Amount Of Supplementary Cementitious Materials Research Articles

Shrinkage and Creep Properties of Low-Carbon Hybrid Cement.

Hybrid cements combine clinker with large amount of supplementary cementitious materials while utilizing hydration and alkali activation processes. This paper summarizes shrinkage and creep properties of industrially produced H-cement, containing only 20% of Portland clinker. In comparison with a reference cement CEM II/B-S 32.5 R, autogenous shrinkage is smaller after 7 days, and drying shrinkage is similar at similar times. A different capillary system of H-cement leads to faster water mass loss during drying. Basic and total creep of concrete remains in the standard deviation of B4 and EC2 creep models. The results demonstrate that shrinkage and creep properties of concrete made from H-cement have similar behavior as conventional structural concrete or high-volume fly ash concrete.

Proportioning Study for Low-carbon Sulfate-resistant Concrete by Microbial Corrosion Testing

In addition to water absorption and chloride permeability measurement, sulfate resistance testing by microbial corrosion was conducted on low-W/B concretes made using large amounts of supplementary cementitious materials, including GGBF slag, for use as sewage pipes. The corrosion testing was conducted in a corrosion chamber at 30°C with a H2S concentration of 100 ppm, in which specimens were exposed to the environment under two conditions: one group in the gas and the other partially submerged in circulating sewage water. After exposure for one year, the corrosion rate in the partially submerged phase tended to be 1.3 to 2.9 times higher than in the gas phase. Also, the amount of corrosion was compared, with the corrosion products being examined by EPMA. Exposure to the gas phase and partially submerged phase was thus found to represent the stage of forming monosulfates and dihydrate gypsum and ettringite, respectively. Deterioration was found to proceed at a higher rate as the pH value on the concrete surfaces decreased. Within the range of this study, the addition of silica fume and small-size GGBF slag led to no appreciable effect.

A Study on Durability and Microstructural Analysis for Macro Synthetic Fiber Reinforced Concrete with Supplementary Cementitious Materials

Background: Thermal cracking, delayed ettringite production and low tensile strength are three significant problems for high-strength concrete. Objectives: The current experimental study aims to determine the durability characteristics of concrete for application in pavements. To test how well the M40 grade of concrete absorbed chloride and water, the amounts of Supplementary Cementitious Materials (SCM) like Granulated Blast-Furnace Slag (GBFS) and fixed amounts of Fly Ash (FA) and Macro Synthetic Fiber (MSF) were optimized. Methods: One sample (S1) was made entirely of Ordinary Portland Cement (OPC) and five samples (S2, S3, S4, S5, and S6) made simply of SCMs, in which OPC was substituted with 20% FA+20% GBFS+1.5% MSF, 20% FA+25% GBFS+1.5% MSF, 20% FA+30% GBFS+1.5% MSF, 20% FA+35% GBFS+1.5% MSF, and 20% FA+40% GBFS+1.5% MSF, respectively, were cast in standard blocks with a volume of one cubic meter for this purpose. Field Emission Scanning Electron Microscopy (FESEM), Fourier-Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) investigations are used to examine the number of hydration products created at 28 days, which differ for different percentages of SCMs. Findings: Furthermore, 501, 520, 535, 565, and 590 coulombs are the measured Rapid Chloride Permeability Test (RCPT) values for the S2 to S6 samples. Similarly, the S1 sample is projected to have more than 2600 coulombs, showing a better endurance of samples based on SCMs. The microstructural characterization findings (i.e., XRD, FTIR and FESEM) suggested that GBFS and FA are promising SCMs for enhancing the strength and durability properties of the mix. Novelty and applications: This study validates the viability of using GBFS, FA, and MSF in pavement applications, yielding noteworthy environmental advantages and lowering dependency on OPC. Keywords: Durability, Microstructural investigation, Macro synthetic fiber, Fly ash, Granulated blast furnace slag, Pavements

Comprehensive evaluation of early-age hydration and compressive strength development in seawater-mixed binary and ternary cementitious systems

