Non-evaporable Water Content Research Articles

A Low-Carbon Composite Cementitious Material Manufactured by a Combined Process of Red Mud

In present study, the effects of varying dosages of combined red mud on the microstructure and hydration process of low-carbon composite cementitious material. The findings indicated a gradual decrease in the reactivity of RM, following a linear trend. The non-evaporable water content of the composite binder exhibited an initial increase followed by a subsequent decrease, with the optimal content identified at 10%, for RM content ranging from 10% to 90%, non-evaporable water decreases linearly. Optimal bending strength and compressive strength were achieved in the mortar when incorporating 10% of RM, reaching 8.56 MPa and 51.2 MPa at 28 days, respectively. The porosity was at its lowest when the RM content was added at 10%, but further increasing RM dosage was reversed. The pore size distribution aligned with the experimental findings on porosity. X-ray diffraction (XRD) analysis revealed the involvement of RM in the secondary hydration reaction, thereby enhancing the mechanical properties of low-carbon composite cementitious material. The optimal content of RM is suggested to be 10%, with a maximum recommended limit of 30%. The analysis has shown that red mud particles serve a dual purpose in low-carbon composite cementitious material. They enhance compactness by acting as fillers and promote cement hydration through surface activity, thereby enhancing mechanical properties, durability, and pore size distribution.

Effects of fineness and substitution rate of GGBFS on material characteristics of GGBFS-blended cement mortars: Hydration, non-evaporable water, pore structure, mechanical properties, self-desiccation, and autogenous shrinkage

This study aims to evaluate the effects of the substitution rate and fineness of ground-granulated-blast-furnace slag (GGBFS) on microstructure formation and autogenous shrinkage in order to improve the usability of GGBFS-blended cementitious materials at construction sites. Specimens were prepared using different GGBFS substitution rates (0, 50, 65, and 80 %) and fineness values (4330 and 7650 cm2/g). The hydration kinetics, non-evaporable water content, pore structure, compressive strength, internal relative humidity, and autogenous shrinkage of each specimen were measured. The experimental results showed that self-desiccation and autogenous shrinkage increased as the GGBFS content increased in specimens with up to 65 % GGBFS substitution rate. This is because GGBFS reduces the volume fraction of capillary pores and increases the capillary stress, although it delays the hydration reaction at an early age. The self-desiccation and autogenous shrinkage decreased in the specimens with an 80 % GGBFS substitution rate because the amount of cement was too small; thus, the hydration reaction of the binder was insufficient. Moreover, adding GGBFS with high fineness increased self-desiccation and autogenous shrinkage owing to the GGBFS particles acting as nucleation sites and inert fillers.

Effect of Steel Slag on the Properties of Alkali-Activated Slag Material: A Comparative Study with Fly Ash.

Slag and fly ash (FA) are mostly used as precursors for the production of alkali-activated materials (AAMs). FA is the waste discharged by power plants, while slag and steel slag (SS) both belong to the iron and steel industry. The effects of SS and FA on the strength, microstructure, and volume stability of alkali-activated slag (AAS) materials with different water glass modulus (Ms) values were comparatively investigated. The results show that adding SS or FA decreases the compressive strength of AAS mortar, and the reduction effect of SS is more obvious at high Ms. SS or FA reduce the non-evaporable water content (Wn) of AAS paste. However, SS increases the long-term Wn of AAS paste at low Ms. The cumulative pore volume and porosity increase after adding SS or FA, especially after adding FA. The hydration products are mainly reticular C-(A)-S-H gels. Adding SS increases the Ca/Si ratio of C-(A)-S-H gel but decreases the Al/Si ratio. However, by mixing FA, the Ca/Si ratio is reduced and the Al/Si ratio is almost unchanged. The incorporation of SS or FA reduces the drying shrinkage of AAS mortar, especially when SS is added. Increasing Ms increases the compressive strength and improves the pore structure, and it significantly increases the drying shrinkage of all samples. This study provides theoretical guidance for the application of steel slag in the alkali-activated slag material.

