Strength Development Of Cement Research Articles

Impact of triethanolamine on the hydration of Portland cement in the presence of high pozzolanic activity supplementary cementitious materials

Triethanolamine (TEA) is a widely employed cement accelerator that has been demonstrated to have a favorable impact on the early strength of cement at moderate dosing levels, while having a slight or negative impact on the later strength. This study systematically investigates the hydration pattern and strength development of Portland cement systems with the incorporation of fly ash microspheres and silica fume at a dosage of 0.02 % triethanolamine. The results proved that the addition of TEA had a positive impact on the early strength of the pure Portland cement system, while the later strength was reduced. However, the presence of high pozzolanic activity supplementary cementitious materials (SCMs) altered this reduction and even reversed it, resulting in an increase in strength. Specifically, TEA inhibits the crystallization nucleation growth of hydration products through complexation, resulting in the inhibition of the hydration of silicate minerals. The nucleation effect of silica fume, however, eliminates this inhibition and promotes the hydration of all minerals. Moreover, the presence of SCMs leads to the formation of more amorphous calcium hydroxide (CH) due to the demand of pozzolanic reaction, and the addition of TEA promotes the formation of amorphous CH, effectively lowering the reaction threshold of the pozzolanic reaction and facilitating it. The results confirm that the interaction of the complexation reaction of TEA with the pozzolanic reaction provides a beneficial complement to cement strength development.

The prediction of compressive strength for recycled coarse aggregate concrete in cold region

Concrete in cold environments may suffer from frost damage, which effects the hydration reaction and early strength development of cement. This study aims to test the early strength development of recycled coarse aggregate concrete in cold region using an assisted heating method. Based on Nurse-Saul and Hansen-Pedersen maturity calculation methods, the early strength of recycled and natural coarse aggregate concrete is fitted and predicted using exponential and logarithmic type functions. The results showed that active heating and thermal insulation can ensure early concrete hydration. The temperature of recycled coarse aggregate concrete was slightly higher than that of natural concrete, while its strength was slightly lower. The early strength development of natural and recycled coarse aggregate concrete correlated more with the logarithmic type function. The prediction error of natural and recycled coarse aggregate concrete is basically within 10% for the first 14 days of compressive strength.

Investigation on effect of EVA on properties of desert sand-based permeable materials

This paper aims at studying the effect of adding ethylene vinyl acetate (EVA) emulsion on the properties of desert sand-based permeable materials and explore the modification effect and mechanism of polymers. EVA emulsion can improve the fluidity of the slurry, and significantly improve the compressive strength, water permeability and freezing resistance at 10 % content. The EVA emulsion cured film is adsorbed on the surface of anhydrous cement particles. At the same time, the ester group in emulsion reacts with Ca2+ following hydrolysis, which inhibits the early hydration process of cement and reduces the early heat release. However, it has a non-significant impact on the later-age hydration and ensures the strength development of cement at the later stage. The emulsion can affect the pore structure of the material and can significantly increase the micropores content at 10 % content. The physical and chemical actions of polymer together influence the hydration process of cement and improve the bonding between desert sand and cement paste.

Mineralogical and Microstructural Characterization of Cement-Stabilized Soft Soils Based on Quantitative Analyses

The effects of cement dosage (percentage by dry soil weight) and initial moisture content (wo) on cement stabilized soft estuarine clay were investigated by effective integration of multi-quantitative analyses, including quantitative X-ray diffraction (XRD), thermalgravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) test and scanning electron microscopy (SEM) with image processing. These quantitative analyses are highly complementary, which greatly improved the scientificalness of this research. The results revealed that the strength development of cement stabilized soft estuarine clay with varying cement dosages, and initial moisture content was ascribed to the combined influence of both soil fabric improvement and cementation bonding enhancement. The increase of wo resulted in larger clay particle spaces, which can counteract the enhancement of soil structure due to the rising hydration products. The hydration degrees of samples with fixed cement dosage but different wo are quite similar, while clay particle spaces were enlarged with an increase of initial moisture content. Thus, the same quantity of hydration products may bind more soil particles when pores are small at lower wo, thus increasing unconfined compressive strength (UCS). Furthermore, BET and quantitative SEM results illustrate that hydration degree plays a dominant role in the development of intra-aggregate pores (<0.2 μm), while wo affects inter-aggregate pores (0.2 μm–2 μm) more.

