scholarly journals Influence of Early Oven Curing on the Alkali Activated Binders with Reactive Magnesia Replacement

2020 ◽  
Author(s):  
Shaoqin Ruan ◽  
Gediminas Kastiukas ◽  
Shuang Liang ◽  
Xiangming Zhou
Keyword(s):  
Mechanical Performance ◽  
Microstructural Analysis ◽  
Construction Materials ◽  
Thermal Shrinkage ◽  
Strength Development ◽  
Natural Clay ◽  
Expansive Agent ◽  
Alkali Activated Binders ◽  
Reactive Magnesia ◽  
Alkali Activated

Magnesia is widely used an expansive agent in construction materials due to its delayed hydration, which will compensate for the thermal shrinkage. This study investigates the influence of magnesia and early oven curing on the mechanical performance and microstructures of alkali-activated natural clay samples under different curing regimes after 28 days. Microstructural analysis and pH measurements were conducted to assess the strength of the samples. Results indicate that the strength was greatly improved (in comparison with the control samples) by the incorporation of magnesia due to the formation of nesquehonite. Meanwhile, oven curing is an effective method in the fast strength development in alkali-activated natural clay. The results also demonstrated the possibility of CO2 curing in the strength development of the magnesia-modified alkali-activated natural clay. Keywords: magnesia, natural clay, oven curing, compressive strength, microstructure

scholarly journals Waste-Based One-Part Alkali Activated Materials

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2911
Author(s):  
Margarida Gonçalves ◽  
Inês Silveirinha Vilarinho ◽  
Marinélia Capela ◽  
Ana Caetano ◽  
Rui Miguel Novais ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Microstructural Analysis ◽  
Construction Materials ◽  
Sodium Metasilicate ◽  
High Compressive Strength ◽  
Hardened State ◽  
First Time ◽  
Furnace Slag ◽  
Alkali Activated

Ordinary Portland Cement is the most widely used binder in the construction sector; however, a very high carbon footprint is associated with its production process. Consequently, more sustainable alternative construction materials are being investigated, namely, one-part alkali activated materials (AAMs). In this work, waste-based one-part AAMs binders were developed using only a blast furnace slag, as the solid precursor, and sodium metasilicate, as the solid activator. For the first time, mortars in which the commercial sand was replaced by two exhausted sands from biomass boilers (CA and CT) were developed. Firstly, the characterization of the slag and sands (aggregates) was performed. After, the AAMs fresh and hardened state properties were evaluated, being the characterization complemented by FTIR and microstructural analysis. The binder and the mortars prepared with commercial sand presented high compressive strength values after 28 days of curing-56 MPa and 79 MPa, respectively. The mortars developed with exhausted sands exhibit outstanding compressive strength values, 86 and 70 MPa for CT and CA, respectively, and the other material’s properties were not affected. Consequently, this work proved that high compressive strength waste-based one-part AAMs mortars can be produced and that it is feasible to use another waste as aggregate in the mortar’s formulations: the exhausted sands from biomass boilers.

Preliminary Studies on the use of Sugar Cane Bagasse Ash (SCBA) in the Manufacture of Alkali Activated Binders

2014 ◽  
Vol 600 ◽  
pp. 689-698 ◽  
Author(s):  
Vinicius N. Castaldelli ◽  
Mauro M. Tashima ◽  
José Luiz P. Melges ◽  
Jorge L. Akasaki ◽  
J.M. Monzó ◽  
...  
Keyword(s):  
Sugar Cane ◽  
Binary Systems ◽  
Mechanical Performance ◽  
Sugar Cane Bagasse ◽  
Mineral Admixtures ◽  
Alkali Activation ◽  
Sugar Cane Bagasse Ash ◽  
Alkali Activated Binders ◽  
Mechanical Strengths ◽  
Alkali Activated

Alkali activated binders require the addition of a mineral-rich amorphous silica and alumina. This paper proposes the use of a mineral residue from the burning of sugar cane bagasse. The alkali activated mixtures were prepared containing binary mixtures of sugar cane bagasse ash (SCBA) and other mineral admixtures: fly ash (FA) or blast furnace slag (BFS). As alkaline activators, mixtures of alkali (Na+ or K+) hydroxide and alkali (Na+ or K+) silicate were used. Alkali-activated pastes and mortars containing binary systems SCBA/FA or SCBA/BFS were prepared and cured at 65 oC. Microstructural properties of these alternative binders were assessed by means of TGA, SEM, XRD and pH measurements. Mechanical strength of mortars was performed after 3 and 7 days at 65 oC. Compressive mechanical strengths of these mortars were in the range 30-55 MPa, showing the good mechanical performance achieved by the alkali activation. Microstructural studies suggested the development of stable matrices and the formation of typical gel.

scholarly journals STRUCTURE FORMATION IN ALKALI ACTIVATED ALUMINOSILICATE BINDING SYSTEMS USING NATURAL RAW MATERIALS WITH DIFFERENT CRYSTALLINITY DEGREE

