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[ES]: El trabajo tiene como objetivo evaluar las resistencias mecánicas y la durabilidad de hormigones de escorias activadas alcalinamente (AASC) utilizando como activador una disolución de silicato sódico hidratado. El comportamiento de estos hormigones en términos de resistencia y porosidad es comparable al rendimiento observado en los hormigones de cemento Portland. Los ensayos realizados mostraron que los hormigones de escoria activada alcalinamente exhibieron una buena durabilidad frente a la penetración de cloruros (multirrégimen UNE 83987) y un buen comportamiento de adherencia a barras de acero corrugado (ensayo de pull-out) comparable a los hormigones de cemento Portland., [EN]: The present study aimed to evaluate the mechanical strengths and durability in alkali activated slag concretes (AASC) using a solution of sodium silicate hydrate as activator. The behaviour of these concretes, in terms of strength and development of porosity, was comparable to the performance observed in ordinary Portland cement concretes. The trials conducted in this study showed that alkali-activated slag concretes exhibited good durability against chloride permeability (UNE 83987) and good adherence behaviour of corrugated steel bars (pull-out test) comparable to Portland concretes.

This study investigates the autogenous self-healing capability of one-year-old engineered cementitious composites (ECC) with different mineral admixtures to understand whether self-healing performance in late ages is similar to that of early ages. Sound and severely pre-cracked specimens were subjected to different environmental conditions including water, air, "CO2-water," and "CO2-air" for one year plus 90 days of initial curing. Self-healing performance of ECC mixtures was assessed in terms of crack characteristics, electrical impedance testing, rapid chloride permeability testing and microstructural analysis. Laboratory findings showed that the presence of water is crucial for enhanced autogenous self-healing effectiveness, regardless of mixture composition. "CO2-water" curing resulted in the best self-healing performance of all curing conditions, which was confirmed with results from different performance tests throughout the experimental study. By further curing specimens under "CO2-water" (depending on the ECC mixture composition), cracks as wide as half a millimeter (458 mu m) were easily closed by autogenous self-healing within only 30 days of further curing, and all cracks closed completely after 90 days. Because high levels of CO2 emission are a global problem, the effectiveness of "CO2-water" curing in closing microcracks of aged cementitious composites specimens through autogenous self-healing can help reduce the increasing pace of CO2 release. The results of this study clearly suggest that late-age autogenous self-healing rates of ECC specimens can be significantly enhanced with proper further environmental conditioning and mixture design. (C) 2018 Elsevier Ltd. All rights reserved.

Mohamed, O., & Al Hawat, W. (2018, March). Durability and Strength of Sustainable Self-Consolidating Concrete Containing Fly Ash. In IOP Conference Series: Materials Science and Engineering (Vol. 324, No. 1, p. 012041). IOP Publishing., In this paper, the durability and strength of self-consolidating concrete (SCC) is assessed through development and testing of six binary mixes at fixed water-to-binder (w/b) ratio of 0.36. In each of the six SCC mixes, a different percentage of cement is replaced with fly ash. The development of compressive strength for each of the mixes is assessed by testing samples after 3, 7, and 28 days of curing. Durability of each of the six SCC mixes is assessed by measuring the charge passed in Rapid Chloride Permeability (RCP) test. Charge passed was measured in samples cured for 1, 3, 7, 14, 28, and 40 days of curing. All mixes out-performed the control mix in terms of resistance to chloride penetration. Binary mix in which 20% of cement is replaced with fly ash exhibited 28-day strength slightly surpassing the control mix.