Influence of low-grade metakaolin on creep behavior of concrete

Clay is an abundant material worldwide, but due to the high demand for pure kaolinite clay, research into the application of low-grade metakaolin (MK) is required. However, research on the effect of low-grade MK on the volume stability of concrete is lacking. In this work, concrete composed of low-grade MK, replacing 20%–60 % of Portland cement, is studied using nanoindentation, thermogravimetric, creep and strength measurement in order to demonstrate the impact of high-volume metakaolin on the long-term volume stability of concrete materials. Results show that although the incorporation of high-volume MK degrades the early-age mechanical properties of concrete (7–28 d), the addition of an appropriate amount of MK (20 %) improves the long-term compressive strength of concrete (60–180 d). Meanwhile, concrete mixed with MK (～60 %) shows lower creep stress than plain specimen, and the specimen mixed with 20 % MK has the lowest creep stress. From a nanoscale perspective, incorporating an appropriate amount of MK increases the content of high-density calcium silicate hydrate (C–S–H), which provides a positive effect on reducing the creep stress of concrete. For the 20 % MK-modified specimen, the volume fraction of C–S–H increases by 4.23 % compared to the reference sample, and the relative volume fraction of high-density C–S–H increases by 146.77 %. Meanwhile, the contents of pore and Ca(OH)2 phase, as well as the widths of interfacial transition zone (ITZ), are decreased in the 20 % MK-modified samples compared to plain concrete. The results of thermogravimetric analysis also show that the content of Ca(OH)2 decreases with the increase in MK substitution level, and the non-evaporable water content of the 20 % MK-modified paste is similar to that of plain paste. This study provides theoretical guidance for the application of low-grade clay minerals in concrete.

Preparation of High-Ductility Cement-Calcined Coal-Gangue-Powder-Composite-Based Rapid Repair Material.

Coal gangue is a kind of solid waste. A high-ductility cement-calcined coal-gangue-powder-composite-based rapid repair material (HD-RRM) was prepared by partially replacing cement with calcined coal gangue powder (CCGP) for achieving high ductility and rapid hardening and conforming to the strength requirements of pavement layers. First, the physical and chemical properties and the reactivity of the CCGP were investigated. Second, HD-RRM material was prepared, and its tensile performance characteristic parameters were investigated. Lastly, the hydration products and microstructure of HD-RRM were characterized through tests (e.g., non-evaporable water content, scanning electron microscopy (SEM), X-ray diffraction (XRD), and comprehensive thermogravimetric analysis and differential scanning calorimetry (TG-DSC)). As indicated by the experimental results, the CCGP with a particle size of 1250 mesh exhibited the maximum potential reactivity. The optimal mixing ratio for HD-RRM in the experiments comprised a water-cement ratio of 0.27, a sand-cement ratio of 0.3, a fiber volume fraction of 2%, a cement content of 70%, a CCGP content of 20%, a fly ash (FA) content of 10%, and a superplasticizer content of 0.1%. Using the abovementioned mix design, the prepared HD-RRM was endowed with a 6 h ultimate elongation of 2.75%, an ultimate tensile strength of 7.58 MPa, a compressive strength of 45.4 MPa, and an average crack width of 125.53 μm, which meets the requirements of repair materials and provides a design method for CCGP resource utilization and asphalt concrete road and bridge deck repair.

Experimental study of pure Class G cement hydration up to 150 °C and 50 MPa

A comprehensive experimental investigation of Portland cement hydration kinetics in a wide temperature range from 35 °C to 150 °C with pressure up to 50 MPa was performed by heat of hydration, chemical shrinkage and ultrasonic measurements. Increasing curing temperature was found to have a stronger acceleration effect during the main hydration period while increasing curing pressure had a stronger acceleration effect during the pre-induction period of cement hydration. By comparing chemical shrinkage test results with other methods of estimating cement degree of hydration, such as quantitative X-ray diffraction, non-evaporable water content measured by thermogravimetric analysis, as well as heat of hydration, it was observed that total chemical shrinkage of cement at complete hydration decreased with curing temperature from 35 °C to 75 °C and then stayed stable between 75 °C and 150 °C. Similarly, the P-wave velocity of cement (which is an indicator of physical and mechanical properties) as a function of hydration degree decreased with increasing curing temperature in the range between 35 °C to 75 °C, then remained relatively stable between 75 °C and 130 °C. The reduction of gel water content in C–S–H from 35 °C to 75 °C is believed to be the primary cause of these observed phenomena.

