Effect Of Pozzolanic Materials Research Articles

A comparative study of mechanical properties and life cycle assessment of high-strength concrete containing silica fume and nanosilica as a partial cement replacement

Employing pozzolanic materials like nanosilica and silica fume as replacements for cement to produce high-strength concrete (HSC) has made investigating the mechanical features of the produced HSC and assessing impacts that producing these materials have on the environment a necessity. Therefore, this paper aimed to assess the mechanical properties, environmental impacts and life cycle of HSC containing silica fume and nanosilica where its compressive performance and microstructure were evaluated and a comparison between the effects of pozzolanic materials were compared with those of ordinary cement on environmental indices. Concrete specimens were made using seven mix designs, and different parameters, namely compressive capacity, toughness, strain at peak stress, relative energy absorption, and stress–strain relationship were evaluated. Afterward, some empirical relationships were proposed to capture concrete mechanical features. Here, silica fume at contents of 0, 8, 10, and 12 % and nanosilica at contents of 0, 1, 2, and 3 % were used as a weight replacement of cement. Further, using the atomic force microscopy (AFM) images, the microstructure of the concrete without the pozzolans and concretes with silica fume and nanosilica was studied. In addition, to investigate the environmental impacts of the concretes containing silica fume and nanosilica and conventional concrete, two methods of problem-oriented CML 2000 and damage-oriented IMPACT 2002+ were employed in SimaPro8.1 program. In this procedure, environmental parameters including acidification, eutrophication, global warming potential (GWP), human health, and ecosystem quality, and natural resources were investigated. Finally, for validation, all the obtained results were compared with those obtained using the building for environmental and economic sustainability (BEES) approach. It was found that the best weight percentages of silica fume and nanosilica replacing cement were 12 and 2 %, respectively, which led to improvement in the performance of the HSC under compression. Moreover, the proposed prediction models for the compressive performance of the HSC using empirical formulations developed for the mechanical features correlate well with the test results. Based on the CML 2000 method, the concrete containing 12 % silica fume has the greatest environmental damage in the acidification, human toxicity, and eutrophication categories, for which the corresponding indices were 6.6, 2.4, and 4.3 times those of the reference concrete. Further, by employing the damage assessment method IMPACT 2002+, the HSC with 12 % silica fume was found to have the highest damage in human health, ecosystem quality, and natural resources, for which the corresponding indices were respectively 4.7, 3.5, and 4.6 times those of the reference concrete. All the environmental indices of the HSC without the pozzolans were lower in comparison with the other concretes except for the climate change index which was higher for the HSC without the pozzolans than the other specimens.

Effect of Pozzolanic Materials on Fiber Reinforced Concrete

Abstract: Different materials like rice husk ash, Ground granulated blast furnace slag, silica fume to obtain the desired needs in this project. Also X-ray diffraction test was conducted on different pozzolanic material used to analyse their content ingredients. I used synthetic fiber (i.e Recronfiber) in different percentage i.e 0.0%, 0.1%, 0.2%, 0.3% to that of total weight of concrete and casting was done. Finally I used different percentage of silica fume with the replacement of cement keeping constant fiber content and concrete was casted. In this study it was used two types of cement, Portland slag cement(PSC) and Ordinary Portland cement(OPC).I have conducted consistency of cement by Vicat apparatus, the workability by Slump cone, compressive strength test by cube test, splitting test, flexural test etc. Finally porosity and Permeability test conducted

Experimental Study on Mechanical Properties and Micro-Mechanism of All-Solid-Waste Alkali Activated Binders Solidified Marine Soft Soil

Utilizing granulated blast furnace slag (GBFS), coal fly ash (FA), and furfural residue incineration ash (FRIA) as pozzolanic materials, then activated with calcium carbide residue (CCR) respectively to prepare all-solid-waste alkali activated binders (ASW binders). The laboratory tests were performed to research the effects of pozzolanic materials with different reactivity on the macro- and micro- characteristics of solidified marine soft soil. Results show that the mechanical properties and alkali-activation process of ASW binders solidified soil was determined mainly by the reactivity of pozzolanic materials, the higher reactivity of the pozzolanic materials in ASW binders couldn’t change the main hydration products, however, it would accelerate the hydrate reaction. The degree of hydrate reaction increased, the microstructure became denser with the increase of the reactivity of the pozzolanic materials in ASW binders solidified soil, on the macro- side, the strength and deformation modulus of the solidified soil increased, meanwhile, the brittleness of the solidified soil will be more obvious during the deformation resistance process. ASW binders (CCR:GBFS=1:1) solidified soil could reach the strength of cemented soil under the same conditions.