The purpose of this study was to investigate the effects of Fiber Reinforced Polymer (FRP) wraps on reducing chloride ingress and increasing the durability of lightweight concrete. Several prior studies have dealt with FRP application on normal weight concrete. However, the literature on externally bonded FRP application on lightweight concrete is sparse. This study involved an accelerated testing to determine concrete degradation and decrease in chloride ingress and associated increased durability that FRP wrapping can provide to lightweight concrete. Forty two cylinders were subjected to electricity induced accelerated testing in a saline solution for 50 days. Samples were removed from the immersion tank after specific failures and analyzed for chloride content and failure modes. Both lightweight and normal weight concrete greatly benefited from FRP wrapping in terms of increased time to failure and reduced concrete chloride. Lightweight concrete generally performed better with Carbon FRP (CFRP), and normal weight concrete with Glass FRP (GFRP). CFRP wraps produced the best overall protection. Multiple wraps were more effective at reducing chloride ingress than single wraps. Lightweight concrete had greater chloride permeability reductions, whereas normal weight concrete benefited more from FRP confinement effects. The majority of sample failures were caused by cracking in the concrete substrate.

Massive concrete structures tend to have high cracking risk due to early temperature rise. High-volume mineral admixture concrete, which has low hydration heat, is suitable for massive concrete structures. In this paper, the properties of high-volume fly ash (HVFA) concrete and high-volume steel slag (HVSS) concrete were compared under two different curing conditions (standard curing condition and temperature match curing condition). The results show that the promoting effect of temperature match curing on the early strength of HVFA concrete is more obvious than that on HVSS concrete. Temperature match curing has negative effect on the late strength and elastic modulus of HVSS concrete. The promotion of temperature match curing to the elastic modulus development is not so obvious as that to the strength development. Temperature match curing can significantly decrease the chloride permeability of HVFA concrete, but its influence on the chloride permeability of HVSS concrete is inconspicuous. Though the adiabatic temperature rise of HVSS concrete is lower than that of HVFA concrete, which is beneficial to its application to the massive concrete structures, its strength especially the splitting tensile strength and resistance to chloride ion penetration need to be improved.

U radu je prikazano eksperimentalno istraživanje čvrstoće i trajnosti geopolimernog betona s granuliranom zgurom visokih peći i crnim pepelom rižinih ljuski. Geopolimerni beton je prvobitno pripremljen s granuliranom zgurom kao primarnim vezivom umjesto cementa, a zatim je zgura zamijenjena s crnim pepelom rižinih ljuski. Dodatak crnog pepela u geopolimernom betonu iznad 10 % usporava razvoj čvrstoće, ali su takve vrijednosti čvrstoće i dalje iznad ciljane sve dok dodatak crnog pepela u betonu ne prelazi 20 %., An experimental study on the strength and durability properties of geopolymer concrete prepared using the ground granulated blast furnace slag and black rice husk ash is presented in the paper. The geopolymer concrete was initially prepared with ground granulated blast furnace slag as the primary binder instead of cement, and then blast furnace slag was replaced with black rice husk ash. The addition of more than 10 % of black rice husk ash in geopolymer concrete retards the strength development, although such strength values are still above the target strength for up to 20 % replacement levels.

The natural pozzolan of volcanic origin has a marked influence on the physico - mechanical characteristics of the concretes. When it is coupled to a water reducing superplasticizer by a correct adjustment of the composition, it greatly improves the concrete properties. The analysis of the experimental results on pozzolana concrete at 5% content and fineness of 9600 cm 2 /g, in a sulphated environment, showed that it contributes positively to the improvement of its durability with respect to the Chloride permeability. This test was performed using the procedures of ASTM C 1202. The resistance of concrete to penetrating chloride ions was measured by the charge passed through two 50 mm disk concrete specimens maintained under an electric tension of 60 V during 6 hours by means of electrodes made of rustproof steel between the two cells of the two compartments. One of the faces of the specimen was in contact with 3% NaCl solution, and the other face was in contact with 0,3N NaOH solution. The test was conducted at 28, 90,180 and 365 days

Analyzing the related literature at home and abroad, this paper summarized the results and shared them with reasearchers involved in the field on the recycled aggregate concrete (RAC). In this paper, the durability of RAC will be described from the following several aspects: absorption, chloride permeability, freezing and thawing resistance, carbonation, the sulfate corrosion resistance, drying shrinkage, creep and abrasion resistance. This paper expounded the present situation and progress in the study of the durability of recycled aggregate concrete.Then, some key technical problems needed to be studied were pointed out and many suggestions were put forward.

