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[EN] Over the past few years, the construction industry has sought to be more sustainable through use of more economically responsible materials and the use of environmentally friendly techniques such as bio-remediation. One promising area in this regard is that of surface treatments, particularly bio-repair techniques, to reduce the deterioration suffered by cement-based materials as a result of environmental conditions. This study presents original work on the use of silicaceous biodeposition by diatoms as a waterproofing surface treatment for recycled concrete. A recycled concrete mix containing a 50% substitution of recycled aggregates (RA) was used as a test substrate and the effectiveness of the bio-treatment was assessed using four different tests: capillary absorption, high-pressure water penetration, low-pressure water absorption and also characterised the biodeposited layer using SEM. Results demonstrate reductions of up to 33% in the capillary absorption test, while high-pressure water penetration decreased by 54.7%, compared to controls. In addition, Karsten tube tests showed low-pressure water absorption was delayed by up to 436 times relative to control samples. In combination these tests confirm the efficacy of diatom biodeposition as a protective surface treatment for cement-based construction materials. SI

Hydraulic road binders (HRB) are factory made blends which are composed of a substantial amount of supplementary cementitious materials and portland cement. Previous studies indicated that the use of chemical stabilizers containing supplementary cementious materials is a sustainable approach that can reduce carbon dioxide (CO2) emission by 5−25%. Thus, the use of HRB in full-depth reclamation process could make the practice more sustainable if strength, stiffness, and durability of treated materials are not compromised. The primary objective of this study is to evaluate the mechanical properties of full-depth reclaimed pavement materials treated with hydraulic road binders. The study was conducted in the form of comparative assessment by using full-depth reclaimed pavement materials treated with General Use (GU) cement as a control mix. For this study, three types of full-depth reclaimed pavement materials and four types of cementitious binders, including GU cement, were used to make eleven different types of mixes. Unconfined compressive strength, modulus of elasticity, and indirect tensile strength tests were used to assess the mechanical properties of the eleven mixes. The test results indicated that hydraulic road binders could provide equivalent strength and stiffness as GU cement. The study also revealed the HRB content, required to attain equivalent strength and stiffness as GU mixes, is the same or less than GU cement content. Based on the study findings, hydraulic road binders can be sustainable alternative binders that can replace GU cement in full-depth reclamation process without compromising the structural function of the treated layer.

Basalt fiber reinforced polymer (BFRP) bars are used in reinforced concrete structures as an alternative to conventional mild steel bars due to their excellent strength and durability properties. The bond of BFRP bars with concrete is a critical design criterion for both flexural strength and crack control. In this paper, the effect of two surface conditions (primary sand coating and secondary sand coating) on the bond of BFRP bars is evaluated experimentally in three investigations: first, twelve pull-out specimens (six specimens for each surface condition) are tested to determine the bond strength; second, eleven beams (three beams with primary sand coated BFRP bars, three beams with secondary sand coated BFRP bars, three beams with bundled BFRP bars, and two beams with mild steel bars) are tested to determine the bond-dependent coefficient (kb) of different surface conditions compared to that of deformed steel bars; third, eleven beams are tested in flexure to determine the ultimate flexural strength and failure modes of beams with different surface conditions and reinforcement ratios. It was observed that the surface condition of BFRP bars has significant effect on bond strength, kb, and flexural strength. Test results are compared to those predicted using ACI 440-15 and ISIS 2007, which found to be conservative.

Numerous studies have been carried out regarding the mixture design of low CO2 slag-blended concrete. However, these previous studies did not consider the constraints of the low carbonation resistance of slag-blended concrete. Due to global warming, carbonation has accelerated and carbonation durability has become more significant. This study shows a calculation procedure for the proportional design of low CO2 slag-blended concrete, considering carbonation durability under the effects of global warming. First, the CO2 emissions of slag-blended concrete were calculated using concrete mixtures. The strength and carbonation depth were determined using an integrated hydration-strength-carbonation model. Three climate change scenarios coupled with two exposure conditions were considered for the carbonation durability design. Other constraint equations, such as the components, component ratios, absolute volume, and slump, were also considered. Second, a genetic algorithm (GA) was employed to find the optimal mixture. The optimal mixture has a minimum CO2 emission level and can meet various constraints, such as strength, carbonation, and workability. The calculated optimal concrete mixture can mitigate the impact of global warming on the design of low CO2 slag-blended concrete.

Cement-based materials modified with SAP have been attracting much attention worldwide due to their excellent crack resistance and durability as well as their wide availability and low cost. This paper reviews the processing and microstructures (hydration process and pore structure) of SAP-modified cement-based composites and discusses the effects of SAP on the rheological properties, mechanical properties, shrinkage, self-healing and durability of cement-based materials. In general, the addition of SAP introduces additional water that can ensure the workability of the mixture and has little impact on their mechanical properties compared with cement-based materials without SAP. Moreover, the addition of SAP can significantly reduce the autogenous shrinkage of cement-based materials, thereby improving their crack resistance and durability (impermeability, carbonation resistance and frost resistance). When SAP is added into cement-based materials, the effects of SAP on the properties of cement-based materials depend on the SAP particle size, content and addition method. Finally, the applications of cement-based materials modified with SAP are introduced in detail, and the challenges and prospects of SAP-modified cement-based composites are discussed.

Moisture and aggressive ions transfer into concrete can be considered a significant threat to the durability of self-consolidating concretes (SCCs). To restrict moisture and aggressive ions transfer into concrete, utilizing damp-proofing agents is expected to be beneficial. These admixtures can decrease permeability of concrete, especially the permeability under non-hydrostatic condition, by providing a water-repellent layer along the capillary pores. This study investigated the impacts of calcium stearate (CS), as a damp-proofing agent, on durability properties of SCCs which were prepared with various types of supplementary cementitious materials (SCMs). In addition to durability properties, the effects of CS on mechanical characteristics and properties of fresh concrete, and microstructure have been studied as well. The outcomes demonstrated that in fresh concrete, CS (up to 7 kg/m3) prompted a decrease in workability and density of fresh concrete without any significant impact on slump loss. The results of hardened concrete evaluation also showed a reduction in either density of hardened concrete or compressive strength. Plus, microstructure analysis showed that incorporation of CS deteriorates both the cement paste and the interfacial transient zone. Eventually, although CS had a negligible impact on electrical resistivity, total water absorption, and chloride diffusivity, it was absolutely effective on permeability of concrete under non-hydro static pressure. In this regard, inclusion of CS drastically reduced the depth of capillary penetration of water in addition to short and long term water absorption. As a case in point, incorporation of 7 kg/m3 of CS decreased the last-mentioned parameters by respectively 60%, 72%, and 40% compared to the reference mixture after 120 days of moist curing.