Experimental Investigation of Self-compacting High Performance Concrete Containing Calcined Kaolin Clay and Nano Lime

The aim of this research is to investigate the effect of pozzolanic materials and nano particles on improve the strength characteristic by the properties of a self-compacting high-performance concrete that includes calcined clay with nano lime. In this study, two blends systems are worked on, they are the binary and the ternary systems. For binary mixtures, test samples were prepared from 5% CC, 10% CC, 15% CC and 3% NL by partial replacement of the cement weight. While ternary mixtures, samples were prepared from 5% CC 3% NL, 10% CC 3% NL and 15% CC 3% NL by partial substitution of cement weight. The tests conducted on mixes are fresh tests like slump flow diameter, V-funnel, L-box, and segregation resistance. The compressive strength test was determined at 7, 28 and 56 days. While splitting tensile strength tests at 7 and 28 days from the SCHPC produced in the study. It was concluded that the replacement of CC and NL in SCHPC binary mixes reduced the fresh results enough for SCHPC production and gave a general improvement in the compressive strength and splitting tensile strength properties of the SCHPC mixture. SCHPC with 10% CC partial replacement of cement showed higher values of compressive and splitting tensile strength, compared to the reference mixture of SCHPC for all days, thus it was considered the best. Whereas, the strength of the concrete mixtures in the ternary cement mixtures was better than the strength of the mixing and control mortar systems for the same replacement levels in 7 , 28 and 56 days.

Effect of pozzolanic materials on mechanical properties and aging of glass fiber reinforced concrete

Glass fibers have shown to improve the mechanical properties of concrete as tensile strength and flexural strength. However, it has been shown that these fibers tend to corrode with concrete aging to affect glass fiber reinforced concrete (GFRC) properties in an adverse manner. To prevent glass fiber corrosion in concrete environment, different percentages of pozzolanic materials were used in this study. It was found that the glass fibers inclusion would lead to partial reduction in concrete compressive strength. Modulus of rupture and toughness index were observed to improve greatly as a result of reinforcing concrete with glass fibers. Moreover, inclusion of nanosilica and metakaolin was found to prevent declines in concrete toughness and modulus of rupture with aging. Investigation of the pozzolanic contribution to modulus of rupture in GFRC revealed that the specific strength of cement declined within 7–90 days. This is while the specific strength of pozzolanic effect increased with time.

Effect of pozzolanic materials on mechanical properties and water absorption of autoclaved aerated concrete

The Autoclaved Aerated Concrete (AAC) is notorious for its insufficient strength and high water absorption leading to problems during the construction phase. To tackle such problems, the current paper examines the effect of silica fume, zeolite and granulated blast furnace on the behavioral characteristics of this concrete type. In doing so, the compressive, tensile strength and water absorption tests were conducted on 100 × 200 mm cylindrical and 100 × 100 × 100 mm cubic specimens. Based on the results, the addition of the pozzolanic materials can effectively enhance the mechanical properties and diminish the water absorption of the autoclaved aerated concrete. Comparatively, the specimens containing silica fume, zeolite, and granulated blast-furnace slag led to increasing the compressive strength of the AAC up to 184, 200 and 172%. Moreover, the inclusion of the pozzolanic materials by 21% of the cement weight, could manage to improve the tensile strength by 25%. Most importantly, the water absorption of the specimens containing silica fume, zeolite, and granulated blast-furnace slag was reduced by 50, 45 and 35%, respectively.

English

This paper presents a preliminary study on the properties of lime-pozzolan based cement and the effect of high temperatures on these properties. Conventional lime-pozzolan cements (LPC), alkali-activated LPC and hybrid alkali-activated LPC pastes were experimentally investigated. Microstructural analyses were performed based on XRD and SEM tests to identify the hydration products. Based on the results, the strength improvement of hybrid alkali-activated LPC cement, where ordinary Portland cement (OPC) was used to enhance the early age strength, could be due to (i) the dissolution of Ca(OH)2 in the mixtures, and (ii) the pozzolanic effect of pozzolanic materials, which interacted with the free Ca(OH)2 during hydration. The residual strength results indicated that the materials lost the strength gradually when exposed to the temperature up to 400°C, except for hybrid cement which showed a slight increase in strength. The microstructure analysis results indicated that the deterioration of the materials was due to the decomposition of hydration products at high temperature.

Effect of pozzolanic materials and curing methods on the elastic modulus of HPC

Abstract The modulus of elasticity of a material is a fundamental property required for the proper modeling of its constitutive behavior and for its proper use in various structural applications. This paper discusses experimental evaluation of the elastic modulus of high-performance concrete made from mixes using various percentages of fly ash, silica fume, and granulated blast furnace slag. Results are compared to those from control specimens at various ages between 1 and 90 days. The results presented are part of a study for the New Jersey Department of Transportation (NJDOT) to develop and implement High-Performance Concrete (HPC) mix design and technical specifications for transportation structures. The study also investigates the effect of curing on the elastic modulus. Three methods of curing were evaluated: (1) air-dry curing, (2) curing compound, and (3) wet curing with burlap. The results showed that adding silica fume resulted in an increase in strength and modulus at early ages, however, there was no change in the modulus at 28 and 56 days. In addition, adding 20% fly ash with various percentage of silica fume had an adverse effect on both strength and modulus values at all ages to 90 days. It is also shown that dry curing and curing compound reduce the modulus of elasticity compared to wet curing with burlap. Results showed the elastic modulus of HPC is proportional to the compressive strength, but the prediction equations of ACI-318 and ACI-363 may not accurately predict the modulus values for high-performance concrete with pozzolans.