Seawater-mixed concrete (SWC) is a proposed solution for catering to the needs of developing nations facing extremely severe water stress. Recent research works advocate the feasibility of producing SWC by adding supplementary cementitious materials (SCMs) and alternative reinforcements without reducing the engineering properties of the same. However, limited information is available for optimising the type and amount of SCMs in binary and ternary blended SW-mixed cementitious systems for achieving desirable strength development and early-age hydration. A comprehensive study to understand the evolution of heat of hydration and strength up to 28 days was conducted on 31 binder compositions mixed with both fresh water (FW) and seawater (SW). Fly ash, slag, metakaolin, and limestone are the supplementary cementitious materials used with CEM I as a primary binder at a replacement level between 10 and 70%. Isothermal calorimetry results revealed an increase in total heat of hydration and a reduction in setting time with SW-mixed cement pastes compared to their FW-mixed counterparts. Similarly, a significant increase in strength between 0 and 50% was observed in SW-mixed cement pastes. Suitable binder combinations showing an increase in compressive strength and not a significant reduction in strength compared to the CEM I reference mix were identified using the strength improvement factor approach. Binary and ternary blended cementitious, consisting of fly ash, slag, and metakaolin at different replacement levels, are amongst the chosen binder combinations.

Modeling the impact of supplementary cementitious materials on compressive strength of recycled aggregate concrete forest-random approach

Recycled concrete aggregates (RCAs) and supplementary cementitious materials (SCMs) may substitute some cement and natural aggregates (NA) in concrete manufacturing. However, their effects on recycled aggregate concrete (RAC) compressive strength are difficult to model. Reactivity, silica, and alumina modulus were examined for cementitious materials' chemical complexity. Random Forest approaches were developed to predict and analyze RAC compressive strength. Even with RCAs and SCMs, the RF model accurately estimated concrete compressive strength. The Variable Importance (VI) research examined how input factors affected RAC compressive strength. VI indicated that silica fume contributes most to RAC compressive strength, followed by cementitious materials' reactivity modulus, cement content, silica modulus, fine natural aggregate content, and coarse natural aggregate dosage. The water dosage, water/binder ratio, and RCA content lower the RAC compressive strength. As a result, to highlight, the amount of SCM was not significant, but its nature was (i.e., hydraulic, silica pozzolanic, or alumina pozzolanic).

Study of flexural strength of concrete containing mineral admixtures based on machine learning

In this paper, the prediction of flexural strength was investigated using machine learning methods for concrete containing supplementary cementitious materials such as silica fume. First, based on a database of suitable characteristic parameters, the flexural strength prediction was carried out using linear (LR) model, random forest (RF) model, and extreme gradient boosting (XGB) model. Subsequently, the influence of each input parameter on the flexural strength was analyzed using the SHAP model based on the optimal prediction model. The results showed that LR, RF, and XGB enhanced the accuracy of forecasting sequentially. Among the characteristic parameters, the most significant effect on the flexural strength of concrete is the water-binder ratio, and the water-binder ratio shows a negative correlation with flexural strength. The effect of maintenance age on flexural strength is second only to the water-binder ratio, and it shows a positive trend. When the amount of fly ash is less than 40% and the amount of slag or silica fume is less than 30%, the correlation between the amount of supplementary cementitious materials and flexural strength fluctuates and a positive peak in flexural strength is observed. However, at a dosage greater than the above, the supplementary cementitious materials all reduce flexural strength. The interaction interval and the degree of interaction between the supplementary cementitious materials and the cement content also differ in predicting flexural strength.

Hydration Processes of Four-Component Binders Containing a Low Amount of Cement.

