High Volume Ground Granulated Blast Furnace Slag Research Articles

Development of sustainable engineered cementitious composite with enhanced compressive performance at elevated temperatures using high volume GGBFS

This study presents the development of an environmentally sustainable hybrid polyethylene (PE)-steel fibre reinforced engineered cementitious composites (ECC) to achieve enhanced compressive performance at elevated temperature. Utilizing a unique blend of industry by-products—ground granulated blast furnace slag (GGBFS), dolomite powder, and fly ash, with supplementary cementitious materials exceeding 50% replacement level, the developed ECC achieves remarkable improvement in compressive strength, both at ambient and elevated temperature conditions. A total of 340-cylinder specimens were tested to analyse the compressive properties after exposure to 20–800 °C, and the effect of different binders, fibre ratio on the residual compressive behaviour was investigated. Additionally, effects of the critical fire test parameters such as pre-drying and cooling treatment were also studied. The research findings indicate that incorporating high-volume GGBFS blends significantly improved the compressive performance of the ECC irrespective of the type of test parameters. Notably, a specific blend comprising of GGBFS, fly ash (GGBFS:fly ash = 1:0.2) and dolomite (15% by binder weight) demonstrated 138 MPa strength at room temperature and at least 75% and 45% strength retention at 600 °C and 800 °C, respectively. This was significantly higher than the values reported in literatures (∼48% at 600 °C and ∼12% at 800 °C) for similar type of ECC. The study also highlights the impact of sudden cooling in water and confirms the occurrence of both thermal shock and rehydration through microstructural analysis. Environmental impact analysis was also conducted to demonstrate the low carbon emission of the developed ECC.

Compressive strength and chloride permeability of cement-based materials with high-volume compound mineral admixtures

Ground granulated blast-furnace slag (GGBFS) is well known to be capable of improving the performance of cement-based materials, but few studies focus on the impact of its large dosage on concrete containing basalt powder. In this study, the compressive strength and chloride permeability of cement-based materials with compound mineral admixtures (CMAs) containing high-volume GGBFS, basalt powder and desulfurisation gypsum were investigated. The results showed that the mortar strengths at 3, 7 and 28 days decreased with increasing GGBFS content, but that at 56 and 84 days increased with the addition of 45 wt% GGBFS. This is because the activity of GGBFS at an early stage has not been stimulated and the pozzolanic effect is exerted at a later stage. Moreover, cement replacement with up to 55 wt% GGBFS caused a significant decrease in the chloride diffusion coefficient of the mortar and concrete. Furthermore, the incorporation of GGBFS led to a remarkable refinement in pore structure of the hardened paste due to pozzolanic and filler effects. Therefore, the partial replacement of cement with high CMA contents (≥70 wt%) in concrete is desirable for ocean projects requiring low chloride permeability, and significantly reduces carbon dioxide emissions.

Particle packing optimization and pore structure assessment of ternary cementitious system based on X-ray computed tomography and mercury intrusion porosimetry

The introduction of high-volume steel slag into ordinary Portland cement (OPC) has a negative effect on the pore structure due to its poor hydraulic reactivity. Synergistic effects between steel slag and ground granulated blast furnace slag (GGBFS) in cementitious system have drawn increasing attention. In this study, the modified Andreasen and Andersen (MAA) model was adopted for the mixture design of ternary cementitious system incorporating high-volume ultrafine steel slag (USS) and GGBFS without a compromise in strength. X-ray computed tomography (X-CT) and mercury intrusion porosimetry (MIP) were applied to characterize the pore structure of various cementitious mortars in terms of porosity, pore size, pore number, pore morphology and homogeneity. Results manifested that the adverse impact of USS addition on the pore structure of binary cement was effectively mitigated in the ternary cement USS-GGBFS-OPC after mixture optimization, whereby the pore size was shifted toward a finer distribution and simultaneously with a higher uniformity and consequently promoting the compressive strength development. An increase of cumulative pore volume as captured by X-CT was associated with an exponential decrease of the number of pores while together with larger pore sizes. The increase in the number of small pores led to an increase in the pore tortuosity and degree of sphericity. The fractal dimension of pores was negatively correlated with pore inhomogeneity and compressive strength. These findings provide new insights into homogeneity-oriented mixture design of composite cementitious binders based on gap-graded particle packing, together with their synergistic effects on hydration progress.