Reuse of Pretreated Red Mud and Phosphogypsum as Supplementary Cementitious Material

The combination of red mud (RM) and phosphogypsum (PG) can exert the alkalinity of RM and the acidity of PG as a calcium source to promote the gel hardening of composite cementitious material, which effectively improves the reutilization efficiency of RM and. In this study, the effects of the ratio and content of pretreated RM and PG on the non-evaporated water, porosity, hydration products, mechanical properties, pore size distribution, and microstructure of composite cementitious materials were investigated. The results show that, with the incorporation of PG, RM, PG, and RM, the non-evaporable water content, reaction degree, compressive strength, and flexural strength show a downward trend after rising first, and their values reach the maximum with 10% PG and 10% RM, which are higher than a pure cement system, while 70% PG, 70% RM, 70% RM + 10% PG, and 70% PG + 10% RM have the reverse effect. The results of hydration products, pore size distributions, and microstructure indicate that adding an appropriate dosage of RM and PG can efficaciously improve the compactness of cement systems. Nevertheless, the research results can contribute to using the combination of PG and RM to manufacture sustainable cementitious materials with good performance, and achieve the purpose of environmental protection and industrial solid waste resource recycling.

Investigating the potential of trass-cement binary blend for enhancing microscopic properties, macroscopic performance, and sustainability of cement paste

• Effects of trass on micro- and macro-level properties of cement paste were evaluated. • Blending cement with trass accelerated the C 3 S and C 3 A hydration. • Higher nonevaporable water contents were detected in blended sample compared to plain one. • The values of compressive strength activity index fluctuated between 106.7 and 124.6%. • Incorporating trass into cement can lead to a cleaner, cheaper, and less energy consumer construction. Due to some physical or chemical incompatibility issues between supplementary cementitious materials (SCMs) and cement, it is necessary to investigate the microscopic properties and macroscopic performance of cement composites containing such blends before their incorporation in construction. Hence, in this study, the hydration kinetics, degree of hydration, microstructural morphology, and pore structure of cement paste blended with trass, as well as its mechanical and transport properties, were profoundly evaluated. Moreover, the potential of trass for enhancing the sustainability of construction was also assessed. The physical properties of trass accelerated the C 3 S hydration, while its chemical composition led to the reduction of induction period, in addition to the acceleration of C 3 A hydration. Significant refinement of pore structure characteristics was found in blended sample after 90 days, when the threshold and critical pore diameters were reduced by respectively 27.7 % and 10.7 %, compared to those of the plain sample. This denser microstructure was reflected in superior electrical resistivity of the blended sample, which was 2.1 times of the plain one at 90 days. Furthermore, the inclusion of trass through refining the morphology of CH crystals in the microstructure, besides lowering the calcium hydroxide (CH) content by 12.1–63.3 % and increasing the nonevaporable water content by 2.1–8.0 %, led to 6.7–24.6 % higher compressive strengths in blended sample. Regarding the sustainability, at a similar 90-day compressive strength of 40 MPa, using trass results in an approximately 21.7 % less energy consumer, 20.3 % cleaner, and 15.8 % cheaper construction. Moreover, at equal levels of energy consumption or CO 2 emission, the blended sample has greater compressive strength and electrical resistivity than the plain one, which can be indicative of an extended service life. Accordingly, the utilization of trass is recommended since it has the potential to improve the sustainability both directly and indirectly.

Hydration Behaviour and Characteristics of Binary Blended Metakaolin Cement Pastes