The binding of chloride can retard the penetration process and is of important significance for the durability of concrete structures. The previous researches calculated the content of C-S-H absorbed chloride mainly through chemical synthesized C-S-H and thermodynamic modeling, rather than in real cement pastes. This study proposed a feasible method for assessing C-S-H adsorbed chloride in real cement pastes by utilizing the order of decomposition of Friedel’s salt, Kuzel’s salt and C-S-H gel during carbonation and the significant content difference between them. All the parameters used for analysis were obtained experimentally, and thus have high reliability. The content of bound chloride adsorbed on C-S-H and combined in Friedel’s salt was determined with this novel method in pastes under two different exposure conditions. The results show that the adsorption amount of chloride within W50-N and W50-C on C-S-H of per unit mass is 0.00418 g and 0.00588 g separately, and the ratio of C-S-H adsorbed chloride to the total bound chloride in pastes is 49.1% and 46.0% respectively.

Previous research studies have proved the beneficial effects of Zycotherm on durability and moisture resistance of asphalt mixes. This study was performed to investigate the long-term performance of bituminous mastic and asphalt mix containing this additive in terms of fatigue behavior. The shear modulus and phase angle master curves of bituminous mastics were developed at 20 °C using the results of frequency sweep DSR test at four temperatures of 13, 19, 25 and 31 °C. Then, the time sweep test was accomplished at 20 °C to examine the fatigue resistance of asphalt mastics. The micro-structural behavior of mastics were analyzed by atomic force microscopy test. The fatigue behavior of asphalt mixes designed with the same additive contents to mastics were performed by indirect tensile fatigue test at 20 °C. The results of time sweep test demonstrated that the addition of Zycotherm up to 0.14% by weight of bitumen, had no detrimental effects on mastic fatigue resistance. It has been recognized from topographical analysis that the micro-structural behavior of Zycotherm containing mastic was highly similar to that of the base one. The variations were came from the difference in the mixing temperature during the preparation of conventional and Zycotherm containing mixtures.

High-strength Engineered Cementitious Composite (HSECC) usually features with low water-to-binder ratio (W/B) and low sand-to-binder ratio (S/B), for obtaining expected workability, mechanical property and multi-crack behavior. However, the low W/B and low S/B of HSECC can cause high shrinkage, which will jeopardize its volume stability and durability. In this paper, the influence of W/B and S/B on HSECC volume stability including chemical shrinkage, autogenous shrinkage and drying shrinkage, mechanical properties including compressive strength, tensile strength, tensile strain and tensile strain energy were investigated. Experiment results showed that in the W/B range of 0.13–0.24, S/B range of 0.3–0.9, the magnitude of chemical shrinkage overwhelms autogenous shrinkage and drying shrinkage; meanwhile, along with the increase of W/B and S/B, the total shrinkage is lowed and the magnitude of autogenous shrinkage tends to be comparable with drying shrinkage. In the W/B range of 0.13–0.24, along with the increase of S/B from 0.3 up to 0.8, the compressive strength and tensile strength was enhanced, however, the ductility of HSECC was lowed especially when S/B was greater than 0.6; when S/B was enhanced to 0.9, all the mechanical properties and ductility was severely injured. So, the optimum S/B of HSECC should be decided by systematically considering its influence on volume stability, mechanical strength and ductility.

Recent studies have demonstrated the advantages of using nano-silica in building materials such as concrete due to its nano-filler effect as well as the pozzolanic reaction. However, most of the previous findings are based on normal strength cement composites. In this study, a wide range of properties of high performance cement composites are investigated with addition of colloidal nano-silica (CNS) at dosage of 0.5%, 1.0%, 1.5% and 2.0%. Attributed to the pozzolanic reaction of CNS, the microstructures are denser and more homogenous. SEM observation, accelerated hydration rate and reduced Portlandite content verify this beneficial reaction. Hence, the CNS can help produce cement composites with higher mechanical strength and better durability regards to the impermeability to water and chloride ions. Also, it is found that the influence of CNS is more pronounced for composites with lower water-cement ratio at 0.30, in comparison with those at 0.50.

The utilisation and reuse of waste tire rubber in concrete can reduce the consumption of raw materials, which leads to economic efficiency and sustainable development of the construction industry. In this review, we conclude the major achievement of crumb rubber concrete (CRC) in nearly 5 years, discuss and analyse its fresh concrete properties, mechanical properties, durability and other properties. Results show that utilising the hydrophobic nature of rubber particles and appropriate admixture can increase slump and improve the workability of concrete. Concrete incorporating crumb rubber (CR) particles decreases the fresh density, and it decreases linearly with the increase in the CR content. The mechanical properties of concrete generally decrease as the CR content incorporated increases. However, the compressive and flexural strength of CRC, which is slightly above that of natural aggregate concrete (NAC), is limited to fine CR size that replaces sand and optimum CR replacement level (CR content from 0% to 10% increases the compressive strength by 2%, and the flexural strength is increased by 7%–21% in mixes with 10%–20% CR). CRC has higher water absorption and permeability than NAC. Nevertheless, small amounts of rubber replacement level (2.5%–7.5% CR) and mixing different rubber particle sizes can reduce the water absorption of concrete. CRC exhibits high freeze–thaw resistance, electrical resistance, abrasion resistance and resistance to sulfuric and sulfate attack when incorporating proper CR content at concrete mixes. The depth of chloride-ion penetration of CRC decreases with low CR content (up to 27.3% of reduction for CR content of 5%) but increases when the CR content exceeds 20%. A clear advantage of CRC is favourable thermal and acoustic insulation. The mechanical properties and durability of CRC can be improved by adding treated CR particles, fibres and supplementary cementing materials. Further research is needed to improve the weak bonding in the interfacial transition zone between CR aggregates and cement paste, thereby increasing the mechanical properties and durability of CRC. Discussions in this paper can provide new knowledge and information on the applications of green and sustainable CRC.

The rapid increase in waste quantities, as well as the depletion of the natural resources in the near future are some of the major concern worldwide. In response to these problems, as well as to the growing demand for concrete in the construction field, the focus has been directed towards the production of artificial aggregates, as an alternative to natural ones. Artificial aggregates are produced either by sintering or cold bonding method. Compared with the sintering method and besides being an effective recycling solution for a wide variety of wastes and by-product materials, the cold bonding method is characterized by minimal energy consumption, low pollutant emissions and low investment requirements. The use of cold-bonded aggregate as a potential construction material in concrete production is summarized in this manuscript. The paper discusses factors influencing manufacturing productivity and the properties of cold-bonded aggregate, such as pelletizer disc angle and speed, pelletization duration, water content and the types of raw materials and binders used. The physical properties of cold-bonded aggregates made of different waste materials and binders are presented. The mechanical characteristics, thermal properties and durability of concrete made of cold-bonded aggregates are also reviewed. The literature in the field has established the potential of using cold-bonded aggregates as sustainable materials in the production of normal-weight concrete, as well as structural and nonstructural lightweight aggregate concrete.

