Influence of Sisal fiber’s treatment on the kinetics of hydration, morphological and thermophysical properties of the composite cementitious mortar

Currently, cement-based bio-composite is a relevant concept for researchers in the building. However, these researches highlighted some handicaps. Plant fibers are acting as a retarder in the setting time of the cement. In this study, Sisal fiber (SF) (4% by mass of cement) was subjected to different treatments to improve bio-composites hydration kinetics (KH) “tested by isotherm calorimetry”. The treatment slowed down both alkaline hydrolysis and mineralization of fiber cell walls by promoting the hydration of cement. This result was coherent with morphological properties. In fact, the images obtained by scanning electron microscopy (SEM) showed a tinier calcium layer around the (SF) treated with NaOH and Paraffin oil on the adhesion surface. The Fourier transform infrared spectroscopy (FTIR) test revealed a disparity in the peaks of the absorption strips of CaCO3 and Ca(OH)2 and thus cement hydration. In addition, the tests results showed a decrease in thermal conductivity (λ) and volumetric heat capacity (ρ.CV) after treatment of (SF). Resistance (RTh) and thermal diffusivity (α) slightly increased with treated fiber. Considering that, the bio-mortar with treated Sisal fiber can be promising material from an insulation point of view.

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Cement-Based Renders Manufactured with Phase-Change Materials: Applications and Feasibility

Advances in Materials Science and Engineering ◽

10.1155/2016/7254823 ◽

2016 ◽

Vol 2016 ◽

pp. 1-6 ◽

Cited By ~ 10

Author(s):

Luigi Coppola ◽

Denny Coffetti ◽

Sergio Lorenzi

Keyword(s):

Compressive Strength ◽

Phase Change ◽

Phase Change Materials ◽

Residential Buildings ◽

Setting Time ◽

Drying Shrinkage ◽

Hydration Kinetics ◽

Mechanical Performances ◽

Entrapped Air ◽

Kinetics Of

The paper focuses on the evaluation of the rheological and mechanical performances of cement-based renders manufactured with phase-change materials (PCM) in form of microencapsulated paraffin for innovative and ecofriendly residential buildings. Specifically, cement-based renders were manufactured by incorporating different amount of paraffin microcapsules—ranging from 5% to 20% by weight with respect to binder. Specific mass, entrained or entrapped air, and setting time were evaluated on fresh mortars. Compressive strength was measured over time to evaluate the effect of the PCM addition on the hydration kinetics of cement. Drying shrinkage was also evaluated. Experimental results confirmed that the compressive strength decreases as the amount of PCM increases. Furthermore, the higher the PCM content, the higher the drying shrinkage. The results confirm the possibility of manufacturing cement-based renders containing up to 20% by weight of PCM microcapsules with respect to binder.

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Role of alkanolamines in ordinary and alternative cement systems

10.5194/egusphere-egu2020-10013 ◽

2020 ◽

Author(s):

Ludovico Mascarin ◽

Luca Valentini ◽

Maria Chiara Dalconi ◽

Enrico Garbin ◽

Gilberto Artioli

Keyword(s):

Raw Materials ◽

Setting Time ◽

High Reactivity ◽

Water Soluble ◽

Raw Material ◽

Alkaline Solutions ◽

Hydration Kinetics ◽

Calcium Complexes ◽

Kinetics Of

Ordinary cement resulting from the reaction of a calcium aluminosilicate-rich powder plus water works as binding matrix in modern concrete. The design of alternative binders is currently a global challenge in order to reduce the environmental footprint associated to the ordinary cement production. Alkali-activated calcined clay materials (AAccMs) represent a class of sustainable binders made of the blending of a concentrated alkaline solution and a solid fraction with thermally treated phyllosilicates. Metakaolin produced by the heat treatment at temperatures between 550-900&#176;C of kaolinite, has long fascinated the scientific community for its high reactivity at high-pH stage. However, the higher costs of commercial metakaolin push towards the use of locally available low-purity kaolinitic soils, such as laterite covers, as potential raw materials to produce low-CO2 cements with the benefit of reducing the cost of feedstock transportation.The work is focused on the role of triethanolamine (TEA) and triisopropanolamine (TIPA) on the reaction kinetics of ordinary cement pastes and AAccMs, the latter with different aluminosilicate reactive fraction and degree of purity. TEA and TIPA are tertiary alkanolamines with a developed molecular structure. It has been assessed that low equal dosages of alkanolamines introduced in advance to the mixing water for cement hydration can act on the setting time and the degree of cement reaction. These chemical compounds, and above all TIPA, are recognized as iron-chelating agents that can increase the dissolution rate of ferric ions from the ferroaluminate phase of cement and promote their complexation. Moreover, alkanolamines can also form water-soluble calcium-complexes that may influence the hydration kinetics of calcium-silicate phases and the precipitation of hydrates in the binder microstructure.The raw and the reacted materials are characterized by X-ray diffraction (XRD) and the kinetic pathways are followed with the aid of a semi-adiabatic calorimetry. The dissolution-precipitation steps of hydration in aqueous and alkaline solutions are subsequently simulated. Ordinary cement is used to clarify the role of alkanolamines as hardening accelerators. Afterwards, the kinetics of alkali-based pastes of high-purity metakaolin and a Fe-rich laterite, both blended with waste marble powder, are compared with the aim of assessing the formation of calcium-complexes in solution and any change in the kinetics due to the presence of iron in the raw material. Mechanical strength tests are performed to make clear the beneficial or detrimental effect of TEA and TIPA on the materials.

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