Cement production consume large amount of energy to form clinker and carbon dioxide (CO2) emitted into the atmosphere causing global warming. To mitigate this challenge, the use of Metakaolin (MK) as supplementary cementitious material cannot be over emphasized. This study evaluated the use of Metakaolin (MK) on hydration development of MK--PC blended cements and strength of Mortars. The MK with a Blaine fineness of 7883 cm2/g was used to replace Portland Cement (PC) at a level of 0, 5, 10, 15, 20, 25 and 30 % by mass of PC at a constant w/b ratio of 0.50 to prepare blended cements. Hydration development of blended cement and compressive strength of Mortars were investigated using chemically bond water and free-lime contents and strength tests respectively. X – Ray diffraction (XRD) and scanning electron Microscopy (SEM) techniques were also utilised in the analysis of Pozzolanic reaction and hydration products. Test results indicates that Water of consistency, setting times for the mixes increased with increase in MK contents, influence of MK on the chemically bond water and free Lime contents of the blended cements were due to its filler and dilution effects and Pozzolanic reaction. The cumulative non-evaporable water and free-lime contents increased by partial replacement of PC with MK due to PC hydration and Pozzolanic reaction. The tested Mortar prepared with blended cements with 30 % PC replacement with MK shows a retardation of strength development with a low value at early ages (7 days) and increased in growth at later ages (28 days). The compressive strength of tested mortar for 90 days curing age for the blended mortar is 31 N/mm2 close to that of control Mortar (35 N/mm2). The results obtained from XRD and SEM analysis indicated increase in Calcium Hydroxide (CH) consumption and Calcium Silicate hydrate (C-S-H) formation in blended cement pastes with curing time. The PC replacement with MK induced changes in Microstructures of blended cement paste and chemical composition of hydration products. These results are potentials for modelling the behaviour of MK-PC blended cements.

Influence of curing temperature on the hydration and strength development of Class G Portland cement

A broad experimental program has been performed to characterize the hydration and strength development of a Class G oil well cement under various curing temperatures from 15 to 87 °C. The progress of hydration was monitored by isothermal calorimetry, thermo-gravimetric analysis, and quantitative X-ray diffraction based on Rietveld refinement; while the strength development was evaluated by both nondestructive ultrasonic tests and destructive crush tests. Test results indicate that heat of hydration, non-evaporable water content and degree of hydration of the cement follow approximately linear relationships, which are largely independent of curing temperature; the obtained proportionality constants agree well with those estimated by previously proposed empirical equations. The influences of curing temperature on the hydration rate and strength development rate can be modeled by an equivalent age method coupled with the Arrhenius law. The apparent activation energy obtained from hydration analysis was higher than that obtained from strength development analysis.

Test research on hydration process of cement-iron tailings powder composite cementitious materials

Cement-based composite cementitious materials (CCMs) were prepared using mechanically ground iron tailings powder (ITP) to partially replace cement. The hydration heat, non-evaporable water (n-EW) content, Ca(OH)2 (CH) content, ITP reaction degree, and mortar compressive strength were tested to understand the hydration of the CCMs. The test results show that the addition of ITP postpones the emergence of the hydration exothermic peak and reduces the hydration cumulative heat release and exothermic rate. Moreover, the n-EW and CH content of the CCM paste at the specified age are lower than those of the cement paste, and the reaction degree of ITP increases with aging. However, it does not exceed 40% at 90d age. Compared with the cement mortar, the composite mortar compressive strength decreases to different degrees, and the rate of decrease declines with age. Early-age high-temperature curing is beneficial to the early hydration of the CCMs. However, it has a lesser or a negative influence on the middle and late hydration. This study shows that the supplementary cementitious effect of mechanically ground ITP changes the hydration process of cement-based cementitious materials, which in turn affects their performance. The result of each test correlates well, laying a reliable foundation for revealing the hydration mechanism of cement-ITP CCMs.

Properties of Blended Cement Containing Iron Tailing Powder at Different Curing Temperatures.

The properties of blended cement containing 0%, 20%, and 50% iron tailing powder (ITP) at 20 °C and 60 °C were investigated by determining the hydration heat, microstructure, and compressive strength. The addition of ITP decreases the exothermic rate and cumulative hydration heat of blended cement at 20 °C. The high temperature increases the hydration rate and leads to the hydration heat of blended cement containing 20% ITP higher than that of Portland cement. Increasing the amount of ITP decreases the non-evaporable water content and Ca(OH)2 content as well as compressive strength at both of the two studied temperatures. The addition of ITP coarsens the early-age pore structure but improves the later-age pore structure at 20 °C. The high temperature significantly improves the early-age properties of blended cement containing ITP, but it is detrimental to the later-age properties development. The reaction of ITP is limited even at high temperature. The large ITP particles bond poorly with surrounding hydration products under early high-temperature curing condition. The properties of blended cement containing a large amount of ITP are much poorer at high temperature.