This paper addresses the durability and microstructural characteristics of lightweight concrete prepared by using fly ash cenosphere (FAC) and sintered fly ash aggregate (SFA) as replacements of natural fine and coarse aggregate, respectively. To fulfil this objective, sixteen concrete mixes are produced by using FAC and SFA, in various combinations i.e. 0%, 50%, 75% and 100% for each. Properties of concrete, such as compressive strength, resistance to sulphate, acid and chloride attack of concrete are studied. Further, the scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses for these concrete mixes are performed in support of the above strength and durability behaviours. The results of the present study reveal that though the compressive strength decreases with incorporation of FAC/SFA/both of these, appreciable strength is achieved using high volume of FAC and SFA (50% FAC and 75% SFA), which is also comparable to the strength of concrete without FAC and SFA. Further, the above mix achieves the required target strength of M25 grade concrete for which design mix is made as per IS 10262 (2009). It is found from the durability results that on one hand, the strength loss in concrete caused by sulphate attack and acid attack increases with increase in percentages of individual and combined substitution of FAC and SFA and hence, the concrete comprising FAC and SFA is not suitable for the structures exposed to acidic environments. On the other hand, when FAC or SFA or both of these contents increases, the depth of chloride ingress decreases, exhibiting better performance in saline environments than the concrete mix without FAC and SFA. The XRD and SEM analyses confirm the strength and durability characteristics of these mixes.

Red mud (RM) is a toxic waste, rich in coloured pigments, which affects landfills and surrounding environments due to its high alkalinity. But it is suitable for architectural coloured concrete production since it contains a high volume of ferric oxide (Fe2O3), aluminium oxide (Al2O3), and Silicon dioxide (SiO2). Therefore, the application of RM in concrete production not only may benefit the construction industry but also helps mitigating the environmental effects of alumina refineries. In addition, using RM can help to achieve a green coloured concrete with similar properties to current concrete made with white cement. This study intends to appraise the effects of RM in self-compacting architectural concrete (SCAC) production as cement and filler replacement. For that purpose, seven concrete mixes incorporating various ratios of RM as partial cement (2.5%, 5.0%, and 7.5%) and filler (25%, 50%, and 75%) replacement were produced in the laboratory. The results revealed that RM does not significantly affect the performance of concrete, as the variations of the results were mostly lower than 5% in relation to the reference concrete. Moreover, incorporating RM in SCAC can improve the durability to sulphate attack in terms of weight loss, a very important parameter when evaluating the performance of architectural concrete, by about 27%. In addition, using RM can help achieve a green coloured concrete with similar properties to current concrete made with white cement.

The need for incorporation of Reclaimed Asphalt Pavement (RAP) in the Stone Matrix Asphalt (SMA) mixtures is becoming a priority in the pavement industries. The RAP offers several benefits such as the reduction in usage of bitumen, and natural aggregates, and reduction in the landfills, emission into the environment and cost. SMA is known for its success in improving rutting resistance, durability and cracking resistance and to utilize the benefits of both RAP and SMA, it seems a logical purpose to incorporate RAP in the SMA mixtures. However, RAP contains an aged binder, which increases the stiffness of the mixtures and a rejuvenator is added to improve the rheology of the aged binder. In this study, Waste Vegetable Oil (WVO) is used as a rejuvenator in the RAP incorporated SMA mixture. In order to determine the maximum RAP content and optimum WVO dosage, four RAP contents (10, 20, 30, and 40% by weight of the aggregate) and four WVO dosages (0, 3, 6, and 9% by weight of bitumen content) are used to prepare the SMA mixtures. The laboratory tests were conducted to evaluate drain down, volumetric properties, Marshall characteristics, stripping behaviour, Retained Marshall Stability (RMS), and Tensile Strength Ratio (TSR) and they are compared statistically to each other and to the control mixture. The results indicate that RAP incorporated SMA mixtures have a substantial positive effect on the volumetric properties and it enhanced the Marshall Stability (MS), stripping resistance and RMS, however, reduced the TSR value. To the contrary, the addition of the WVO improved the TSR value to a great extent and increased the RAP content. The statistical analysis, Analysis of Variance (ANOVA) results, showed that the RAP content and WVO dosage have a significance on the properties of the SMA, and the main effect plot results concluded that it is possible to incorporate 40% of RAP content with 6% WVO in the SMA mixtures.

This study investigates the performance of three different types of cenosphere as a lightweight supplementary cementitious material for alkali-activated binder for lightweight carbon-negative hemp-concrete for non-load bearing applications. Mechanical performance of hemp concrete exposed to three temperatures, room temperature (RT), 300 °C and 600 °C are studied using mechanical testing, thermogravimetric analysis (TGA) and Fourier-transform Infrared Spectroscopy (FTIR). Hemp concrete with cenosphere binder remained its integrity and showed a lower load carrying capacity even after exposure to elevated temperatures. Compressive strength capacity and elastic modulus of the samples reduced with the increase of temperature and shows the composite material is more suitable for non-load bearing application considering its mechanical behavior and fire requirements. The density, age, and type of cenosphere showed effects on mechanical properties at room temperature and elevated temperatures. The study shows that alkali activated cenosphere binders can potentially be a sustainable alternative to the lime binder.

This study experimentally investigates the durability characteristics of rubberized concrete up to 30% rubber content. The durability characteristics including the carbonation depth, standard potential, water absorption, and initial rate of absorption of rubberized concrete were investigated. The experimental results have shown that rubberized concrete absorbed more water than conventional concrete, and the water absorption increased with the rubber content. Therefore, rubberized concrete is more susceptible to water, chloride, and chemical attacks. The carbonation depth of rubberized concrete was also higher than that of the conventional concrete and it increased with the rubber contents, indicating more susceptibility to corrosion. Although the estimated service life of rubberized concrete is shorter than that of conventional concrete, with 15% rubber contents it exceeds 50 years according to fib CEB-FIP [1] and AS 3600 [2]. Rubberized concrete thus can be used for structural components with sufficient strength and adequate service life up to 15% rubber content. In addition, the pre-treatment methods with NaOH or water were found to have considerable effects on carbonation depth but marginal effects on the water absorption and standard potential of rubberized concrete.

