Compressive Strength Of Blended Cement Research Articles

Concrete Modification for Hot Weather Using Crushed Dolomite Stone

Crushed dolomite stone can be used as a part of concrete for hot weather. Fine dolomite as a filler is not commonly included in Portland cement. In this paper, the properties of a blended binder based on Portland cement and dolomite filler are presented. Dolomite filler was obtained from dust grains by mechanical activation in a laboratory ball mill to increase the specific surface area and its chemical activity. It is shown that the impact of mechanical activation allows to obtain dolomite filler with a median particle size of 1.4 μm and a specific surface area of 639.9 m2/kg. The content of dolomite filler in Portland cement was 10, 30 and 50%. The main properties of blended cements, i.e., the standard consistency, setting time, compressive strength, average density, and drying shrinkage, were determined on pastes. The mineralogical composition of the hydrated pastes was determined by XRD at 28 days. The presence of dolomite filler at levels higher than 10% decreases the compressive strength of blended cements. The dolomite filler decreases the water demand, shortens the setting time, and mitigates the development of drying shrinkage in the blended binder. To prevent concrete cracking, the application of dolomite filler in blended cement is relevant in hot weather due to its reduced drying shrinkage.

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.

Effect of GGBS and curing conditions on strength and microstructure properties of oil well cement slurry

The addition of any supplementary cementitious materials has a significant influence on cement paste properties and its microstructure. In this paper, the effects of micro-fine Ground Granulated Blast Furnace Slag (GGBS) on the properties Oil Well Cement (OWC) slurry are investigated. The class G cement is replaced in a varying percentage (30–70%) with GGBS at intervals of 10%. Further, the influence of different curing conditions (i.e., dry curing, moist curing, curing at 60 °C, curing at 110 °C) on the compressive strength of blended cement with GGBS are also studied. The microstructure analysis of blended cement with GGBS is investigated using isothermal calorimetry, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), and Mercury Intrusion Porosity (MIP). The results show that the compressive strength of blended cement with 40 % GGBS have significantly increased and more than that of unblended cement. Further, micro-fine GGBS has influence on the emission of hydration heat due to pozzolanic reaction. The heat of hydration of blended cement is decreased significantly with partial replacement of cement with GGBS. The most significant finding in this study is that the permeability of blended cement paste with 40 % GGBS is decreased by 51 % of that of unblended cement, which is very important because it is one of the main factors affecting the gas migration in the wellbore.

Pozzolanic activity of argentine vitreous breccia containing mordenite

A vitreous breccia with variable amount of mordenite was studied for its use as pozzolan. The raw material was characterized by optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), and the zeolite content was estimated by the methylene blue staining technique. After being ground, physical characteristics, cation exchange capacity (CEC), pozzolanicity, and the compressive strength activity index (SAI) were determined. The staining technique and the CEC measurement were used to evaluate the average content of zeolite. The vitreous breccia has pozzolanic activity after 7 days, the water demand increases slightly, and its addition stimulates the early hydration of portland cement. At later ages, the pozzolanic reaction around the grains, as revealed by SEM studies, improves the compressive strength of blended cements having a SAI > 0.85 at 28 days.

Mechanical Activation of Granulated Copper Slag and Its Influence on Hydration Heat and Compressive Strength of Blended Cement.

Mechanical activation of granulated copper slag (GCS) is carried out in the present study for the purposes of enhancing pozzolanic activity for the GCS. A vibration mill mills the GCS for 1, 2, and 3 h to produce samples with specific surface area of 0.67, 1.03 and 1.37 m2/g, respectively. The samples are used to replace 30% cement (PC) to get 3 PC-GCS binders. The hydration heat and compressive strength are measured for the binders and derivative thermogravimetric /thermogravimetric analysis (DTG/TGA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) are used to characterize the paste samples. It is shown that cumulative heat and compressive strength at different ages of hydration and curing, respectively, are higher for the binders blending the GCS milled for a longer time. The compressive strength after 90 d of curing for the binder with the longest milling time reaches 35.7 MPa, which is higher than the strength of other binders and close to the strength value of 39.3 MPa obtained by the PC pastes. The percentage of fixed lime by the binder pastes at 28 days is correlated with the degree of pozzolanic reaction and strength development. The percentage is higher for the binder blending the GCS with longer milling time and higher specific surface area. The pastes with binders blending the GCS of specific surface area of 0.67 and 1.37 m2/g fix lime of 15.20 and 21.15%, respectively. These results together with results from X-ray diffraction (XRD), FTIR, and SEM investigations demonstrate that the mechanical activation via vibratory milling is an effective method to enhance the pozzolanic activity and the extent for cement substitution by the GCS as a suitable supplementary cementitious material (SCM).

