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Now days where being expenses is increased and abundant waste material is produced by stone processing units, it is necessary to have certain knowledge where economical substitutes in concrete can resolve this issue of waste materials. Mechanical and Durability properties of concrete are studied here when sand and cement are substituted for quartzite rock dust up to 70 percent and 40 percent. Compressive and Flexural Strength test were being carried out for different concrete samples of embedded quartzite rock dust at age of 7 and 28 days. Rapid chloride permeability test (RCPT) as per ASTMC1202 were being performed on various cylindrical concrete specimens cured at 28 days. Total Charge passed value unbelievably decreased with addition of quartzite rock dust suggesting that its accumulation improve concrete durability.

Various challenges encountered in the construction industry has led to the production of concrete, with not just high strength, but also with enhanced durability properties. Several research works have been carried out using replacement of constituent materials and introduction of various admixtures in concrete. Alccofine is one of such promising micro fine material. This study investigates the performance of hardened concrete using nano materials. Effects of alccofine (AL) and zinc oxide (ZnO) on the durability and strength of hardened concrete were explored. Series of tests were conducted by substituting cement by weight with 10% AL and adding ZnO in proportions, 0.25%, 0.5%, 0.75% and 1%. Based on the results obtained, the strength properties of concrete reduced as cement replacement level rose beyond 10%. The durability performance of the concrete, in terms of rapid chloride permeability, water permeability test, sea water attack and chloride resistance, was within acceptable limist, even as the ZnO was increased. This study has generally proposed a sustainable solution to produce durable concrete that could have useful aaplication in the construction industry.

Antimony (Sb) is a trace element applied widely in modern industry. A large number of tailing solid wastes are left and accumulated in the mining area after purifying the precious antimony from the antimony ores, causing serious pollution to the environment. The major aim of this study is to investigate the feasibility of utilizing antimony tailing coarse aggregate (ATCA) as a complete substitute for natural coarse aggregate (NCA) in high-strength concrete. Concrete specimens with 25%, 50%, 75%, and 100% ATCA replacing the NCA in conventional concrete were prepared for evaluating the performance of ATCA concrete. The investigators find that ATCA concrete has good workability, and the mechanical properties and long-term behavior (shrinkage and creep) of ATCA concrete with all replacement levels are superior to those of NCA concrete. The durability indices of ATCA concrete, such as the frost-resistant, chloride permeability, and resistance to carbonation, are better than those of NCA concrete. While the alkali activity and cracking sensitivity behavior of ATCA concrete seem to be decreased, nevertheless, the difference is not significant and can be neglected. The researchers demonstrate that all of the control indices of ATCA concrete meet the requirements of the current industry standards of China. Overall, ATCA can be used in concrete to minimize environmental problems and natural resources depletion.

It has been proven by various studies that adding silica fume (SF) alone or nano-silica (NS) alone can provide significant beneficial effects on the durability of concrete. In theory, SF and NS may also be added together, but up to now, such possible combined usage of SF and NS for improving the durability of concrete, especially the sulphate and chloride resistance, has not been deeply explored. In this paper, the individual and synergistic roles of SF and NS in the sulphate and chloride resistance of concrete were investigated by producing a series of concrete mixes containing varying SF, NS and water contents for strength test, sulphate attack test and rapid chloride permeability test. It was found that the combined addition of SF and NS can further enhance the sulphate and chloride resistance to higher than possible with the single addition of SF or NS. From the experimental results, the cementing efficiencies of SF and NS were evaluated, from which it was revealed that there exist certain synergistic effects offered by the combined addition of SF and NS on the sulphate and chloride resistance.