Recycled aggregate concrete (RAC) has attracted increasing attention over the past decades due to its sustainable development in the environment, society and economy. However, compared with natural aggregate concrete (NAC), the mechanical performances of RAC involving the strength, stiffness, and durability are poor, limiting the application of RAC. In this paper, RAC-filled glass fibre-reinforced polymer (GFRP)-steel composite tube columns, which can overcome the shortages of RAC, was proposed. A systematic experimental study was conducted to investigate the seismic performance of RAC-filled GFRP-steel composite tube columns, in which the FRP on the steel tube is manufactured through a filament-winding process. Different aspect ratios and axial compression ratios were considered for these columns. Their failure modes, lateral moment-drift hysteretic responses, skeleton curves, energy dissipations, stiffness degradations and equivalent viscous damping ratios were discussed in detail. It is showed that compared with RAC-filled steel tube columns, RAC-filled GFRP-steel composite tube columns exhibited a superior seismic performance, especially for the ductility factor. Finally, an empirical model was developed to predict the lateral moment-drift skeleton curves of RAC-filled GFRP-steel composite tube columns. The findings can expand the application of RAC and provide a seismic design guidance of RAC-filled GFRP-steel composite tube columns.

Deterioration due to corrosion is a key issue affecting the durability, safety, and sustainability of buildings and structures. Most cities are located in coastal areas and many reinforced concrete structures in these areas are exposed to aggressive marine environments. Therefore, it is important to provide protection and offer appropriate repair methods of buildings vulnerable to the degrading effects of corrosion. The first step of implementing recovery is determining the level of degradation undergone by exposed concrete structures. However, there is a lack of integrated guiding principles in this field. Thus, this review paper identifies the tests of determining the level of deterioration, with particular attention given to carbonation issues and chloride ion attacks. The paper also provides a categorization of solution methods for protection, maintenance, and repair, based on standards and codes culled from around the world. This research contributes to the field by providing a readily-available reference for practitioners and researchers, on the current state of knowledge on corrosion and repair strategies for coastal concrete structures.

Carbon dioxide concentration is steadily increasing in large cities. Consequently, durability evaluation of RC (Reinforced Concrete) structures considering carbonation is becoming a serious issue. Construction joints are used for the effective construction of concrete structures. However, cold joints which are caused by delayed placing and poor surface treatment are vulnerable to shear force and the inflow of carbon dioxide. In this study, an accelerated carbonation test was performed for normal-strength concrete using NPC (Normal Portland Cement) and slag after applying tensile and compressive stresses. The carbonation characteristics were quantified considering the effects of cold joint and the induced stress, and structural analysis was performed using the section laminae approach for a 2-span continuous reinforced concrete T-beam bridge. The service life of top and bottom concretes was evaluated considering the calculated stress, existing carbonation velocity equation, and carbonation function according to the stress. The service life showed a similar trend to that of the applied moment. Changes of 103.6%–64.7% (NPC) and 78.0%–108.8% (slag) were observed on the top surface, whereas changes of 103.8%–65.9% (NPC) and 112.9%–79.6% (slag) were observed on the bottom surface. The service life significantly decreased owing to the increasing carbonation depth for the cold joint in the tension part. This suggests that special care should be taken for cold joints during maintenance.

The main idea of this study is to evaluate the mechanical and durability properties of high strength concrete specimens by incorporating an alternative for cement along with bacteria for healing cracks. The classic methods which are used for healing cracks involve the use of ordinary synthetic polymers which further cause a lot of damage to the environment. Therefore, the use of sustainable strategies like ingesting bacterial culture into the concrete mix along with an alternative replacement for cement can act as an active support for both nature as well as construction industries. In this paper, control concrete, concrete made by replacing cement with Micronized Biomass Silica (MBS) at 4%, 8% and 12% and bacteria induced concrete are compared. The bacteria used is Bacillus Sphaericus with optical density as 1.00 and is mixed in control as well as MBS made concrete specimens at different levels of 10 ml, 20 ml, 30 ml for each. With a total of 16 mix designs of characteristic compressive strength 60 N/mm2 at the age of 28 days curing (M60 grade) high strength concrete cubes, cylinders and beams are compared on grounds of compressive strength, splitting tensile, flexural strengths, water absorption and sorptivity. It was concluded that, specimens with 8% MBS and 20 ml bacteria showed optimum results based on strength and durability characteristics. Further, an artificial crack was induced in the specimen and the bacteria’s healing activities along with calcite precipitation were examined through X-Ray diffraction, Scanning Electron Microscope (SEM) and visualization analysis. A high intensity of peaks was observed with MBS and bacteria and the cracks were visualized for 3 days and 7 days which ratified the healing of cracks due to the formation of calcite precipitate which was confirmed through SEM Analysis.

Accumulation of waste is subsequently increased to hazardous levels. Tire waste is one of them that cause serious environmental issues because of the rapid rise in and numerous variations of modern developments worldwide. Thus, recycling waste tire rubber in the form of aggregates as supplementary construction material is advantageous. This paper reviews the source of waste tire rubbers and rubberized cementitious composites along with their material properties, usages, durability, and serviceability performances. This study also aims to provide a fundamental insight into the integrated applications of rubberized concrete (RuC) composite materials to improve construction methods, including applications to enhance environmental sustainability of concrete structures in the construction industry. Inclusion of recycled rubber aggregate (RA) lightens concrete, increases its fatigue life and toughness, advances its dynamic properties, and improves its ductility. Concrete with recycled RA performs well in hot and cold weather and achieved significant results under critical exposure and various loading conditions. Though RuC possesses low mechanical strength in general, specific treatment and additives inclusion can be a good solution to improve those properties reliably. Investigations of RuC as materials are available significantly, but researches on the structural members of RuC should be enriched.

Asphalt pavement often suffers from rutting, aging, cracks, and pits during the life cycle. Although traditional polymer modifiers can improve asphalt properties to some extent, its storage stability and aging resistance still need to be improved. Polyurethane (PU) has been used in asphalt pavement engineering because of its high mechanical properties, durability and fatigue resistance. This paper introduces the relationship between the structure and properties of PU and describes possible optimization of the raw materials of PU suitable for modified asphalt according to the pavement performance. The applications of PU in modified asphalt, pavement maintenance, foamed asphalt, and its mixture are reviewed. The results show that modified with PU asphalt has good deformation resistance, aging resistance, fatigue resistance, and high-temperature storage properties after physical and chemical modification. At the same time, PU can also improve the temperature stability and mechanical properties of emulsified asphalt. The PU mixture has excellent properties and can be used to prepare functional pavement such as water penetration, noise reduction, and anti-skidding. The application of PU waste materials in asphalt pavement opens up a new direction for its recycling.

The pore structure and permeability of cement-based materials have great influence on the durability of application of this materials. The effects of bentonite on the pore structure and permeability of cement mortar were investigated in this paper. Bentonite, as a swelling potential clay, was added to mortar at content 0, 4 and 8% by weight of cement. The compressive strength, flexural strength, and impermeability pressure were determined for cement mortar with bentonite and compared with plain cement mortar specimens. Test results showed that the addition of 8% bentonite could cause a significant increase of 61.48%, 42.09% and 76.47% for compressive strength, flexural strength, and impermeability pressure, respectively. The enhancement of impermeability is mainly due to the pore structure refinement by the bentonite, which is validated by test results of the Mercury intrusion porosimetry (MIP). Moreover, needle-like and amorphous hydration products grow on the surface or edge of bentonite resulting in more tortuous penetration path to improve the barrier performance of cement mortar.