A discussion of the paper “Study on the pozzolanic properties of rice husk ash by hydrochloric acid pretreatment” by Q. Feng, H. Yamamichi, M. Shoya, S. Sugita

This brief commentary discusses a recent study (Feng et al, 2004) on the pozzolanic properties of rice husk ash by hydrochloric acid pretreatment. In the study, the heat evolution and the hydration heat of cement, the Ca(OH)2 content in the mortar and the pore size distribution of mortar were determined. The results showed that pozzolanic activity of rice husk ash (RHA) is not only stabilized but also enhanced by pretreatment. In this commentary, Demirbas notes that the very high surface area of RHA increases its pozzolanic activity to compete with those of much finer admixtures. Demirbas calls for additional attention on the chemical effects of pozzolanic materials on crystal formation during the hydration. Demirbas also refers readers to another study in which the pozzolanic properties of hydrochloric acid-treated RHA were systematically investigated (Yalcin and Sevinc, 2001).

Reply to the discussion by Ayhan Demirbas of the paper “Study on the pozzolanic properties of rice husk ash by hydrochloric acid pretreatment”

In this article, Feng et al reply to a brief commentary on their recent study (Feng et al, 2004) on the pozzolanic properties of rice husk ash by hydrochloric acid pretreatment. In the study, the heat evolution and the hydration heat of cement, the Ca(OH)2 content in the mortar and the pore size distribution of mortar were determined. The results showed that pozzolanic activity of rice husk ash (RHA) is not only stabilized but also enhanced by pretreatment. In the commentary, Demirbas noted that the very high surface area of RHA increases its pozzolanic activity to compete with those of much finer admixtures. Demirbas called for additional attention on the chemical effects of pozzolanic materials on crystal formation during the hydration. Demirbas also referred readers to another study in which the pozzolanic properties of hydrochloric acid-treated RHA were systematically investigated (Yalcin and Sevinc, 2001). In their reply, the study authors agree with the comment that the chemical effects of pozzolanic materials on crystal formation and development during hydration should be expanded. The authors also provide some additional details regarding the pore distribution of rice husk ashes. They conclude by stressing that many more studies of this agricultural waste material need to be carried out.

A reply to the discussion by A. Demirbas of the paper “Influence of natural pozzolan, colemanite ore waste, bottom ash, and fly ash on the properties of Portland cement”

In this discussion paper, the original authors of a study of the effects of natural pozzolan, colemanite ore waste, bottom ash, and fly ash on the properties of Portland cement (PC) reply to a commentator. The commentator stated that the original article should have clarified the chemical effects of pozzolanic materials on crystal formation and development during the hydration process and should have provided more details about the physical properties. The authors reply that they did indeed provide the details about the physical properties such as specific gravity, specific surface, grain size distribution, aggregate to cementitious/pozzolanic material ratio, fineness, water demand, and moisture content should be available. Most of the properties of the materials were given in the text and in the tables of the original research article.

A discussion of the paper “Influence of natural pozzolan, colemanite ore waste, bottom ash, and fly ash on the properties of Portland cement” by Ş. Targan, A. Olgun, Y. Erdogan, and V. Sevinc

This discussion paper comments on a study of the effects of natural pozzolan, colemanite ore waste, bottom ash, and fly ash on the properties of Portland cement (PC). This commentator states that the original article should have clarified the chemical effects of pozzolanic materials on crystal formation and development during the hydration process. The commentator notes that the addition of pozzolanic blending agents, each different in composition, introduces a great diversity into cement systems. In addition, mechanical interlocking plays a significant role in chemical forces during crystal formation and development.

Mechanical properties of polypropylene fiber reinforced concrete and the effects of pozzolanic materials

A comprehensive set of experimental data were generated regarding the effects of collated fibrillated polypropylene fibers at relatively low volume fractions (below 0.3%) on the compressive, flexural and impact properties of concrete materials with different binder compositions. Statistical analysis of results produced reliable conclusions on the mechanical properties of polypropylene fiber reinforced, concrete and also on the interaction of fibers and pozzolanic admixtures in deciding these properties. Polypropylene fibers were observed to have no statistically significant effects on compressive or flexural strength of concrete, while flexural toughness and impact resistance showed an increase in the presence of polypropylene fibers. Positive interactions were also detected between fibers and pozzolans.