Results of research on hydration of four-component binders containing very high amounts of supplementary cementitious materials were presented. The samples were composed of blended pozzolana (a mix of conventional fly ash and spent aluminosilicate catalyst), cement (about 20 wt.% in the binder) and Ca(OH)2. Spent aluminosilicate catalyst was proposed as activating component which can improve properties of low-cement blends, while the role of Ca(OH)2 was to enhance pozzolanic reaction. Early and later hydration periods of such blends were investigated by calorimetry, TG/DTG, FTIR and X-ray diffraction. Initial setting time as well as compressive strength were also determined. It was concluded that enhancement of reactivity and improvement of properties of fly ash–cement binders are possible by replacing a part of fly ash with more active fine-grained pozzolana and introducing additional amounts of Ca(OH)2. The spent catalyst is mainly responsible for accelerating action during the first hours of hydration and for progress of early pozzolanic reaction. Fly ash develops its activity over time, thus synergic effect influences the later properties of composites. Samples containing blended pozzolana exhibit shorter initial setting times and higher compressive strength, as well as faster consumption of Ca(OH)2 compared to the reference. Investigated mixtures seem to be promising as “green” binders, alternatives to cement, after optimizing their compositions or additional activating procedure.

Hydration-Strength-Workability-Durability of Binary, Ternary, and Quaternary Composite Pastes.

At present, reducing carbon emissions is an urgent problem that needs to be solved in the cement industry. This study used three mineral admixtures materials: limestone powder (0–10%), metakaolin (0–15%), and fly ash (0–30%). Binary, ternary, and quaternary pastes were prepared, and the specimens’ workability, compressive strength, ultrasonic pulse speed, surface resistivity, and the heat of hydration were studied; X-ray diffraction and attenuated total reflection Fourier transform infrared tests were conducted. In addition, the influence of supplementary cementitious materials on the compressive strength and durability of the blended paste and the sustainable development of the quaternary-blended paste was analyzed. The experimental results are summarized as follows: (1) metakaolin can reduce the workability of cement paste; (2) the addition of alternative materials can promote cement hydration and help improve long-term compressive strength; (3) surface resistivity tests show that adding alternative materials can increase the value of surface resistivity; (4) the quaternary-blended paste can greatly reduce the accumulated heat of hydration; (5) increasing the amount of supplementary cementitious materials can effectively reduce carbon emissions compared with pure cement paste. In summary, the quaternary-blended paste has great advantages in terms of durability and sustainability and has good development prospects.

Effect of supplementary cementitious materials on viscosity of cement-based pastes

Assessment of viscosity is important for development of new concrete technologies. In this study, the effect of particle size and type of supplementary cementitious materials (SCM) and their interactions with the main mixture parameters (i.e., cement type, solid volume fraction (ϕT), amount of SCM) on the viscosity of cementitious paste is analyzed. It is shown that the effect of particle size on viscosity is better explained by the particle number density than by the specific surface area of the cementitious particles. The viscosity can be increased by increasing 1) the number of contact points, which is governed by ϕT and particle number density, or 2) the interparticle force between cementitious particles, which is controlled by the roughness of the cementitious particles and ϕT, which affects the zeta potential of the cementitious paste. ϕT has a greater effect on viscosity than the particle size and interparticle force of the cementitious particles.

Effect of nano-silica on Portland cement matrices containing supplementary cementitious materials

abstract: For a controlled granulometry, this study evaluates the effect of nano-silica on mechanical and rheological properties, as well in the microstructure of Portland cement matrices containing a fixed amount of supplementary cementitious materials and three different types of cements. The rheological behavior of cement pastes was evaluated by rotational rheometry and mechanical performance was measured througth the compressive strength. The microstructure was analyzed by intrusion mercury porosimetry and scanning electron microscopy. There was an increasing on the viscosity of the cementitious matrices, as a consequence of the reduction in the inter particle separation of these suspensions. The optimum content of nano-silica varied according to Ca/Si ratio of Portland cement matrices containing supplementary cementitious materials. The use of nano-silica allowed to modify the pore size distribution of cementitious matrices. And the structure of nano-silica in cementitious matrices has occurred in layers or agglomerates of nano-particles covered by hydration products.