Effect of Ground Granulated Blast-Furnace Slag on the Bond Strength of Recycled Aggregate Concrete

This research experimentally investigated the bond strength of recycled aggregate concrete containing high volume ground granulated blast-furnace slag (GGBFS). Concrete mixtures made with 0%, 15%, 45% and 75% replacement of cement with GGBFS were prepared. Water-to-binder ratios ranged from 0.30 to 0.50. The fresh properties, compressive strength and pullout bond strength of concrete were measured and presented. Test results shows that the compressive strength and bond strength of concrete containing GGBFS were superior to the concrete without GGBFS at all ages. In addition, the bond strength of the recycled aggregate concrete containing high volume GGBFS (75% cement replacement) could exceed that of natural aggregate concrete without GGBFS. This result shows that it is feasible for applying recycled aggregate concrete incorporating high volume GGBFS in concrete constructions.

Improvement of early strength of structural lighweight concrete using large volumes of Ground-Granulated Blast Furnace Slag

This paper presents the experimetal results on the influence of chemical additive, i.e. Ca(NO¬3)2, on the compressive strength of structural lighweight concrete (LWC) containing high volume ground-granulated blast-furnace slag (GGBFS). Structural LWC using 27% (by vol. of concrete mixture) fly ash hollow microspheres, also known as cenosphere (FAC) is used up to 27% by volume of concrete mixture with a density in the range from 1.600 to 1.900 kg/m3, compressive strength over 40 MPa. Achieving high early age compressive strength is difficult and challenging for lightweight concrete with high volume GGBFS. Therefore, the present study focused on the influence of Ca(NO3)2 on the strength development (under curing condition of 27 ± 2oC and relative humidity of 60 ± 5%) of structural LWC containing 50, 65 to 80% GGBFS (replacing cement content by weight). The experimental results show that the addition of Ca(NO3)2 enhanced the early-age compressive strength of structural LWC up to 11,6% and 9,0% at the age of 3, 7 days, respectively.

Mass GGBFS Concrete Mixed with Recycled Aggregates as Alkali-Active Substances: Workability, Temperature History and Strength.

This study provides the results of an experiment on the possibility of using high-volume ground granulated blast furnace slag (HVGGBFS)-based concrete as mass concrete. In addition to the control concrete, the total weight of the binder was 75% ground granulated blast furnace slag (GGBFS) and 25% ordinary Portland cement (OPC). For the aggregates, both natural and recycled aggregates were used. Three specimens with dimensions of 800 mm × 800 mm × 800 mm were prepared to simulate mass concrete. The workability, temperature aging and strength of the mass concrete were tested. The test results showed that utilizing HVGGBFS concrete as mass concrete can significantly reduce the heat of hydration due to the low heat of hydration of GGBFS, while the heat of hydration of GGBFS and recycled aggregate combination is 11.2% higher than normal concrete, with a slump that is 31.3% lower than that of plain concrete. The results also showed that the use of recycled aggregates in HVGGBFS concrete can significantly reduce workability. However, the compressive strength is higher than when natural aggregates are used due to the alkali activation effect caused by the recycled aggregates. The compressive strength at 7 and 28 days increased by 33.7% and 16.3%, respectively.