In this study, the influence of nanosilica hydrosols and rice husk ash (RHA) on the compressive strength, chloride permeability, electrical resistivity and capillary absorption of single and binary blended mortars was investigated. Results showed that the incorporation of nanosilica improved mortar performance, while RHA did not have a significant influence and mainly attributed to lower strength and durability at early ages. It was found that the addition of RHA in mixes containing nanosilica, dramatically decreased compressive strength at ages of 3 and 7 days. However, binary mixtures displayed the best results for strength development and durability at ages of 28 and 90 days.

Microcracking has been suspected of influencing the transport properties and durability of concrete structures, but the nature and extent of this influence is unclear. This paper focuses on the influence of drying-induced microcracking. Samples were prepared with sample thickness/maximum aggregate size (t/MSA) ratios ranging from 2 to 20 and dried to equilibrium at 105 °C or 50 °C/7% RH or 21 °C (stepwise: 93% RH → 55% RH) prior to characterisation of microcracks and transport tests. Results show for the first time that there is a significant size effect on microcracks and transport properties. Samples with smaller t/MSA had more severe microcracking and higher gas permeability. Gas permeability decreased with increasing t/MSA (for a decreasing MSA), and remained constant beyond t/MSA of 10. However, this size effect was not seen on gas diffusivity and sorptivity. The implications of these findings particularly regarding the influence of drying-induced microcracks on the durability of concrete structures are discussed.

The effect of added carbon black to concrete mix on corrosion of steel reinforcement was studied. This was achieved by inserting steel bars in different concrete mixes containing 0.1, 0.2, 0.3, 0.4, and 0.5, carbon black/cement. Samples were cured, immersed in 3.5% chloride solution for 6 months. Chloride permeability and corrosion rates were measured. Tests showed that corrosion rate and chloride ions penetration decreased with increased carbon black content. This was expressed due to filling effect of very fine particles of carbon black and was in the order less than 250 nm.