Generalized strength prediction equation for cement stabilized clayey soils

The role of clay minerals on the strength development of cement stabilized clays at different cement contents, water contents and curing times was studied in this research. Kaolin and sodium bentonite were used to represent non-swelling and high swelling soils respectively. The soils studied were mixtures of kaolin and bentonite at replacement ratios of 0, 25, 50, 75, and 100% of the dry weight of bentonite to have various swelling potentials. The water content of the soil samples was adjusted to the optimum water content (OWC) and to the liquidity index (LI) of 0.25–1.50, so as to simulate different initial soil phases. The macro- and micro-observation indicated that the clay mineral, water content and cement content were the predominant influence factors controlling the strength development of cement stabilized clays, at a particular curing time. For a particular clay mineral, the total soil water to cement content, s-w/c was found to be the prime parameter reflecting the effect from both water content and cement content on the strength development in cement stabilized clay. The generalized strength model can be represented in the form: qu = A/B(s-w/c) where qu is unconfined compression strength, and A and B are constant. The values of parameters A and B were found to be primarily controlled by the clay mineral, which was found to be described by plasticity index. The generalized strength model was validated using separated test data. This model will facilitate the engineering decision of selecting the water content and cement content to attain the target strengths of clayey soils at required curing time with minimum number of trials.

Improved mechanical and microstructure of cement-stabilized lateritic soil using recycled materials replacement and natural rubber latex for pavement applications

• Natural rubber latex is used as a polymer additive for cement stabilized recycled materials. • The influence of dry rubber to cement ratio, curing time, and soil/recycled material ratios is discussed. • The relationship between strength and microstructural characteristics is discussed. • The optimum dry rubber to cement ratio can improve the mechanical properties of the mixtures. • Polymer firms increased the interparticle bond strength and matrix of mixtures. Soil replacement with medium-graded waste materials is an effective means to improve the physical properties of marginal soil prior to cement stabilization and to minimize the input of cement at the target mechanical properties. Natural rubber latex possesses superior elastic properties, which can improve the fatigue properties of cement stabilized material. This research aims to study the influence of NRL on the strength development of cement stabilized lateritic soil (LS) and recycled aggregate blends as a sustainable pavement base. The steel slag (SS) and recycled concrete aggregate (RCA) replacement ratios of 50% and 70% were studied. The cement content of 5% by weight and dry rubber to cement (r/c) ratios of 0%, 3%, 5%, and 10% were investigated. The r/c ratio was found to be a significant effect on the compactability, unconfined compressive strength (UCS), and indirect tensile (ITS) of cement stabilized SS:LS and RCA:LS blends. The microstructural analyses using scanning electron microscopy and X-ray diffraction indicated that the degree of cement hydration of cement-NRL stabilized SS/RCA:LS blends decreased with increasing NRL content due to the retardation of thicker NRL films. However, at the optimum r/c ratio, the coexistence between cement hydration products and NRL films can reduce the pore space and enhance the interparticle bond strength, resulting in UCS and ITS development of cement-NRL stabilized blends. Although the optimum r/c ratio indicating the maximum UCS and ITS of cement-NRL stabilized SS:LS and RCA:LS sample were found to be different, the percent improvement by NRL is practically the same. The r/c ratio is a dominant factor affecting the interparticle bond strength, hence the relationship between UCS and ITS was developed, which is cost-effective and time-saving for geotechnical and pavement engineering design. The result from this research is a demonstration of the effective usage of natural rubber latex and recycled materials in sustainable pavement applications.

Valorization of deep soil mixing residue in cement-based materials

This study examined the potential of recycling deep soil mixing residue (DSMR), a cement-soil waste, as a partial Portland cement substitute. The chemical and mineral compositions of DSMR before and after calcination were determined. For the calcined DSMR blended cement pastes, the compressive strength and phase assemblage (characterized using TGA and XRD) were evaluated. Results revealed pozzolanic and hydraulic properties of the calcined DSMR, due to the formation of reactive calcium-rich glassy phases and hydraulic C2S. The calcined DSMR can contribute to the strength development of cement because of the pozzolanic reactions and the formation of additional hydrates. With up to 20% calcined DSMR, negligible side-effect on the strength of the blended cement paste was noticed. The compressive strength development of the blended cement pastes was linearly correlated to the reactive phase content in the calcined DSMR. This work demonstrated the potential of using DSMR to develop greener composite cement.