In this paper, effects of natural pozzolan, called Chekneh, as a part of cement replacement and wood chips as a part of mixture aggregates on the mechanical and durability properties of concrete were studied. Nine concrete mixtures proportions within two categories were prepared. In the first category, the properties of concrete were evaluated by adding 10 and 15% of Chekneh pozzolan or wood chips and the second category containing combination of Chekneh pozzolan and wood chips was prepared. The results showed that adding optimal content of natural Chekneh, 10% of cement weight replacement to concrete improves the mechanical properties including flexural, compressive and tensile strength and durability properties of concrete including volumetric water absorption, electrical resistance and rapid chloride permeability. Also, the replacement of 10% wood chips as a part of aggregates causes improvement in mechanical properties of concrete. The combined effect of natural pozzolan and wood chips has the most positive effect on increasing the compressive, tensile and flexural strength in concrete, and the sample which contains 10% pozzolan and 10% wood chips has the most improvement compared to the control sample.

Carbonation treatment was recently developed to enhance the properties of recycle concrete aggregate and prepared concrete, but the durability of concrete with carbonated recycled aggregate have received little consideration in the previous studies. This study investigates the chloride permeability and the resulting steel corrosion of concrete with carbonated recycled fine and coarse aggregates, and the effects of recycled aggregate quality on chloride permeability are presented. The carbonization treatment was first applied to recycled aggregate to prepare carbonated recycled aggregate; then, the chloride permeability and steel corrosion experiments were conducted on concrete with carbonated recycled aggregate. The results exhibit that carbonation treatment improves the physical performance of recycled aggregate, which results in an increase in the compressive strength of preparing recycled concrete. Concrete with carbonated recycled aggregate has a lower chloride permeability than that with non-carbonated recycled aggregate, and the improvement in the chloride permeability resistance is more obvious for concrete with carbonated recycled fine and coarse aggregates. In particular, the improvement of chloride permeability resistance becomes more distinct with the reduction of recycled aggregate quality. The addition of carbonated recycled aggregate reduces the steel corrosion risk of reinforced recycled aggregate concrete, and the chloride permeability and steel corrosion risk follow a linear trend.

The objective of this study was to determine the utilization potential of Spray Dryer Absorber Material (SDAM) as an additive in concrete made with portland cement. Utilizing SDAM for beneficial use such as portland cement replacement reduces the CO2 impact for every cubic meter of concrete placed, and provides a means for utilities to avoid the impacts of landfilling. The utilization of SDAM in concrete is often avoided due to delay in setting time, i.e. early-age strength-gain, and expansion related durability issues. The study included SDAM collected from five different coal combustion utilities. A series of laboratory experiments were conducted on the fresh and hardened concrete made by replacing 20 wt% of the portland cement. The findings of this research demonstrates that despite slow strength gain at early ages, a 20 wt% replacement of portland cement yielded a concrete that met the desirable 28-day performance criteria. Additionally, the incorporation of SDAM containing elevated levels of fly ash content improved the resistance to chloride permeability, and autoclave expansion resistance of concrete. These results provide evidence against the stigma of poor durability when using SDAM in concrete.

The durability of concrete cast near the conventional formwork (steel or wood) is reduced because of higher water-cement (w/c) ratio as compared with the concrete present in the core of the member. Various controlled permeability formwork (CPF) liners absorb or drain out excess water near formwork, can reduce the increase in w/c ratio of concrete near the formwork. This paper presents a quantitative study showing improvement in the properties of near surface concrete (NSC) by the use of a commercially available CPF liner, and comparing the performance of more easily available and cheaper alternatives to CPF liner used. Two types of concrete mixes with identical w/c ratio but different water contents were used. Three specimens were made for each of the two types of concrete mix and one surface for each of the specimen was cast using one of the CPF liners among a commercially manufactured CPF, particle board, and gunny bag. Four tests: Rapid chloride permeability test, AgNO3 colorimetry test, initial surface absorption test and pull off test were performed to study durability properties of NSC. Study of physical appearance in terms of blowholes and grey area on the concrete surface using image processing is also presented in the paper. Though commercially manufactured CPF produces better surface than the particle board and gunny bag, the improvement in NSC properties by use of gunny bag is also noteworthy.