Development of high-strength pervious concrete incorporated with high percentages of waste glass

This study presents the use of waste glass (WG) in pervious concrete, aiming to maximizing the reuse of WG in concrete. The effect of WG aggregate replacement and aggregate to binder ratio (A/B) on the mechanical properties, permeability, thermal conductivity, volume stability and pore structure were determined. The microstructures with and without immersing in 1 M NaOH 80 °C solution were also characterized. The results showed that the compressive strength decreased with the increasing replacement of WG aggregate and A/B, but the water permeability was improved. The presence of WG aggregate was effective in improving the permeability due to the smooth surface of WG aggregate and broader pore size distribution. With 100% WG aggregate replacement with A/B of 2–4, the permeability and compressive strength of the pervious concrete were still higher than the requirement of JIS A 5371. Another encouraging result was that the incorporation of a large amount of WG aggregate showed limited alkali-silica reaction (ASR) expansion in the pervious concrete, which was attributed to the low water to binder ratio, high amount of supplementary cementitious materials (SCMs), and accommodation effect of the porous structure to relieve the expansion pressure caused by ASR gel. Meanwhile, pervious concrete with a WG content of 80.95% could be produced with satisfactory functional properties and low thermal conductivity. Therefore, it is feasible to use WG aggregate to completely replace natural aggregate to achieve the maximum reuse of WG for producing pervious concrete.

Experimental investigation surface abrasion resistance and surface frost resistance of concrete pavement incorporating fly ash and slag

ABSTRACT This investigation was carried out to study the effects of the type and amount of supplementary cementitious materials on mechanical properties and surface durability of Portland cement concrete (PCC) pavement. Three supplementary cementitious materials, two types of fly ash and one ground granulated blast furnace slag, were selected to substitute for a portion of Portland cement with three level contents (5, 15, 25 wt% and 15, 25, 35 wt% for single and compound adding, respectively) in the concrete mixtures. Properties of the concrete were evaluated in laboratory including compressive strength, flexural strength, surface abrasion resistance, surface frost resistance,and microstructure analysis. The results show that the early age strength values of concretes were affected as increasing the replacement contents regardless of fly ash and slag. Effects of both the type and dosage of supplementary cementitious materials on surface abrasion resistance and frost resistance of concrete were remarkable. The concrete with slag had poorer wear resistance than reference concrete and those with fly ash. In addition, general fly ash concrete had worse surface frost resistance than other mixtures, and concrete with slag exhibited better surface frost resistance in saturated sodium chloride solution than reference one and fly ash concrete.

Treatment of weak subgrade materials with cement and hydraulic road binder (HRB)

Portland cement has been widely used to improve the engineering performance of pavement materials. On the other hand, hydraulic road binder (HRB) is now a frequent option in Europe for the treatment of road base, and subbase, and earthworks. HRB contains high amounts of supplementary cementitious materials (SCMs) and by-products. HRB has the potential of reducing the amount of cement clinker thereby making it more cost effective and environmentally friendly. Moreover, the HRB treated materials also have improved workability due to its slower setting and hardening. The primary objective of this study is to investigate the chemical and physical properties of organic clayey subgrade materials treated by different HRBs. The paper first introduced a brief background for the development of hydraulic binders and their current applications for soil stabilisation. Then, it presented the results of laboratory testing for cement- and HRB- treated subgrade soils. Test results indicated that all the three subgrade soils named Dresden, Blenheim, and Niagara were fine-grained soils with substantial silt and cvnlay particles and organic matters. Cement and HRBs significantly improved soil’s engineering properties. The improvement included the change of soil’s environment from acidic to alkaline and prevent development of organics, the significant improved strength, durability, and resilient modulus. In addition, HRB-treated subgrade soils had lower sulfate included than cement-treated one that could reduce the risk of sulfate-induced problems. Among all HRB-treated materials, with abundant curing, the subgrade soils treated with the HRB composed of GUL and slag (HRB-4LS) had the highest UCS values, followed by the soil treated with HRB-4LF (composed of GUL and fly ash), and HRB-3S (GU and GGBFS). It should be noted as well that the soil types played an important role in the treatment. Soils with high plasticity, high organic matters had lower strength and modulus than less plastic and organic soils. Lastly, the differences of the soils could be visualised from the environmental scanning electron microscopy (ESEM) images. This research contributed to a tentative treatment of weak subgrade soil with locally blended HRBs. The results also proposed a potential solution for the treatment of weak subgrade soils at the top of the natural subgrade.