This paper aims to evaluate the effectiveness of different crystalline coating materials concerning of chloride ions penetration. The concrete ages at the coating installation and its moisture conditions were addressed; where, these two factors may play a dominant role for the effectiveness of the used materials. Rapid chloride ions penetration test (RCPT) was conducted at different ages and moisture conditions according to the relevant standard. In addition, the contaminated area and the penetration depth of the chloride ions were investigated immediately after the RCPT test using chemical identifier, 0.1 M silver nitrate AgNO3 solution. Results have shown that, the very low chloride ions penetrability, for the studied crystallization materials, were investigated only with the old age concrete (G1). The significant reduction in chloride ions’ penetrability was illustrated after 7 days of installing the crystalline coating layers. Using imageJ is more reliable to describe the contaminated area of chloride ions, where the distribution of aggregate and heterogeneous of cement mortar was considered in the images analysis., {"references":["M. Baykal, Carrasquillo, R.L. and Fowler, D., Implementation of Durability Models for Portland Cement Concrete into Performance-Based Specifications, Research Report 1706-4, Center for Transportation Research, Austin, TX, 2002.","B.Z. Savas, Effects of microstructure on durability of concrete, North Carolina State University, Ann Arbor, 2000, p. 190.","M.V. Diamanti, A. Brenna, F. Bolzoni, M. Berra, T. Pastore, M. Ormellese, Effect of polymer modified cementitious coatings on water and chloride permeability in concrete, Construction and Building Materials 49 (2013) 720-728.","R.N. Swamy, S. Tanikawa, An external surface coating to protect concrete and steel from aggressive environments, Mater Struct 26(8) (1993) 465-478.","BS EN 1504, Products and systems for the protection and repair of concrete structures, EN 1504 Part 2: Surface protection systems for concrete, BSI, www.bsigroup.com, 2004, p. 50.","L. Bertolini, B. Elsener, P. Pedeferri, R.P. Polder, Surface Treatments, Corrosion of Steel in Concrete, WILEY-VCH Verlag GmbH & C o. KGaA, Weinheim2004, pp. 231-248.","ASTM C1202-12, Standard Test Method for Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration, ASTM International, West Conshohocken, PA, 2012, www.astm.org, 2012, p. 8.","BS EN 206-1:2000, Concrete. Specification, performance, production and conformity, BSI, www.bsigroup.com, 2000, p. 74.","ASTM C494/C494M-15, Standard Specification for Chemical Admixtures for Concrete, ASTM International, West Conshohocken, PA, 2015, www.astm.org, 2015, p. 10.\n[10]\tF. He, C. Shi, Q. Yuan, C. Chen, K. Zheng, AgNO3-based colorimetric methods for measurement of chloride penetration in concrete, Construction and Building Materials 26(1) (2012) 1-8.\n[11]\tQ. Yuan, C. Shi, F. He, G. De Schutter, K. Audenaert, K. Zheng, Effect of hydroxyl ions on chloride penetration depth measurement using the colorimetric method, Cement and Concrete Research 38(10) (2008) 1177-1180.\n[12]\tM.H. Morteza Haeri, ImageJ Plugin for Analysis of Porous Scaffolds used in Tissue Engineering, Journal of Open Research Software 3(1):e1 (2015) 4.\n[13]\tP.F. McGrath, R.D. Hooton, Re-evaluation of the AASHTO T259 90-day salt ponding test, Cement and Concrete Research 29(8) (1999) 1239-1248.\n[14]\tA.R. Mohamed, W.W. El-Nadoury, M.T. Ayyob, Generalized Chloride Permeability Test for Blended and Nonblended Concrete, ACI Materials Journal V. 111, No. 3 (2014).\n[15]\tV. Baroghel-Bouny, P. Belin, M. Maultzsch, D. Henry, AgNO3 spray tests: advantages, weaknesses, and various applications to quantify chloride ingress into concrete. Part 1: Non-steady-state diffusion tests and exposure to natural conditions, Mater Struct 40(8) (2007) 759.\n[16]\tV. Baroghel-Bouny, P. Belin, M. Maultzsch, D. Henry, AgNO3 spray tests: advantages, weaknesses, and various applications to quantify chloride ingress into concrete. Part 2: Non-steady-state migration tests and chloride diffusion coefficients, Mater Struct 40(8) (2007) 783.\n[17]\tV. Baroghel-Bouny, M. Dierkens, X. Wang, A. Soive, M. Saillio, M. Thiery, B. Thauvin, Ageing and durability of concrete in lab and in field conditions: investigation of chloride penetration, Journal of Sustainable Cement-Based Materials 2(2) (2013) 67-110."]}

A comparison was made between the impact of raising the thermostatic temperature and the impact of prolonging the thermostatic time on the performance of steam-cured concrete containing a large portion of fly ash (FA) or ground granulated blast furnace slag (GGBS) by analysing the form removal strength, chemically combined water content, reaction degree, strength development, chloride permeability, and volume stability. For the materials and test conditions reported in this study, raising the thermostatic temperature is more favourable for concrete containing FA, as indicated by the significantly higher form removal strength and the higher growth of reaction degree of FA compared with prolonging the thermostatic time. With an increase in the thermostatic temperature, the hydration degree of a binder containing FA or GGBS initially increases and subsequently decreases. Although concrete containing FA can obtain satisfactory form removal strength with steam curing at 80°C, the late strength development of concrete containing FA is slow for the same curing conditions. The effect of the late performance of resistance to chloride ion permeability improved by FA is better than the effect improved by GGBS. The risk of destroying the structure of concrete containing a large portion of FA or GGBS due to delayed ettringite formation (DEF) is minimal when specimens were steam-cured at 80°C.

