Cementing Efficiency Factor Research Articles

Influence of Brazilian fly ash fineness on the cementing efficiency factor, compressive strength and Young's modulus of concrete

This work investigates the cementing efficiency, determined by the k-value, of a Brazilian fly ash. The analyzed variables are the fly ash fineness and content, the water content in the mixtures and age of concrete. Further, the influence of the fineness of fly ash on the Young's modulus was also investigated. The results indicate that the k-values evaluated for Brazilian fly ash are higher than the one recommended by European standard for concrete, EN 206. Furthermore, k-value depends on fly ash content and decrease when the content in the mixture is raised. Water/binder ratio and hydration time significantly influence the k-value, too. The results also indicate an improvement of k-value and relationship between compressive strength, Young's modulus and the fly ash amount in the mixture with an increase in fly ash fineness. New relationships between compressive strength and water/effective cementitious materials ratio, considering the k-values, are proposed for fly ash-concretes.

Contribution of fly ash to mortar strength development under steam and internal curing

The purpose of this study is to quantitatively evaluate the effects of steam curing and internal curing on contribution of fly ash to strength development of mortar by using cementing efficiency factor (k-value) that represents strength development performance as a binder of fly ash. In addition, the pozzolanic reaction of fly ash was evaluated from the viewpoint of calcium hydroxide consumption by using thermogravimetry and differential thermal analysis as well as the degree of fly ash reaction by using selective dissolution method. The result indicated that steam curing improved early compressive strength and internal curing improved compressive strength and k-value at all ages. Also, a linearrelationship between the degree of fly ash reaction and the k-value was shown regardless of the age and the replacement ratio of fly ash.

Mechanical, environmental and economic performance of sustainable Grade 45 concrete with ultrahigh-volume Limestone-Calcined Clay (LCC)

Low-grade calcined clay mixed with limestone powder (Limestone-Calcined Clay, LCC) is a new kind of cement replacement material in the face of the inadequate availability of conventional pozzolans such as fly ash. Because of the high water demand and likely insufficient strength gain of LCC, the information on using more than 50% of LCC in the binder is extremely limited, which hinders using LCC in a higher replacement level to develop greener concrete. This study attempts to address this knowledge gap by producing Grade 45 structural concrete with ultrahigh-volume LCC (UHV-LCC). UHV-LCC mortar mixes with various LCC/binder ratios (50-80%) and water/binder ratios (0.3-0.4) were firstly examined to determine the cementing efficiency factor of LCC. Four Grade 45 UHV-LCC concrete mixes with different LCC/binder ratios (50%, 60%, 70% and 80%) were then designed and demonstrated. With the judicious choice of water/binder ratio, UHV-LCC concrete achieved compressive strength of 33-37 MPa at 3 days, 47-51 MPa at 7 days, 56-58 MPa at 28 days, and 62-64 MPa at 90 days. The flexural strength of UHV-LCC concrete was 2-10% higher than that of plain Portland cement concrete with identical compressive strength class. Additionally, UHV-LCC concrete showed 36.8-44.4% lower total embodied carbon than plain Portland cement concrete, and a higher LCC/binder ratio resulted in lower embodied carbon in Grade 45 concrete. A 5-D representation was used to evaluate different concrete mixes by comprehensively considering the mechanical, environmental, and economic performance. Our findings are useful for the mix design of sustainable concrete with LCC.

Reuse of drinking water treatment sludge in mortar as substitutions of both fly ash and sand based on two treatment methods

In this paper, attempts were made to employ both heat-treated and sodium hydroxide (NaOH) treated drinking water treatment sludge (DWTS) as replacement of both fly ash and silica sand at varied substitution ratios in mortar mixes. For fly ash replacement, the heat treatment method results in improved compressive strength with up to 15% replacement ratio and the NaOH treatment method results in higher compressive strength with substitution ratios of up to 10% compared with reference samples. For sand replacement, the replacement ratio associated with improved mortar compressive strength is limited to 5% by weight for both treatment methods, however, heat-treated DWTS mixes showed higher strength than NaOH-treated mixes at the same substitution ratios. Cementing efficiency factor (CEF) for fly ash replacement mixes were analysed and results showed higher CEF with increased DWTS substitution ratio. Considering both the compressive strength and the micro-structural analysis results, treatment of DWTS subjected to evaluated temperature produced better performance mortar than that of NaOH-treated method.

Contribution of fly ash to the strength development of mortars cured at different temperatures

This study aims to determine the contribution of fly ash to the compressive strength development of mortars cured at different temperatures based on the cementing efficiency factor. The strength development of mortar specimens with different fly ash replacement ratios cured at 10 °C, 20 °C, and 30 °C was analyzed considering the apparent activation energy. Subsequently, the contribution of fly ash was assessed using the cementing efficiency factor. The results indicate that the cementing efficiency factor is significantly affected by the curing temperature and can be estimated using the cumulative temperature and the appropriate datum temperature for fly ash cement.

