This study aims to investigate the feasibility of utilizing waste rubber as a partial replacement for silica sand in the development of self-consolidating engineered cementitious composite (SCECC). The effects of the percentage of rubber (0–50%), rubber size [crumb rubber (CR) and powder rubber (PR)], and supplementary cementing materials (SCMs) (fly ash, ground-granulated blast-furnace slag, silica fume, and metakaolin) on the fresh and hardened properties of SCECC were studied. The results indicated that both CR and PR had promising potentials to be more economical and environmentally friendly alternative aggregates to develop sustainable SCECC with higher ductility. Although the inclusion of CR negatively affected the fresh and mechanical properties of SCECC, a number of successful mixtures with up to 30% CR could be developed with strengths greater than 40 MPa. The addition of PR showed a better performance in terms of fresh and mechanical properties compared with CR, allowing up to 40% replacement of rubber to be safely used. The inclusion of CR appeared to continuously increase the deformation capacity of SCECC up to 20% replacement level, while PR continued to improve the deformation capacity up to 50% replacement. Combining PR and different SCMs, especially metakaolin, allowed higher percentages of rubber to be used, achieving semi-lightweight concrete with adequate mechanical properties for multiple structural applications.

This study assessed the impact resistance of self-consolidating engineered cementitious composite (SCECC) using the American Concrete Institute (ACI) Committee 544’s repeated drop-weight impact test and flexural impact loading test. The investigation also evaluated the compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity of the tested mixtures. Fly ash (FA), which is typically used in common SCECCs, was partially replaced by slag (SL), silica fume (SF), and/or metakaolin (MK). Also, the microsilica sand (SS), which is the primary aggregate used in SCECCs, was replaced by crushed granite sand (CS) of different sizes to develop different SCECC mixtures. Standard SCECC mixture (made with only FA), vibrated engineered cementitious composite mixture, and traditional self-consolidating concrete (SCC) made with 10 mm coarse aggregate were tested for comparison. The results indicated that combining SL, SF, or MK with FA in SCECC mixtures can create composites with improved mechanical properties, adequate ductility, and enhanced impact resistance. The highest improvement in the impact resistance in both drop-weight and flexural impact loading tests was obtained when 15% to 20% MK was combined with FA. SCECC containing CS provided comparable performance with that of SCECC made with SS, indicating promising potentials for developing cost-effective composites. The impact resistance results in both drop-weight and flexural impact loading tests also indicated that SCECC mixtures exhibited significantly higher impact resistance compared with their SCC counterpart mixtures with comparable compressive strengths.

An extensive experimental study was performed to apply acoustic emission (AE) monitoring to assess the bond strength of corroded large-scale RC beam specimens. This paper demonstrates the data obtained from AE monitoring of these RC beams, while being exposed to localized, accelerated corrosion procedures at one of the end sides of each beam. Five RC beams were corroded through an electrically accelerated corrosion process to reach 5, 10, 20, and 30% of steel mass loss. The beams were constantly monitored during the accelerated corrosion tests via half-cell potential (HCP) measurements and three attached AE sensors distributed along the span of the beam. During the test, the corrosion and cover crack initiation were monitored and the crack width measurements were attained daily. The results showed that the analysis of AE signal parameters acquired throughout the corrosion period enabled the detection of both corrosion and cover crack onset earlier than HCP readings and prior to any signs of visual cracking, regardless of sensor location. Acoustic emission parameters examined in this paper {cumulative number of hits, cumulative signal strength (CSS), historic index [$H$ ($t$ )], and severity ($S_r$ )} were shown to be highly correlated with the level of corrosion propagation. The study also presents developed damage classification charts interrelating the results of crack growth and mass losses to the average values of $H$ ($t$ ) and $S_r$ . These charts can be used to quantify the level of deterioration of RC structures due to reinforcement corrosion.

This article presents the results of an experimental investigation on the application of acoustic emission technique for monitoring the steel-to-concrete bond integrity of reinforced concrete structures. A series of direct pull-out tests were performed on 54 reinforced concrete unconfined prism samples with variable rebar diameter (10, 20, and 35 mm), embedded length (50, 100, and 200 mm), and concrete cover (20, 30, and 40 mm). The samples were tested under incrementally increasing monotonic loading while being continuously monitored via attached acoustic emission sensors. These sensors were utilized to acquire different acoustic emission signal parameters emitted throughout the tests until failure. Also, an acoustic emission intensity analysis was implemented on acoustic emission signal strength data to quantify the damage resulting from loss of bond in all tested specimens. This analysis employed the signal strength of all recorded acoustic emission hits to develop two additional parameters: historic index ( H ( t)) and severity ( S _r ). The results of bond behavior, mode of failure, and free end slip were compared with the recorded acoustic emission data. The results showed that the cumulative number of hits, cumulative signal strength, H ( t), and S _r had a good correlation with different stages of bond damage from de-bonding/micro-cracking until bond splitting failure and bar slippage, which caused cover cracking or delamination. The analysis of cumulative signal strength and H ( t) curves enabled early identification of two progressive stages of bond degradation (micro-cracking and macro-cracking) and recognized the various modes of failure of the tested specimens. The variations of bar diameter, concrete cover, and embedded length yielded significant impacts on both the bond behavior and acoustic emission activities. The results also presented developed intensity classification charts, based on H ( t) and S _r , to assess the bond integrity and to quantify the bond deterioration (micro-cracking, macro-cracking, and rebar slip) in reinforced concrete structures.

The aim of this study was to develop and optimise self-consolidating rubberised concrete (SCRC) modified by different types and volumes of synthetic fibres (SFs). Steel fibres were also tested in this investigation for comparison. The investigation particularly sought to utilise the beneficial effect of fibres to alleviate the reduction in splitting tensile and flexural strengths resulting from adding crumb rubber (CR) to SCRC mixtures. The results indicated that the addition of SFs reduced the fresh properties, which limited the maximum percentage of CR that could be used in SCRC mixtures to 20%, compared to 30% maximum percentage of CR used in developing successful SCRC mixtures without SFs. However, the use of SFs beneficially contributed to alleviating the reduction in the splitting tensile strength and flexural strength of SCRC mixtures resulting from adding CR. Although increasing the length of SFs further reduced the fresh properties of the mixtures, this also enhanced further the splitting tensile and flexural strengths of SCRC mixtures. The results also showed that when self-compactability was disregarded, it was possible to use a higher combination of CR (30%) and fibre (1% volume fraction) in the development of vibrated rubberised concrete, resulting in mixtures with further improvements in splitting tensile and flexural strengths, and reduced self-weight.