In this study, the influence of nanosilica hydrosols with specific surface areas of 100 m 2 /g, 200 m 2 /g and 300 m 2 /g and silica fume with specific surface area of 21 m 2 /g on chloride permeability and electrical resistivity of concrete is investigated. The results indicate that the nanosilicas, especially at higher replacement levels, enhanced the chloride and electrical resistance of concrete at early ages, while silica fume did not have a significant influence on these characteristics at early ages. The results also show that the nanosilicas with lower surface areas had better performance in enhancing the chloride and electrical resistance of concretes compared to the finer ones, especially at 28 days and 90 days. Silica fume achieved a similar performance to the best performing nanosilica at 28 days and surpassed it at 90 days.

Ductile self-compacting concrete (DSCC) is one of the advanced materials which combines self-compacting abilities and ductility to address the current industry problems. As the fly ash and microwave incinerated rice husk ash (MIRHA) are beneficial to the properties of concrete, it has led to a research on the effects of ternary blends of MIRHA, fly ash and cement in DSCC. Up to 20% of cement in DSCC was replaced with MIRHA and fly ash with 10% by weight respectively whilst maintaining satisfactory self-compacting abilities. The effects of MIRHA and fly ash on mechanical strength and chloride penetration depth of DSCC were determined. The control DSCC mix was compared with the DSCC mix with MIRHA and fly ash. The results shown that substitution of MIRHA and fly ash into DSCC gave positive effects, it improved the mechanical properties and chloride permeability.

Durability means the resistance to physical or chemical deterioration of concrete resulting from interaction with environment (physical deterioration) or interaction between constituents (chemical deterioration) of concrete. A durable concrete ensures corrosion resistance of embedded steel which in turn ensures a better longevity of the structure as a whole. Concrete in structures in the coastal areas are the most susceptible to chemical deterioration as sea water, with high concentration of chloride ions, has quite a detrimental effect on durability of concrete. In these cases, the lower the chloride permeability, the better the durability of concrete. As instruments for standard chloride permeability test is very expensive, an experiment has been conducted to carry out Rapid Chloride Permeability Test (RCPT) using improvised apparatus made of readily available low-cost materials. Several RCPT tests were performed using this simple method and results showed marked variation in chloride permeability for concrete with different quality.

In this paper, the durability properties of self-compacting concrete (SCC) containing rice husk ash (RHA), metakaolin (MK) and a combination of MK and RHA (1:1 ratio) were evaluated and their relationships discussed. The durability properties of the various mixtures were studied. The results showed that SCC blended with RHA and a combination of RHA and MK showed a considerable improvement in durability than unblended SCC (100% OPC). However, the performance of SCC blended with MK was unsatisfactory in an acid environment. In addition, it was found that resistance to acid attack was directly related to the silica ratio (SR).

The influence of high-temperature curing on the compressive strength and chloride permeability of the concrete containing ground iron and steel slag (GISS) was investigated. Under standard curing condition (20°C), the early-age compressive strength of the concrete with GISS is much lower than that of the pure cement concrete. The activity of GISS is more sensitive to the increase of curing temperature than that of cement. The increase amplitude of early-age strength of the concrete with GISS is much greater than that of the pure cement concrete by increasing curing temperature. Increasing curing temperature tends to decease the late-age strength and enhance the late-age permeability of concrete. The negative effect of increasing curing temperature on the late-age properties of the concrete with GISS is smaller than that of the pure cement concrete.

Surface treatment on the concrete surface using sealers reduces the rate of permeability of chloride and moisture through the concrete. The delaying of onset of corrosion is evaluated for surface treated and untreated concrete using electrochemical techniques. After conducting rapid chloride permeability test (RCPT), using Nernst–Plank equation, the diffusion coefficient of chloride ( D eff ) is calculated. Substituting threshold chloride concentration of rebar ( C th ) from cyclic polarization test in the ficks second law, the time to initiation of corrosion ( T i ) is arrived. From the results it is found that the treated concrete with alkyltrialkoxy silane sealer delays the onset of corrosion by four times than that of untreated concrete.