Mechanical and thermal modification of mordenite-rich tuff and its effect on cement pastes

To overcome performance deficiencies of the raw mordenite-rich tuff in the partial replacement of Portland cement in cement paste, the material was subjected to different treatments: calcination at 300 °C and 500 °C, grinding to very high specific surface areas, co-grinding with Portland cement, and separate or co-grinding with granulate blast furnace slag. The resulting materials were examined by tracking changes in density, particle shapes, and size distributions. The blended cement pastes were examined by monitoring the water demand, setting time, hydration process by isothermal microcalorimetry, degree of hydration, non-evaporable water content and free Ca(OH)2 by TGA-DSC analysis. The findings provide clear evidence that with the activation techniques, the performance of the raw mordenite-rich tuff is improved.

Durability of eco-friendly blended cements incorporating ceramic waste from different sources

Environmental conservation is mandatory for the sustainable development of the construction industry. A large amount of ceramic waste results from construction and demolition waste (C&DW). In addition, the extended service life of the structure is essential. This paper assesses the effectiveness of powder ceramic wastes (PCWs) from C&DW to improve the durable performance (chloride diffusion, sulfate resistance, and alkali–silica reaction) of blended cement (replacement 24% by mass). The suitability of blended cement is supported by the proven pozzolanicity (Frattini test, XRD, FTIR, and nonevaporable water content). Additionally, PCWs incorporation effect on the life cycle analysis of concrete is included. All samples containing ceramic waste show pozzolanic activity at 28 days, significantly reduce the apparent chloride diffusion coefficient, present good performance against the sulfate attack and reduce the expansion caused by ASR. In addition, PCWs reduce CO2 emissions. Results reveal a comparable performance of PCWs, indicating the unnecessary classification of them.

An assessment method of hydration degree of Rice husk ash blended cement considering temperature effect

Rice husk ash (RHA) has been considered as a suitable cement mineral additive. A key issue in the study of RHA blended cement is to evaluate the contribution of RHA to hydration kinetics. Although numerous methods have been given to assess the hydration degree of blended cement, there are still some controversial aspects, such as the effect of temperature is not well considered. Therefore, this study aims at developing a method for evaluating the hydration degree of blended cement which can consider the influence of temperature. The key of this method is to adopt a hydration kinetic model of nonevaporable water (NEW) to determine the ultimate NEW content of blended cement when it is completely hydrated. In the hydration kinetic model, the Arrhenius equation is introduced to reflect the relationship between hydration rate and temperature, and the inversion phenomenon between ultimate NEW and temperature is considered simultaneously. Furthermore, the hydration process of portland cement pastes containing RHA (two types of RHA: RHA-1 from the factory and RHA-2 by controlled combustion) is analyzed by this assessment method. It is found that the effect of temperature on RHA cement is similar to that of ordinary Portland cement (OPC), which has an inversion phenomenon between hydration degree and temperature. Under the same temperature, the hydration degree of RHA cements is lower than that of OPC, while the difference in hydration degree gradually decreases with the progress of hydration. Moreover, according to the fitting results of the model when m = 3, the addition of RHA could reduce the apparent activation energy (Ea) of blended cement, the Ea values of OPC, RHA-1 cement and RHA-2 cement are 37.64 kJ/mol, 35.39 kJ/mol and 34.18 kJ/mol, respectively.

A Method for Internal Curing Water Calculation of Concrete with Super Absorbent Polymer

The internal curing method is effective in reducing the self-desiccation of concrete, and the amount of internal curing water (IC water) is greatly important to the shrinkage and strength of concrete. A method for calculating IC water of concrete with and without mineral admixture has been developed. The method is derived from Powers’ model for the phase distribution of a hydrating cement paste. To verify the method, a series of autogenous shrinkage and compressive strength of concrete with and without super absorbent polymer (SAP) were evaluated compared with the method proposed previously. To explain the macro performance of hardened concrete, the nonevaporable water content and calcium hydroxide content measurement were utilized to evaluate the degree of hydration of cement pastes. And, mercury intrusion method and image analysis method were used to explore the pore structure in hardened cement pastes and air void characteristics in hardened concrete, respectively. Furthermore, the evolution process was also studied for the relative humidity inside the concrete.

