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© 2018 The Authors, published by EDP Sciences. Pore structure characterization is a key aspect when studying the durability of cementitious materials. When supplementary cementitious materials (SCMs) are used changes in pore structure are expected, and the complexity of its analysis is increased. The purpose of this paper is to describe the pore structure variation of mortars with two types of SCMs: natural pozzolan from volcanic origin (NP), and limestone powder (LP). We tested mixes with cement replacements (in weight) of 20 % and 40% by NP, and 10 % and 20% by LP. To analyse the pore structure, two widely accepted and complementary techniques were applied: dynamic water vapour sorption (DVS) and mercury intrusion porosimetry (MIP). With the DVS data, the Barret-Joyner-Halenda (BJH) model was used for pore size distribution assessment. Calculations with the Dubinin-Radushkevich (DR) model were also made for the smallest pore size range. Tests were performed at 28 and 90 days. MIP and DVS allowed evaluating the effect of the studied SCMs on different pore size ranges. Both techniques provided comprehensive information over a wide range of pore sizes. The mix with 40 % of NP had the best evolution, showing a significant volume decrease in the mesopore range. ispartof: INTERNATIONAL CONFERENCE ON CONCRETE REPAIR, REHABILITATION AND RETROFITTING (ICCRRR 2018) vol:199 ispartof: 5th International Conference on Concrete Repair, Rehabilitation and Retrofitting (ICCRRR) location:Cape Town, SOUTH AFRICA date:19 Nov - 21 Nov 2018 status: published

Concrete cracking can result in a significant reduction of the durability and the service life due to the ingress of aggressive agents Self-healing concrete is able to heal cracks without external intervention, thereby mitigating the need for manual repair. In the assessment of the healing efficiency of self-healing concrete the to-be-healed crack width is an important parameter and different researchers have emphasised that the variability of the crack width significantly hampers an accurate assessment of the healing efficiency. With two new crack control techniques the variability of the crack width was reduced in order to decrease the variability on the calculated healing efficiency. This paper reports on the application of these techniques for the assessment of self-healing mortar containing encapsulated polyurethane. The healing potential was investigated by looking at the degree of sealing using a water flow test setup. It was observed that by using a crack control technique the variability on the crack width can indeed be reduced. Nonetheless, this does not translate in an equivalent reduction on the variability of the healing efficiency. This indicates that other factors contribute to the variability of the healing efficiency.

Cracks in reinforced concrete structures exposed to a marine environment or de-icing salts can cause major durability issues due do accelerated ingress of chloride ions. In this study, the influence of autonomous crack healing by means of encapsulated polyurethane on the chloride ingress perpendicular to cracks was evaluated. This was done quantitatively by determining perpendicular-to-crack chloride profiles by means of profile grinding followed by potentiometric titration and qualitatively through visualization of the chloride penetration front by means of the AgNO3 spray method. The resulting chloride profiles showed that the healing mechanism was able to reduce the chloride concentrations in the direct vicinity of the crack to a large extent and to reduce the perpendicular-to-crack chloride penetration, especially further away from the exposed surface. Visualization of the chloride penetration front showed some variation in crack healing. For some healed samples almost no additional chloride ingress was found compared to uncracked samples, others showed a slightly enhanced ingress at the crack location but less perpendicular-to-crack chloride penetration compared to untreated cracked samples. Generally, the reduced amount of chlorides present in the concrete matrix due to crack healing will enhance the durability and service life of concrete structures.

Over the last years, nanotechnology is getting more attractive and nanomaterials are being used more commonly in construction industry. One of these materials is nanosilica: the nano-sized, engineered form of silica fume. The replacement of cement by these nanoparticles is said to enhance both the mechanical performance and the durability of the concrete material. In this paper colloidal silica will be used, which is nanosilica in solution. A characterization of mortar mixtures containing different amounts of silica is done and a comparison is made with respect to a reference mixture.

After several years of research in the Magnel Laboratory (Belgium) to obtain concrete with self-healing properties, the most promising mechanisms were tested on a larger scale. Instead of small mortar samples with self-healing properties, real-scale self-healing concrete beams (150 mm × 250 mm × 3000 mm) were made and the efficiency of autonomous crack repair was evaluated over time after loading the beams in four-point bending. In addition to a reference beam without self-healing properties, a beam with encapsulated polyurethane and a beam containing superabsorbent polymers were investigated. While for the beam with polyurethane, crack repair is obtained as the healing agent is released as soon as cracks damage the embedded capsules, the superabsorbent polymers absorb water which intrudes into the cracks, immediately blocking the crack through swelling and later on by continued hydration and precipitation of calcite. The efficiency of both self-healing approaches was compared by measuring the reduction in water ingress into the cracks and by measuring the crack width reduction over time.