In this paper, effect of steam and water curing on the compressive strength development and transport properties such as water sorptivity, rapid chloride ion permeability, and gas permeability of concretes containing various volumes of lightweight fly ash aggregate (LWA) were investigated. In production of concrete, a fixed amount of lightweight coarse (LWCA) aggregate plus varying amounts of lightweight fine aggregate (LWFA) were used. Utilization of LWFA was achieved by volumetric substitution of fine aggregate with five different replacement levels namely, 0%, 25%, 50%, 75%, and 100%. Therefore, five different concrete mixtures were produced for this experimental study. The produced concretes were divided into two parts one of which was initially steam cured while the other was directly exposed to water curing. After initial steam curing regime, the steam cured (SC) concretes were also transferred to water until testing Mechanical properties of concretes were monitored through compressive strength development over 56 days, while transport properties were measured by means of water sorptivity, gas permeability and rapid chloride permeability tests conducted at 28 and 56 days. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.

The chloride diffusion coefficients of different water-binder ratio high performance concrete (HPC) subjected to different one-way loads，freeze-thaw cycles and different standard curing ages were measured by electro-migration (RCM) tests and the results were analyzed. The test results indicate that with the increase of one-way load, its influence on the chloride permeability of different water-binder ratio HPC rises in the same proportion. The influence of the curing age on the chloride permeability of HPC will decrease with the reduction of the water-binder ratio of HPC. Under the same freeze-thaw cycle conditions, the relationships between chloride diffusion coefficients of different water-binder ratio HPC and curing ages are nearly suitable to power function.

In this paper, the Rapid Chloride Permeability Test (RCPT)-ASTM C1202-91 and Conductance test were employed to measure the effect of curing time on the chloride penetration resistance of concrete. The results indicate that the concrete specimens with longer curing time have higher chloride penetration resistance no matter the concrete with or without mineral admixtures, the concrete conductance has the similar variation trend and similar mathematical descriptions as the chloride diffusion coefficient D with the passage of curing time, and it is a very useful method to measure concrete conductance to estimate the chloride permeability variation at different curing or exposure time.

In this paper, the effect of pore structure on the chloride ions ingress into concrete was investigated. The most probable diameter was measured by Mercury intrusion porosimetry (MIP) and the total porosity was measured by evaporative water method (EWM). The results indicate that the most probable diameter by MIP has better linear relationship with chloride diffusion coefficient than the total porosity by EWM, the most probable diameter has significant influence on chloride diffusivity, and the smaller most probable diameter will lead to higher chloride penetration resistance.

A concrete surface was treated by in situ synthesised super-absorbent resin (SAR) of poly(acrylic acid-co-acrylamide). Experiments aimed at determining the resistance to carbonation and the chloride permeability of SAR-treated concrete compared with control concrete specimens were conducted. The corrosion risk and corrosion rate for the rebar embedded in SAR-treated and control concrete specimens at various periods of carbonation were evaluated through the accelerated corrosion test, wherein the rebar was subjected to 3·5% sodium chloride solution. The results show that the resistance to carbonation and chloride permeability of SAR-treated concrete is higher than that of control concrete, and that the corrosion risk and corrosion rate of steel embedded in SAR-treated concrete is smaller than that of steel in control concrete. Lighter carbonation can effectively decrease the chloride permeability of concrete, but serious carbonation is harmful to the long-term maintenance of the passive film of steel in concrete.

This paper presents a portion of a state highway agency pooled fund research project to develop performance criteria for concrete that will be resistant to penetration of chlorides, cycles of freezing and thawing, and sulfate attack. This paper presents the portion of the study pertaining to penetration of chlorides. To simulate standard and service conditions, specimens were subjected to either immersion or to a cyclic wetting and drying exposure in chloride solution. Measured apparent chloride diffusion coefficients, determined in accordance with American Society for Testing and Materials (ASTM) C1556, were correlated with results of rapid index test methods that provide an indication of the transport characteristics of concrete. Rapid index test methods included were rapid chloride permeability, rapid migration, conductivity, absorption, and initial and secondary sorptivity. A set of rapid index test methods and specification criteria that can reliably classify mixtures based on their resistance to chloride ion penetration are proposed.

