Ordinary portland cement based solidification of toxic wastes: The role of OPC reviewed

1993 ◽  
Vol 23 (1) ◽  
pp. 196-212 ◽  
Author(s):  
C.D. Hills ◽  
C.J. Sollars ◽  
R. Perry
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Toxic Wastes

scholarly journals Role of Carbon Nanofiber on the Electrical Resistivity of Mortar under Compressive Load

2020 ◽  
pp. 036119812094741
Author(s):  
Thanyarat Buasiri ◽  
Karin Habermehl-Cwirzen ◽  
Lukasz Krzeminski ◽  
Andrzej Cwirzen
Keyword(s):  
Electrical Resistivity ◽  
Portland Cement ◽  
Carbon Nanofibers ◽  
Ordinary Portland Cement ◽  
Carbon Nanofiber ◽  
Compressive Load ◽  
Chemical Vapor ◽  
Load Sensing

A nanomodified cement consisting of particles with in situ synthesized carbon nanofibers was developed to introduce a strong load-sensing capability of the hydrated binder matrix. The material was produced using chemical vapor deposition. The nanomodified cement contained 2.71 wt% of carbon nanofibers (CNFs). The electrical properties of the composite were determined. Several mortar samples were prepared by partially substituting ordinary Portland cement with 2, 4, 6, 8, and 10 wt% of the nanomodified cement. Additionally an ordinary Portland cement mortar was used as reference. The results show that the strongest piezoresistive response and therefore the best load-sensing was obtained for the mortar containing the highest amount of CNFs. This mortar contained 10 wt% of nanomodified cement. The fractional change in electrical resistivity of this mortar was 82% and this mortar had a compressive strength of 28 MPa.

Mineralogical Aspects of Durable Geocement Matrix Formation - Role of Alkali

2014 ◽  
Vol 1004-1005 ◽  
pp. 1523-1530 ◽  
Author(s):  
Pavlо Krivenko ◽  
Hai Lin Cao ◽  
Lu Qian Weng ◽  
Еlena Kаvalerova
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Ceramic Matrix ◽  
Cementitious Materials ◽  
Cement Matrix ◽  
New Materials ◽  
New Class ◽  
High Durability ◽  
Alkali Activated

Less than half a century ago just an idea of presence of free alkalis in a ceramic matrix was considered by ordinary Portland cement people as an absurd one and this was a basic postulate accepted in chemistry of cements. In 1957 a scientist from Ukraine (USSR) Viktor Glukhovsky put forward an assumption which was taken as a base for development and bringing into practice of construction a principally new class of cementitious materials which first appeared in the field under a name of alkaline (now also known under a general name of alkali-activated) cementitious materials. A validity of these ideas was confirmed by more than 50 years of evolutional development and vast experience collected on practical use of new materials in different applications. The paper covers theoretical views on role played by alkali in the formation of an alkali-activated cement matrix with high durability. Examples of compositional build-up of the alkali-activated cementitious materials vs. quantity of added alkali and type of aluminosilicate component are reported together with results of 50-year experience obtained from observation of concrete structures made from these cements.

PENGARUH JENIS SEMEN DAN PENAMBAHAN SILICA FUME TERHADAP KEKUATAN DAN DURABILITAS BETON

2012 ◽  
Vol 2 (1) ◽  
pp. 25
Author(s):  
Ariyadi Basuki ◽  
Maulana Ikhwan Sadikin
Keyword(s):  
Portland Cement ◽  
Silica Fume ◽  
Ordinary Portland Cement ◽  
Composite Cement