Mechanical properties and microstructure of engineered cementitious composites with high volume steel slag and GGBFS

Engineered cementitious composites (ECC) achieve exceptional ductility and durability, but the heavy reliance on cement has notable environmental impacts. In this work, the steel slag (SS) and ground granulated blast furnace slag (GGBFS) are introduced into ECC by largely substituting cement. The impact of SS and GGBFS content on ECC’s mechanical performance is analyzed at macro and micro scales in terms of fiber dispersion, mechanical properties, cracking patterns, cement hydration, and microstructure. The results demonstrate that SS can enhance fiber dispersion due to the low water demand and the strong electronic double layer formed on the surface of SS particles. While ECC with a high volume of SS alone (60 wt% SS) lacks the necessary strength for structural applications, the combination of GGBFS and SS exhibits favorable hydration properties and can effectively refine the pore structure. Thus, ECC with GGBFS and SS attains ideal toughness. ASTM C 1018 based toughness indices reveal that the Imax of ECC with 30 wt% GGBFS and 30 wt% SS is 2.30 times that of OPC based ECC. A sustainability analysis demonstrates that substituting 30 wt% SS and 30 wt% GGBFS for cement leads to a 33% reduction in energy consumption and a 53% decrease in CO2 emissions of ECC.

Efficacy of high-volume fly ash and slag on the physicomechanical, durability, and analytical characteristics of high-strength mass concrete

In the last decade, the use of high-strength mass concrete has increased for the building of various high-impact infrastructure projects. Due to the larger size of sections and greater volume of Portland cement, the reduction of core strength and durability is often witnessed in these concrete sections. In this study, an attempt has been made to minimize the above issues by substituting ordinary Portland cement (OPC) with high-volume fly ash (FA) and ground granulated blast furnace slag (GGBFS). For this purpose, six types of samples viz. S1 (100% OPC), S2 (20% FA + 80% OPC), S3 (35% FA + 65% OPC), S4 (50% GGBFS + 50% OPC), S5 (70% GGBFS + 30% OPC), and S6 (33% FA + 33% GGBFS + 34% OPC) were prepared. The performances on the actual core concrete were evaluated by analyzing the peak temperature, compressive strength of cylindrical cores, rapid chloride migration test (RCMT), X-ray diffraction (XRD), thermogravimetry (TG), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM). Additionally, the bulk densities (wet and dry), water absorption, apparent porosity, and compressive strength of cube samples are also reported. Analyzing the results critically, it was observed that the use of high-volume FA and GGBFS (S5 and S6 samples) lowered the peak core temperature by 11–13 °C, increased the compressive strength of cores by 8–10 MPa, and lowered the RCMT values of cores by 12 × 10−12 - 13 × 10−12 m2/s as compared to the S1 (control) sample. Additionally, the increase in the ratio of the core-to-cube strength for the S5 and S6 samples is noted to be 24% and 29%, respectively, more than the control sample at 56 days of curing. The enhanced performance of the high-volume FA and GGBFS-based samples is due to the less core temperature rise due to less hydration reaction at the early ages and more secondary hydration reaction at the later ages, which has been justified by the XRD, FTIR, TG, and FESEM analyses. Finally, the sustainability and cost analysis revealed that the use of high-volume FA and GGBFS can significantly reduce embodied energy by 39–42%, embodied carbon by 53–58%, and production costs by 16–17%. The approach proposed in the article regarding the use of high-volume FA and GGBFS results in more green, durable, sustainable, and cost-effective high-strength mass concrete.

Autogenous deformation induced- stress evolution in high-volume GGBFS concrete: Macro-scale behavior and micro-scale origin

This study aims to experimentally investigate the autogenous deformation and the stress evolution in restrained high-volume ground granulated blast furnace slag (GGBFS) concrete. The Temperature Stress Testing Machine (TSTM) and Autogenous Deformation Testing Machine (ADTM) were used to study the macro-scale autogenous deformation and stress evolution of high-volume GGBFS concrete with w/b ratios of 0.35, 0.42, and 0.50. The early-age cracking (EAC) risk (quantified by stress-strength ratio) and stress relaxation were analyzed extensively based on ADTM and TSTM results. Furthermore, Environmental Scanning Electron Microscopy (ESEM), X-ray Diffraction (XRD), and Mercury Intrusion Porosimetry (MIP) were conducted to explore the micro-scale origin of the autogenous deformation of high-volume GGBFS concrete, which supports the observations on the macroscale measurement of TSTM/ ADTM tests. This study finds that the ettringite formation in the first two days results in autogenous expansion, which can delay the appearance of tensile stress. The magnitude of autogenous expansion depends on the compatibility of ettringite content and pore size. The w/b ratio of 0.42 turns out to be optimal because it produces the highest amount of ettringite and results in the highest autogenous expansion. In comparison, the w/b ratio of 0.35 introduces significant autogenous shrinkage after the expansion peak and therefore corresponds to a high early-age cracking risk.