Rapid chloride permeability test (RCPT) is one of the widely used test methods to rapidly assess the durability of concrete, specifically its resistance against chloride ion penetrability. Many researchers have questioned the applicability of RCPT in mixes having supplementary cementitious materials (SCMs). The present work analyses the performance of RCPT in concretes that contain different dosages of three SCMs such as slag, Class F fly ash and Class C fly ash. In addition to the conventional measurements of current at half an hour interval, other details of the tests such as initial current, temperature development during the experiment, and depth of chloride ion penetration are also measured. Good correlations are obtained between total charge passed and other additional measurements such as initial current, depth of chloride ion penetration, temperature reached during the experiment etc., which are reported by other researchers with mixes having only OPC as binder. Furthermore, the results of RCPT are well correlated with the results of Wenner 4-probe surface resistivity test, which is free from many of the criticisms of RCPT. The paper concludes that RCPT can be used as a reliable accelerated test method to assess chloride ion penetrability in concretes that have supplementary cementitious materials such as fly ash and slag.

This paper presents the results of an experimental investigation carried out to evaluate the influences of curing methods and mineral admixtures on the strength and chloride permeability of concrete. Rapid chloride ion penetration tests (ASTM C 1202) were used to measure the chloride permeability of concrete. Test results indicated that steam curing decreased the 28 days compressive strength of plain concrete by 11 %. Incorporating slag, fly ash, and silica fume can significantly mitigate this harmful consequence. After autoclave curing however, all concrete’s strength exceeds 80 MPa. Steam and autoclave curing increase the electrical charge passed through plain cement concrete by 110 and 224 %, respectively, when compared with normal curing. For steam curing, incorporating silica fume is the most efficient means to reduce the chloride permeability of concrete. For autoclave curing however, incorporating 30 % fly ash is the most efficient means to reduce chloride permeability.

In this work, the effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties and durability of ultra high strength concrete (UHSC) is reported. First, the MWCNTs were dispersed by a nano sand-mill in the presence of a surfactant in water. The UHSC specimens were prepared with various amounts of MWCNTs, ranging from 0% to 0.15% by weight of cement (bwoc). Results indicated that use of an optimal percentage of MWCNTs (0.05% bwoc) caused a 4.63% increase in compressive strength and a 24.0% decrease in chloride diffusion coefficient of UHSC at 28 days curing. Moreover, the addition of MWCNTs also improved the flexural strength and deformation ability. Furthermore, a field-emission scanning electron microscopy (FE-SEM) was used to observe the dispersion of MWCNTs in the cement matrix and morphology of the hardened cement paste containing MWCNTs. FE-SEM observation revealed that MWCNTs were well dispersed in the matrix and no agglomerate was found and the reinforcing effect of MWCNTs on UHSC was thought to be pulling out and microcrack bridging of MWCNTs, which transferred the load in tension.

This chapter addresses the subject of marine concrete structures with reference to marinas in the Arabian Gulf region. The emphasis is on the durability and long-term performance of these structures. The first part of this chapter provides the reader with information on the development of marine concrete structures in the Arabian Gulf, including the historical background, the challenges of executing the construction in this environment and the types of marine structures used for marinas in the Arabian Gulf region. In the second part of the chapter, a case study of a significant marina is presented in which the measures implemented to ensure the long-term durability of the reinforced concrete elements are presented with regard to the durability specification, concrete mixture, service life predictions and quality assurance procedures adopted on site. The monitoring and results of the durability testing conducted on site are presented and discussed. Rapid chloride permeability (RCP) testing, carried out in accordance with ASTM C1202–05, was specified for precast concrete wall projects situated on the coast of Abu Dhabi in the Arabian Gulf, to provide a rapid indication (within 28 days) of resistance to the penetration of chloride ions and serve as an indicator of the potential durability of the concrete. This second part of the chapter describes how the service-life of the concrete was predicted, making allowance for the Arabian Gulf conditions (temperature and salinity), using the UCT service-life model. It describes how acceptable limits were set for the RCP test and compares these with the values obtained from testing on site. The RCP test results failed to meet the specification early during construction, and an investigation was undertaken into the reasons for the high RCP test values. This case study confirms that quality control testing using the RCP test is effective and appropriate for use in concrete durability specifications.

