Data on the physical and mechanical properties of soilcrete materials modified with metakaolin.
ABSTRACT: During the last decades eco-friendly, low-cost, sustainable construction materials for utilization in civil engineering projects have attracted much attention. To this end, soilcretes are non-conventional construction materials produced by mixing natural soil such as natural clay or limestone sand with a hydraulic binder and are recently under detailed and in-depth investigation by many researchers. In this paper the results of the physical and mechanical characteristics of a large set of cylindrical specimens under uniaxial compression, are presented. Specifically, two types of soils such as sand and clay with metakaolin as a mineral additive have been used. This database can be extremely valuable for better understanding of the behavior of soilcrete materials. Furthermore, the results presented herein expected to be of great interest for researchers who deal with the prediction of mechanical properties of materials using soft computing techniques such as artificial intelligence (AI) techniques.
Project description:The effective activation and utilization of metakaolin as an alkali activated geopolymer precursor and its use in concrete surface protection is of great interest. In this paper, the formula of alkali activated metakaolin-based geopolymers was studied using an orthogonal experimental design. It was found that the optimal geopolymer was prepared with metakaolin, sodium hydroxide, sodium silicate and water, with the molar ratio of SiO₂:Al₂O₃:Na₂O:NaOH:H₂O being 3.4:1.1:0.5:1.0:11.8. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were adopted to investigate the influence of curing conditions on the mechanical properties and microstructures of the geopolymers. The best curing condition was 60 °C for 168 h, and this alkali activated metakaolin-based geopolymer showed the highest compression strength at 52.26 MPa. In addition, hollow micro-sphere glass beads were mixed with metakaolin particles to improve the thermal insulation properties of the alkali activated metakaolin-based geopolymer. These results suggest that a suitable volume ratio of metakaolin to hollow micro-sphere glass beads in alkali activated metakaolin-based geopolymers was 6:1, which achieved a thermal conductivity of 0.37 W/mK and compressive strength of 50 MPa. By adjusting to a milder curing condition, as-prepared alkali activated metakaolin-based geopolymers could find widespread applications in concrete thermal protection.
Project description:Superplasticizers (cement concrete water reducers) are applied to improve the flowability of calcium-rich, alkali-activated materials, with inconsistent results. However, superplasticizer applications are limited in metakaolin-based geopolymers. The possibility of using polycarboxylate superplasticizers and methyl isobutyl carbinol (MIBC) to ameliorate the flowability of metakaolin-based geopolymers was investigated. The ratio of metakaolin, fumed silica, NaOH or KOH, and water in geopolymers at a Na2O or K2O:Al2O3:SiO2:H2O ratio = 1:1:4:10 or 1:1:4:11 was maintained in the formulations. In this study, ether- or ester-based polycarboxylate superplasticizers did not improve the workability of fresh metakaolin-based Na-geopolymers. A low MIBC dose (0.5 wt.% of metakaolin) improved the flowability by 19% and additionally increased the 7-day compressive strength by 22% from 68 to 83 MPa for plain Na-geopolymers. The entrained fine froths produced by adding MIBC during mixing likely reduced friction between metakaolin particles, and the slurry became more workable. Hence, the geopolymer mixture with an improved flowability became more homogenous, which ensured more extensive metakaolin dissolution and hydrolysis. A low MIBC dose could be effective for Na-geopolymers with dual benefits of improved workability and enhanced compressive strength.
Project description:The effects of 10% metakaolin addition on compressive strength, water absorption, shrinkage and microstructure evolution of cement paste after elevated temperatures exposure from room temperature to 800 °C were evaluated. The experimental results show that compressive strength increases at 200 °C and 400 °C compared with that obtained at ambient temperature. Up to 800 °C, compressive strength decreases rapidly. The addition of 10% metakaolin leads to the enhancement of compressive strength regardless of exposure temperatures. After thermal exposure at 400 °C, compressive strength reaches the maximum value. Thermal exposure degrades pore structure. A polynomial equation was used to indicate the shrinkage of cement paste or metakaolin-blended cement paste with testing days. Mechanical properties, permeability resistance, and shrinkage in cement pastes are closely related to the microstructure development. 10% metakaolin addition presents better thermal resistance, lower shrinkage and denser microstructure compared with pure cement paste before and after thermal exposure.
Project description:Geopolymers are generally appreciated for their good resistance against high temperatures. This paper compares the influence of thermal treatment with temperatures ranging from 200 to 1200 °C on the mechanical properties and microstructure of geopolymers based on two different aluminosilicate precursors, metakaolin and fly ash. Moreover, the paper is also aimed at characterizing the effect of chamotte aggregate on the performance of geopolymers subjected to high temperatures. Thermal treatment leads to a deterioration in the strength of metakaolin geopolymer, whereas fly ash geopolymer gains strength upon heating. The formation of albite above 900 °C is responsible for the fusion of geopolymer matrix during exposure to 1200 °C, which leads to the deformation of the geopolymer samples. Chamotte aggregate improves the performance of geopolymer material by increasing the thermal stability of geopolymers via sintering of the aggregate particles with the geopolymer matrix in the contact zone.