Synergistic effect of nanosilica and high-volume granulated blast furnace slag on pore structure and mechanical properties of cementitious materials

High-volume ground granulated blast furnace slag (GGBS) is often used in cementitious materials to produce environmentally friendly building materials. However, high-volume GGBS (HVS) can lead to numerous problems including low strength and loose structure of concrete at the early age. To overcome these drawbacks, nanosilica (NS) is used to compensate the early strength insufficiency of high-volume granulated blast furnace slag (HVS) cementitious material by improving the pore structure. Currently, it is still a challenge to perform accurate testing of the pore structure. Although mercury intrusion porosimetry is widely used to test the pore structure of cementitious materials, there is still some controversy. In this study, the 1H NMR tests are used to measure the pore structure of NS and HVS blended materials and compared with standard MIP tests to comprehensive evaluate the effect of NS on the pore structure of HVS cementitious materials. Results indicate that NS can significantly improve the early strength of HVS cementitious materials and the greater the volume of GGBS, the greater the degree of enhancement exhibited by NS. The compressive strength increases of 23.5% and 30.2% were presented by 3-day S6N2 and S8N2 samples while flexural strength increases of 25.3% and 68.7% was resulted. NS significantly reduces the amount of harmful pores and increases the amount of harmless pores (smaller than 100 nm) in the HVS cementitious materials, it was also found that NS had no significant effect on the reduction of the total pore volume. Results showed that the strength of samples with high porosity was not necessarily low, the pore distribution and pore composition have a greater effect on the strength than the total porosity. The pore volume (>3 nm) obtained from the MIP test was larger than the pore volume measured by 1H NMR for early age samples. The difference in the porosity and pore size distribution obtained from the MIP and 1H NMR test was large at early age. The effect of NS on the pore structure of HVS system was investigated in more detail by 1H NMR and MIP techniques to provide a further theoretical basis for the application of NS in HVS cementitious materials.

Enabling sustainable rapid construction with high volume GGBS concrete through elevated temperature curing and maturity testing

Nowadays, low carbon footprint concrete for construction relies heavily on ground granulated blast-furnace slag (GGBS) as a partial cement replacement material (CRM) in places where other CRMs are in short supply. However, it is relatively well-known that the low early-age strengths of GGBS concretes discourage the maximisation of cement replacement in most applications; a constraint which can be potentially overcome through exploitation of hydration acceleration under elevated temperature curing. Concrete and mortar mixes of 47 MPa 28-day target mean cube strength were developed and investigated in this study with various percentages of GGBS (0, 20, 35, 50 and 70%) and cured under isothermal and non-isothermal regimes (20, 30, 40 and 50 °C and adiabatic). Higher temperatures appeared to significantly accelerate the strength gain of GGBS concretes, particularly those containing high GGBS percentages. In-situ strength development may be estimated through maturity functions which were initially developed for neat Portland cement concretes. The accuracy of several maturity functions, such as the Nurse-Saul, Arrhenius, Weighted Maturity, Weaver-Sadgrove and Rastrup ones, were examined together with two strength-maturity/time correlations. It was found that although maturity methods can be used to optimise a concrete mix in terms of GGBS content and depending on the application, it is not possible to obtain consistently reliable estimates for GGBS concretes from the current functions. Nonetheless, from the current models considered, the Arrhenius, Weighted Maturity and Rastrup functions appear as more appropriate for higher replacement levels of cement with GGBS. Overall, the present study highlighted a need for further improving maturity functions to account for the strength development of GGBS concrete.