Compressive strength prediction model of high-strength concrete with silica fume by destructive and non-destructive technique

The study proposes a new model for estimating the compressive strength of high-strength concrete using destructive and non-destructive testing. The effect of silica fume replacement level and its cementing efficiency factor on compressive strength and ultrasonic pulse velocity (UPV) were experimentally examined. In the present work, the cementing efficiency factor (k) for silica fume at different percentage replacement level has been assumed, and at the constant water-to-binder ratio, the compressive strength has been obtained. An exponential relationship is proposed between UPV and compressive strength with a high correlation coefficient. A statistically noteworthy model with a high correlation coefficient R2 > 0.90 is established to study the influence of the variables (%SF and k) on UPV results. Finally, the two proposed models were amalgamated to develop a new model to predict the 28-day compressive strength of high-strength concrete. The validity of the model has been verified with the results obtained by different researchers on different types of specimens. The proposed new model is for the strength range of the 40–75 MPa.

Adding ceramic polishing waste as filler to reduce paste volume and improve carbonation and water resistances of mortar

The use of ceramic waste in concrete/mortar production as aggregate replacement or cement replacement has been under consideration in the last decade to find an effective way to tackle the growing hazard of ceramic waste disposal. In this study, the authors reutilize ceramic polishing waste (CPW) as a filler to replace an equal volume of cement paste in mortar while keeping the mixture proportions of the cement paste unchanged, i.e., in a new way as paste replacement. This mixture design strategy allows a larger amount of CPW to be added to substantially reduce the paste volume, cement and carbon footprint. The mortar mixes so produced had been subjected to carbonation and water absorption tests, and the results showed that as paste replacement, the CPW can significantly enhance the carbonation and water resistances, in addition to the environmental benefits of reducing waste, cement and carbon footprint. Regression analysis of test results indicated that for carbonation resistance, the cementing efficiency factor of the CPW was around 0.5, whereas for water resistance, the cementing efficiency factor was higher than 1.0 at low CPW content and lower than 1.0 at high CPW content.

Evaluation of the cementing efficiency factor of low-calcium fly ash for the chloride-penetration resistance of concretes: A simple approach

This paper aims at simply evaluating the cementing efficiency factor (k-value) of low-calcium fly ash (FA) for the chloride-penetration resistance of concretes using the chloride-penetration depth (xd). Results indicate that xd could be used as a concrete-durability property to obtain the k-value of FA in a simple approach compared to the chloride-diffusion coefficient. The k-value of the FA based on the xd was approximately higher than 2, and it increased linearly with the increment in the FA reaction degree subsequent to the start of immersion. In addition, the correlation between the k-value for the chloride-penetration resistance and that for the strength development of the concrete was obtained.

Compressive strength and environmental impact of sustainable blended cement with high-dosage Limestone and Calcined Clay (LC2)

Replacing half of the clinker by a blend of limestone powder and low-grade calcined clay (in 1:2 weight ratios) has been recently proposed as a new version of economical and green cement named Limestone-Calcined Clay (LC2) cement, also known as LC3. The LC2 blend emits much less carbon dioxide than traditional Portland clinker and has a sufficiently high cementing efficiency factor for maintaining compressive strength under high replacement levels. In this study, the feasibility of blending more than 50% of LC2 in cement was explored in order to achieve greener blended cement. Five LC2 replacement levels were studied, including 25%, 50%, 60%, 70% and 80% by weight of cement. Compressive strength of BS EN 196-1 standard mortar mixes at 3–360 days was evaluated, and the fresh property, hydration heat as well as environmental impact of the blended cement were investigated. The results showed that the blended cements with 50%, 60% and 70% LC2 achieved the compressive strength of 53.6 MPa, 43.9 MPa and 33.4 MPa at 28 days, respectively; thus they fulfill the 28-day strength requirements for 52.5N, 42.5N and 32.5N cements, respectively. The blended cements with 50–60% LC2 had a lower material cost index than Portland cement and blended cement with fly ash. In addition, blended cements with 50–60% LC2 showed lower embodied energy/carbon emission indices at the early age but higher at the later age as compared to blended cements with fly ash. In the context of the substantial contribution of Portland cement manufacture towards the climate crisis, these findings can help the efforts to reduce the carbon footprint in the construction industry.