Chemical composition and physicomechanical characteristics of sawdust ash blended cement

The production of blended cement by incorporating sawdust ash (SDA) in Ordinary Portland Cement (OPC) clinker, during manufacturing of cement was investigated. Sawdust was collected from sawmill industry at Olope Marun, Ogbomoso, Oyo State, Nigeria. It was burnt to ash and then added as percentage replacement for OPC clinker. Chemical and physical properties of both SDA and OPC clinker were determined. The production of the SDA – blended cement was carried out by intergrinding 5–25% by weight of SDA with OPC clinker during cement manufacturing. The blended cement produced was analyzed for chemical composition and physical properties. The chemical compositions of SDA – blended cement with 5–25% SDA replacement were 19.96–22.52% for silicon oxide, 5.57–5.72% for aluminum oxide, 3.47–3.63% for iron oxide, and 65.39–57.28% for calcium oxide. The physical properties of SDA – blended cement were 5–7 mm for soundness, 391–410 m2/kg for fineness, 27.6–30.0% for consistency, 45–160 min for initial and 75–210 min for final setting time, 2.5–2.2 for specific gravity, and 1.33–1.45 for loss on ignition. The compressive strength of blended cement with 5–25% SDA replacement ranged from 5.2 to 9.9, 11.2–27.8, 13.9–44.0, 14.3–56.0, 15.8–58.9, 20.4–62.4, and 23.6–65.2 N/mm2 for 1, 3, 7, 14, 28, 56, and 90 days, respectively while the flexural strength ranged from 1.8 to 2.3, 2.5–5.3, 2.8–6.3, 3.4–7.4, 3.5–8.9, 3.9–10.1, and 4.1–11.5 N/mm2, respectively. The partial replacement of OPC clinker with SDA during cement manufacturing was established. A maximum replacement level of 15% by weight of cement gave desirable engineering properties.

Size fractionation of brown fly ash: utilisation of grey fraction as a pozzolanic material in blended cement

The work aimed to classify a raw brown colour fly ash (RFA) into coarse grey fly ash (GFA) and fine brown fly ash (BFA) using a laboratory air classifier and to study the properties of grey fly ash-based blended cement. Portland cement (OPC) was partially replaced with 10–30% GFA by mass at 5% intervals to make blended cement. The physical and mechanical properties were determined as per Bureau of Indian Standards (BIS). The incorporation of GFA in cement mixes decreases the specific gravity, fineness, consistency, volume expansion and drying shrinkage while increases the setting time and flow-ability. The compressive strength of blended cement was observed lower than that of OPC at all ages, but the rate of strength development increases with the age. The replacement level up to 20% meets the BIS strength requirement of 33 MPa at 28 d for fly ash-based blended cement. The hydration studies were done using Isothermal Conduction Calorimetry (ICC) at 27 °C. The total heat of hydration was observed to decrease with the increasing GFA content. The microstructural characterisation of hardened cement pastes after 60 d using XRD, FTIR and SEM-EDS revealed the variations in mineralogical, structural and morphological properties.

Predicting compressive strength of blended cement concrete with ANNs

Predicting the compressive strength of concrete is important to assess the load-carrying capacity of a structure. However, the use of blended cements to accrue the technical, economic and environmental benefits has increased the complexity of prediction models. Artificial Neural Networks (ANNs) have been used for predicting the compressive strength of ordinary Portland cement concrete, i.e., concrete produced without the addition of supplementary cementing materials. In this study, models to predict the compressive strength of blended cement concrete prepared with a natural pozzolan were developed using regression models and single- and 2-phase learning ANNs. Back-propagation (BP), Levenberg-Marquardt (LM) and Conjugate Gradient Descent (CGD) methods were used for training the ANNs. A 2-phase learning algorithm is proposed for the first time in this study for predictive modeling of the compressive strength of blended cement concrete. The output of these predictive models indicates that the use of a 2-phase learning algorithm will provide better results than the linear regression model or the traditional single-phase ANN models.