The main cause of reinforced concrete deterioration is chloride attack. Chloride ions penetrated into the concrete can destroy the passive layer around steel reinforcement provided by the high alkalinity and low pH of cement paste, activating electrochemical corrosion. Durable concrete gives more corrosion resistance of embedded steel that continuously ensures a stronger long life of the reinforced concrete structure. The concrete structures within the seashore areas allow chloride ions to easily penetrate into the concrete and reduce the life span of the structure. In this paper, the rapid chloride permeability test (RCPT) as per ASTM C1202 is presented to determine the chloride profile, concrete chloride resistivity and rate of corrosion. The specimens were prepared with concrete incorporating three different type fibres including steel, E-waste copper wire and E-glass fibres of 1.0% by volume of concrete. The RCPT was conducted for time period of 28 days, 56 days and 90 days. The final RCPT results of fibre-reinforced concrete mix with control mix concrete were compared. The test result shows that the E-glass fibre-reinforced concrete was more durable than the other concrete mixes.

It is well known that aggressive environments like the sulfate attack are the major factor affecting the durability of concrete. Thus, this research was carried out to estimate the durability of rice husk ash (RHA) concrete exposed to sodium sulfate attack through wetting and drying cyclic. Five levels of cement replacement namely 0, 10, 20, 30 and 40% (by weight) were studied. After being kept in the sodium sulfate solution for 3, 7, 28, 56, 90 and 180 days, the RHA concrete specimens were evaluated based on the rapid chloride permeability and its correlation. It was found that the total charge passed in Portland cement concrete was higher than that of RHA-blended cement concrete. However, it continued to decrease along with increasing levels of RHA replacement. In addition, the use of 40% RHA in the cement resulted in better resistance to sulfate attack when the concrete specimen was exposed to the wetting and drying cycles. It can be concluded that the use of 10 to 40% RHA effectively decreased the penetration depth (charge passed) in the concrete under sulfate attack.

The main focus of this study is to investigate the pozzolanic attribute of the recycled waste glass powder used as cement replacement. A coarser glass powder (

Herein, a new geopolymer is recognized as a potential alternative cementing material of ordinary Portland cement (OPC), which is used for reducing carbon emissions and efficiently recycling the waste. Therefore this paper mainly studied the alkali-activated coal gangue-slag concrete (ACSC) was prepared by using the coal gangue-slag and Na2SiO3 and NaOH complex activator. The ratio of coal gangue (calcined and uncalcined) coarse aggregate replacing the gravel was 0%, 30%, 50%, 70%, and 100%. The water and salt freeze-thaw resistance, compressive strength, chloride permeation, microstructure, performance mechanism, inner freeze-thaw damage distribution, and mechanics models of ACSC were investigated. Results show that ACSC displayed excellent early age compressive strength, and the compact degree and uniformity of structure were better compared with the ordinary Portland cement (OPC) when the coal gangue replacement rate was less than 50%. The ACSC demonstrated the best chloride penetration resistance under 30% uncalcined coal gangue content, which was less than 27.75% lower than that of using OPC. At the same number cycles, especially in the salt freezing, the calcined coal gangue had lowered advantages of improving resistance freeze-thaw damage resistance. Water and salt accumulative freeze-thaw damage mechanics models of ACSC were established by using the relative dynamic elasticity modulus. The exponential function model was superior to the power function model with better precision and relativity, and the models accurately reflected the freeze-thaw damage effect.

Many researches has been carried out regarding the possible reuse of the waste materials like marble and granite powder in a economical and eco-friendly manner. The use of marble and granite products waste is identified as a substitute to cement in mortar mix to an option that come up with concrete products in a cheaper cost in the construction industry. In the sustainable point of view, an experimental study is conducted on the cement mortar with the replacement ratio of 0%, 5%, 10%, 15%, 20%, 25% and 30% of marble powder and granite powder in the cement content to examine the durability properties. For this durability study, the mortar disc specimens of dimensions 80 mm × 50 mm are prepared, cured for a period of 28 days and tested for rapid chloride permeability test. The experimental results are showing that the granite powder replaced mortar is moderately better than marble powder replaced mortar. The optimum replacement is found as 5% for marble dust and 10% for granite powder, since the penetration is low based on the experimental results.