2020 ◽  
pp. 38-43 ◽  
Author(s):  
N. Kozhuhova ◽  
V. Strokova ◽  
M. Kozhuhova ◽  
Igor' Zhernovskiy
Keyword(s):  
Structure Formation ◽  
Raw Materials ◽  
Construction Material ◽  
Construction Materials ◽  
Deep Understanding ◽  
Science Field ◽  
Crystallinity Degree ◽  
Classic Problem ◽  
Alkali Activated Binders ◽  
Alkali Activated

the efficiency of traditional raw materials using as well as expanding of potential uses for non-conventional and alternative raw materials with different origin is the tasks exiting interest among material scientists and manufacture stuff. Investigation of the above is oriented on solution of such scientific problem as more deep understanding of structure and features of material. The results obtained also allow solution of some technological, technical and economical tasks. Greatly, it is actual when using of new types of raw materials as well as when synthesis of new composites. Concerning the construction material science field, the classic problem is the looking for ways to study the reactivity of raw components under different conditions, its control and, generally, its increasing to produce higher performance materials. Among the popular and widely-used construction materials are alkali-activated binders and relevant composites. In this study the results of granulometric analysis of suspension based on alkali-activated aluminosilicate with different crystallinity degree are presented. It was found, when treatment of aluminosilicate grain by alkali activator leads to the grain solubilizing (but differently depending on crystallinity degree of aluminosilicate) and formation of alkali-aluminosilicate gel that reacts with unreacted part of the grain according to structure affinity principle. It was also determined the crystallinity degree of aluminosilicate component is inversely proportional to its solubility in highly-alkali environment. The model of structure formation for geopolymer system under alkali effect is offered.

scholarly journals Early-Age Behaviour of Fiber Reinforced High Performance Concretes

2018 ◽  
Vol 4 (2) ◽  
pp. 7
Author(s):  
Valeria Corinaldesi ◽  
Jacopo Donnini ◽  
Glauco Merlonetti
Keyword(s):  
Flexural Strength ◽  
High Performance ◽  
Mechanical Performance ◽  
Mechanical Tests ◽  
Strength Development ◽  
Early Age ◽  
Fiber Reinforced ◽  
Expansive Agent ◽  
Significant Difference ◽  
Hardened State

The aim of this experimental activity was to study the early-age behavior of several Fiber-Reinforced Concretes (FRCs) containing expansive agent. The investigation concerned the evaluation of the influence of different amounts of fibers (dosages of 2.0%, 1.75% and 1.5% by volume of FRCC) on the mechanical performance of FRCs. In particular, hooked brass-coated fibers were used and dead-burnt calcium oxide based expansive agent was employed at a dosage of 40 kg/m3. The attention was focused on the strength development at early ages. Mechanical tests were carried out at 0.25 (i.e. 6 hours, that is time of demolding), 1, 2, 7 up to 28 days of curing. The properties of FRCs were characterized at the fresh state, by measuring flow ability and consistency as well as at hardened state by measuring compressive and flexural strength up to 28 days. Flexural strength was measured on prismatic specimens according to the procedure described in EN 12390-5. The different dosage of fibers did not influence the values of compressive strength, while there is a significant difference in terms of 28-day flexural strength between the several mixtures depending on the different amount of fibers. In all cases at least 20 MPa of 28-day peak flexural strength were achieved.

Review of Geopolymer Materials for Thermal Insulating Applications

2015 ◽  
Vol 660 ◽  
pp. 17-22 ◽  
Author(s):  
Emy Aizat Azimi ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Liew Yun Ming ◽  
Cheng Yong Heah ◽  
Kamarudin Hussin ◽  
...  
Keyword(s):  
Chemical Resistance ◽  
Mechanical Performance ◽  
Raw Materials ◽  
Good Resistance ◽  
Thermal Insulating ◽  
Cementitious Binder ◽  
Alkali Activated Binders ◽  
Alkali Activated ◽  
Geopolymer Composites ◽  
Geopolymer Material

Geopolymer is an environmentally cementitious binder that does not require the existence of ordinary Portland cement (OPC). Geopolymer has many excellent advantages, including high early strength, low shrinkage, good thermal resistance and good chemical resistance. Based on previous research, geopolymer offered good resistance to corrosion, abrasion and heat. Fly ash, metakaolin, kaolin, and slag are regularly used raw materials for the preparation of geopolymer composites. Geopolymer composites also offer a potential environmental friendly product by reduce the carbon dioxide (CO2) emissions. This geopolymer material also offers an innovative and sustainable solution for maintaining infrastructure and also provides superior thermal, chemical and mechanical performance. This paper summarizes some research outcomes on alkali-activated binders along with the potential of geopolymer composites for thermal insulating applications.

Discussion on Properties and Microstructure of Geopolymer Concrete Containing Fly Ash and Recycled Aggregate

2012 ◽  
Vol 450-451 ◽  
pp. 1577-1583 ◽  
Author(s):  
Xiao Shuang Shi ◽  
Qing Yuan Wang ◽  
Xiao Ling Zhao ◽  
Frank Collins
Keyword(s):  
Fly Ash ◽  
Carbon Dioxide Emission ◽  
Construction Materials ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Strength Development ◽  
Geopolymer Concrete ◽  
Ordinary Concrete ◽  
Alkali Activated

Construction materials dominate the main responsibility to maintain the environmental sustainable development in human’s activities. Geopolymer concrete containing fly ash and recycled aggregate is a new concrete which can reuse the by-product of power station and waste concrete, as well as reduce the production of cement which contribute a lot of carbon dioxide emission in the manufacturing process. In this paper, experiments were carried out to investigate the mechanical properties and microstructure of geopolymer concrete with different recycled aggregate contents. Six mixtures were designed including alkali-activated fly ash geopolymeric recycled concrete and corresponding ordinary concrete as the comparison. The compressive strength of the concrete with 0%, 50% and 100% recycled aggregates was tested. The microstructure of these concrete were investigated by petrographic microscope under transmit light. According to experimental results, the strength development and failure mechanism are discussed. Furthermore, the application of such geopolymer concrete is discussed and suggested.

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