Age Hydration Research Articles

Experimental behaviors of prefabricated members made of ferronickel slag concrete

As a by-product of nickel production, a large amount of ferronickel slag (FNS) puts great pressure on the environment. Therefore, there is an urgent need to treat the FNS to solve serious challenges to the environment. The FNS can be used as a partial replacement of Portland cement in concrete, so this industrial by-product may act as a suitable alternative of conventional building materials with high carbon footprint to achieve sustainable development. The concrete containing 0%, 15% and 30% FNS was prepared and assessed for its compressive strength, modulus of elasticity, tensile strength, resistance to chloride ions penetration and bond behaviors. The obtained results showed that the use of FNS had positive effects on the mechanical properties and durability of concrete due to the higher pozzolanic activity of FNS at the late hydration age and its finer particles than cement. Moreover, 15% FNS addition brought more significant increase in compressive strength, modulus of elasticity, tensile strength and bond strength than the use of 30% FNS as a replacement of cement. But the increasing FNS content resulted in the increase of resistance to chloride ions penetration of concrete. In addition, static loading tests and cyclic loading tests were carried out to assess the effects of the FNS on the overall structural behaviors of the prefabricated members. The specimens exhibited similar failure modes which mainly involved yielding of longitudinal steel bars. The ultimate bearing capacity attained by FNS concrete members was similar to that of conventional concrete members, but the specimens made of FNS concrete exhibited higher ductile capacity. The FNS concrete members also experienced more cracking and concrete crushing at the end of test, thus showing better energy dissipation capacity.

Influence of maltodextrin retarder on the hydration kinetics and mechanical properties of Portland cement

In this study, the effect of maltodextrin on the hydration kinetics of ordinary Portland cement was investigated. Additionally, the impact of maltodextrin on the physical and mechanical properties of cement is further studied via setting time, fluidity and mechanical strength tests which has been conducted with different curing times (16 h, 1 d, 3 d, 28 d). The results revealed the impact on the mechanical properties of OPC is dosage and time dependent. At the early curing time of 16 h, the addition of maltodextrin decreased the compressive strength of all mortar samples substantially; a higher dosage of maltodextrin resulted in even lower compressive strength. However, at extended curing times such as 1 d, 3 d or 28 d, the impact on the compressive strength of OPC is dependent on dosage: relatively low dosages (0.01–0.05%) of maltodextrin increased the compressive strength of mortar, whereas higher dosages (≥0.1%) of maltodextrin was found to decrease the compressive strength of mortar. Furthermore, the time – dependent development of hydration products was monitored via in-situ XRD at the different ages of cement hydration. The results showed that the addition of maltodextrin delays cement hydration which results in less hydration products like Portlandite and ettringite. Finally, the mode of interaction between maltodextrin and cement was assessed through adsorption and zeta potential measurements. The adsorption as well as zeta potential measurements confirm that the retarding mechanism of maltodextrin relies on adsorption on the surface of cement particles.

Research on the incorporation of untreated flue gas desulfurization gypsum into magnesium oxysulfate cement

The growing concern of low-carbon economy and sustainable development has obliged the researchers to investigate green building materials through utilizing industrial by-products. In this study, the industrial waste material, flue gas desulfurization gypsum (FGDG), is incorporated into the magnesium oxysulfate cement (MOSC). The performance of FGDG-incorporated MOSC is evaluated by testing the setting time, compressive strength, density, water absorption, water resistance, volume stability and SO42− releasing. The hydration products are detected by X-ray diffraction, while microstructure is observed by optical microscope and scanning electron microscope. Increasing the proportion of FGDG retards the initial and final setting times of paste. Compressive strength for MOSC mixtures varies from 52.4 to 62.4 MPa at hydration age of 3 days. The water absorption and the release of SO42− increase when increasing the FGDG content. The FGDG-incorporated MOSC presents a superior water resistance and volume stability in contrast with the FGDG-free MOSC. The main hydration products of the paste are Mg(OH)2 and 5 Mg(OH)2·MgSO4·7H2O (5·1·7) phase. The microstructure analysis is in agreement with the results of mechanical properties. Finally, the FGDG-incorporated MOSC is identified as a promising building material by the evaluation of economic and environmental sustainability.