Durability of concrete designed for radiation shielding structures is an important issue in nuclear power plant safety. An investigation of the permeability of concrete containing heavyweight aggregates and water-bearing aggregates was performed with respect to gaseous and liquid media. Mix design was developed using Portland and slag cement, crushed magnetite and serpentine aggregate. The use of slag cement in concrete containing magnetite and serpentine aggregates resulted in the substantial improvement of the compressive strength in comparison with Portland cement concrete. The application of slag cement was found to reduce the chloride ingress, regardless of the special aggregate use. The coefficient of chloride migration was within the range 5 ÷ 8 × 10−12 m2/s and 17 ÷ 25 × 10−12 m2/s for slag cement concrete and Portland cement concrete, respectively. At the same time, the carbonation depth was increased twice for slag cement concrete in comparison to Portland cement concrete. However, the maximum carbonation depth after one year of exposure to 1% CO2 was only 14 mm for slag cement concrete, and 7 mm for reference concrete. The total pore volume evaluated using mercury intrusion porosimetry was influenced by the type of special aggregate used. It was shown that concrete with various contents of magnetite aggregate and slag cement achieved the smallest total pore volume. While serpentine coarse aggregate caused an increase in total pore volume in comparison to concrete with magnetite aggregate.

This paper presents the long-term durability performance of semi-lightweight concrete containing various levels of supplementary cementing materials (SCM) and steel fibers when exposed to a harsh marine environment for up to 25 years. Concrete specimens (305 × 305 × 915 mm [1 × 1 × 3 ft.]) were casting using W/CM in the range of 0.26 to 0.60. The depth of chloride penetration was greater than 90 mm (3.5 in.) for all the control specimens (without fly ash and silica fume). However, mixes containing both silica fume and fly ash (with W/CM ranging from 0.40 to 0.60) performed very well resulting in chloride penetration of approximately 40 mm (1.6 in.) during the same period. The results from the chloride permeability testing also indicate significant increases in the resistance to chloride-ion penetration for ternary concrete containing fly ash and silica fume.

An experimental study on the durability of thermal insulation concrete with recycled aggregates (RATIC) subjected to the combined action of chloride salt erosion with 3.5% NaCl solution and freeze-thaw cycles (referred to as salty F-T cycles) has been carried out. In this study, the volume of the natural coarse aggregates has been replaced by recycled coarse aggregates (RCA) at replacement rates of 0%, 30%, 50%, 70%, and 100%. The results show that thermal insulation aggregate glazed hollow beads (GHBs) had a positive effect on the durability of concrete and RCA had an enormous negative influence on the durability of RATIC exposed to the salty F-T cycles. After 100 salty F-T cycles, the relative dynamic modulus of the elasticity of samples with RCA was below 60% compared to at the start of the F-T cycles. RCA has a significant effect on the chloride permeability of RATIC compared to natural aggregates. This phenomenon was caused by the special multi-interfaces structure of RATIC that are the result of the old interfacial translation zones (ITZs). These aggravate frost damage and negatively affect the durability of concrete in the salty F-T cycles environment.

Portland cement concrete and fly ash concrete were subjected to the ASTM C1202 rapid chloride permeability test (RCPT). When the RCPT was complete, the chloride profiles of the specimens were determined by collecting concrete powder samples at controlling depths. Based on Faraday's laws of electrolysis, the mass of electrolysis deposition is directly proportional to the quantity of electricity (coulombs). This study showed a same phenomenon that a linear relationship was found between the charge passed during the RCPT and the total amount of chloride obtained from the chloride profile. The total amount of chloride in the specimen can be determined by measuring the 6 h charge passed from RCPT. The chloride profile can be obtained based on the measurement of charge passed and the surface chloride content. After the completion of the RCPT, additional step taken during the modified RCPT procedure entails measuring the surface chloride content. Based on the chloride penetration depth obtained from the chloride profile, a modified RCPT method was used to compute the chloride migration coefficient and assess the chloride permeability of concrete.

