scholarly journals SHRINKAGE OF VARIOUS TYPES OF PORTLAND CLINKER-BASED CEMENTS WITH RESPECT TO THEIR HYDRATION DEGREE

2020 ◽  
Vol 60 (2) ◽  
pp. 88-97 ◽  
Author(s):  
Vendula Davidová ◽  
Pavel Reiterman
Keyword(s):  
Previous History ◽  
Blended Cement ◽  
Heat Evolution ◽  
Experimental Program ◽  
Strength Development ◽  
Contact Method ◽  
Volume Changes ◽  
Hydration Degree ◽  
Suitable Material ◽  
Blended Cements

The volume changes of cement based composites are significantly exhibited in the hardening process. Initial phases of the hardening are complemented by the expansion due to the heat evolution that is subsequently alternated by the shrinkage. Both could cause a crack initiation. It is evident that ultimate volume changes of cement based composites are a complex process, because the final shrinkage is determined by the binder used, exposition and also by the previous history. The paper focuses on the evaluation of the main types of cements based on the Portland clinker by using a conventional procedure for the determination of the shrinkage on the standard cements mortars. These mortars were exposed to drying after 1 and 3 days of curing, related to the actual degree of hydration, which was estimated on the basis of compressive strength development. The hydration process was additionally monitored using thermogravimetry on the accompanying paste specimens during one year. The performed experimental program confirmed the essential sense of the curing regime especially for blended cement systems, which exhibited very low values of the hydration degree at applied curing intervals. Despite the slightly higher values of shrinkage of blended cements, the obtained results signalize the crucial effect of prolonged curing for these types of binders. The conclusion highlighted the necessity of taking into consideration the hydration degree during cement testing by using the conventional contact method. Otherwise, the simple interpretation leads to an overestimation of the less-suitable material solution.

scholarly journals Physicochemical Properties of Hydrated Portland Cement Blended with Rice Husk Ash

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Joseph Mwiti Marangu ◽  
Cyprian Muturia M’thiruaine ◽  
Mark Bediako
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Rice Husk ◽  
Elevated Temperatures ◽  
Rice Husk Ash ◽  
Blended Cement ◽  
Strength Development ◽  
Carbonation Depth ◽  
Blended Cements ◽  
Carbonation Resistance

In the presence of significant quantities of carbon dioxide (CO2) and elevated temperatures in the atmosphere due to climate change, cement-based materials are susceptible to carbonation. Blended cements are more prone to carbonation attack than Portland cement. There is a need to evaluate the carbonation resistance of blended cements in a carbonation-prone environment. This paper presents experimental findings obtained from an evaluation of carbonation resistance tests on Rice Husk Ash- (RHA-) blended cement. The blended cement was made by intergrinding of Portland Cement (PC) and RHA to make the test cement (PC-RHA). The RHA dosage in the PC-RHA was varied from 0 to 30% by mass of PC. Pozzolanicity, standard consistency, and setting time tests were conducted on PC-RHA. Mortar prisms measuring 160 mm × 40 mm x 40 mm were separately cast at a water/cement ratio ( w / c ) of 0.50 and 0.60 and cured in water for 2, 7, 14, 28, and 90 days. Compressive strength tests were conducted on the mortar prisms at each of the testing ages. The prepared mortars were also subjected to accelerated carbonation tests in two Relative Humidity (RH) curing regimes, one maintained at an RH greater than 90% and the other between 50–60%. Carbonation resistance of the mixtures was evaluated in terms of the changes in carbonation depth using a phenolphthalein test at the age of 7, 14, 28, and 56 days of curing in a continuous flow of CO2. Compressive strength measurements were also taken during each of the carbonation testing ages. For comparison, similar tests were conducted using commercial PC. The results showed that PC-RHA was pozzolanic while PC was nonpozzolanic. Higher water demand and longer setting times were observed in PC-RHA than in PC. Moreover, there was increased strength development in water-cured samples with increased curing duration. Carbonation results indicated that there was a marked increase in carbonation depth with increased dosage of RHA in PC-RHA binders, increased duration of exposure to CO2, and decreased RH (RH between 50–60%). PC-RHA binders exhibited lower carbonation resistance than PC. In conclusion, for mortars at any w / c ratio, carbonation resistance decreased with increase in RHA dosage and increased w / c ratio.

Fiber Reinforced Alkali Activated Blended Cement Materials

1990 ◽  
Vol 211 ◽  
Author(s):  
M. R. Silsbee ◽  
D. Wolfe-Confer ◽  
D. M. Roy
Keyword(s):  
Blended Cement ◽  
Strength Development ◽  
Alkali Activation ◽  
Fiber Reinforced ◽  
Blended Cements ◽  
Alkali Activated

AbstractRecently there has been renewed interest in the use of alkali activation to increase the rate of strength development in blended cements. The objective of this study was to examine the advantages-disadvantages of using alkali activated blended cement materials with fiber reinforcing. There are advantages of the rapid set for certain applications.