The use of high-performance concrete (HPC) is widespread as an eco-efficient building solution because it provides greater durability and, hence, a longer lifetime than conventional concrete, reducing the need for repairs and demolitions. In addition, HPCs require lower binder contents per unit of compressive strength. However, self-compacting HPCs (HPSCCs) generally require high binder contents to ensure the fresh state stability of the concretes, which could hinder the ecological advantage. Thus, this work aimed to produce HPSCCs with low binder contents. A mix design method was proposed to optimise the material proportions. A fine fly ash was used to replace Portland cement from 0 to 30%. The rheological properties of the SCCs were evaluated by the workability tests slump flow, T500, V-funnel, L-box and VSI. Compressive strength, resistance to chloride ion penetration, volume of permeable voids and capillary water absorption were determined at 28 and 91 days. Finally, the CO2 intensity (kg CO2/m3·MPa) of the mixtures produced was estimated and compared to those of HPSCCs reported in the literature. The mix design method allowed for the production of SCCs with 365 kg of binder/m3 of concrete, with slump flow of 700 ± 25 mm and stable in the fresh state (VSI of 0 or 1). The fly ash-containing concretes showed compressive strengths up to 59 MPa at 28 days (10% fly ash) and 71 MPa at 91 days (20 and 30% fly ash), with good indicators of durability: down to 403 Coulombs for RCPT and up to 41.8 kΩ·cm for surface electrical resistivity. The CO2 intensity of the concretes produced are among the lowest reported in the literature for HPSCCs (down to 4.7), together with the lowest binder content reported for this type of concrete (365 kg/m3 of concrete).

This paper investigates the possibility of using garnet waste as river sand replacement in high-strength alkali-activated mortars (AAMs) containing fly ash (FA) and ground blast furnace slag (GBFS). The garnet waste replacing river sand was used at varying levels of 0, 25, 50, 75, and 100%, by weight. In this study, the ratios of binder to aggregate (B:A), alkaline activator solution to binder (S:B) and the activator solution modulus (Ms) remained the same in all samples tested. The tests conducted were slump flow, compressive strength, flexural strength, drying-shrinkage, porosity, and resistance to acid, etc., which indicated the impacts of using garnet waste on the mechanical and durability performance characteristics of AAMs. The tests data revealed that as the level of waste garnet content increased in AAMs, there was a corresponding improvement in the workability of said samples. Notably, when the garnet waste content level exceeded 25% in the tested samples, there was a decrease in flexural and compressive strength in comparison with the control sample. Therefore, it would appear that the garnet waste could act as a potential replacement of river sand up to a maximum of 25% without any strength loss. It also meets the need for a cost-effective alternative which is eco-friendly and a renewable resource. It is recommended that spend garnets waste should be used in AAMs as river sand replacement to minimize the environmental problems, cost and natural resources depletion.

Salt crystallization is the crucial damaging mechanism which affects the durability of porous masonry units like bricks. Improper selection of protective treatments and replacement strategies often degrade the situation further and result in frequent future interventions. In this paper, the role of pore size distribution of the bricks in resisting salt crystallization and its effect on the performance of protective coatings has been discussed. Bricks with different microstructural properties were treated with common water repellent coatings - silicone-based and acrylic siloxane-based and were subjected to accelerated salt weathering tests. The performance of the coatings was studied using standard methods, and the coatings were then evaluated for their compatibility with various bricks with varying microporosity, when exposed to sodium sulphate. Bricks highly prone to salt crystallization have been found to be more sensitive to the properties of treatments over them, as breathability assumes a greater significance.

Plastic cracking is probably one of the earliest defects for concrete structures, and is capable of reducing a structure’s durability and service life if not prevented. Over the last 60 years, researchers have attempted to unravel the complex nature of mechanisms leading to plastic cracking of concrete. The main driving mechanisms of plastic cracking have been found to be settlement of solid particles, bleeding, evaporation, capillary action, as well as surface finishing. These, in combination lead to a 3-dimensional volume contraction which if restrained, causes plastic cracking of concrete. Several methods, tests, and models have been developed to enumerate the effect of the respective mechanisms leading to the plastic shrinkage and cracking of concrete. Plastic cracking has thus been uniformly understood to mean both plastic settlement cracking and plastic shrinkage cracking. Several mitigation strategies of plastic cracking have been proposed, such as fogging, using less amount of fines, use of fibers, among others. This state-of-the-art paper traces the extensive development of research on the subject matter, and updates it with what is considered to be state-of-the-art and up-to-date.

The current study focusses on the utilisation of stone processing dust (SPD) on the properties of concrete. The stone processing dust was used as a fine aggregate (up to 100%) for reducing the requirement of river sand in the production of concrete. The incorporation of 30% stone processing dust was found to improve the mechanical and durability properties of concrete. The sustainability and economic studies carried out were also found to show the beneficial role of stone processing dust in reducing the embodied energy, embodied carbon and cost of concrete mixes.

Hot-Mix Asphalt (HMA) is a designed pre-mix of graded aggregates and bituminous-based binder, hot applied on road pavements to provide a smooth and safe riding surface and protect the underlying layers. Current HMA mix design methods are focusing, mostly, on the strength of the mixture. However, the mixture permeability, which is an equally important performance parameter of an HMA layer – strongly influencing the durability of the HMA and underlying layers – is not always pertinently used as a mix design parameter. Exclusion of permeability is attributed to uncertainty on the accuracy of measured permeability, as well as poor correlation among predicted, field, and laboratory results. In this paper, it is hypothesised that practical and reliable methods are available to predict and measure the permeability of HMA in the field and laboratory as well as to successfully relate permeability parameters to long-term performance of HMA. The objective of the study is to establish these relationships and validate an HMA design model to predict durability. Numerous theoretical models were evaluated and the selected model is based on regression analysis of field data. Initially, predominant variables influencing layer permeability were found to be void proportion, binder content as well as aggregate grading and packing. Subsequently, regression analyses of data showed that within reasonable variation of the other variables, layer permeability is strongly correlated to aggregate grading and packing, as described by rational Bailey ratios, hence the focus of refining the model on the latter parameters. The research confirmed the hypothesis by showing an acceptable level of confidence in the relationships. The study objective was achieved to the extent that the predicted levels of permeability correlated well with field observations of durability performance. This was enhanced with machine learning modelling of the data sets available from recent as-built road sections with similar design and specifications and different permeability observations in the field. It is concluded that permeability can indeed be introduced as a primary design objective in HMA design practice. It is recommended that, while further machine learning refinement is being done, the model be used by designers in enhancing the prediction of design life of HMA surfacing and structural pavement layers.