In this paper, the influence of steel slag on the compressive strength, permeability to chloride ion and carbonation resistance of steam-cured concrete was investigated. The results show that for steam-cured concrete with water to binder ratio (W/B) of 0.45, replacing 30% of cement by steel slag tends to decrease its compressive strength, increase its chloride permeability and weaken its carbonation resistance. But the properties of steam-cured concrete with steel slag can be improved by decreasing the W/B. When the W/B of concrete containing 30% steel slag is 0.38, its strength, chloride permeability and carbonation resistance are all very close to that of pure cement concrete with W/B of 0.45 under steam curing condition.

This paper presents the results of a study conducted to evaluate the corrosion resistance of self-compacting concrete (SCC) prepared using quarry dust powder (QDP), silica fume (SF) plus QDP or fly ash (FA). SCC specimens were prepared and tested for corrosion resistance, chloride permeability and chloride diffusion. The results indicated that the time to initiation of reinforcement corrosion in M4 (8% QDP plus 5% SF and w/c = 0.4) specimens and M2 (8% QDP and w/c = 0.38) specimens was more than that in M5 (30% FA and w/c = 0.4) specimens. The corrosion current density on steel in the SCC specimens was very low in the initial stage of exposure to 5% NaCl solution and it increased with increasing period of exposure. Corrosion activation was noted on steel in M1, M3, and M5 specimens. However, it was not noted in M2 and M4 specimens even after 990 days (33 months) of exposure. The chloride permeability in SCC specimens incorporating QDP or FA was moderate and it was low in the specimens incorporating QDP plus SF. The lowest diffusion coefficient was noted in M2 specimens while it was the highest in M5 specimens.

In the present research work, investigations were carried out to improve the performance of concrete in terms of strength and resistance to chloride-ion-penetration by incorporating metakaolin (MK) as mineral admixture in concrete. Parametric study was carried out by considering w/cm ratio, various percentage of MK and age of concrete as parameters to understand the effect of each parameter. The study was conducted for different water-to-cement metakaolin ratio (w/cm) ratios of 0.32, 0.35, 0.4 and 0.5. The MK proportion was varied from 0 to 15% with an increment of 5% and ages of concrete from 3 to 90 days were considered and experiments performed accordingly. The effects of above said parameters on the various properties of concrete such as workability, compressive strength, chloride penetrability (Rapid chloride permeability test as per ASTM C 1202), pH of concrete and depth of penetration of chloride ions were investigated, and the results of MK concrete were compared with the conventional concrete. From the results, it was observed that MK concrete showed greater strength for higher w/cm ratios (0.4 and 0.5) and its resistance to chloride ion penetration was more or less consistent for all w/cm ratios and the optimal amount of MK resulted significant reduction in chloride ion penetration. A Multiple non-linear regression analysis was used to develop a statistical model to predict the strength and found to have good correlation between the observed and predicted values. It was concluded that the concrete developed in this study have significant potential for use on real time projects.

The effect of ground granulated blast-furnace slag (GGBFS) and silica fume (SF) on the chloride migration through concrete subjected to repeated loading was examined. Portland cement was replaced by 20%, 30%, 40% GGBFS and 5%, 10% SF, respectively. Five times repeated loadings were applied to specimens, the maximum loadings were 40% and 80% of the axial cylinder compressive strength (f′c), respectively. Chloride migration through concretes was evaluated using the rapid chloride migration test and the chloride concentration in the anode chamber was measured. The results indicate that the transport number of chloride through concrete containing 20% and 30% GGBFS replacements and 5% and 10% SF replacements is lower than that of the control concrete, but 40% GGBFS replacement increases the transport number of chloride. Five loadings at 40% f′c or 80% f′c increase the transport number of chloride for all mixes investigated in this study. 5% SF replacement has a very close effect on the chloride permeability of concrete with 20% GGBFS when concrete is subjected to 40% f′c or 80% f′c.