Natural radioactivity of barite concrete shields containing commonly used supplementary materials

The recycling of hazardous materials within new composites has a sustainable importance as it contributes on the reduction of high radionuclide concentrations. In this study, the effect of cementitious materials i.e. viscosity modifier, silica fume and fly ash on the 226Ra, 232Th and 40K activity levels of barite concrete shields was researched by using different mixing compositions in terms of binder content, w/b ratio and the amount of supplementary cementitious materials. In comparison to cement, silica fume and fly ash used in the production of concrete shields were found to have significantly higher activity levels of 40K, as well as 226Ra, 232Th and 40K, respectively. The 226Ra, 232Th and 40K activity levels of concrete shields range between 2.2 and 20.7 Bq kg−1; 2.6 and 7.0 Bq kg−1; 51.5 and 89.3 Bq kg−1, respectively. These activity values were found similar or less than those of building materials in the world. These satisfactory results are mostly caused by the barite source which has lower radioactivity levels. The concrete mixture details used in the study caused significant variation in the natural radioactivity of barite concrete shields. The introduction of silica fume which has high 40K activity levels and fly ash with high 226Ra, 232Th and 40K activity levels compared to cement and barite aggregate, significantly increased the radiological hazard parameters, although all results were found to be below the limits recommended by international reports. In conclusion, 226Ra activity levels of the concrete shields were significantly increased (up to 8.4 times) by the variation of mix design parameters used in comparison with concrete mixtures that have the least 226Ra activity level. The 232Th and 40K activity levels were as well increased in relatively less amounts (1.7 and 0.73 times higher, respectively).

Development of gravitational search algorithm model for predicting packing density of cementitious pastes

Wet packing approach is recently used to design different kinds of concrete. To achieve an optimal particle packing density, the particles should be chosen in a way to fill the voids between larger particles with smaller ones for obtaining a dense and stiff particle structure. The majority of past research on packing density has focused on the evaluation of the particle size distribution of granular matrix to gain improvements in the packing density of cementitious materials, while limited attention has been paid to the construction of a model to estimate the packing density value. To serve that purpose, in this study, a series of 216 collected samples were used for proposing a model. The dataset was divided into two main sets for construction and verification of the model. As the basis for the packing density modeling, use of the gravitational search algorithm (GSA) was proposed. Design of experiment (DOE) software was used to evaluate the contribution of each variable on the proposed model. The outcomes indicate that among different parameters, water amount has the largest effect on the packing density value of cementitious pastes. Moreover, increases in the amounts of supplementary cementitious materials up to certain levels increase the packing density. The coefficient of variation (CoV) of the proposed model is 6.3% which reflects the accuracy and consistency of the model.

Characterisation of full-depth reclaimed pavement materials treated with hydraulic road binders

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.

Determination of optimum mixture design method for self-compacting concrete: Validation of method with experimental results

This paper describes the mixture design method for self-compacting concrete (SCC) while making use of supplementary cementitious materials (SCMs) for the design of concrete mixture to assess early age strength and self-compactability. The proposed procedure “strength-based mixture design method” also makes use of packing theory to achieve targeted strength, enhanced durability, and minimum paste volume. The factors that primarily influence the strength and durability of concrete are the amount of SCM, cement, and water. Depending on data from past studies, a relationship between compressive strength and the water-cementitious material ratio is introduced in the proposed mixture design method to achieve targeted early age strength. The optimal percentage of SCM for use in concrete was assessed using strength efficiency method. The proposed mixture design method shows that SCC made with an optimal percentage of metakaolin as SCM at W/CM of 0.38, 0.26, and 0.17 achieved the expected strengths of 60, 90, and 120 MPa, respectively, after 28 days of standard curing.