Hydration, mechanical properties, and microstructural characteristics of cement pastes with different ionic polyacrylamides: A comparative study

Polyacrylamides (PAMs) have been widely used as chemical admixtures to modify the workability of cement-based materials. However, polymers possess variable molecular characteristics that have different effects on the macro- and micro-properties of cement, which need to be further explored. In this study, three different ionic PAMs, namely anionic PAM (APAM), cationic PAM (CPAM), and nonionic PAM (NPAM), were applied to investigate their effects on the hydration and mechanical properties of Portland cement. Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) tests were carried out to reveal the evolution of cement phase compositions. The results indicate that APAM significantly delays the cement hydration, increases the cement drying shrinkage, and reduces the cement strength development. However, CPAM and NPAM promote total heat release from the cement. CPAM and NPAM have minor effects on the cement drying shrinkage and strength development compared with APAM. Phase composition analysis reveals that APAM inhibits the dissolution of C3S and promotes the formation of Ca(OH)2 after 1 d. In contrast, CPAM and NPAM mainly enhance the dissolution of C3S before 4 h.

Controlling the soundness of Portland cement clinker synthesized with solid wastes based on phase transition of MgNiO2

A Portland cement clinker containing high content of ferrite phase (>18%) is synthesized with high fractions (60 mass%) of solid wastes, including steel slag, copper tailing, coal gangue and phosphate tailing. Controlling the soundness of clinker caused by the MgO (about 9% in mass) is the key challenge. Adding NiO into the raw meal of clinker controls its soundness via the formation of MgNiO2 with free MgO, showing little effect on the hydration and strength development of cement synthesized with solid wastes. The cement satisfy the 42.5 grade according to the Chinese standard GB 175–2007.

The influence of calcium sulfate content on the hydration of belite-calcium sulfoaluminate cements with different clinker phase compositions

The influence of different amounts of gypsum on the hydration of a belite-rich and a ye'elimite-rich belite-calcium sulfoaluminate clinker (BCSA) was investigated. The hydration kinetics, phase assemblages and compressive strength development of cements prepared using ye’elimite/ calcium sulfate molar ratios of 1, 1.5 and 2 were studied. Besides ettringite and monosulfate, aluminium hydroxide, strätlingite, C−S−H, iron-containing siliceous hydrogarnet and hydrotalcite were present as hydration products. Increasing the amount of gypsum increased the ratio of ettringite to monosulfate formed in the cement paste, lowered the amount of pore solution, delayed the dissolution of belite and ferrite, decreased the formation of strätlingite and, in the case of the ye’elimite-rich BCSA, led to an increase in compressive strength. Increased amounts of belite in the clinker led to the formation of higher quantities of C–S–H, at the expense of strätlingite and a lower compressive strength, as belite has a lower degree of reaction than ye’elimite and due to the formation of more C–S–H and strätlingite compared to the more space-filling ettringite. The thermodynamic model established for BCSA cement hydration agrees well with the experimental data. Compressive strength directly correlated with bound water from thermogravimetric analyses and inversely correlated with the porosity calculated from thermodynamic modelling.

Impact of Alkali Salts on the Hydration of Ordinary Portland Cement and Limestone–Calcined Clay Cement

AbstractSoluble alkalis play a vital role during early age hydration and strength development in cement. This study investigates the influence of alkali addition on the hydration, phase assemblage,...

Curing conditions impact on compressive strength development in cement stabilized compacted earth

Cement is a common candidate for soil treatment when stabilization is required. Its employment in compacted earth blocks requests curing the product as efficiently as possible to obtain satisfactory performances. In this context, many practitioners’ recommendations exist. However, no studies have stated clearly optimum curing method required to achieve best possible strength for cement stabilized compacted earth. In this study, an exploratory analysis was used to assess the influence of moist curing duration on strength development in cement stabilized compacted earth. For this investigation, two natural earths stabilized with different types of cement were considered. The main differences between the chosen cements are their clinker content and strength class. The applied moist curing method consists of conditioning samples in moist environment (99.8% ± 0.2%RH) at ambient temperature (21 °C). Curing duration was varied between 0 (no curing) and 21 days. The uniaxial compressive strength was used as a practical indicator to inspect strength development in dry and wet conditions. Results demonstrate that moist curing is profitable until 7 days regardless of the formulation. In addition, results show that efficiency of cement stabilization depends on earth characteristics rather than cement composition. To discuss moist curing in more detail, accelerated curing conditions performed at 60 °C in ambient and moist environment were analyzed. In conclusion, some recommendations on the optimization of cement usage in compacted earth were provided.