Insights into the properties and chloride binding capacity of β-hemihydrate in the presence of slag powder and white calcium aluminate cement

Calcium chloride (CaCl2) as a common concomitant in flue-gas desulfurization gypsum has a great negative impact on gypsum-based construction materials. Chloride binding in the form of Friedel's salt in the gypsum-dominating system is of great significance, but the feasibility of this approach has not yet been systematically clarified. In this paper, granulated blast-furnace slag (GBFS) powder and white calcium aluminate cement (CAC) were used as the components to explore their roles on the properties and chloride binding capacity of β-hemihydrate. Experimental results prove that CAC significantly improves compressive strength, water resistance, and chloride binding capacity of hardened paste. The XRD, DTG, SEM-EDS and thermodynamic modeling confirm that Friedel's salt forms in this system even at an early hydration time of 30 min. Mercury intrusion porosimetry and SEM results verify that the use of CAC decreases the volume of the pores in the 0.1–100 μm range. Thermodynamic modeling outcomes are consistent with the experimental data helping to explain the hydration and evolutions of β-hemihydrates in the presence of CaCl2, GBFS, and CAC at early hydration ages.

Positive impact of ultra fine-ceramic waste on the physico-mechanical features and microstructure of white cement pastes composites

In our present work, the impact of ceramic wastes (CW) on chemical, physicomechanical properties and microstructure of blended white cement (WC) was studied. In ceramic plants around 31% of production was going as industrial wastes with negative environmental impact. These wastes could be recycled then substituted from WC for production of green environment and the mitigation of carbon dioxide emissions. Ceramic wastes (CW) were act as silicate source to enhance performance of WC additionally, act as filler with nucleating side effect. Ceramic wastes (CW) are crushed and milled till reaching to micro- particles called “ultra-fine ceramic wastes”. Different ratios of CW (1, 3 and 5 wt, % by weight of binder) were substituted from WC meanwhile, physico-mechanical properties such as compressive strength, water absorption, whiteness reflection and setting time were evaluated. The results showed that, WC-pastes which containing 1 wt., % of CW (MW1-mix) have the highest compressive strength, shortest setting time and marginally decreasing in whiteness reflection as well as decrement in water absorption, comparing with other pastes which containing 5 wt.,% of CW (MW5-mix) and control sample (M0) at all ages of hydration. These results confirmed by using x-ray diffractograms (XRD) and scanning electron microscope (SEM) techniques. These results proved that, MW1-mix with excessive hydration products, filling open pores as nucleation effect yielding densification of microstructure.

Hydration study and characteristic analysis of a sulfoaluminate high-performance cementitious material made with industrial solid wastes

A sulfoaluminate high-performance cementitious material (SHCM) was prepared using flue gas desulfurization (FGD)-gypsum, coal gangue, limestone tailings, and aluminum ash as raw materials. The composition of the SHCM clinker, mechanics and hydration properties of the SHCM, and heavy metal leaching characteristics of the SHCM pastes were studied. The results showed that the mineral phases of the SHCM clinker were similar to that of ordinary sulfoaluminate cement (SAC) clinker, mainly including calcium sulfoaluminate and dicalcium silicate, and the key differences were that the SHCM clinker had an excessive content of calcination-formed anhydrite and contained some gehlenite. The 3-day and 28-day compressive strength of the SHCM mortars reached up to 45.7 MPa and 67.8 MPa, respectively, and a continuous strength gain was observed in the later age, unlike that in the case of ordinary SAC. The cumulative hydration heat during the first 3 days of the SHCM was 283 J/g, which is lower than that of ordinary SAC under the same conditions. Additionally, the SHCM pastes also showed good immobilization ability of heavy metals in the hydration process, with the leaching concentrations of Zn, Cr, As, and Cu much lower than the limits of Chinese National Standard, and with retention ratios of Zn, Cr, As, and Cu in SHCM pastes over 90%, at each hydration age. This work provides a practical and effective way to transform industrial solid wastes to value-added, high-performance and green sulfoaluminate cementitious material.

Hydration properties of Portland cement-copper tailing powder composite binder

Copper tailing powder with different grinding time and different replacement ratio for cement was used as alternative mineral admixture in Portland cement-copper tailing powder composite binder. The results show that the compressive strength reduces with the increasing content and grinding time of copper tailing powder. Copper tailing powder content, especially higher than 30%, has a far greater impact on later hydration age than early age, which is beneficial for compressive strength development at later hydration stage. The end time of induction period of most mixtures prolongs after the incorporation of copper tailing powder and also shortens with increasing grinding time and the content. With the increase of copper tailing powder content, the most probable pore size increases, and the number of innocuous pores and less harmful pores decrease. The main hydrates of the binders are C-S-H gel, Ca(OH)2, ettringite, CaCO3 and a small amount of dolomite. The Ca(OH)2 content of most mixtures decreases compared with pure cement and also decreases with the increasing content of copper tailing powder, especially for the content higher than 30%. Ca/Si ratio of C-S-H gel is high because of the dissolution rate of Ca2+ at early age and decreases due to the reaction between superfluous SiO2 in copper tailing powder and high Ca/Si ratio C-S-H gel at later hydration period.