Chemical Composition and Physical Characteristics of Rice Husk Ash Blended Cement

2017 ◽  
Vol 32 ◽  
pp. 25-35 ◽  
Author(s):  
Akeem Ayinde Raheem ◽  
Mutiu A. Kareem
Keyword(s):  
Compressive Strength ◽  
Rice Husk ◽  
Rice Husk Ash ◽  
Blended Cement ◽  
Physical Characteristics ◽  
Chemical Compositions ◽  
Minimum Requirement ◽  
Suitable Material ◽  
Blended Cements ◽  
Renewable Material

Applications of agricultural by-product as substitute for non-renewable material in cement production are desirable in stimulating socio-economic development. In this study, Rice Husk Ash (RHA) blended cement was produced by replacing 5%, 7%, 11.25%, 15%, 20.25% and 25% by weight of Ordinary Portland Cement (OPC) clinker with RHA. The cement without RHA serves as the control. The chemical compositions of RHA, OPC-clinker and the blended cements were determined using X-ray fluorescence analyzer. The physical characteristics of RHA blended cements that were considered are fineness, soundness, consistency, initial and final setting times and compressive strength at 2, 7, 28, 56 and 90 curing ages. The results showed that RHA is a suitable material for use as a pozzolan as it satisfied the minimum requirement by having the sum of SiO2, Al2O3 and Fe2O3 of more than 70%. Incorporation of RHA led to an increase in the composition of SiO2 and reduction in that of CaO. An increase in RHA content showed a decrease in compressive strength at early ages and slightly increase at a later age (90 days). The blended cement produced with lower levels of RHA replacement conforms to standard specifications specified in BS EN 197-1:2000, NIS 439:2000 and ASTM C 150-02. The minimum Strength Activated Index (SAI) of 75% at the age of 28 days of curing as specified by ASTM C 618 was satisfied by RHA replacement of up to 15%. It was concluded that blended cement with the maximum of 15% RHA content is suitable for use for structural purposes.

scholarly journals The effects of seawater and nanosilica on the performance of blended cements and composites

2020 ◽  
Vol 10 (12) ◽  
pp. 5009-5026 ◽  
Author(s):  
Pawel Sikora ◽  
Didier Lootens ◽  
Maxime Liard ◽  
Dietmar Stephan
Keyword(s):  
Transport Properties ◽  
Reaction Rate ◽  
Mechanical Performance ◽  
Setting Time ◽  
Blended Cement ◽  
Heat Of Hydration ◽  
Strength Development ◽  
Cement Pastes ◽  
Blended Cements ◽  
Setting Times

AbstractThis study investigates the effects of seawater and nanosilica (3% by weight of cement), on the fresh and hardened properties of cement pastes and mortars produced with two types of low heat cements: Portland pozzolana cement (CEM II) and blast furnace cement (CEM III). The heat of hydration, initial and final setting times, rheological properties, strength development, sorptivity and water accessible porosity of the cement pastes and mortars were determined. The data reveal that cement type has a significant effect on the reaction rate of cement with seawater and nanosilica (NS). Specimens produced with slag-blended cement exhibited a higher cement reaction rate and the composite produced exhibited better mechanical performance, as a result of the additional reaction of alumina rich phases in slag, with seawater. Replacement of freshwater with seawater contributes mostly to a significant improvement of early strength. However, in the case of slag-blended cement, 28 day strength also improved. The incorporation of NS results in additional acceleration of hydration processes, as well as to a decrease in cement setting time. In contrast, the addition of NS results in a noticeable increment in the yield-stress of pastes, with this effect being pronounced when NS is mixed along with seawater. Moreover, the use of seawater and NS has a beneficial effect on microstructure refinement, thus improving the transport properties of cement mortars. Overall, the study has showed that both seawater and NS can be successfully used to accelerate the hydration process of low heat blended cements and to improve the mechanical and transport properties of cement-based composites.

Conversion of Red Muds into Pozzolans

1991 ◽  
Vol 245 ◽  
Author(s):  
Jean Pera
Keyword(s):  
Red Mud ◽  
Mineralogical Composition ◽  
Waste Materials ◽  
Strength Development ◽  
Blended Cements ◽  
Temperature Range ◽  
Lime Consumption ◽  
Red Muds ◽  
Mineralogical Compositions

ABSTRACTRed muds are waste materials obtained from the aluminium extraction industry. They consist mainly of clays, aluminium and iron hydrated oxides. Three muds were studied; they differed in chemical and mineralogical compositions. They were converted into reactive pozzolans by calcination in the temperature range 600–800°C for five hours. Pozzolanicity was investigated on calcined red mud-OPC mixes studying strength development and lime consumption as evaluated by DTA. The nature of hydrates formed during hardening was also identified.The mineralogical composition of the mud is the most important factor affecting its pozzolanicity. Blended cements containing 30% calcined red mud develop significant strengths.

