An overview on the activation of reactivity of natural pozzolans

2001 ◽  
Vol 28 (5) ◽  
pp. 778-786 ◽  
Author(s):  
Caijun Shi
Keyword(s):  
Chemical Activation ◽  
Setting Time ◽  
Construction Materials ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Natural Pozzolan ◽  
Natural Pozzolans ◽  
Early Strength

Natural pozzolan is one of the oldest construction materials. Lime-pozzolan cements have been used for several thousands of years and have an excellent reputation for their durability. Pozzolans are being widely used as a cement replacement in Portland cement concrete. The use of pozzolans has the advantage of lower costs and better durability, but the disadvantage of a longer setting time and a slower early strength development. Different techniques have been tried to increase the reactivity of natural pozzolans to overcome these disadvantages. This paper has reviewed various methods used to activate the pozzolanic activity of natural pozzolans. All activation methods can be classified into three catalogues: thermal, mechanical, and chemical activation. A comparison based on strength–cost relationship indicates that the chemical activation method is the most effective and cheapest one.Key words: activation, reactivity, natural pozzolans, pozzolanic reaction, calcination, elevated temperature curing, chemical activators, strength, cost.

scholarly journals Utilization of Iraqi Metakaolin in Special Types of Concrete: A Review Based on National Researches

2021 ◽  
Vol 27 (8) ◽  
pp. 80-98
Author(s):  
Mahmood Fawzi Ahmed
Keyword(s):  
Construction Material ◽  
Cementitious Materials ◽  
Pozzolanic Reaction ◽  
Supplementary Cementitious Materials ◽  
Partial Replacement ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Concrete Technology ◽  
Natural Pozzolans ◽  
Sustainability Issue

Portland cement concrete is the most commonly used construction material in the world for decades. However, the searches in concrete technology are remaining growing to meet particular properties related to its strength, durability, and sustainability issue. Thus, several types of concrete have been developed to enhance concrete performance. Most of the modern concrete types have to contain supplementary cementitious materials (SCMs) as a partial replacement of cement. These materials are either by-products of waste such as fly ash, slag, rice husk ash, and silica fume or from a geological resource like natural pozzolans and metakaolin (MK). Ideally, the utilization of SCMs will enhance the concrete performance, minimize environmental pollution and mitigate the drawbacks of cement production attributed to the highly CO2 emission. In general, MK's ultra-fineness and high pozzolanic activity are exhibited a remarkable performance of concrete in terms of strength and durability. However, the filler effect, acceleration of cement hydration, and the pozzolanic reaction with calcium hydroxide (CH) are the main factors influencing the performance of metakaolin as a cementitious material. Therefore, numerous researches have been undertaken on inclusion MK in concrete and mortar and production of (free-cement concrete) geopolymer concrete. This paper reviews some of previous native researches on effect of using Iraqi metakaolin as a pozzolanic material in different types of concrete. The standpoint of this review will guide the researchers on the importance of utilization of local MK and highlight the missing researches toward completing a comprehensive understanding of incorporation Iraqi-metakaolin in concrete technology.

scholarly journals The potential use of pumice in mine backfill

2020 ◽  
Vol 1 ◽  
Author(s):  
Mohammed A. Hefni
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Mining Industry ◽  
Strength Development ◽  
Natural Pozzolan ◽  
Mine Backfill ◽  
Natural Pozzolans ◽  
Cemented Backfill ◽  
Compressive Strength Development ◽  
Potential Use

Abstract The use of natural pozzolans in concrete applications is gaining more attention because of the associated environmental, economic, and technical benefits. In this study, reference cemented mine backfill samples were prepared using Portland cement, and experimental samples were prepared by partially replacing Portland cement with 10 or 20 wt.% fly ash as a byproduct (artificial) pozzolan or pumice as a natural pozzolan. Samples were cured for 7, 14, and 28 days to investigate uniaxial compressive strength development. Backfill samples containing 10 wt.% pumice had almost a similar compressive strength as reference samples. There is strong potential for pumice to be used in cemented backfill to minimize costs, improve backfill properties, and promote the sustainability of the mining industry.

Low Cement/High Fly Ash Concretes: Their Properties and Response to Chemical Admixtures

1987 ◽  
Vol 113 ◽  
Author(s):  
V. H. Dodson
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Calcium Hydroxide ◽  
Pozzolanic Reaction ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Fly Ashes ◽  
Chemical Admixtures ◽  
Reaction With Water

ABSTRACTIn practice, the amount of fly ash added to portland cement concrete varies depending upon the desired end properties of the concrete. Generally, when a given portland cement concrete is redesigned to include fly ash, between 10 and 50% of the cement is replaced by a volume of fly ash equal to that of the cement. Sometimes as much as twice the volume of the cement replaced, although 45.4 kg (100 lbs) of cement will only produce enough calcium hydroxide during its reaction with water to react with about 9 kg (20 lbs) of a typical fly ash. The combination of large amounts of certain fly ashes with small amounts of portland cement in concrete has been found to produce surprisingly high compressive strengths, which cannot be accounted for by the conventional “pozzolanic reaction”. Ratios of cement to fly ash as high as 1:15 by weight can produce compressive strengths of 20.7 MPa (3,000 psi) at I day and over 41.4 MPa (6,000 psi) at 28 days. Methods of identifying these “hyperactive” fly ashes along with some of the startling results, with and without chemical admixtures are described.

scholarly journals Effect of Soil Organic Matters in Dredged Soils to Utilization of their Mixtures Made with a Steel Slag