Modification of chitosan as chemical admixture for cement pastes

Three different composition ratios of chitosan-g- acrylic acid, P[Ch-g-AA] were prepared in the presence of potassium persulphate as an initiator using free radical technique. The grafted copolymers were characterized through FT-IR, TGA, DSC, and SEM. The results showed that these grafted copolymers have a single glass transition indicating that these copolymers can form a miscible phase. The P[Ch-g-AA] exhibit thermal stability. SEM of the grafted copolymers showed no phase separation, when compared with the pure Ch. The effect of grafted copolymers on the physico-mechanical properties of cement pastes was investigated. The addition of water mixed with grafted copolymer to the cement, improves properties of cement pastes. As the ratios of AA in the grafted copolymer increases, the water-to-cement (WC) ratio, setting time as well as water absorption decreases. While The compressive strength was sharply increased at nearly all hydration ages.

Effect of microcrystalline and microfibrillated cellulose on the evolution of hydration of cement pastes by thermogravimetry

The interest in the use of cellulose fibers of increasingly smaller sizes in cementitious materials has increased in recent years. This paper brings new contributions in this field showing from respective paste thermal analysis data, how microcrystalline cellulose (MCC) and microfibrillated cellulose (MFC) affect differently the formation of Class G cement pastes hydration products from early (2 h) to later hydration ages (672 h). Pastes containing 0, 0.25 and 0.5% of cellulose per cement mass and a water/cement mass ratio of 0.45 were cured at 23 °C, and the TG/DTG tests were carried out after 2, 6, 12, 24, 168 and 672 h. The results show that the pastes with MCC and MFC additions presented higher total combined water content than the reference paste, especially after 24 h of hydration. However, this is strongly related to the quantity of water adsorbed by different celluloses and their concentrations in the mixture. Comparing cellulose pastes, MFC pastes showed lower total combined water up to 28 days, attributed to the fiber’s microfibrillar form. No higher amount of calcium hydroxide was formed in the presence of cellulose, but it was more crystalline than that obtained in the reference. Other hydrated phases (dehydration from 200 to 400 °C) are differently affected by the presence of the celluloses, the highest formation occurring for 0.25% MCC paste. This behavior was attributed to an additional cure of these mixtures related to morphological characteristics and water retention capacity of cellulose.

Shape effect of cement particles on the ionic diffusivity of hardened cement paste—a three-dimensional numerical investigation

A three-dimensional numerical investigation is presented to study the shape effect of cement particles on the ionic diffusivity of hardened cement paste (HCP), whose microstructure is generated based on the random packing models of spherical and polyhedral particles. The microstructure of HCP composed of four phases is first generated and then converted into a voxel-presented one. Based on the digitized microstructure, the diffusivity of HCP can be obtained by a lattice modelling. The reliability of simulations is validated by comparing to experimental data and the shape effect of cement particles on the diffusivity of HCP is discussed. The results indicate that the shape of cement particles significantly affects the ionic diffusivity of HCP due to its effect on the hydration degree: the cement particles with smaller sphericity contribute to the hydration of HCP, which reduces the ionic diffusivity of HCP. This effect decreases as the hydration age elapses and increases with the increasing water-cement ratio. The intrinsic reason causing this effect is illustrated from the microstructural view of HCP: the shape effect has an influence on the volume fractions of three diffusive phases and pore structures.

Bauxite free iron rich calcium sulfoaluminate cement: Preparation, hydration and properties

For the preparation of calcium sulfoaluminate (CSA) cement without bauxite, the iron rich CSA cement was prepared by the partial substitution of Al for Fe in C4A3s-. Besides, the hydration and properties of iron rich CSA cement were investigated. Raw meal proportioning shows that iron rich CSA cement clinker can be prepared without bauxite when the x value of C4A3-xFxs- exceeds 0.7. Results demonstrate that the iron rich CSA cement clinker can be prepared at 1175–1225 °C with the heat preservation time of 10 min. With the rise of Fe2O3 content in the raw meal, the C4A3s- content of iron rich CSA cement clinker lowers down, more C4AF and C2F forms, more c-C4A3s- forms at the expense of o-C4A3s-, and the crystal size of C4A3s- becomes smaller. For the iron rich CSA cement, the setting time is prolonged and the expansion rate lowers down with the rise of Fe2O3 content. For the compressive strengths, the iron rich CSA cements are lower than that of CSA cement at early hydration age. However, the compressive strength of iron rich CSA cement exceeds that of CSA cement at 90 d. Therefore, it is available to prepare bauxite-free iron rich CSA cement with high late age strength.