GGBS Use in Concrete as Cement Constituent: Strength Development and Sustainability Effects – Part 1

2021 ◽  
pp. 1-41
Author(s):  
Haotian Fan ◽  
Ravindra K. Dhir ◽  
Peter C. Hewlett
Keyword(s):  
Concrete Strength ◽  
Blended Cement ◽  
Data Matrix ◽  
Strength Development ◽  
Design Strength ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Granulated Blast Furnace Slag ◽  
Data Points ◽  
Class F Fly Ash

This study, third in the series, following from ground limestone and Class F fly ash, evaluates, as a cement constituent, the effect of using ground granulated blast furnace slag (GGBS) on the strength development of concrete, and consequently its embodied carbon dioxide (CO2e). The paper has been built from systematically analysing, evaluating and modelling the extensive data-matrix developed, having 85,099 data points, from the information sourced from 663 studies published in English, during 1974 to 2020, by 1,672 authors, working in 718 institutions in 49 countries, globally. It is shown that, at a given water/cement ratio, in comparison to Portland cement (PC), the use of GGBS results in a reduction in 28-day concrete strength, which increases with GGBS content, at a rate determined by the strength of concrete, GGBS fineness, and curing of concrete. It is also shown that, as to achieve a 28-day design strength, a lower water/cement ratio is required with a PC/GGBS blended cement than PC, this will reduce the actual CO2e savings that can be realised with the use of GGBS as cement constituent in manufacturing concrete. Finally, it is shown that GGBS is more effective in lowering CO2e of concrete than FA and GLS.

scholarly journals Influence Of Volcanic Scoria On Mechanical Strength, Chemical Resistance And Drying Shrinkage Of Mortars

2014 ◽  
Vol 61 (3) ◽  
pp. 143-150 ◽  
Author(s):  
A. Al-Swaidani ◽  
S. Aliyan ◽  
N. Adarnaly ◽  
B. Hanna ◽  
E. Dyab
Keyword(s):  
Mechanical Strength ◽  
Sulphuric Acid ◽  
Chemical Resistance ◽  
Control Sample ◽  
Acid Resistance ◽  
Drying Shrinkage ◽  
Strength Development ◽  
Acid Solutions ◽  
Test Results ◽  
Blended Cements

Abstract In the study, three types of cement have been prepared; one CEM I type (the control sample) and two blended cements: CEM II/A-P and CEM II/B-P (EN 197-1), each of them with three replacement levels of volcanic scoria: (10 %, 15 %, 20 % wt.) and (25 %, 30 %, 35 % wt.), respectively. Strength development of mortars has been investigated at 2, 7, 28 and 90 days curing. Evaluation of chemical resistance of mortars containing scoria-based cements has been investigated through exposure to 5 % sulphate and 5 % sulphuric acid solutions in accordance with ASTM C1012 & ASTM 267, respectively. Drying shrinkage has been evaluated in accordance with ASTM C596. Test results showed that at early ages, the mortars containing CEM II/B-P binders had strengths much lower than that of the control mortar. However, at 90 days curing, the strengths were comparable to the control mortar. In addition, the increase of scoria significantly improved the sulphate resistance of mortars. Further, an increase in scoria addition improved the sulphuric acid resistance of mortar, especially at the early days of exposure. The results of drying shrinkage revealed that the CEM II/B-P mortar bars exhibited a greater contraction when compared to the control mortar, especially at early ages. However, drying shrinkage of mortars was not influenced much at longer times.

scholarly journals Beneficial Effect of Incorporation of Slag on the Hydration Heat, Mechanical Properties and Durability of Cement Containing Limestone Powder

2020 ◽  
Vol 330 ◽  
pp. 01047
Author(s):  
Toufik Boubekeur ◽  
Bensaid Boulekbache ◽  
Mohamed Salhi ◽  
Karim Ezziane ◽  
EL.Hadj Kadri
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Ordinary Portland Cement ◽  
Blended Cement ◽  
Dilution Effect ◽  
High Strength ◽  
Limestone Powder ◽  
Blended Cements ◽  
Hydration Mechanism ◽  
Durability Performance

This paper presents the experimental results of a wide research program, tending to determine the hydration mechanism, mechanical properties and the durability performance of ternary cement containing limestone powder and slag. The limestone powder increase the hydration at early ages inducing a high strength at, but it can reduce the later strength due to the dilution effect. On the other hands, Slag (S) contributes to increase the compressive strength at later ages. Hence, at medium blended cement (OPC-LP-S) with better performance could be produced. Results show at later age the Slag is very effective in producing ternary blended cements with similar on higher compressive strength than the ordinary Portland cement at 28 and 90 days. For durability, the incorporation of the slag into the cement containing limestone powder improves remarkably resistance to attack by acids and sulfates and it has been found that the durability of the cements never depends on the mechanical strength.

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