The performance of wollastonite-reinforced portland cement-based binders hydrated in saturated Ca(OH)2 solution, 1N NaOH solution, 1N KOH solution, distilled water and saturated moist air was evaluated as a precursor to the development of a test for assessing the durability of these composites. The cementitious binders are made of cement and silica fume. The effect of the different solutions on the mechanical behavior and microstructural characteristics of the systems investigated at 24 degrees Celsius and 80 degrees calicoes was determined. Porosity and pore structure determinations were made using mercury intrusion porosimetry, helium pycnometry, and isopropyl alcohol saturation techniques. Flexural strength and fracture toughness behavior was also determined. Pore structure modifications, leaching effects and mechanical test results were stability of wollastonite micro-fibers in cement binders. Wollastonite microfiber appears to merit serious consideration as a candidate reinforcement for the development of new composite systems.

Concrete berth faces in the St. Lawrence river at the Port of Montreal constructed in the early 1900's are undergoing continuing deterioration from the combined effects of frost damage, alkali aggregate reactivity and in some areas attack from deicing chemicals stored on the adjacent wharves. In some places the concrete is turning to rubble, and a major retrofit program is required to restore the berth faces to a serviceable condition. Both cast-in-place reinforced concrete and anchored and tied-back fiber reinforced shotcrete remedial potions are being evaluated to establish the most technically sound and cost-effective remedial alternatives for this work. This paper describes a prototype construction project in which about two thirds of a berth face, 122m long and 7.1m. High, was repaired with a synthetic fiber reinforced shotcrete and the remaining third with a steel fiber reinforced 25mm long by .38mm diameter added at an addition rate of 1.25 percent by volume of the shotcrete. The deformed steel fiber 38mm long was added at an addition rate of .75 percent by volume of the shortcrete. The shotcrete used was air entrained, silica fume modified, supplied by transit mixers from a central-mix plant and applied by the wet-mix plant and applied by the wet-mix shotcrete process. This paper describes the remedial design, shotcrete mixture designs, preconstruction mock-up production and quality control testing and provides a summary of construction quality control test results. Test results reported include plastic shotcrete properties such as as-batched and as-shot slump and air-content, compressive strength, boiled absorption and volume of permeable voids and toughness. The behavior of the shotcrete repairs is being monitored service is described. Comparative data is provided regarding the relative costs of the cast-in-place reinforced concrete and fiber reinforced shotcrete alternatives.

Following a brief introduction on the definition of high-performance fiber reinforced cement composites (HPFRCCs), this paper suggests that HPFRCCs are very well suited for repair and rehabilitation applications. It describes the range of tensile properties currently achievable using HPFRCCs, focusing in particular on the trade-off between strength and strain capacity and the importance of large strains, as evidenced by quasi-strain hardening behavior and multiple cracking. Particular attention is given to describing the tensile stress-strain response of slurry infiltrated fiber concrete (SIFCON), and the parameters influencing that response such as type of fiber, type of matrix, fiber orientation, fiber length, and fiber bond. Also a brief summary of three representative applications involving the use of HPFRCCs in repair and rehabilitation is given, namely: the use of fibers in the tensile zone area of reinforced concrete beams to control cracking and improve durability; the use of SIMCON for repair and rehabilitation of reinforced concrete beams and columns to satisfy seismic requirements; and the use of SIMCON as a jacket in reinforced concrete columns, also to improve seismic resistance. It is concluded that exceptional structural performance such as strength and ductility, particularly in reinforced and prestressed concrete structures, can be achieved if the matrix material is an HPFRC composite.

Three reinforced concrete columns with inadequate strength, non-contact, lap splices at their base were tested to failure under reversed cyclic loading. An investigation was then made a method for jacketing such damaged columns in order to reinstate and improve their seismic performance. The damaged columns were jacketed using a steel fiber mat infiltrated with slurry and then again tested to failure under reversed cyclic loading. The degree of restoration and improvement in the seismic performance of the columns was partially dependent on the degree of damage suffered by the column during the initial non-jacketed testing. However, in all cases the jacketed columns exhibited load-deflection hysteretic characteristics equal to, and ductility characteristics exceeding, those of the non-jacketed column. Details are provided of the seismic performance characteristics of the columns, and the repair techniques used.

A large variety of materials and techniques are available to increase strength of existing concrete structures in an effort to extend their service life. The way to make repaired and strengthened concrete structures durable is to ensure that the new composite system is "tailored" to serve the intended service life, and that the composite human system, the team involved with a project, is knowledgeable and experienced enough to recognize the complexity of their task. The paper reviewed traditional methods and also offers a review on the use of advanced composite materials for strenghening existing comcrete structures. The advantages and limitations of different techniques are presented. It is concluded that, in the futrue, advanced composite materials will be widely used for repair and strengthening. To achieve this, it is vital that research and engineering education in cement-based and advanced composite materials are improved.