Compressive Strength Of Portland Cement Research Articles

Effects of triisopropanol amine, sodium chloride and limestone on the compressive strength and hydration of Portland cement

The effect of triisopropanol amine (TIPA), sodium chloride (NaCl) and limestone (LS) on compressive strength and hydration of Portland cement were studied using Design of Experiment (DoE) and isothermal calorimetry, respectively. The results showed that combination of TIPA and NaCl could increase both early age and later age compressive strength of Portland cement mortars and Portland cement–limestone mortars. No major interactive effects on strength enhancement were observed for these three additives. However, the results of isothermal calorimetry showed clear interaction between TIPA and NaCl. It was found that NaCl increased the effectiveness of TIPA through promotion of two transitions: (i) conversion of AFt to AFm for Portland cement sample, (ii) conversion of carboalumiante phases for Portland–limestone cement sample.

Prediction of the steel-concrete bond strength from the compressive strength of Portland cement and geopolymer concretes

The oldest and simplest bond test, which is the standard concentric pull out test, is usually used as a comparative test for different concretes in order to assess the bond with deformed bars. In this paper, two types of concrete are considered: Ordinary Portland cement (OPC) concrete and a novel concrete technology, namely geopolymer concrete (GPC). Bond strength was investigated by conducting pull-out tests on ribbed bars with a nominal diameter of 10mm and/or 12mm. The specimens were tested at various ages ranging from 1 to 28days. Compression tests were performed at all ages as well. The main objective of the extensive research program involving 260 pull-out tests was to develop empirical models correlating the steel-concrete bond strength to the mean compressive strength of concrete for both OPC and geopolymer concretes. The models developed are compared to the existing model adopted by FIP Committee.

Effect of different mixing methods on the physical properties of Portland cement.

BackgroundThe Portland cement is hydrophilic cement; as a result, the powder-to-liquid ratio affects the properties of the final mix. In addition, the mixing technique affects hydration. The aim of this study was to evaluate the effect of different mixing techniques (conventional, amalgamator and ultrasonic) on some selective physical properties of Portland cement.Material and MethodsThe physical properties to be evaluated were determined using the ISO 6786:2001 specification. One hundred sixty two samples of Portland cement were prepared for three mixing techniques for each physical property (each 6 samples). Data were analyzed using descriptive statistics, one-way ANOVA and post hoc Tukey tests. Statistical significance was set at P<0.05.ResultsThe mixing technique had no significant effect on the compressive strength, film thickness and flow of Portland cement (P>0.05). Dimensional changes (shrinkage), solubility and pH increased significantly by amalgamator and ultrasonic mixing techniques (P<0.05). The ultrasonic technique significantly decreased working time, and the amalgamator and ultrasonic techniques significantly decreased the setting time (P<0.05).ConclusionsThe mixing technique exerted no significant effect on the flow, film thickness and compressive strength of Portland cement samples. Key words:Physical properties, Portland cement, mixing methods.

Hydration process and compressive strength of cement pastes containing natural zeolite

This paper presents the results of the study examining the effect of natural zeolite from Igroš, Serbia, on the hydration and compressive strength of Portland cement based pastes, in which a part of cement has been replaced by natural zeolite. The experimental part comprises three stages. In the first stage, the chemical composition of natural zeolite and the textural properties of both natural zeolite and Portland cement have been examined. In the second stage, Portland cement based pastes incorporating 0%, 10%, 20% and 30% per weight of natural zeolite have been prepared and cured for 28 and 60 days. Finally, mineralogical properties and compressive strength of pastes have been examined. The products of hydration and relative changes of portlandite consumption throughout hydration process (28 and 60 days) have been studied by the means of X-ray diffraction and Fourier transform infrared spectroscopy. Additionally, mercury intrusion porosimetry has been used to characterise pore structure.

Influência da utilização de procedimentos não padronizados de ensaio para a determinação experimental da resistência à compressão simples e do módulo estático de elasticidade do cimento Portland

A resistência à compressão é um dos parâmetros fundamentais usados para controle e caracterização do cimento. O ensaio padrão para determinação da resistência à compressão simples do cimento Portland, normatizado pela NBR 7215 (1), especifica o uso de areia com granulometria determinada e estabelece procedimentos de mistura rigorosos na preparação dos corpos de prova. Sabe-se que, nem sempre, os procedimentos padrão são rigorosamente seguidos, seja devido a fatores relacionados com competência técnica ou pela simplificação da norma, entre outros fatores. O objetivo principal deste trabalho foi avaliar a influência de determinadas simplificações dos procedimentos padrão de ensaio na determinação experimental da resistência à compressão simples do cimento Portland. Foram testados diferentes procedimentos de mistura e utilizados diferentes tipos de agregado miúdo, especificamente, areia média comum ou com granulometria controlada, tomando como referência a denominada areia do Tietê. Foram utilizadas duas amostras de cimento CPV-ARI, provenientes de fabricantes distintos. Para todas as combinações foram realizados ensaios de resistência à compressão e módulo estático de elasticidade nas idades de 1, 3, 7 e 28 dias. Foi efetuada uma análise de variância (ANOVA) para avaliar se as variáveis estudadas geravam diferenças estatisticamente significativas nos resultados experimentais. Foi possível concluir que, de forma geral, a moldagem simplificada não influenciou significativamente a resistência à compressão simples nem o módulo estático de elasticidade do cimento Portland. Por outro lado, o tipo de agregado miúdo utilizado influenciou significativamente a resistência à compressão, mas não impactou o módulo de elasticidade das amostras.