Dalam penelitian ini dilakukan serangkaian pengujian untuk mengetahui sifat fisik dari material penyusun (agregat), yang kemudian dirancang komposisi rencana beton dengan mutu K250 (normal/kontrol) dan K250 dengan aditif Silica Fume 10% dari berat semen. Variasi campuran menggunakan tiga tipe semen yang berbeda yaitu Ordinary Portland Cement (OPC)/ Semen Tipe I, Portland Composite Cement (PCC) dan Semen Tipe II. Proses dilanjutkan dengan pembuatan sampel uji silinder berukuran 15 cm x 30 cm (karakteristik kuat tekan, ketahanan sulfat), sampel uji prisma berukuran 20 cm x 20 cm x 12 cm (karakteristik permeabilitas) dan sampel uji kubus berukuran 15 cm x 15 cm x 15 cm (untuk penetrasi klorida). Pengamatan dilakukan untuk melihat karakteristik beton K250 dengan penambahan silica fume 10%, dibandingkan dengan beton normal sebagai acuan, serta aplikasinya dalam lingkungan normal maupun asam (Sulfat, Klor). Hasil kuat tekan memperlihatkan, bahwa campuran dengan menggunakan semen PCC memiliki nilai kuat tekan rata-rata diatas semen OPC. Penambahan silica fume pada campuran semen PCC akan menaikkan nilai kuat tekan sebesar 4,2% dibandingkan beton normal dengan produk semen yang sama, meskipun nilai rasio air-semen nya membesar menjadi 0,71 karena penambahan air. Nilai kuat tekan terbesar diperoleh untuk campuran beton dengan semen Tipe II. Campuran dengan semen PCC (2) menunjukkan nilai penetrasi yang lebih kecil dibandingkan campuran lainnya, hal ini mengindikasikan produk beton yang terbentuk memiliki kepadatan yang lebih baik dari produk campuran lainnya dan tidak porous, sehingga dapat dikatakan memiliki tingkat durabilitas yang cukup baik. Untuk ketahanan terhadap serangan sulfat, beton dengan menggunakan campuran semen tipe II mengalami tingkat pelapukan/penggerusan penampang (scaling) yang lebih besar dibandingkan campuran beton lainnya, meskipun begitu hal ini tidak mempengaruhi nilai kuat tekannya. Untuk produk dengan semen PCC, serangan sulfat tidak mempengaruhi nilai kuat tekannya, bahkan cenderung naik bila dibandingkan pada usia 28 hari.Kata kunci: aspek durabilitas, tipe semen, pemanfaatan silica fume

Utilization of petroleum sludge wastes for increasing productivity of ordinary portland cement

2021 ◽  
Vol 19 (4) ◽  
pp. 315-328
Author(s):  
N.M. Khalil ◽  
Yousif Algamal
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Production Capacity ◽  
Hydration Product ◽  
High Energy ◽  
Cement Industry ◽  
Blended Cements ◽  
Petroleum Waste ◽  
Waste Sludge ◽  
Suitable Amount

This work aims at maximum exploitation of petroleum waste sludge as additive to portland cement to prepare blended cements and hence increasing its production capacity without further firing. This will decrease the main cement industry problems involving environmental pollution such as releasing gases and high-energy consumption during industry and hence maximizes the production economics. Six batches of ordinary portland cement (OPC) mixed with different proportions of petroleum waste sludge (PWS) donated as C1 (control batch contains no PWS), C2 (contains 90 wt.% of OPC+10 wt.% of PWS), C3 (contains 80 wt.% of OPC+20 wt.% of PWS), C4 (contains 70 wt.% of OPC+30 wt.% of PWS), C4 (contains 60 wt.% of OPC+40 wt.% of PWS) and C6 (contains 50 wt.% of OPC+50 wt.% of PWS), were prepared and mixed individually with the suitable amount of mixing water. Cement mixes C2, C3 and C4 showed improved cementing and physicomechanical properties compared with pure cement (C1) with special concern of mix C4. Such improvement is due to the relatively higher surface area as well as the high content of kaolinite and quartz in the added PWS (high pozzalanity) favoring the hydration process evidenced by the increase in the cement hydration product (portlandite mineral (Ca (OH) 2).

scholarly journals A Review of the Mechanical Properties and Durability of Ecological Concretes in a Cold Climate in Comparison to Standard Ordinary Portland Cement-Based Concrete

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3467
Author(s):  
Ankit Kothari ◽  
Karin Habermehl-Cwirzen ◽  
Hans Hedlund ◽  
Andrzej Cwirzen
Keyword(s):  
Carbon Dioxide ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Cementitious Materials ◽  
Cold Climate ◽  
Supplementary Cementitious Materials ◽  
Short Exposure ◽  
Chemical Admixtures ◽  
Composite Cements ◽  
Alkali Activated