Characterization and prediction for the strength development of cement stabilized dredged sediment

Cement stabilized clay (CSC) from dredged sediment or sludge is receiving increasing attention for its use as construction material. In this paper, seven CSC mixture samples were tested to investigate the effect of constituent proportion parameters and curing time (T) on strength characteristics. Results illustrate that clay-water/cement ratio (W/C) is significantly related to the unconfined compression strength () of CSC. This relationship can be expressed by power function with a great degree of accuracy. After fitting and modeling the test data, two experiential formula models for the characterization of CSC strength are developed, which contain multiple parameters without other variable coefficients or parameters. Finally, methods derived from two experiential formulas to estimate the CSC strength under various parameter variables are proposed, and the prediction accuracy evaluation of derivation data and validation data are analyzed. Highlights Relationship of CSC strength and clay-water/cement ratio can be expressed by a power function. Strength coefficients are modeled with the moisture content of clay and the curing time. Prediction model are developed to estimate CSC strength under various parameters without variable coefficients. Estimation results correspond well with the actual measured strength.

Effect of phosphogypsum on physiochemical and mechanical behaviour of cement stabilized dredged soil from Fuzhou, China

Chemical treatment is one of the popular methods dealing with geoenviromental problems related to soil, such as waste dredged materials, soil with heavy metal pollutions, among others. This paper performed a series of laboratory tests to investigate the effect of phosphogypsum on water content, density, pH, unconfined compressive strength and deformation modulus of cement stabilized soil. It is found that the water content and pH value decreased whereas the density increased, as the phophogysum content increased. These changes were attributable to the formation of ettringite related to the chemical reaction between phosphogypsum and cementitious materials (calcium aluminate hydrates). The unconfined compression strengths of the cement stabilized soil with phosphogypsum content of 1.4% to 8.6% were approximately 1.7 to 9.4 times of those without phosphogypsum. Particularly, the earlier strength of the stabilized soil with phosphogypsum cured at 3 and 7 days increased by 1.3 and 2.1 times in comparison with those lacking phosphogypsum. The mineralogical changes revealed that when the cementation bonding was sufficiently formed at 28 days of curing, the increase in ettringite with phosphogypsum content behaved positive influence on strength development of cement stabilized soil. When cementation bonding was relatively low before 7 days of curing, adequate phosphogypsum content might produce moderate level of ettringite, tended to swell and make denser fabric, resulting in the strength increase. It should be also noted that over-dosage of phosphogypsum might cause volume increase and structure disruption, leading to the strength loss.

An empirical model for calculating uniaxial compressive strength of oil well cements from ultrasonic pulse transit time measurements

Thirty-five cement samples were tested in an Ultrasonic Cement Analyzer (UCA) at varying curing conditions and for varying curing times, and then uniaxially compressed to failure in a hydraulic press. An attempt was made, using the ultrasonic transit time data measured with a UCA and the uniaxial compressive strength data measured using a hydraulic press, to derive an empirical model capable of accurately predicting uniaxial compressive strength from the ultrasonic transit time. Using the Levenberg-Marquardt algorithm, the experimental data was fit to two models. In addition to the transit time dependence, the first model presented incorporates a term that accounts for the curing time while the second model contains terms that account for both the curing time and cement composition. The results obtained illustrate the complexity of deriving a correlation with general applicability to all well cements. The best performing model based on both curve fit error and prediction performance for the samples tested was the model that accounted only for the curing time dependency of the cement strength development rate in addition to the measured transit time, indicating that the transit time measurement history is sufficient as a tool for characterizing well cement strength development.

Monitoring the strength development of alkali-activated materials using an ultrasonic cement analyzer

The ultrasonic cement analyzer (UCA) is used as an aid to develop new cement formulations or perform quality assessment on existing formulations prior to on-site application. The non-destructive UCA technique monitors the strength development of cements by measuring the time required for ultrasonic waves to travel through the cement sample and predicting the strength using empirical correlations, which were developed for ordinary Portland cement slurries. Unfortunately, these empirical correlations cannot be used to accurately predict the strength development for fly ash-based alkali activated materials (AAMs), which are a viable alternative to ordinary Portland cement slurries for oil-well cementing applications. Therefore, a new empirical correlation linking the transit time (i.e. the time required for ultrasonic waves to travel through a unit length of the cement sample) to the compressive strength of fly ash-based AAMs was developed in this study.Class F fly ash was activated by four different alkaline solutions, two sodium hydroxide solutions with 6M and 8M concentrations and two sodium silicate solutions with SiO2/Na2O weight ratio of 0.12 and sodium concentration of 6M and 8M, to produce 4 different slurries which were cured under downhole conditions. 50 mm cubes were crushed to determine the compressive strength of these AAMs after 18, 24, 48, and 72 h of curing. UCA testing was conducted to measure the transit time up to 72 h of curing. Linear regression was performed to develop a correlation linking the measured compressive strength to the measured transit time and AAM mix design parameters.One-way ANOVA analysis revealed that the change in transit time, the concentration of sodium in the activator solution, the SiO2/Na2O weight ratio of the activator solution, and the CaO content of the FA were all significant in predicting the compressive strength of the resulting AAM. The proposed model is applicable for AAMs prepared using Class F fly ash and sodium hydroxide/silicate activating solution with sodium concentration and SiO2/Na2O weight ratio ranging between 6M and 8M and 0 and 0.12, respectively.