Effect of cement composition on the early hydration of blended cements with natural zeolite

This paper studies the addition (0–40% w/w) of natural zeolite (NZ, 84% clinoptilolite) in blended cements made with Portland cement (PC) with low and medium C3A content. The isothermal calorimetry was used to understand the effect of NZ on the early cement hydration. For low C3A cement, the addition of NZ produces mainly a dilution effect and then the heat released curve is similar to plain cement with lower intensity. For medium C3A cement, the curve shows the C3S peak in advance and a high intensity of third peak attributed to C3A hydration. The high cation fixed of NZ reduces the ions concentration (especially alkalis) in the mixing water stimulating the PC hydration. The flowability decreases when the NZ replacement level increases. Results of Fratini’s test show that NZ with both PCs used presents slow pozzolanic activity. At early age, XRD and FTIR analyses confirm that hydration products are the same as that of the corresponding PC and the CH is progressively reduced after 28 days and some AFm phases (hemi- and monocarboaluminate) appear depending on the NZ percentage and the PC used. For low replacement levels, the compressive strength is higher than the corresponding PC from 2 to 28 days. For high replacement levels, the early compressive strength is lower than that of corresponding plain PC and the pozzolanic reaction improves the later compressive strength of blended cements.

Hydration Kinetics and Strength Development of Waste Paper Sludge Ash (WPSA) with Different Particle Size as Binary Blended Cement

In this study, four types of Waste Paper Sludge Ash (WPSA) were explored for use as Supplementary Cementitious Materials (SCM) in binary system. The WPSA use varies in particle size range and surface area however similar in chemical composition. At first stage, Ordinary Portland Cement (OPC) was replaced by WPSA at 5% mass to mass basis as blended cement. Four size of WPSA was prepared which are unsieve, retained at 63μm, retained at 45μm and pan. WPSA blended cement (WPSABC) was introduced from the four size of WPSA that prepared earlier. Water to cement ratio selected was 0.50 and it keep constant at all type of blended cement. When compared with the control mix, result shows that hydration kinetics is affected by the particle size of WPSA. Pan WPSA has slightly higher peak of hydration kinetics and compressive strength of blended cement. At second stage, Pan WPSA was selected to undergo the further investigation on its performance. Pan WPSABC were prepared at replacement level of 5%, 10%, 15% and 20%, mass to mass basis. Same method and w/c ratio was used and compared with control mix. From the result, it is found that the peak for rate of heat evolution of Pan WPSABC occur earlier and slightly lower as compared to OPC. Pan WPSA also achieved it optimum strength at 5% replacement level which is more than control mix.

Compressive strength and drying shrinkage of fly ash-bottom ash-silica fume multi-blended cement mortars

This paper studies the physical properties, compressive strength and drying shrinkage of multi-blended cement under different curing methods. Fly ash, ground bottom ash and undensified silica fume were used to replace part of cement up to 50% by weight. Specimens were cured in air at ambient temperature, water at 25, 40 and 60°C, sealed with plastic sheeting for 28days. The results show that absorption and volume of permeable pore space (voids) of blended cement mortars at 28day under all curing methods tend to increase with increasing silica fume replacement. The compressive strength of blended cement with fly ash and bottom ash was lower than that of Portland cement control at all curing condition while blended cement with silica fume shows higher compressive strength. In addition, the compressive strength of specimens cured with water increased with increasing curing temperature. The drying shrinkage of all blended cement mortar cured in air was lower than that of Portland cement control while the drying shrinkage of blended cement mortar containing silica fume, cured with plastic sealed and water at 25°C was higher than Portland cement control due to pore refinement and high autogenous shrinkage. However, the drying shrinkage of blended cement mortar containing SF cured with water at 60°C was lower than that of Portland cement control due to lower autogenous shrinkage and the reduced microporosity of C–S–H.