Mechanical properties and microstructure of multi-walled carbon nanotube-reinforced cement paste

Carbon nanotubes (CNTs) have great potential to improve the strength and toughness of traditional cement-based building materials. After effective dispersion in water with a surfactant, followed by separation using a centrifuge, multi-walled carbon nanotubes (MWCNTs) can be stored stably for over three months. Our study focused on the microstructure and compressive strength of Portland cement reinforced with MWCNTs. As the proportion of added MWCNTs was increased from 0% to 0.2% by weight of cement, the mechanical properties of the cement paste correspondingly improved. With the addition of 0.1wt% MWCNT, the 7-day and 28-day compressive strengths increased by 22% and 15%, respectively. The cement paste flexural strength was also improved by addition of MWCNTs. Scanning electron microscopy (SEM) analysis showed that the carbon nanotubes were well dispersed in the cement hydration products. Debonding, bridging, and mesh filling were also observed by SEM. Pressured-mercury testing was used to measure pore distribution in the MWCNT-reinforced cement pastes, and it was found that the pore size distribution tilted in favor of gel pores, pores that have a positive influence on mechanical strength.

The Influence of Zinc on the Hydration and Compressive Strength of Portland Cement

The aim of this work was to investigate the effect of addition of elements present in secondary raw materials on the hydration and compressive strength of Portland cement. Ordinary Portland cement (OPC) has been used to solidify hazardous waste for about 25 years and the effect of waste components on the hydraulic activity is an interesting object for the research. In this study Zn nitrate, chloride and oxide were added to Portland cement. The concentrations of 0.1 and 1.0 weight percent of zinc in cement were tested. After 1, 7 and 28 days the compressive strength was reduced or similar by the addition of zinc in comparison with pure cement. This difference is probably due to a delay in tricalcium silicate hydration as shown by isothermal calorimetry.

Compressive Strength of Blended Portland Cement Mortars Incorporating Fly Ash and Silica Fume at High Volume Replacement

Fly ash has been widely used as a replacement of Portland cement at high content levels, but the compressive strength of Portland cement blended with fly ash is lower at early ages. Thus, this study compares the compressive strength of ternary blended Portland cement mortars incorporating fly ash (40-70 wt%) and silica fume (5-10 wt%) with binary blended Portland cement mortars incorporating fly ash only. Blended Portland cement mortars were designed with a constant water/binder ratio of 0.485 and the flow table tested was carried out. A fine aggregate to binder ratio of 2.75 was used. The compressive strength of all blended Portland cement mortars that cured in water at 23 °C was tested at 28 days. The results show that the flow of blended Portland cement mortars increased with increasing fly ash content and tended to decrease with increasing silica fume content, at the same replacement level. Moreover, the compressive strength of blended Portland cement mortars decreased with increasing fly ash content. However, compressive strength gains were obtained from ternary blended Portland cement mortars incorporating silica fume, tending to increase with increasing silica fume content.

Influence of 15 and 80 nano-SiO2 particles addition on mechanical and physical properties of ternary blended concrete incorporating rice husk ash

This study demonstrates the effects of SiO2 nanoparticles as additives with two different sizes of 15 and 80 nm on compressive strength and porosity of rice husk ash (RHA) blended concrete. Up to 20% of ordinary Portland cement (OPC) was replaced by RHA with average particle size of 5 micron. Also, SiO2 nanoparticles were added to the above mixture at four different weight percentages of 0.5, 1.0, 1.5 and 2.0 and cured in lime solution. The results indicated that compressive strength of Portland cement–nano SiO2–rice husk ash (PC–NS–RHA) ternary blended concrete was considerably increased. Moreover, the total amount of porosity decreased to a minimum with respect to the control concrete. This improvement was observed at all the curing ages and replacement levels, but there was a gain in the optimal point with 20% of RHA plus 2% of 80 nm SiO2 particles at 90 days of curing.

Serviceability and reinforcement of low content whisker in portland cement

In order to explore the serviceability and reinforcement of CaCO3 whisker in portland cement matrix, the durability of CaCO3 whisker and effect of low whisker content(0%–4.0%) on the working performance and mechanical properties of portland cement were investigated. The experimental results show that CaCO3 whiskers have a good stability and serviceability in cement, and should not significantly alter the rheological properties of the cement paste. The flexural and compressive strength of portland cement reinforced by CaCO3 whiskers was increased by 33.3% and 12.83%, respectively.