Investigation on the Role of Steel Slag Powder in Blended Cement Based on Quartz Powder as Reference

To clarify the role of steel slag powder in blended cement, steel slag powders with different amounts and particle sizes were mixed into blended cement and the inert quartz powder was selected as the reference. The influences of steel slag powder with different amounts and particle sizes on the hydration and hardening properties of blended cement were studied from hydration heat, nonevaporable water content, porosity, hydration products, and strength. The results show that the influence coefficient of nonevaporable water content (ՓWn) of blended cement paste is in an exponential relationship with the amount of steel slag powder. Moreover, at a dosage of 30%, ՓWn of blended cement gradually decreases with the increase of steel slag particle size. Both the early and late compressive strengths of blended cement are in a binomial relationship with the amount of steel slag powder. The influence coefficient of steel slag powder on the compressive strength of blended cement is negative at the age of 3 days, whereas it is positive at the age of 28 days. The chemical filling effect of 30% steel slag powder with different particle sizes in the blended cement paste is very small, only 1.13%–5.06%. The hydration products of blended cement containing steel slag are mainly amorphous C‐S‐H gels and platy Ca(OH)2, and their density are consistent with the law of their porosity.

Hydration Properties of Mechanically Activated Muscovite in the Presence of Calcium Oxide

AbstractThe harm caused by mine tailings has become increasingly problematic in recent years, so efforts are needed to dispose of or reutilize them in environmentally friendly ways. The objective of the present study was to find out if the hydration properties of muscovite contained in mine tailings are suitable for it to be used as a pozzolan in cement, after undergoing mechanical activation. Aqueous suspensions of mechanically activated muscovite were blended with 10, 20, or 30 wt.% calcium oxide and then allowed to harden. The hardened paste samples were analyzed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) techniques. The results revealed that the mechanically activated muscovite exhibited pozzolanic reaction activity in the alkaline environment provided by calcium oxide, and the activated muscovite possessed a capacity to react with calcium hydroxide to form hydration products. The calcium oxide content affected significantly the quantities and kinds of hydration products, non-evaporable water content, and the compressive strength development of the paste samples. The hydration products of the 10% calcium oxide-activated, mechanically activated muscovite pastes were Al-containing hydrated calcium silicate (C-A-S-H) gel, stratlingite, and, upon addition of 20% and 30% calcium oxide, Ca-Al hydrotalcite-like (Ht) phases. The present study was helpful in evaluating the hydration properties of the mechanically activated muscovite and also provided a research basis for evaluating the hydration properties of mine tailings containing muscovite after mechanical activation. The results provided a theoretical basis for muscovite-containing mine tailings to be used as a cement additive, and was conducive to the large-scale utilization of mine tailings.

The effects of Graphene Oxide addition on hydration process, crystal shapes, and microstructural transformation of Ordinary Portland Cement

In this study, Graphene Oxide (GO) is used as a reinforcing material to strengthen cement composites. GO has great potential in modifying properties of traditional cementitious materials. Several researchers have suggested their views on mechanical properties and microstructural behaviour of GO reinforced cement composites. In this study, characterization of GO-cement composite is done to investigate the interaction, mechanical strength, and thermal behaviour by reinforcing GO at several percentages. The effects of GO percentage addition on cement hydration, formation process, and crystal shapes of hydrated cement were investigated. Microstructural developments such as XRF, SEM, XRD, FTIR, and TGA tests have been reported to determine GO interaction with Ordinary Portland Cement. Improved mechanical properties, non-evaporable water content, hydration rate have been observed by incorporating GO in cement composites. The results obtained would suggest scope for understanding the reinforcement mechanism of GO and provides potential as a Nano-reinforcing material in cement composites.

Effects of curing methods of concrete after steam curing on mechanical strength and permeability

The accelerated hardening of concrete caused by steam curing has adverse effects on the microstructure and properties of concrete, so it is necessary to adopt appropriate curing method to reduce the damage caused by steam curing. The effects of curing methods on the properties of concrete after steam curing are worth studying. The compressive strength, non-evaporable water content and permeability (air, water and ion) of steam-cured concrete were tested under different subsequent curing conditions. Meanwhile, the internal microstructure was also investigated by image processing and SEM. The results show that the compressive strength of steam-cured concrete with four curing methods increases with the curing time, but the growth rates are different. The permeability of the concretes cured in the air decreased first and then increased with the curing time, while other curing methods decreased with curing time. The microstructure also shows that adequate subsequent wet curing can effectively reduce the adverse effects of steam curing on concrete.