Experimental investigation on high volume ground granulated blast furnace slag concrete

The present confront among the construction industry is to curtail the production of the ordinary Portland cement (OPC), which is directly responsible to the emission of harmful gases like CO2 during the manufacturing and also depletion of natural resources like lime stone, coal etc. The present investigation is focused to develop the sustainable concrete using complementary cementing materials (CCMs) for the sustainable environment. Ground granulated blast furnace slag (GGBS) is one among the sustainable alternatives for ordinary Portland cement (OPC) to produce green concrete and because of its high calcium silicate content it has excellent cementious content and has been used in the construction industry for years as a replacement for ordinary Portland cement (OPC). The paper presents the performance of the Binary concrete made by replacing the OPC with high volume GGBS up to 70%. In total 6 binary mixtures and conventional mix were prepared for M40 grade of concrete. Flow characteristics and strength properties (compression, split tensile and flexural strength) are determined for both conventional and binary concrete at the age of 7, 28, 60, 90 days. The test results proved that the binary concrete had considerable performance regarding workability and strength of the binary concrete over conventional mix.

Hydration and Microstructure of High-Volume Ground Granulated Blast Furnace Slag Concrete Incorporating Metakaolin

In order to relieve the carbon emission of concrete industry, the application of high-volume ground granulated blast furnace slag (HVGGBFS) concrete is one of low cost and effective methods, but its properties develop slowly which needs to be solved. The impact of metakaolin (MK) on the microstructure and hydration evolution of HVGGBFS concrete has been investigated through the compressive strengths, non-evaporable water, morphology and nanoindentation. The results show that the non-evaporable water evolution of HVGGBFS concrete with MK has a similar trend with the compressive strength evolution. The use of 10% MK increases the compressive strengths of HVGGBFS concrete, and from the beginning of 28 days, its strengths are higher than those of the control concrete without GGBFS and MK. The use of 10% MK replacing cement reduces pores and unhydrated particles of HVGGBFS concrete, and however, increases high density calcium-silicate-hydrate (HD C–S–H) and ultra-high density C–S–H (UHD C–S–H), which may be attributed to C–S–H generated by the pozzolanic reaction of MK largely being HD C–S–H and UHD C–S–H.

Promoting utilization rate of ground granulated blast furnace slag (GGBS): Incorporation of nanosilica to improve the properties of blended cement containing high volume GGBS

Utilization of high volume ground granulated blast furnace slag (GGBS) to produce cement-based materials (CBMs) meets the requirements of sustainable development. However, high volume GGBS will significantly reduce some properties of CBMs. Incorporation of nanosilica is a potentially feasible approach to solve the problem. In present paper, effects of nanosilica (1 wt%, 2 wt% and 3 wt%) on hydration and microstructure of blended cement incorporating high volume GGBS (80 wt%) have been studied by testing setting time, compressive strength, hydration heat, hydration products and pore structure. Results reveal that nanosilica shortens the initial and final setting time of blended cement by 10.75%–20.56% and 10.45%–23.00%, respectively. Furthermore, nanosilica enhances early hydration heat release rate of cement and GGBS. Meanwhile, nanosilica increases cumulative heat release of blended cement by 23.40%–26.46%. However, nanosilica hinders cement hydration after curing for 7 d. Results of thermal analysis indicate that 80 wt% GGBS significantly reduces the content of chemically bound water, while nanosilica improves the parameter by 1.32%–5.91% at 56 d. Additionally, 80 wt% GGBS increases cumulative porosity by 31.89% at 28 d, but nanosilica decreases cumulative porosity by 3.05% at 28 d. Both high volume GGBS and nanosilica can decrease average pore diameter and enhance microstructure of cement paste. Ultimately, nanosilica increases the 28 d compressive strength by 8.27%–19.23%, which partially compensates for the reduction of compressive strength caused by high volume GGBS. This paper can provide the essential foundation for the theory of nanosilica-modified CBMs with high volume GGBS, help to improve the effective utilization rate of GGBS and realize sustainable development of CBMs.