Evaluation of the strength and radiopacity of Portland cement with varying additions of bismuth oxide

To study the effect of addition of various proportions of bismuth oxide on compressive strength and radiopacity of Portland cement. The compressive strength of white Portland cement and cement replaced with 10, 15, 20, 25 and 30% bismuth oxide was evaluated by testing cylinders 6 mm in diameter and 12 mm high. Twelve cylinders were tested for each material under study. The radiopacity of the cements tested was evaluated using an aluminium step-wedge and densitometer. The optical density was compared with the relevant thickness of aluminium (Al). Statistical analysis was performed using Analysis of Variance (ANOVA) with P = 0.05 and Tukey test to perform multiple comparison tests. Various additions of bismuth oxide had no significant effect on the strength of the material when compared with the unmodified Portland cement (P > 0.05). The radiopacity of the cements tested ranged from 2.02 mm Al for Portland cement to 9.79 mm Al for the highest bismuth replacement. Addition of bismuth oxide did not affect the compressive strength of Portland cement. All the bismuth oxide cement mixtures had radio-opacities higher than 3 mm thickness of aluminium.

A linguistic model for evaluating cement strength

This paper presents a soft methodology for predicting the 28-day compressive strength of Portland cement (CCS) by making use of the 1-day, 3-day and 7-day CCS values. Data taken from a cement plant in Turkey have been employed in the model construction and testing. For implementation, linguistic models were designed based on if-then fuzzy rules. In addition, predictions of these models were compared with results of the regression models. The performance evaluations showed that the linguistic-based fuzzy predictions are very satisfactory in estimating cement strength and the linguistic modeling performs better than regression modeling.

Effect of Incorporating Nanoporous Metal Phosphate Materials on the Compressive Strength of Portland Cement

Nanoporous metal phosphate (NP-MPO) materials are being developed for removal of contaminant oxyanions (As(OH), , and ), and cations (mercury, cadmium, and lead) from water and waste streams. Following sequestration, incorporation of metal laden NP-MPOs as a portion of cement formulation would provide an efficient and low-cost way to immobilize metal laden NP-MPOs in an easily handled waste form suitable for permanent disposal. There are no known investigations regarding the incorporation of NP-MPOs in concrete and the effects imparted on the physical and mechanical properties of concrete. Results of this investigation demonstrated that incorporating of NP-MPO materials requires additional water in the concrete formulation which decreases the compressive strength. Thus, incorporation of NP-MPOs in concrete may not serve as an efficient means for long-term disposal.

Effects of milling Al(OH) 3 prior to mix with Ca(OH) 2 for a rapid cement hardener

Positive effects of milling Al(OH) 3 prior to mix with Ca(OH) 2 are elucidated to develop a rapid hardener for portland cement. With the hardener thus obtained, compressive strength of portland cement exceeds 5 MPa within 2 h. Rapid formation of calcium aluminate hydrate (CAH) in cement paste is found to be a key issue. Milling a mixture of Al(OH) 3 and Ca(OH) 2 in contrast, results in an in situ formation of CAH to decrease considerably the effect of rapid hardening.

The effect of boric acid sludges containing borogypsum on properties of cement

The effects on the compressive strength of Portland cement directly mixed with boric acid wastes such as reactor waste, borogypsum and sludges were studied. It was found that as the percent of the sludges increase in the cement mixture the compressive strength decreased.

Predicting a compressive strength of portland cement and optimizing its raw mixture composition

This paper describes a numerical procedure as well as a computer program for predicting the changes of cement compressive strength caused by varying raw components in an initial mixture. It was achieved by statistical processing of the measured values. As a result the coefficients for correlating function of beforehand chosen type were determined. So aquired correlation was adopted as an objective function of the optimization problem, which mathematical model was completed after taking into account certain process-, market- and empirical constraints. By solving the model two combinations of raw components (for two different requirements) were defined.

A shrinking unreacted core model for estimating the compressive strength of portland cement

A method for estimating the compressive strength of concrete from physical characterization of ground cement is developed. The estimation method is based on data obtained from a granulometry curve of ground cement and a so-called shrinking unreacted core model. It is shown that the model gives essential information about the hydration characteristics of concrete, and is found to be a far more relevant grinding parameter than the Blaine specific area measure of cement that is used in most grinding mills today. The method has been tested on an industrial grinding mill with the capacity of 750 tons/day.

Calcareous fillers and the compressive strength of portland cement

The effect of two calcareous fillers (ground limestone and reagent quality CaCO 3) on the compressive strength of Portland cement, was studied and compared with the corresponding effect of two pozzolanic fillers (ground scoria and Rhine trass) and one non-calcareous, non-hydraulic filler (reagent quality CaF 2). It was concluded that fillers affect strength through their accelerating effect on the cement hydration. This effect was found to be essentially the same for all the fillers studied irrespective of their specific chemical composition. It was also concluded that the formation of calcium carboaluminate, if it took place when calcareous fillers were involved, did not necessarily affect the cement compressive strength. Further tests are being carried out to show that the use of fillers is, indeed, associated with an increased rate of hydration.