Aggregate packing is a key factor controlling the durability of asphalt mixtures. Considering the complex system of the aggregate structures, multiscale method was utilized by dividing asphalt mixtures into four scales, including asphalt binder, mastic, mortar and asphalt mixtures. Six asphalt mixtures with different gradation types and nominal maximum aggregate size (NMAS) were prepared and the corresponding mastics or mortars were also designed. Comprehensive image analysis methods, including high-resolution scanning, Scanning Electron Microscope (SEM), and Laser Diffraction Analyzer (LDA), were utilized to obtain the 2D images of asphalt mixtures, mortars and mastics. Then, the distribution curves of the binder within mastics, mastic within mortars, and mortar within asphalt mixtures were calculated and compared. New packing indexes were proposed, such as: expected value (E binder ) and peak value (P binder ) of the binder distribution at mastic scale, expected value (E mastic ) and peak value (P mastic ) of the mastic distribution at mortar scale, expected value (E mortar ) and peak value (P mortar ) of the mortar distribution at mixture scale. By comparing with volumetric parameters, it was found that E binder and P binder could correlate well with the volume ratio of filler to mastic. E mastic could correlate with the volume fraction of fine aggregate within the mortar, but the P mastic may also influence by the fine aggregate gradation. The void filled with asphalt (VFA) has weak correlation with both packing indexes, E mortar and P mortar , which indicates that VFA has limitation for evaluation of the packing properties of asphalt mixtures, and more indexes from the internal structure need to be considered.

The accelerated aging test results of the study on the compressive performance of glass fiber reinforced polymer (GFRP) bars under sustained compressive stress in the marine environment simulated by a salt solution and the concrete environment simulated by an alkaline solution were presented in this paper. The test parameters were sustained stress levels (0%, 20%, 40% of the ultimate compressive strength), exposure temperature (40 °C, 60 °C, 80 °C) and exposure time (16 d, 60 d, 90 d). The test results indicated that high temperature led to postcure of the resin matrix which was beneficial to the compressive performance of the GFRP bars. The conditioned GFRP bars failed due to the longitudinal splitting of the resin matrix or the fracture of the fibers and the debonding of the fiber/matrix interface. After immersing in the salt solution at 80 °C for 90 d, the strength retentions of the specimens with stress levels of 0%, 20% and 40% were 67%, 62% and 55% respectively. After immersing in the alkaline solution at 80 °C for 90 d, the strength retentions of the specimens with stress levels of 0%, 20% and 40% were 44%, 36% and 24% respectively. The compressive strength retention of the conditioned GFPR bars decreased with the increase of the sustained stress level, exposure temperature or exposure time. Increasing the exposure temperature or the sustained stress level could increase the degradation rate of the compressive strength of the GFRP bars. The compressive strength retention of the GFRP bars conditioned in the alkaline solution was lower than that in the salt solution. And the higher the temperature, the more obvious the detrimental effect of the stress level on the compressive strength of the GFRP bars was. Based on the test results, a degradation model for the compressive strength of the GFRP bars under sustained compressive stress in the simulated marine and the simulated concrete environments was proposed.

The present review paper examines the essential stages in the developments of the innovative category of eco-friendly inorganic Geopolymer concrete throwing lights on the Waste of Glasses valorisation concerning their amalgamation in producing Geopolymer concrete particularly pertaining to its durability properties. The process of Geopolymerization is capable enough to produce diverse GPC in the field of sustainable infrastructures and constructions industries. Nevertheless, more advanced investigations with respect to its durability viz., Drying shrinkage behaviours, Sulphate Attack, Leaching Test, Ultrasonic Pulse Velocity and thermal properties as well as heavy metals immobilization along with micro-structural attributes like porosity, XRD and SEM analyses will altogether prove to be worthy to people related to construction industries, researchers, engineers, etc. Though, the literature in this novel sector is little and isolated and found mostly on their blending with other profuse wastes. Until now, their character is not fully outlined and not broadly accepted in contrast to Ordinary Portland Cement based building composites. For this reason, a review of its literature to focus on the valorisation of incorporating of Waste of Glasses in production of Geopolymer concrete emphasizing on its durability characteristics to promote it as durable and sustainable large-scale construction material along with cost-effectiveness too. When GPC is produced employing accessible precursors, activators blending with glass wastes under the standard quality control of principally durability properties and low carbon footprints of alkali activators, valorisation of these types of GPCs are vital approaching part of the future toolbox of durable and sustainable as well as cost-effective building materials. Ultimately, the manuscript categorizes its endorsement as durable structural materials for widespread applications as a promising new-fangled kind of edifice material.

This experimental study was aimed to investigate the effect of elevated temperature on the mechanical properties of self-compacting mortars (SCMs) incorporating raw vermiculite (RVM) as partial sand replacement at the substitution rates of 10%, 20%, 30% and 40%. Within this scope, five SCMs series were prepared, including the control mix consisting of 10%, 20%, 30% and 40% of RVM as fine aggregate on 0–2 mm particle sizes of sand weight basis. A total of 45 specimens of 40 × 40 × 160 mm were fabricated and exposed to water curing for 3, 28 and 90 days for mechanical strength properties. 30 cube specimens of 50 × 50 × 50 mm were fabricated and exposed to curing in water for 28 and 90 days to perform durability tests including water absorption, sorptivity, porosity and density tests. The slump flow diameter, V-funnel flow and viscosity tests were performed to evaluate the fresh characteristics of SCMs. The SCMs specimens were subjected to the temperatures of 300 °C, 600 °C and 900 °C after 28 days curing then cooled to room temperature before performing experiments. The results indicated that the compressive and flexural strengths of all SCMs mixtures has decreased at water curing for all ages as RVM rates increases. The compressive and flexural strengths loss for SCMs incorporating RVM remained very low compared to the strength loss of control samples at all temperature ranges. Mini-slump flow values are acceptable for consistency and workability for many applications. SCMs containing RVM can be used in the production of lightweight concrete with excellent properties such as low density and heat insulation.

This paper investigates numerically the two-dimensional diffusion-reaction behavior of sulphate ions in cement-based materials in accordance with Fick’s second law of diffusion and reaction kinetics, and the tensile constitutive law, on account of ettringite formation. Further, a durability-based limit state function and a predictive model are proposed to forecast the crack growth in structures made with cementitious materials exposed to adverse sulphate environment. The results show that the amount of calcium aluminates in the binder and the initial diffusion coefficient are most influential in resisting external sulphate attack. Whereas, the initial porosity has minor significance, the sulphate concentration in the surrounding environment is inconsequential. Stochastic analysis confirms that sulphate-resisting Portland cement accords high reliability even after lengthy exposure, whereas an ordinary Portland cement or that blended with fly ash present a risk of failure in due course.