Minimising the risk of thermally induced cracking in mass concrete structures through suitable materials selection and processing

ABSTRACTThe hydration of cement is an exothermic reaction which generates around 300 kJ/kg of cement hydrated. In mass concrete structures such as dams and large foundations, this heat of hydration causes a significant rise in temperature in the internal sections of the concrete. If thermal gradients between the internal sections and the near-surface zone of the concrete element are sufficiently large, the thermal stress can cause cracking of the concrete. This cracking may cause functional or structural problems in the operation of the structure. In order to minimise the potential for such cracking, it is necessary to minimise the rate and amount of heat that is evolved, particularly during the early period of the hydration process. This can be achieved by design engineers and concrete technologists through judicious selection and processing of concrete-making materials. This paper presents the observations and results obtained over a number of years from adiabatic testing of concretes, computational modelling of temperature development in large concrete structures and direct temperature measurements in actual structures, with a view to understanding the effects of concrete-making materials on temperature development in concrete. The paper considers the effects of different types of rock aggregates, different types of Portland cement, fineness of grinding of the cement, the addition of supplementary cementitious materials and variations in the concrete starting temperature on temperature development in a large concrete element over time. The results indicate that using a coarser ground cement, adding significant amounts of supplementary cementitious materials and cooling the concrete mixture before placing has a more significant effect in reducing the risk of cracking than varying the aggregate type of the Portland cement type.

Flexural strength reduction of cement pastes exposed to CaCl2 solutions

Calcium chloride (CaCl2) can react with calcium hydroxide (Ca(OH)2) to form calcium oxychloride which can reduce flexural strength and damage concrete. This paper aims to characterize the reduction in flexural strength of cement pastes exposed to CaCl2 solutions using the ball-on-three-balls test. The amounts of Ca(OH)2 and calcium oxychloride in the cement paste are measured using thermogravimetric analysis and low-temperature differential scanning calorimetry, respectively. The volume change that occurs as a result of the reactions between the cement paste and CaCl2 is also measured. The reduction in flexural strength increases as the concentration of the CaCl2 solution increases and the exposure temperature decreases. The flexural strength reduction can be mitigated by increasing the amount of supplementary cementitious materials (fly ash) in the cement pastes. Lowering the water-cementitious materials ratio also reduces the flexural strength reduction. The flexural strength reduction is correlated with the amount of calcium oxychloride and the volume change in the cement pastes exposed to the CaCl2 solution. While the flexural strength reduction is believed to be primarily due to the formation of calcium oxychloride, the formation of Friedel's salt and Kuzel's salt also contributes to the flexural strength reduction.

Coupled effects of crack width, slag content, and conditioning alkalinity on autogenous healing of engineered cementitious composites

Engineered cementitious composite (ECC) is a unique group of fiber-reinforced strain-hardening cementitious composites exhibiting crack self-healing. Due to the absence of coarse aggregates in the ECC mix design, high amount of supplementary cementitious materials (SCM) are generally used to reduce the cement content. The inclusion of slag not only changes the chemical compositionss of the matrix but also alters the crack width of ECC. Both may influence the autogenous healing potential of the slag-based ECC. This paper systematically investigates the influence of the individual factor, i.e. slag content, crack width, and environmental alkalinity, on the autogenous healing efficiency of ECC. Specifically, single-cracked ECC specimens with different slag content and crack width were conditioned under water/dry or NaOH/dry cycles. The autogenous healing performance was evaluated based on crack width reduction, resonant frequency recovery and microstructure analysis. The results show that autogenous healing is determined by a couple effect of physical properties (crack width), chemical compositionss (slag content), and environmental conditions (conditioning alkalinity). At a given slag content and certain alkalinity, there exists a maximum allowable crack width for complete healing, beyond which only partial or no healing would happen. The dominant healing product for the water/dry conditioning is CaCO3 while the NaOH/dry cycles promote slag hydration and results in the formation of CSH and CaCO3 as main healing products. It is concluded that CaCO3 precipitation is more effective to engage autogenous healing than the formation of CSH. The concept to associate allowable crack width and slag content is proposed, which would guides ingredients selection and component tailoring to engage robust autogenous healing in ECC in the future.