Structural performance of RC beams containing high-volume ground granulated blast furnace slag and recycled coarse aggregate with lime

In this paper, the structural performance of reinforced concrete (RC) beams containing high volume ground granulated blast furnace slag (GGBFS) and recycled coarse aggregate (RCA) in replacement of Ordinary Portland cement (OPC) and natural coarse aggregate (NCA), respectively, with lime activator is studied. Nine beams of different combinations of RCA and GGBFS with/without lime and superplasticiser are designed as per IS: 456 (2000). The beams are subjected to two-point loading under universal testing machine. Various structural parameters like cracking, load bearing capacity, load vs. deflection, stiffness and energy absorption are studied. All the beams except two beams have failed in shear. These two beams, which are prepared using RCA, GGBFS, lime and superplasticiser, fail in flexure and show better structural performance than the control beam. It may be due to the reason that the above combination enhances the compressive strength of the concrete significantly, i.e. up to 16% more than that of the control mix, and consequently the shear strength. The enhanced shear strength changes the failure mode from shear failure (brittle) to flexural failure (ductile) showing better structural performance. Moreover, these two beams have shown up to 7.14%, 8.18%, 18.3%, 45% and 53.3% enhancements in cracking load, load bearing capacity, stiffness, deflection and energy absorption, respectively, as compared to those of the control beam. A comparison between the results obtained experimentally in the present investigation and predicted from different standard codes and model shows that the experimental results are in a conservative side due to which these codes/guidelines can be used safely for the GGBFS based RAC. This study clearly reveals that the concrete containing high volume GGBFS and RCA with addition of lime and superplasticiser having better structural performance in comparison to the normal can be used safely in structural applications by utilising high volume of wastes, preserving huge natural resources, reducing cement consumption and enhancing the environmental soundness due to which it can achieve sustainability in the construction industry.

Assessment of Mechanical, Thermal and Durability Properties of High-Volume GGBS Blended Concrete Exposed to Cryogenic Conditions.

The purpose of this study is to suggest the optimum mix design with a high volume of GGBS (Ground Granulated Blast-furnace Slag) replacement and the procedure of the cryogenic test to consider mechanical and thermal properties, and durability performance. To decide the optimum mix design, four mix designs with high-volume of GGBS replacement were suggested, in terms of the slump and retention time. Based on the test results, with respect to the workability and compressive strength, the mixtures with 65% of GGBS (C40-2 and C40-4) were better than the mixtures with 50% and 60% of GGBS (C40-1 and C40-3). After selecting two mixtures, two types of cryogenic test methods were conducted under one-cycle cryogenic condition (Test A) and 50-cycles cryogenic condition (Test B). As a result, in Test A, the compressive strength and elastic modulus of the C40-2 and C40-4 mixtures tended to be decreased over time, because of the volume expansion of ice crystals contained in the capillary pores. In Test B, the mechanical properties of the C40-4 mixture were better than those of the C40-2 mixture, in terms of the reduction rate of compressive strength and elastic modulus. In the view of the heat of hydration, the semi-adiabatic test was conducted. In the results, the C40-4 mixture was better to control the thermal cracks. Thus, the C40-4 mixture would be more suitable for cryogenic concrete and this procedure could be helpful to decide the mixture of cryogenic concrete. In the future, the long-term performance of cryogenic concrete needs to be investigated.

Impact of high volume GGBS replacement and steel bar length on flexural behaviour of reinforced concrete beams

The Ordinary Portland Cement (OPC) is one of the major ingredient utilized for the manufacture of concrete. The manufacturing of cement includes the release of huge amounts of CO2 gas as a main contributor for greenhouse influence and global warming. Several researchers have investigated the characteristics of OPC concrete utilizing cementitious materials like fly ash, silica fume, and Ground Granulated Blast furnace Slag (GGBS) as replacement materials. The article aims to investigate experimentally the flexural behavior of concrete beams with GGBS. The experimental work was divided into three stages, the first one consists of six reinforced concrete beam specimens with (0%, 40% and 60%) of GGBS. During this stage, the used steel bars were 8 mm diameter and 500 mm in length. In the second stage, the length of the steel bars was reduced to 400 mm with the best mixture of (GGBS+OPC) that obtained from stage 1. In the third stage, the best length of steel bars was used with the best (GGBS+OPC) ratio to be tested at 7, 14 and 28 days from the date of casting. Consequences of this exploration suggests that replacement of OPC with 40 percent GGBS with 500 mm steel bar length can be used in reinforced concrete specimens as it shows comparable results relative to control mixtures (0% GGBS).