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5450
Author(s):  
Kanako Toda ◽  
Ryosuke Kikuchi ◽  
Tsubasa Otake ◽  
Satoshi Nishimura ◽  
Yuzoh Akashi ◽  
...  
Keyword(s):  
Humic Acid ◽  
Steel Slag ◽  
Construction Materials ◽  
Engineering Application ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Organic Matters ◽  
Development Indicators ◽  
Dredged Soil ◽  
Accelerate Evaluation

Dredged soils have been used as construction materials by alkaline activation with steel slag (steel slag-dredged soil mixtures) at harbors. Such mixtures develop strength chiefly by calcium silicate hydrate (C-S-H) formation by the pozzolanic reaction. However, the strength of such mixtures is unpredictable, and in some cases, mixtures have been too soft for the intended engineering application. An identification of strength development indicators would accelerate evaluation processes for strength development to facilitate and promote the utilization of such materials. This paper focuses on the relationship between the characteristics of soil organic matters in dredged soils and the strength development of the mixtures by a comparison of eight dredged soils collected from eight different Japanese harbors. The characteristics of the soil organic matters were identified to determine as indicators of mixtures with weak strength development, i.e., enriched sulfur content in extracted soil organic matter (humic acid) fraction, and the N/C ratio of humic acid similar to land humic acid standards. Increases in the validated fraction of dredged soils and steel slag by replacing fractions disadvantageous to construction resources would contribute to reduce waste production, which would lower the environmental impact of the use, aiming to achieve sustainable utilization of such materials.

Long-Term Performance of Recycled Portland Cement Concrete Pavement

1996 ◽  
Vol 1525 (1) ◽  
pp. 115-123 ◽  
Author(s):  
Stephen A. Cross ◽  
Mohamed Nagib Abou-Zeid ◽  
John B. Wojakowski ◽  
Glenn A. Fager
Keyword(s):  
Portland Cement ◽  
Test Section ◽  
Load Transfer ◽  
Construction Materials ◽  
Concrete Pavement ◽  
Recycled Concrete ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Cement Concrete Pavement ◽  
Portland Cement Concrete Pavement

Over the past years there has been an increasing interest in recycling construction materials, particularly hot-mix asphalt (HMA) and portland cement concrete pavements (PCCP). To this end the Kansas Department of Transportation (KDOT) participated in Demonstration Project 47, Recycling Portland Cement Concrete Pavement, by recycling a moderately D-cracked concrete pavement and monitoring the performance over a 10-year period. The recycled concrete pavement (RCP) aggregate was evaluated in four test sections consisting of two control sections, one test section of portland cement-treated base (CTB) with RCP aggregate, and one test section using RCP aggregate in the PCCP and CTB. An HMA shoulder using RCP as coarse aggregate was also constructed. The test sections were monitored over a 10-year period for performance including faulting, roughness, load transfer, and friction measurements. Faulting, roughness, performance level, and joint distress measurements from KDOT's 1995 pavement condition survey were used to compare the performance of the recycled sections with PCCP of similar age and traffic in the same area of the state. All test sections performed well, with the CTB and PCCP sections with RCP aggregates showing slightly more distress.

Monitoring of Fluctuations in the Physical Properties of a Class C Fly Ash

1986 ◽  
Vol 86 ◽  
Author(s):  
Scott Schlorholtz ◽  
Ken Bergeson ◽  
Turgut Demirel
Keyword(s):  
Fly Ash ◽  
Physical Properties ◽  
Setting Time ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Soil Base ◽  
Volume Stability ◽  
Testing Procedures ◽  
Physical Tests

ABSTRACTThe “quality” of fly ash produced during 1985 at Ottumwa Generation Station, was evaluated by two different experimental programs. The first consisted of the physical tests specified in ASTM C 311; these results are applicable to the use of fly ash as an admixture to portland cement concrete. The second consisted of monitoring the changes in the physical properties of fly ash pastes; these results would be applicable to the use of fly ash as a grout or a soil base stabilization agent. The physical properties monitored during the testing program were compressive strength, volume stability and setting time. In general, the results obtained from the two testing programs were quite different. When using testing procedures defined by ASTM C 311 the fly ash appeared quite uniform, but results obtained from the fly ash pastes were quite erratic. It was found that compressive strengths of the pastes can vary by a factor of five in rather short periods of time.

Effects of Consumption of Cement in Mechanical Properties of Lightweight Concrete Containing Brazilian Expanded Clay

2013 ◽  
Vol 368-370 ◽  
pp. 925-928 ◽  
Author(s):  
Andressa Fernanda Angelin ◽  
Lubienska Cristina L.J. Ribeiro ◽  
Marta Siviero Guilherme Pires ◽  
Ana Elisabete P.G.A. Jacintho ◽  
Rosa Cristina Cecche Lintz ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Portland Cement ◽  
Building Materials ◽  
Lightweight Concrete ◽  
Construction Materials ◽  
Lightweight Aggregates ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Conventional Concrete ◽  
New Techniques

Concrete is one of the oldest building materials known to humankind. From 1824, with the advent of Portland cement, concrete assumed a prominent place among the construction materials, due to large amounts of strength, durability and versatility it offered compared to other products, allowing the molding of various forms architectural. Until the early 80s, the concrete remained only as a mixture of cement, aggregates and water, however, in recent decades, due to the development of new techniques and products, the concrete has been undergoing constant changes. The concrete with lightweight aggregates have been used since the beginning of the last century, with low values of density (< 2000 kg/m3), demonstrating the great potential of using this material in several areas of construction [. With the objective of analyzing the influence of the consumption of cement in conventional concrete and light, were molded, tested and compared body-of-evidence containing two different amounts of cement consumption: a) 350 kg/m3 and b) 450 kg / m3. The results were compared with those obtained by other researchers, as well as with [ and [.

Sign in / Sign up

Export Citation Format

Share Document