansi, Aseel Shaban
Publisher: name: No Publisher Supplied
Year: 2019

description: As the global transportation infrastructure aged, the need for effective maintenance has become necessary to maintain not only strength but also durability. Although many materials used in repair provide adequate strength, they can suffer early failure and degradation as a result of several phenomena such as rigidness and rapid shrinkage. In instances where such repair materials are used, cracking and debonding can quickly occur because of the high stresses developed in the system. The Portland cement repair material considered reliable repair materials; however, they require sufficient curing time which leads to detours or lane closures. Hence, the efficient repair and replacement of concrete pavements often require a rapid setting material that can be placed, cured, and opened to traffic in a relatively short period of time. Rapid-hardening cementitious repair materials have been widely used. The use of very early strength materials will minimize the out-of-service time of the effective repairs. In this dissertation, experimental and analytical programs were carried out. The experimental program included three phases. The first phase was conducted to design and test the fresh and shrinkage properties of high early strength rapid set materials (HES-RSM) and high early strength fiber reinforced rapid set materials (HES-FR-RSM) mixtures. These mixtures were developed for concrete repair applications in transportation infrastructures with low cracking potential. For this purpose, three of the most common ready patch repair materials and approved from the most of DOT’S were selected, the samples were cured using dry curing to simulate the critical condition in the repair process. As a fiber reinforcement, three types of fibers (steel, carbon, and basalt) with different percentages were prepared to select the best mix designs that satisfy various requirements. The second phase was performed to investigate the mechanical properties of the optimized mixtures which selected from the first phase depending on its shrinkage strain and flowability requirements. The third phase contains the validation of the model. The analytical part of this research included the development of a finite element model (FEM) that can be used for the analysis and prediction of the structural behavior of the composite repaired beams due to the shrinkage effect of the repair materials. The results showed that the developed HES-FR-RSM can achieve high early compressive strength more than 3000 psi and modulus of rupture more than 1400 psi at the age of 4hrs. The free shrinkage strain values were below than 500 microstrains for the most optimized mixtures. The best performance mixture was C1S0.5 with 268 microstrains which is less than the tensile strain capacity of concrete which ranges from 200 to 300 microstrains. The model establishes the development of a good basic tool to study the effects of free shrinkage of the repair materials on the repaired composite and make the selecting repair materials easiest for the engineers for practical purpose. The model is also capable of simulating the crack initiations and could describe the real structural behavior.