Project description:Ternary clay-based composite material (TCC), composed of lime, clay and sand, and usually modified with sticky rice and other organic compounds as additives, was widely used historically in Chinese construction and buildings due to its high mechanical performance. In this study, to gain an insight into the micromechanical mechanism of this cementitious material, the nanomechanical properties and volume fraction of mechanically different phases of the binder matrix are derived from the analysis of grid nanoindentation tests. Results show that there are five distinct mechanical phases, where the calcium silicate hydrate (C-S-H) and geopolymer present in the binder matrix are almost identical to those produced in ordinary Portland cement (OPC) and alkali-activated fly-ash geopolymer materials in nano-mechanical performance. The nano-mechanical behavior of calcite produced by the carbonation of lime in this binder is close to the calcite porous outer part of some sea urchin shells. Compared to OPC, the C-S-H contained in the TCC has a relatively lower ratio of indentation modulus to indentation hardness, implying a relatively lower resistance to material fracture. However, the geopolymer and calcite, at nearly the same volume content as the C-S-H, help to enhance the strength and durability of the TCC by their higher energy resistance capacity or higher strength compared to the C-S-H. Rediscovering of TCC offers a potential way to improve modern concrete's strength and durability through synergy of multi-binders and the addition of organic materials if TCC can be advanced in terms of its workability and hardening rate.
Project description:In this study the development of a metakaolin based geopolymeric mortar to be used as bonding matrix for external strengthening of reinforced concrete beams is reported. Four geopolymer formulations have been obtained by varying the composition of the activating solution in terms of SiO₂/Na₂O ratio. The obtained samples have been characterized from a structural, microstructural and mechanical point of view. The differences in structure and microstructure have been correlated to the mechanical properties. A major issue of drying shrinkage has been encountered in the high Si/Al ratio samples. In the light of the characterization results, the optimal geopolymer composition was then applied to fasten steel fibers to reinforced concrete beams. The mechanical behavior of the strengthened reinforced beams was evaluated by four-points bending tests, which were performed also on reinforced concrete beams as they are for comparison. The preliminary results of the bending tests point out an excellent behavior of the geopolymeric mixture tested, with the failure load of the reinforced beams roughly twice that of the control beam.
Project description:The addition of a range of micro- and nano-particles to high-performance concrete has been the focus of recent research. At present, studies are mainly aimed at designing customised mortars, providing them with specific properties for each application. Improving the durability of mortars is one of the main objectives in such research, as a result of increasing environmental concern. The research presented herein analyses the synergistic effect of nanosilica and metakaolin as additives on the service life of cement-based mortars subject to aggressive environments (i.e., chloride exposure) at early ages. The effects of the additives on the durability properties of submerged samples after two and three days of curing were analysed. Tests were conducted on several different properties: resistivity, porosity, mechanical properties, chloride diffusion, and service life. It is observed that metakaolin and nanosilica exhibit a synergistic effect as additives, which is related to porosity refinement and chloride ion binding capacity, which contributes to enhanced resistance against chloride penetration from very early ages.
Project description:Hybrid cement has become one of the most viable options in the reduction of CO2 emissions to the environment that are generated by the cement industry. This could be explained by the reduction of the content of clinker in the final mixture and substitution of the remaining percentage with supplementary cementitious materials with the help of an alkaline activation. Following that, properties that are provided by an Ordinary Portland Cement and of a geopolymer are mixed in this type of hybrid material and could be achieved at room temperature. Thereafter, the main objective of this research was to synthesize hybrid cements reducing the clinker content of Portland Cement up to 20% and use metakaolin and fly ash as supplementary cementitious materials in different proportions. The mixtures were alkaline activated with a mixture of sodium silicate and sodium hydroxide, calculating the amounts according to the percentage of Na2O that is present in each of the activators. The samples were then characterized using Compressive strength, X-ray diffraction, Fourier Transform Infrared Spectroscopy, and Scanning Electron Microscopy with energy-dispersive X-ray spectroscopy. The results indicated that the hybrid cements have similar mechanical properties than an Ordinary Portland Cement, and they resulted in a dense matrix of hydration products similar to those that are generated by cements and geopolymers.
Project description:Pottery was a traditional art and technology form in pre-colonial Amazonian civilizations, widely used for cultural expression objects, utensils and as cooking vessels. Abundance and workability of clay made it an excellent choice. However, inferior mechanical properties constrained their functionality and durability. The inclusion of reinforcement particles is a possible route to improve its resistance to mechanical and thermal damage. The Amazonian civilizations incorporated freshwater tree sponge spicules (cauixí) into the clay presumably to prevent shrinkage and crack propagation during drying, firing and cooking. Here we show that isolated siliceous spicules are almost defect-free glass fibres with exceptional mechanical stability. After firing, the spicule Young's modulus increases (from 28?±?5?GPa to 46?±?8?GPa) inferring a toughness increment. Laboratory-fabricated ceramic models containing different inclusions (sand, glass-fibres, sponge spicules) show that mutually-oriented siliceous spicule inclusions prevent shrinkage and crack propagation leading to high stiffness clays (E?=?836?±?3?MPa). Pre-colonial amazonian potters were the first civilization known to employ biological materials to generate composite materials with enhanced fracture resistance and high stiffness in the history of mankind.
Project description:Systematic investigation of filtrates and filter residues resulting from a 24 h treatment of metakaolin in different alkaline solutions were performed. On filtered metakaolin particles, inductively coupled plasma-optical emission spectrometry (ICP-OES) measurements reveal an enrichment of iron and titanium, which suggests an inhomogeneous distribution of these cations. Since the SiO2/Al2O3 ratio remains constant in all filter residues examined, the dissolution of the Si and Al monomers is congruent. Structural differences, identified by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) as a consequence of alkali uptake, influence the X-ray scattering contribution of metakaolin, and thus quantifications with the partial or no known crystal structure (PONKCS) method. This leads to deviations between the degree of reaction calculated from Si and Al solubility from filtrate and that quantified by quantitative powder X-ray diffraction (QPXRD) using the filter residue. Nevertheless, the described changes do not cause a shift in the X-ray amorphous hump in case of congruent dissolution, and thus allow the quantification of the metakaolin before and after dissolution with the same hkl-phase model.