Hydration-drying interactions in a high-volume ground granulated blast-furnace slag mortar

An experimental study of interactions between hydration and early drying was carried out on a mortar with a GGBFS volume as high as the OPC volume. 1 day after casting, the mortar was subjected to 6-month unidirectional drying in natural surrounding conditions in laboratory. At the end of the exposure period, Portlandite content, water porosity and pore size distribution were found to be not uniform along the material. When approaching the exposed surface, due to the early drying, the material gradually becomes less hydrated, more porous, and less dense. This causes strong gradients of transfer properties between the exposed surface and the core of the material, which facilitates exchanges with the surrounding environment near the surface and lowers the resistance against the penetration of aggressive agents. For instance, it was shown that considering properties only within the core of the material, sheltered from drying, significantly underestimates the risk of carbonation, and thus the risk of corrosion of reinforcement in concrete.

Assessment of Optimum CaO Content Range for High Volume FA Based Concrete Considering Durability Properties

There have been many studies on the effect of durability and compressive strength on the increase of the mixing rate of admixtures. However, there is no research that can provide a guide on the optimal mixture proportions for maintaining compressive strength and secure durability properties when using local materials. Therefore, the purpose of this article is to assess the durability and engineering performances of concrete based on local fly ash (FA), as well as to derive the optimum CaO content scope for ensuring durability. The results of this study were compared with the results of the previous study of high-volume ground-granulated blast-furnace slag (GGBFS) concrete. To achieve this, tests were carried out by increasing the admixture mixing rate in 10% increments from 0% to 70%. The unit water was set at 175 kg/m3 and the amount of binder was set at 330 kg/m3. It was found that the overall compressive strength of the hardened concrete decreased when the admixture mixing rate increased. In addition, the compressive strength of specimens tended to improve as all the CaO contents of the admixture types increased. When the durability properties were examined, it was found that the relative dynamic elasticity modulus and carbonation depth decreased, and the chloride penetration depth increased as the CaO content increased for both GGBFS and FA. The weight loss rate, however, remained similar. Based on the results of this study, the optimal CaO content that achieved satisfactory engineering and durability properties was found to be between 39% and 48% for FA. The results of this study will be able to offer guidelines for the mixture rates of FA when mixing durable concrete for use in the field. Additionally, these results are expected to be utilized as a basis for determining instructions relating to chemical composition in order to develop binders with improved durability.

Characterization of lime activated recycled aggregate concrete with high-volume ground granulated blast furnace slag

The present paper explores the effect of inclusion of hydrated lime on the strength, durability, physical and non-destructive characteristics of recycled aggregate concrete (RAC) containing high-volume ground granulated blast furnace slag (HV-GGBFS). For fulfilling this objective, seven numbers of concrete mixes inclusive of one control mix are considered. Three concrete mixes have 0%, 50% and 100% recycled coarse aggregates (RCA) and 60% ground granulated blast furnace slag (GGBFS) for each mix. Other three concrete mixes have RCA percentage of 0%, 50% and 100% and the combination of 7% lime and 60% GGBFS for each mix. The characterization of these concrete mixes includes the evaluation of compressive strength, durability, physical and non-destructive parameters after designated curing period. The durability study comprises of the evaluation of resistance to sulphate, acid and chloride attack as well as water sorptivity. The physical properties like density, water absorption, and volume of voids of the above concrete mixes are also evaluated. In addition, the non-destructive characteristics of mixes are accessed by performing rebound hammer and ultrasonic pulse velocity tests. The experimental results conclude that the above mentioned durability aspects show superior performance with inclusion of high-volume GGBFS with lime. Similarly, water absorption and volume of voids of NAC/RAC also reduce with the inclusion of high-volume GGBFS (60%) along with 7% lime. Further, the non-destructive parameters of designated concrete mixes investigated in this study confirm the strength variation of all the mixes.