Effects of alkali sulfates in clinker on hydration and hardening performance of Portland cement

In this study, two main alkali sulfates – aphthitalite and calcium langbeinite – fabricated in a laboratory are added to an industrial clinker with low alkali and sulfate content in order to adjust the contents of alkali sulfates in the clinker. Based on measuring the dissolution rate of the alkali sulfates and ion concentration in tricalcium aluminate (C3A)–alkali sulfate–water (H2O) systems compared with gypsum, and testing the heat flow, compressive strength, setting time and linear deformation of cement with different alkali sulfate contents, the differences between the alkali sulfates and gypsum are analysed. It is shown that aphthitalite could not act as a retarder, whereas calcium langbeinite can act to achieve almost the same retardation as gypsum. In view of the volume stability and strength development of cement, aphthitalite has a negative action when the equivalent sodium (Na2Oe) content induced is above 1·42%. The X-ray diffraction analysis patterns and scanning electron microscopy images show that aphthitalite restrains ettringite formation. It is suggested that more attention should be paid to the negative action of aphthitalite when alkali and sulfate contents in clinker appear to be high.

Compression and strength behavior of cement–lime–polymer-solidified dredged material at high water content

ABSTRACTThe potential use and engineering properties of cement-solidified clay with superabsorbent polymer (SAP), which is implemented as raw material for backfill or reclamation, are investigated. SAP is added, as water-reducing agent, into the cement mixing method to improve the effectiveness of cementation for high-water content-dredged material in China. Test results show that the vertical yield stress () and unconfined compression strength qu significantly increase with SAP content, cement and lime content, and curing time, which are attributed to greater degree of cementation bonding. By contrast, the influence of SAP on the compressibility of cement-treated clay at postyield state is negligible. The clay–water/cement ratio hypothesis was used successfully to analyze the strength development of cement–lime–polymer-solidified Kemen clay at various SAP contents. For given clay–water/cement ratio, the strength of the cement-solidified clay increases with an increasing SAP content. Hence, to increase cementation efficiency and improve the economic impact, SAP can be used to enhance the strength of cement-solidified clay at notably high water content.

Sealing of cracks in cement using microencapsulated sodium silicate

Cement-based materials possess an inherent autogenous self-healing capability allowing them to seal, and potentially heal, microcracks. This can be improved through the addition of microencapsulated healing agents for autonomic self-healing. The fundamental principle of this self-healing mechanism is that when cracks propagate in the cementitious matrix, they rupture the dispersed capsules and their content (cargo material) is released into the crack volume. Various healing agents have been explored in the literature for their efficacy to recover mechanical and durability properties in cementitious materials. In these materials, the healing agents are most commonly encapsulated in macrocontainers (e.g. glass tubes or capsules) and placed into the material. In this work, microencapsulated sodium silicate in both liquid and solid form was added to cement specimens. Sodium silicate reacts with the calcium hydroxide in hydrated cement paste to form calcium-silicate-hydrate gel that fills cracks. The effect of microcapsule addition on rheological and mechanical properties of cement is reported. It is observed that the microcapsule addition inhibits compressive strength development in cement and this is observed through a plateau in strength between 28 and 56 days. The improvement in crack-sealing for microcapsule-containing specimens is quantified through sorptivity measurements over a 28 day healing period. After just seven days, the addition of 4% microcapsules resulted in a reduction in sorptivity of up to 45% when compared to specimens without any microcapsule addition. A qualitative description of the reaction between the cargo material and the cementitious matrix is also provided using x-ray diffraction analysis.

The effect of size and replacement content of nanosilica on strength development of cement treated residual soil

In this study, effects of size and replacement content of nanosilica on physical, chemical, and microstructural characteristics of cemented residual soil were investigated. Accordingly, UCS and electrical resistivity tests were conducted on cemented specimens with replacement contents of 0.2%–1% nanosilica of 15 and 80nm at 7, 14 and 28days. XRD, Zeta potential, CEC, FTIR, and SEM tests were performed to identify chemical and microstructural changes over time. The results showed that smaller size nanosilica had an accelerated influence on samples while nanosilica of larger size was more effective at ages after 14days of curing.