Most of the currently used concretes are based on ordinary Portland cement (OPC) which results in a high carbon dioxide footprint and thus has a negative environmental impact. Replacing OPCs, partially or fully by ecological binders, i.e., supplementary cementitious materials (SCMs) or alternative binders, aims to decrease the carbon dioxide footprint. Both solutions introduced a number of technological problems, including their performance, when exposed to low, subfreezing temperatures during casting operations and the hardening stage. This review indicates that the present knowledge enables the production of OPC-based concretes at temperatures as low as −10 °C, without the need of any additional measures such as, e.g., heating. Conversely, composite cements containing SCMs or alkali-activated binders (AACs) showed mixed performances, ranging from inferior to superior in comparison with OPC. Most concretes based on composite cements require pre/post heat curing or only a short exposure to sub-zero temperatures. At the same time, certain alkali-activated systems performed very well even at −20 °C without the need for additional curing. Chemical admixtures developed for OPC do not always perform well in other binder systems. This review showed that there is only a limited knowledge on how chemical admixtures work in ecological concretes at low temperatures and how to accelerate the hydration rate of composite cements containing high amounts of SCMs or AACs, when these are cured at subfreezing temperatures.

Study on Waterproof and Water-Resistant Properties of Gypsum

2012 ◽  
Vol 476-478 ◽  
pp. 1585-1588
Author(s):  
Hong Pan ◽  
Guo Zhong Li
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Portland Cement ◽  
Water Absorption ◽  
Ordinary Portland Cement ◽  
Experimental Results ◽  
Softening Coefficient

The comprehensively modified effect of cement, VAE emulsion and self-made acrylic varnish on mechanical and water-resistant properties of gypsum sample was investigated and microstructure of gypsum sample was analyzed. Experimental results exhibit that absolutely dry flexural strength, absolutely dry compressive strength, water absorption and softening coefficient of gypsum specimen with admixture of 10% ordinary Portland cement and 6% VAE emulsion and acrylic varnish coated on its surface can respectively reach to 5.11MPa , 10.49 MPa, 8.32% and 0.63, respectively.

scholarly journals Strength Development and Elemental Distribution of Dolomite/Fly Ash Geopolymer Composite under Elevated Temperature

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 1015 ◽  
Author(s):  
Emy Aizat Azimi ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Petrica Vizureanu ◽  
Mohd Arif Anuar Mohd Salleh ◽  
Andrei Victor Sandu ◽  
...  
Keyword(s):  
Elevated Temperature ◽  
Fly Ash ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Raw Materials ◽  
Liquid Sodium ◽  
Strength Development ◽  
Elemental Distribution ◽  
Distribution Analysis ◽  
Geopolymer Composites

A geopolymer has been reckoned as a rising technology with huge potential for application across the globe. Dolomite refers to a material that can be used raw in producing geopolymers. Nevertheless, dolomite has slow strength development due to its low reactivity as a geopolymer. In this study, dolomite/fly ash (DFA) geopolymer composites were produced with dolomite, fly ash, sodium hydroxide, and liquid sodium silicate. A compression test was carried out on DFA geopolymers to determine the strength of the composite, while a synchrotron Micro-Xray Fluorescence (Micro-XRF) test was performed to assess the elemental distribution in the geopolymer composite. The temperature applied in this study generated promising properties of DFA geopolymers, especially in strength, which displayed increments up to 74.48 MPa as the optimum value. Heat seemed to enhance the strength development of DFA geopolymer composites. The elemental distribution analysis revealed exceptional outcomes for the composites, particularly exposure up to 400 °C, which signified the homogeneity of the DFA composites. Temperatures exceeding 400 °C accelerated the strength development, thus increasing the strength of the DFA composites. This appears to be unique because the strength of ordinary Portland Cement (OPC) and other geopolymers composed of other raw materials is typically either maintained or decreases due to increased heat.

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