This paper presents the durability performance of concrete incorporating high-volumes of fly ash exposed to a harsh marine environment for 19 to 24 years. Concrete specimens (305 × 305 × 915 mm [1 × 1 × 3 ft.]) were cast using W/CM in the range of 0.31 to 0.46, various types of fly ash with replacement levels of 56 or 58%, and various types of normal density and lightweight aggregates. Surface erosion/scaling was seen on all specimens; the extent of erosion was slightly worse for fly ash concrete with normal density aggregate compared to the controls (without fly ash), but fly ash concrete with two of the three lightweight aggregates exhibited severe surface erosion. Laboratory testing included taking cores from each block and determining the existing chloride profile, compressive strength and “chloride permeability” (ASTM C1202). The depth of chloride penetration was found to be in excess of 100-mm (4 in.) for the concrete specimens without fly ash, whereas the presence of fly ash significantly decreased the depth of penetration to approximately 30 and 40 mm in specimens containing either normal density or lightweight aggregate, respectively. The increased penetration in the concrete with lightweight aggregates is attributed to the surface erosion observed with these concretes. The results from the chloride permeability testing also indicate significant increases in the resistance to chloride-ion penetration for fly ash concrete.

Influence of nanosilica and sugar cane bagasse ash (SCBA) on the mechanical and durability properties of mortar, is investigated in this study. Sixteen mortar mixtures were designed with a particular water to binder ratio of 0.485 and a sand to binder ratio of 2.75. Test specimens were prepared with 3% and 6% replacement of cement weight with nanosilica and a 10–30% replacement of cement weight with SCBA. A compressive strength test was applied to evaluate the mechanical performance of mortars containing nanosilica and SCBA. In addition, transport tests, chloride permeability, electrical resistivity and mercury intrusion porosimetry of single, binary, and ternary blended mortars were conducted to investigate the influence of replacement materials on durability properties of mortars. Nanosilica improved mechanical and durability properties of mortar, while SCBA did not have a substantial influence on mortar performance according to lower strength and durability at early ages. The addition of SCBA in mixtures containing nanosilica intensely decreased compressive strength at the ages of 3 days and 7 days. However, ternary mixture results showed the best performance in the long term.

Most of the states in our country have banned sand quarrying from the river beds, causing a scarcity of natural river sand for the construction sector. Manufacture sand (M-sand) is one of the alternate solutions to replace the river sand (R-sand) in concrete. The main aim of the present study is to evaluate the durability parameters of concrete with M-sand when compared to that of concrete with R-sand. Corrosion of reinforcement is one of the main deteriorating mechanisms of reinforced concrete due to the ingress of chloride ions or carbon-di-oxide. For comparative evaluation of durability parameters, accelerated tests such as Rapid Chloride Permeability Test, Rapid Chloride Migration Test and accelerated carbonation test were carried out on specimens of R-sand and M-sand. All tests were carried out after 90 days of casting. Test results reveal that the durability parameters of the concrete with M-sand in chloride induced environment is relatively better than that of concrete with R-sand and hence is recommended to use M-sand as a replacement to R-sand.

This study investigated the effects of nano rice husk ash (NRHA) and micro rice husk ash (MRHA) on chloride permeability, electrical resistivity, capillary absorption and compressive strength of mortars. It was found that the incorporation of NRHA and MRHA enhanced mortar performance in the long term, whereas NRHA contributed to considerable enhancements at both early and long-term ages. Results proved that the strength and durability properties of mortars containing NRHA up to 7.5% levels of replacement by weight of cement gradually enhanced in comparison with control mix. However, mortars incorporating 2.5% NRHA together with 12.5% MRHA demonstrated the best improvements for durability and strength development at the age of 90 days.

