Analysing the flexural behaviour of one-way spanning reinforced concrete slabs repaired and strengthened using SRG (steel-reinforced grout) and HPC (high-performance concrete)

Abstract

At present, the current situation within the local industry, regarding the concrete environment and its infrastructure often depicts the requirement of rehabilitation, repair and strengthening due to the degradation of structures caused by the chemical, physical and mechanical processes incurred upon them. Strengthening and repair of concrete structures is another additional procedure to structures not capable of withstanding the loads they were designed to carry. This recently-increasing demand in upgrading the current infrastructure has led to the creation of efficient and advanced systems which will aid in the promotion of rehabilitation, repair and strengthening processes with the use of composite materials. These systems include the utilisation of fibre reinforced polymers (FRP) which can be externally bonded or near-surface mounted. However, some argue that FRPs are not a feasible option, due to their high cost, lack of reliable data and long-term durability. Recently, a new composite has been developed, making use of steel fibre sheets which have resulted in the creation of a very promising and cost-effective material and a suitable alternative for external strengthening of concrete structures. In spite of the fact that in precedent studies, the use of steel-reinforced grouts (SRGs) proved advantageous and practical over other materials and methods, its main failure was mainly attributed to mainly debonding which limits the maximum potential strength the composite material can reach. Such negative aspects must be considered important for this study since the aim is to obtain a stronger structural element. This study mainly focuses on both the analytical and experimental procedures of one-way spanning simple supported concrete slabs. These slabs were strengthened on the compression side (top) with a high performance concrete (HPC) and on the tension side (bottom) with a steel reinforced grout. A total of six 3000mm X 1000mm one-way reinforced concrete slabs were cast for this research. The six slabs were split into two groups, three of them being of a C12/15 grade and the other three being of a C20/25 grade. One slab from each grade was tested as a reference control specimen without any strengthening material. Another two slabs were first exposed to a degree of pre- damage which were then repaired and tested. The final two slabs were only strengthened with the externally bonded materials and tested. The slab specimens were subjected to four-point bending tests. The behaviour of the strengthened slabs was investigated and compared to the control slabs. The main features which were observed and reported related to the load - deflection curves, load - strain curves, failure modes and crack patterns for all the slabs. All results obtained are presented below in the results section. Analysis of the results section was carried out in order to estimate the ultimate load capacity of each slab. The analysis was done analytically in order to draw comparisons and any deviations from the experimental results. Both the experimental results and the analytical results were compared to the predictions given from the software program developed by Kerakoll, the company involved in the manufacturing of the steel reinforced grout and the high performance concrete utilised in the aforementioned procedure. The conclusions drawn from this study are present within the last chapter of this dissertation along with recommendations and propositions for future research work of similar background.