Hydration of a calcium sulfoaluminate cement blended with zincite

A calcium sulfoaluminate (CSA) cement has been characterised by X-ray diffraction and energy-dispersive X-ray spectroscopy analysis. Selective extraction methods have been used to improve detection limits for identification and quantitative measurements. Perovskites are present in the cement in the form of brownmillerite and a phase with the following average chemical composition Ca1·95Mg0·05Al0·29Ti0·39Fe1·03Si0·22O5·18. The zincite is known as a strong retarder for ordinary Portland cement (OPC), and its effect on the hydration of CSA cement was investigated using isothermal calorimetry, thermal analysis and X-ray diffraction. The low pH of the pore solution in the CSA cement compared to the OPC considerably reduces the solubility of zincite and, at an early age of hydration, zincite behaves as a filler in the CSA cement.

Evaluation of thermal conductivity of cement-based foam reinforced with polypropylene fibers

This study quantifies the results of the thermal conductivity for cement-based foam reinforced with polypropylene fibers and correlates the influence with pozzolans, porosity, moisture content, and pore parameters. Here, the mixtures were prepared for the densities range of 400–800 kg/m3 in which cement was replaced in the ratios of 10% and 20% (by weight) with fly ash, silica fume, and metakaolin. Along with pozzolan, polypropylene micro-fibers were added at the volume fraction of 0.2%. The thermal conductivity was measured variously at the hydration age of 60–210 days by using the transient plane source technique. While the porosity and the pore parameters were evaluated by using X-ray microtomography, a non-destructive technique. The results revealed that polypropylene fibers contributed to reducing the conductivity and among the three pozzolans, fly ash was the most efficient. However, the porosity increases with the inclusion of fibers but drops significantly with the addition of pozzolans, especially for lower densities mixtures. Also, it was found that D50 relates linearly with conductivity. However, based on experiment results, a modified thermal conductivity predictive model for cement-based foam reinforced with fiber was developed.

The role of sulfate ions in tricalcium aluminate hydration: New insights

As a major mineral of Portland cement, the hydration of tricalcium aluminate (C3A) has a significant impact on various properties of cement-based materials. However, there is little consensus on its mechanism, especially the interaction between C3A and gypsum which usually co-exist in cement systems. Recent researches have shown that sulfate ions play an important role in the kinetics of C3A hydration, which may provide more promising alternatives on controlling cement hydration besides the present solution on adjusting gypsum contents. In this study, effects of different kinds of solid sulfates (gypsum, Na2SO4, MgSO4) on the heat released during the early age of C3A hydration as well as hydration products were investigated first by isothermal calorimetry, SEM, XRD and thermal analysis. Retardation was observed in all the three systems (C3A-gypsum, C3A-Na2SO4 and C3A-MgSO4). But the duration of induction period varied with cations. Then barium nitrate (Ba(NO3)2) aiming to remove the sulfate ions was innovatively employed to highlight the role of sulfate ions. Interestingly, the renewed hydration of C3A occurred immediately after Ba(NO3)2 solution was added into the three systems with different amount of AFt remained. According to the characterization of hydration products, little monosulphoaluminate (s-AFm) was detected in the induction period of C3A-gypsum hydration and a large amount of h-AFm was found to cover the surface of C3A particles after adding Ba(NO3)2 solution. It is concluded that the coexistence of calcium and sulfate ions absorbed at C3A surface is more likely to dominate the retardation of C3A hydration in the presence of gypsum, rather than the alleged physical barrier mechanism caused by the precipitation of hydration products.

Effect of high metakaolin content on compressive and shear-bond strengths of oil well cement at 80 °C

This paper reports the effect of high metakaolin content on compressive and shear bond strengths of oil well cement cured at 80 °C. X-ray diffraction (XRD), and thermo gravimetric-differential scanning calorimetry (TG-DSC) used to study cement phases. Both compressive and shear bond strengths increased with hydration age. The binary system with 20% metakaolin displayed better compressive strength relative to the neat oil well cement samples. It increased by 17 and 20% at 3 and 28 days of hydration, respectively. The shear bond strength equally increased by 145 and 56% at 3 and 28 days, respectively. The results of this study, therefore, point to a feasible cement system for the long life of the oil and gas wells.