Since China hosted the Olympic Games in 2008, a mass of construction and demolition (C&D) wastes were produced with the rapid urbanization construction. Recycling the C&D waste into recycled aggregates (RA) is an effective method for reducing the amount of C&D wastes. Many studies on the properties of RA and the durability of recycled aggregate concrete (RAC) were conducted in China over the past decade. Due to the restrictions of various languages, some valuable studies on the durability of RAC are hard to be acquired by the scholars around the world. Therefore, this paper is developed to review the studies on the durability of RAC in China, and the shrinkage behavior, chloride permeability, carbonation behavior, and freeze-thaw resistance of RAC are, respectively, introduced. Considering the waste concrete, bricks, and ceramics used in preparing RA are frequently mixed together in China, this study proposes an index of average water absorption rate to quantify the effects of RA types, quality, and replacement percentages on the durability of RAC. Meanwhile, the relationship between the average water absorption rate of RA and the durability parameters of RAC is established. Finally, the improving methods of RAC durability are introduced, and the RA particle shaping and carbonation modification are emphasized.

Durability characteristics of self-compacting concrete (SCC) made with iron slag (IS) are presented in this paper. For this purpose, initially, a control SCC was designed, and then fine aggregates were partly (0, 10, 25 and 40%) replaced with iron slag. Various tests were done for fresh SCC properties, compressive strength and durability properties such as rapid chloride permeability, water absorption, resistance to sulphate attack and ultra-sonic pulse velocity up to the age of 365 days. SEM and XRD analysis was also carried out. The test result shows that SCC incorporating iron slag gives better strength and durability than control mixture of SCC, and can be suitably used in SCC.

For structural health monitoring, electrical resistivity measurement (ERM) method is commonly employed for the detection of concrete's durability, as indicated by the chloride permeability and the corrosion of steel reinforcement. However, according to previous experimental studies, ERM results are susceptible to significant uncertainties due to multiple influencing factors such as concrete water/cement ratio and structure curing environment as well as their complex interrelationships. The present study therefore proposes an XGBoost algorithm-based prediction model which considers all potential influential factors simultaneously. A database containing 800 experimental instances composed of 16 input attributes is constructed according to existing reported studies and utilized for training and testing the XGBoost model. Statistical scores (RMSE, MAE and R2) and the GridsearchCV feature are applied to evaluate and optimize the established model respectively. Results show that the proposed XGBoost model achieves satisfactory predictive performance as demonstrated by high coefficients of regression fitting lines (0.991 and 0.943) and comparatively low RMSE values (4.6 and 11.3 kΩ·cm) for both training and testing sets respectively. The analyses of the attribute importance ranking also reveal that curing age and cement content have the greatest influence on ERM results.

Chloride penetration frequently leads to a steel corrosion and reduces the durability of reinforced concrete. Although the previous studies have investigated the chloride permeability of recycled aggregates concrete (RAC), the chloride permeability of RAC with pre-damage received little considerations. Considering that the RAC may be subjected to various exposure environments, this paper focused on exploring the chloride permeability of RAC under the coupling effect of freezing-thawing, elevated temperature or mechanical damage. The freezing-thawing, elevated temperature or applied loading test was first employed to induce initial damage on RAC, and then the chloride diffusivity test was conducted on RAC with various pre-damages. The findings showed that the chloride permeability of RAC increased with increasing recycled coarse aggregate (RCA) content. Exposing to harsh environment, the incorporation of RCA increased the freezing-thawing, elevated temperature or mechanical damage of RAC. The chloride permeability increased with increased initial damage, and a good relation could be observed between them. The incorporation of RCA improved the sensitivity to the chloride permeability of RAC exposed to harsh environment; such as, the chloride diffusion coefficient of RAC with 100% RCA was 51.4% higher than that of the plain concrete without pre-damage, while the results were 233.3% and 62.1% after 75 freezing-thawing cycles and 80% fc.

[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.

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.

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.