Concrete is well known for its durability. However, it is exposed to aggressive agents, such as water and chlorides, leading to its degradation. The DC-electrical resistivity method is a technique devoted to non-destructive evaluation (NDE). However, when applying this measurement technique to reinforced concrete structures, the measurements may be highly influenced by the presence of reinforcement. To study the influence of reinforcements and estimate the impact of their effect on resistivity measurements on concrete, we model their contribution by finite element numerical analysis. Electrical measurements in reinforced and unreinforced concrete slabs were modelled and actual experimental measurements were used. This article presents the numerical study results that are compared to the experimental data for validation purposes. By validating the presented approach, it will be possible to fully account for the effect of the reinforcements, as an alternative to measurement strategies that aim at minimizing the disturbance due to reinforcements.

This work aimed to analyze the thermal, electrical and mechanical properties of cementitious composites (CCs) modified with SNs in dispersed and powdered forms, using experimental design methods and image analysis techniques. It was concluded that SNs have smaller particle size increase thermal conductivity, ultrasonic pulse velocity and splitting tensile strength, and decrease electrical resistance, percentage of water absorption and porosity of CCs. It was found that the optimum usage level of powdered SNs in CCs is 2% by mass because of its tendency to agglomerate. However, it is more advantageous to use dispersed SNs when considering CC performance properties.

Chloride ions in marine environment can cause corrosion of steel reinforcement in reinforced concrete (RC) structures and result in structure deterioration. This study investigates a dual-functional intervention method, i.e. impressed current cathodic protection – structural strengthening (ICCP-SS) method, using carbon fibre reinforced polymer (CFRP) as both the anode material for impressed current cathodic protection and strengthening material for structural strengthening system. The effectiveness of the ICCP-SS method on the improvement of durability of RC structures is considered in a long-term timeframe. An experimental programme comprising nine simply supported beams is presented in this paper. The beams experienced 360-day accelerated corrosion and 180-day cathodic protection, followed by four-point bending tests. Flexural behaviour and capacities of the degraded beams repaired by using ICCP technology, structural strengthening technology and ICCP-SS technology were obtained. After the tests, the steel reinforcement bars inside concrete were taken out and cleaned to measure the section reduction due to corrosion. Results showed that the ICCP-SS technology can prevent the corrosion of the steel reinforcement effectively and increase the capacities of the beams at the same time. Finally, the appropriateness of existing design approaches for the intervened beams was also discussed in the paper. The ICCP-SS intervention method is found to be beneficial for the durability of RC structures in marine environment.

This paper proposes an analytical model to calculate the critical corrosion level of reinforcements embedded in the concrete. The porous zone, the plasticity and strain softening of concrete were considered. The proposed model was verified by the simulation and test results, and the test validation shows that the predicted critical corrosion level of reinforcements for both natural aggregate concrete (NAC) and recycled aggregate concrete (RAC) based on the proposed model has a relative error lower than 5.0% compared with the test result when the replacement ratio of recycled aggregates is lower than 33.3%. It concludes that the proposed model can be applied to the prediction of the critical corrosion level of reinforcements in both NAC and RAC, and further the analysis of durability of concrete structures.

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 order to find effective confining pressure in concrete members externally wrapped with Fiber Reinforced Polymer (FRP) jackets, different values of the so-called strain efficiency factor have been suggested by several researchers. In this paper, the durability of Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) sheets in aggressive marine environment is assessed, and the effect of such environments on the strain efficiency factor in compressive members is investigated. A set of 3D finite element analyses (FEA) are performed to find the strain efficiency factor. The strain efficiency factor of GFRP jackets is lower than that of CFRP jackets in different environmental conditions. Furthermore, the strain efficiency factor decreases as the exposure time increases, which is more evident in GFRP-wrapped concrete. After 3000 and 9000 h of marine exposure, the strain efficiency factors decrease by 11% and 43%, respectively, in GFRP jackets. In CFRP-wrapped members, the reduction is about 18% and 25%, respectively.

This paper presents a study regarding the durability of concrete containing Recycled Coarse Aggregate (RCA) from the largest civil construction waste plant in Latin America, CTR Grajau, located in Sao Paulo, Brazil. Conventional reference concretes were produced with natural aggregates and water/cement ratios of 0.35, 0.45, and 0.55. The recycled concretes were produced by replacing the Natural Coarse Aggregate (NCA) of the reference concretes with RCA in percentages of 50% and 100% by volume. Specimens were submitted to tests to determine the apparent porosity, capillary absorption coefficient and compressive strength. To verify durability aspects, the diffusion coefficients of chlorides (obtained by a procedure adapted from ASTM C 1202:2017) and electrical resistivity (obtained using a Wenner probe) were determined. Results demonstrated that NCA substitution with RCA increased porosity, with a consequent increase in the capillary absorption coefficient and a reduction in compressive strength. Total replacement of NCA with RCA reduces the concrete service life, calculated using Fick’s Second Law of Diffusion, by at least 40% for concretes with water/cement (w/c) ratio equal to 0.35, while a partial replacement (50%) reduces the service life by approximately 22%, considering a marine environment and 40 mm of cover thickness. The use of w/c minimum ratios, detailed RCA characterization and pre-wetting are some of the methods proposed for the application of the material for structural purposes. The lifetimes of the different concretes were determined.

Concrete should preserve its adhesion property and workability during the process of transportation to the construction site so that no sign of instability (e.g., bleeding and segregation of aggregates) takes place in concrete. In some cases, long-time mixing process of concrete in truck mixers and the imported energy caused by them inside this system may lead to workability loss or dynamic instability (as the essential factors affecting mechanical properties and durability) in the concrete, and this issue is deemed more important in self-consolidating concrete (SCC) that contains chemical and mineral additives. This study investigated the effect of hauling time and pozzolanic minerals on the fluidity, viscosity, stability, and compressive strength of self-consolidating mortars (SCMs). Therefore, 16 mix designs were totally made as binary and ternary mixtures, including metakaolin (MK) and natural zeolite (NZ), and were subjected to the prolonged mixing time (8, 30, 60, 90, 120, and 150 min). The results showed that when the hauling time increased up to a certain level, which is called stabilization time (the shortest mixing time that has been considered to be 30 min in this study), the fluidity and viscosity of mixtures increased and decreased, respectively. However, by prolonging the hauling time up to 150 min, the workability of binary and ternary mixtures will be reduced to 64% and 68%, respectively. Moreover, dynamic segregation resistance in all ternary mixtures was considered in a stable workability region after mixing for 90 min, while all mixtures were subject to high viscosity and high accumulation (at the center of mixture) at intervals of 120 min and 150 min. Moreover, when the hauling time increases up to 150 min, the compressive strength is reduced in binary mixtures with MK and NZ contents maximally to 54% and 57%, and this rate is equal to 67% in ternary mixtures.