Effect of cementing efficiency factor on the mechanical properties of concrete incorporating silica fume

ABSTRACT Silica fume is a recognized pozzolan which can contribute unique properties to Portland cement products. The use of silica fume in cement and concrete technology has unexpectedly increased over the most recent couple of years with the advent of high-performance concrete. All the previous researches in estimating the cementing efficiency factor of silica fume have been built on the strength prediction of concrete at different w/c ratio for different percentage replacement of silica fume. In the present work, the cementing efficiency factor for silica fume at different percentage replacement level has been assumed, and at the constant water to binder ratio, the compressive strength has been obtained. Further, the results of 28-day compressive strengths of silica fume concrete have been examined using a response surface model and a relationship has been projected. This model, which relates compressive strength with water to binder ratio, cementing efficiency factor and percentage silica fume, might find a useful application in the strength prediction of silica fume concretes.

Cementing efficiency factors of ceramic polishing residue in compressive strength and chloride resistance of mortar

During the polishing process of ceramic tiles, plenty of ceramic polishing residue (CPR) is generated. In order to evaluate the reutilization of CPR as a supplementary cementitious material (SCM) in mortar/concrete, and investigate its effects on the strength and durability, a series of mortar mixes containing different CPR contents were made for conducting compressive strength test and rapid chloride permeability test. It was found that adding CPR as a SCM up to 20% could still markedly improve the compressive strength and chloride resistance, while at the same time reduce the waste disposal, cement consumption and carbon footprint for sustainable development. Moreover, the cementing efficiency factor of the CPR in 28-day compressive strength was generally higher than 1.5 whereas that in chloride resistance was generally higher than 4.0, indicating that the CPR is a highly effective SCM for replacing part of the carbon-intensive cement and improving the strength and durability performance.

Adding ceramic polishing waste as paste substitute to improve sulphate and shrinkage resistances of mortar

Ceramic polishing waste (CPW) is a solid waste generated during the polishing process of ceramic tiles. Its disposal as waste has been causing lots of environmental problems. In this study, the authors made an attempt to reutilize the CPW in mortar as paste substitute (substituting part of the paste without changing the paste compositions) and a series of mortar mixes containing various CPW, cement and water contents were made for conducting the sulphate attack test and drying shrinkage test. The test results showed that as paste substitute, the CPW added can significantly enhance the compressive strength, sulphate resistance and shrinkage resistance of mortar, and at same time substantially cut down the cement demand to lower the carbon footprint. Regression analysis also revealed that for strength enhancement, the cementing efficiency factor of the CPW was as high as 1.10, whereas for sulphate resistance enhancement, the cementing efficiency factor was about 0.69.

Mechanical properties of green structural concrete with ultrahigh-volume fly ash

Using a high dosage of fly ash in concrete is an effective approach to control the heat release rate, reduce the material cost and enhance the sustainability. However, ultrahigh-volume fly ash (UHVFA) concrete, with fly ash replacing over 60% of the binder by weight, often exhibits low compressive strength at an early stage, which limits the material to non-structural or semi-structural applications. Though different approaches have been proposed to increase the strength, the efficacy of some of the methods is debatable, because of the high energy consumption and/or low cost-benefit ratio. This study aims to increase the compressive strength of UHVFA concrete by the simple and practical method of reducing the water/binder ratio while adding super-plasticizers to maintain workability. Mortar samples were used to explore the influence of silica fume, and Portland cement was replaced with fly ash at five different percentages (20%, 40%, 60%, 80% and 98%). Mechanical properties up to 360-day age were recorded, and the cementing efficiency factor of the fly ash was studied. With a suitable mix proportion, even with 80% of the binder replaced by fly ash, the compressive strength of the mortar and concrete can reach over 40MPa at 7-day age, and over 60MPa at 28-day age. Compared to commercial Grade 45 concrete, the proposed green structural concrete shows a reduction in CO2 emission of around 70%, a reduction in embodied energy of more than 60%, and a reduction in material cost of 15%.

Prediction of compressive strength of concrete with fly ash as sand replacement material

Fly ash (FA) acts as a partial replacement material for both Portland cement and fine aggregate. The published information on FA as sand (fine aggregate) replacement material (SRM) is limited and rational guidelines to estimate the compressive strength of concrete are not available. This aspect was investigated and a formula to predict the compressive strength of concrete at 28 day is suggested in this paper. This formula, containing cementing efficiency factor, k, of FA, is useful also when the quantity of FA used is more than that of sand replaced. Application of the formula to the test data in published literature, indicate that it can estimate the compressive strength of concrete containing different levels of sand replacement by fly ash.

Water permeability of fly ash concretes

The water permeability of two series of concretes made with one type of fly ash and two types of Portland cement (OPC and SRPC) was tested by the method prescribed by DIN 1048. It is concluded that the cementing efficiency factor of the fly ash with respect to water permeability is approximately 0.3, independent of type of cement and curing time (28 days and 56 days). In practical terms this means that 1 kg of cement would have to be replaced by approximately 3 kg of fly ash in order to maintain the same watertightness of the hardened fly ash concretes. Thus, addition of fly ash is not likely to improve the watertightness of concrete.