The effect of blend copolymers on physico-mechanical properties of mortar

The present study investigates the effect of blend copolymers on the physico-mechanical properties of mortar mixes. Blend copolymers were synthesized based on poly vinyl alcohol (PVA) and urea (U) in aqueous solution with different blend ratios 65/35, 50/50 and 35/65 respectively, using glacial acetic acid as crosslinking. Physico-mechanical properties of mortar examined included water/cement ratio, setting time, workability, water absorption and compressive strength. The addition of blend copolymers to the mortar affected the physico-mechanical properties of mortar mixes. As the content of PVA increases in the blend copolymers, the water of consistency decrease, whereas the setting times (initial & final) were shortened. The compressive strength of the hardened cement pastes was increased at all ages of hydration while water absorption decreased.

Study on composite solid alkali-activated slag/fly ash concrete

Through FTIR, SEM/EDS and XRD analysis of hydration products of slag/fly ash concrete paste activated by composite solid alkali, the activation effect of composite solid alkali activator on slag/fly ash system was studied. The results show that the hydration products of the excitation system are mainly C-S-H gels, and the crystallization of C-S-H gels with 28 days hydration age tends to be perfect. The hydration products have good bonding and compact structure, which greatly improves the strength of the matrix. The damage pictures of 28-day-old C30 concrete blocks after compression test further show that the composite solid alkali activator has a good activation effect on slag/fly ash system.

Retraction

Abstract Original Article Title: Effect of Particle Size of Silica Nanoparticles on Hydration Reactivity and Microstructure of C-S-H Gel Original Authors: U. Sharma,1 L. P. Singh,2 D. Ali,1 and C. S. Poon3 This article has been retracted due to duplicate publication. ASTM International August 2021

Development of lime-pozzolan green binder: The influence of anhydrous gypsum and high ambient temperature curing

This study aims to improve the physico-mechanical properties of slaked lime – fly ash (FA) – ceramic waste powder (CWP) pastes through the incorporation of anhydrous gypsum (G) supported by thermal curing. Initially, the lime- FA paste was prepared with a ratio of (30/70 wt) as a reference binder. The FA was partially replaced with 5–25% of CWP material. The substitution of FA by CWP up to 20% exhibited a slight enhancement in the compressive strength at early and later ages of hydration. Adding 10% G provided additional improvements in the compressive strength, capillary water absorption and microstructure; this is confirmed by the thermogravimetric (TGA) and scanning electron microscopy (SEM) analyses. The high ambient temperature curing at 50 ͦC was found to be remarkably useful for improving the compressive strength of the gypsum containing composites at early age. The developed composites showed high solar reflectivity values which recommend for green building rendering applications. Such a kind of binder material could be helpful in reducing the negative impact of traditional Portland cement (PC), decreasing the ceramic waste disposal and contributing to the energy saving approach in building sectors.

Effect of pre-carbonation hydration on long-term hydration of carbonation-cured cement-based materials

In the context of CO2 storage in construction materials, early-age carbonation curing of cement-based materials has been extensively studied in recent decades. Here, the effect of cement chemical and mineralogical alterations caused by initial hydration before early-age carbonation (i.e., pre-carbonation hydration) on subsequent hydration and strength development after early-age carbonation (i.e., post-carbonation hydration) is studied as a new parameter for controlling the curing process. Cement pastes were examined immediately after early-age carbonation using thermogravimetric analysis (TGA) and at 28 d by means of TGA, X-ray diffraction and vapor sorption, and were further associated with mortar strength development. The efficiency of early-age carbonation was found to noticeably decrease by delaying CO2 exposure. The post-carbonation hydration, however, was enhanced under the same condition and formed higher 28-d strength and bound water content compared to the non-carbonated reference. The use of limestone cement emphasized this observation and tended to advance its occurrence at shorter pre-carbonation hydrations. It is inferred that carbonation introduced after the late deceleration period of cement hydration can potentially enable a nucleation seeding effect to promote long-term hydration. The findings of this study confirm the importance of controlling pre-carbonation hydration age as a critical parameter for synergistically optimizing CO2 sequestration and technical properties of CO2-embodied materials.