To study the frost resistance of recycled concrete in a sulfate-rich environment, we prepared recycled concrete with 0%, 30%, 50%, and 100% recycled aggregate replacement rate. The physical and mechanical properties of the recycled concrete in the coupled action of freeze-thaw cycles and a sulfate environment for different replacement rates of aggregate was then studied. We analyzed the micro-structure and the reaction products of the recycled concrete. We used a two-factor Weibull distribution model to establish the damage equation, then predict the service life of the recycled concrete. The results show that when the replacement rate of recycled aggregate increases, the physical and mechanical properties of the recycled concrete gradually deteriorate in the later stages of the freeze-thaw test. When the number of freeze-thaw cycles increases, ettringite and gypsum are gradually formed due to the reaction with sulfate. The Weibull model accurately describes the damage variation in the recycled concrete. Through the prediction of the service life of the recycled concrete, we found that the durability was reduced. Given our analysis, we found that the proportion of recycled aggregate should not exceed 30% to meet the requirements for durability design of a concrete structure in China (GB/T 50746-2008).

A single calcite crystal shows a pronounced anisotropy that can be transferred to the bulk stone, especially in the case of marbles. The aim of this paper is to analyse the effect of the preferential crystallographic orientation of the anisotropic calcite crystals on the surface properties of foliated marbles. Variations of microhardness, roughness, solubility and contact angle in rock surfaces are studied taking into account their relative position with respect the metamorphic foliation. Results show that more than 50% of the crystals have their c-axis oriented close to the normal of the axial foliation plane. This fact has a direct response on its surface properties: i) the microhardness in surface parallel to metamorphic foliation is a 14% higher than it is in the perpendicular surface; ii) contact angle of the water on the parallel faces is slightly lower than it is on the perpendicular one (42.75° and 53.25°, respectively); and iii) a lower chemical reactivity is estimated on parallel faces, which results in a lesser roughness of weathered surfaces. Results from this paper determine the optimal direction in which an ornamental piece should be cut in order to guarantee its maximum durability. This study was financed by the Spanish Government (Consolider-Ingenio Programme CSD2007-0058) and MCI CGL2008-05929/BTE. Predoctoral fellowships were awarded to N. Cueto by the MEC (Project MAT 2003-01823).

The mechanical-, physical- and durability- properties of cementitious composites depend on the material structure and its interaction behaviour at the micro and nano scales. To tailor the properties of cementitious composites according to design requirement at macro scale, it is necessary to comprehend the mechanical properties of the constituent phases at micro and nano scales. With recent interest and application of nanoindentation technique on heterogeneous materials: bone matter to cementitious materials, nanoindentation has proven to be a reliable method to explore microstructural mechanical properties and expand the knowledge base in respect to the process and structure of hydration of cementitious composites. However, complexities like heterogeneity, stringent requirement for sample preparation, no straight forward way of interpretation of results, time consuming experiments, etc., are considered as deterrents for use of such modern technique for cement research. Hence, this study will provide comprehensive knowledge, promising aspects and latest understandings towards the use of nanoindentation for evaluation of mechanical properties of cementitious composites.

Stress-absorption interlayer (SAI) is one of the most important methods to prevent reflection cracking. This paper analyzed the properties of SAI with the waste tire rubber (WTR) and amorphous ploy alpha olefin (APAO) complex modified asphalt binder. Research found that WTR/APAO modified asphalt works excellently as a binder in SAI. The SAI with base asphalt, WTR/APAO, WTR and SBS modified asphalt mixture were prepared for comparative analysis. The mechanical properties and durability of four SAIs were determined using Marshall stability, Indirect tensile (IDT) strength, immersion Marshall and Marshall stability after aging procedure. The bond strength and shear resistance of three SAIs with modified asphalt were determined using slant shear tests under different conditions. The overlay tests (OT) were used to characterize the fatigue and anti-reflection cracking performance. Besides, the Paris’ Law was used to characterize the fracture properties based on OT. Research found that WTR/APAO SAI had the strongest high temperature stability, deformation resistance, bond strength and shear resistance. WTR/APAO and SBS SAIs had excellent water stability and anti-aging performance. WTR/APAO SAI had the highest bond strength at both high and normal temperatures. The OT number of cycles of all three SAIs reached 1200 times. This indicator showed that all three SAIs had excellent fatigue and anti-reflection cracking performance. Further research found that the fracture properties n in Paris’ Law showed that WTR/APAO and SBS SAIs had better cracking resistance. The addition of APAO improved the cracking resistance of WTR SAI.

Pervious concrete has been studied widely considering its environmental benefits. Owing to its porous nature, it reduces the runoff quantity recharging the groundwater and as well reduces the effect of urban heat island. Previous studies have been focused on characterizing and understanding structural and functional properties of pervious concrete. However, very few studies have been made on incorporating supplementary cementitious materials (SCMs) in pervious concrete. SCMs, which are by-product of production processes from industries, pose several environmental concerns and hence it becomes imperative to utilize them as partial replacement for OPC considering their pozzolanic action, which is beneficial in improving strength and durability properties. In this study, fly ash and metakaolin were used as partial replacement for OPC with curing condition as another variable. Basic tests such as porosity, density, compressive strength, and permeability were conducted to determine the effect of test variables. The curing conditions were found to be insignificant in affecting the properties of pervious concrete unlike fly ash and metakaolin. A 2% addition of metakaolin decreased porosity by 10%, while the optimum range of fly ash replacement in pervious concrete was found to be between 5 and 15%. Statistical tests indicated that fly ash content dominated the effect on influencing permeability and compressive strength.

Alkali-activated slag was first used as cementing material in seawater coral aggregate concrete (SCAC) production in this paper. It would contribute to both the environmental protection and raw materials obtained locally in island construction far away from the mainland. However, cracks would be harmful to structural durability of SCAC especially under ocean environment. Thus, the present study is mainly aimed at the fracture properties of alkali-activated slag SCAC (ASSCAC) by virtue of three-point-bending tests. Two types of slag (Types A and B) and two types of coral aggregates, namely columnar and crushed coral coarse aggregates (CCA), are considered. Besides, two beam depths of 100 mm and 150 mm are prepared and the initial notch-to-depth ratios are set from 0.1 to 0.7 for each depth. Results show that the failure modes of all the beams are fracturing of CCAs. Then an analytical approach was proposed to predict the fracture parameters of ASSCAC. The size-independent uniaxial tensile strength and fracture toughness are obtained by using the experimental maximum fracture loads and the former proves to be the maximum tensile stress at the fictitious crack-tip. Then the correlation between the maximum fracture load and the local fracture energy at crack-tip region is obtained. The size-independent fracture energy is derived based on the comparison between the analytical and experimental maximum fracture loads. The tensile strengths of ASSCAC mixed by Type A slag and crushed CCAs are larger. But the fracture toughness and fracture energy are slightly higher when the ASSCAC is made by Type B slag.