Production Of Cement Composites Research Articles

Lignocellulosic Materials for Production of Cement Composites: Valorization of the Alkali Treated Soybean Pod and Eucalyptus Wood Particles to Obtain Higher Value-Added Products

Brazil, as a predominantly agricultural country is the second largest world producer of soybean. Consequently, these plantations are responsible for high production of agricultural wastes. For reusing the large volume of one type of this material generated, the soybean pods, one type of waste generated by this crop, could be applied as a raw material for production of higher value-added products. Good examples of value-added product are those applied in the field of construction. The building construction is an intensive activity and it requires a great variety of materials. A great ideal in this field would be the obtainment of a material that relates good mechanical strength and reuse of wastes. In this context, the aim of this study was to produce cement composites with soybean pods associated with eucalyptus wood, both treated with alkaline solution and evaluate their physical properties and mechanical strength. The wood and the wastes particles were submitted to alkaline treatment in NaOH solution (5%) during 48 h in order to removing chemical compounds that could harm the cement solidification. For the composites production, the soybean pods addition was performed in proportions of 0, 25, 50, 75 and 100% and mixed with the complementary percentage of Eucalyptus grandis wood particles until achieve the amount of 100% of lignocellulosic material which constitutes the composite. The lignocellulosic materials were evaluated by basic density and chemical composition. The physical properties of water absorption (WA) (2 and 24 h) and thickness swelling (TS) (2 and 24 h) and the mechanical properties modulus of elasticity (MOE), modulus of rupture (MOR), compression strength and janka hardness of the cement composites were evaluated. Scanning electron microscopy (SEM) images showed the occurrence of cavities in the composites produced with higher proportions of soybean pods. All the properties were analyzed by ANOVA and in case of significance, the regression equation was adjusted to correlate the property with the percentage of soybean waste added. It was noted an increase of WA 24 h in the samples with high insertion of soybean pods. The TS was not affected by the different compositions of the composites. The mechanical properties decreased with the increase of soybean pod in the cement composites. However, the cement composites could be produced with up to 48% of soybean pods associated to eucalyptus wood and applied, for example, as partition walls or thermal and acoustic insulation walls.

Evaluation of pre-treatment efficiency on sugarcane bagasse fibers for the production of cement composites

In the present study, physical, chemical, morphological, crystallographic analysis of the non-treated and treated (100°C during 30min) sugarcane bagasse fibers were examined. Sugarcane bagasse fibers pre-treatment effect on the Portland cement hydration was monitored by inhibition tests and differential scanning calorimetry in the first 24h. Furthermore, 28 days age physical-mechanical properties of cement composite materials with sugarcane bagasse fibers were also evaluated. Inhibition index of treated sugarcane bagasse fibers was 5.9%, while for the non-treated sugarcane bagasse fibers it was 67.3%. Cement composites containing treated sugarcane bagasse fibers showed lower physical properties (water absorption and thickness swelling) than the cement composites reinforced with non-treated sugarcane bagasse fibers (p<0.05). Likewise, mechanical properties under flexure (modulus of rupture, MOR, and modulus of elasticity, MOE) of cement composites with treated sugarcane bagasse fibers showed higher values than the cement composites with non-treated sugarcane bagasse fibers (p<0.05), thus proving the pre-treatment efficiency on sugarcane bagasse fibers for cement composites.

The Utilization of Waste Water from a Concrete Plant in the Production of Cement Composites

This article presents the results of a study dealing with the utilization of sludge water from a concrete plant as a partial replacement for mixing water in the production of cement composites. The replacement of mixing water with sludge water from a concrete plant was carried out in the amounts of 20% and 50%. The following tests were carried out in order to determine the effect of the replacement of mixing water with sludge water from a concrete plant on the physical and mechanical properties of the cement composites: cement mortar consistency, beginning and end of setting, strength characteristics (compressive strength and flexural strength), and thermal properties. The measured values of the strength characteristics of the test specimens after 28 days of age confirm the possibility of replacing mixing water with sludge water from a concrete plant without significantly reducing the compressive and flexural strength.

Synergistic Effect of High Temperature Fly Ash with Fluidized Bed Combustion Fly Ash in Cement Composites

Using high temperature fly ash for his pozzolan properties to cement composite production is known a few years ago. New ways combustion of fossil fuels also creates a new type of fly ash, named fluidized bed combustion fly ash. However, this fly ash has same pozzolan properties as has high temperature fly ash, this type is not using for production of cement composites. Fluidized bed combustion fly ash has highly variable chemical composition but usually it has a higher amount of free CaO together with sulphates. This higher amounts of free CaO after mixing of fluidized bed combustion fly ash with water to some extent becomes an activator for the beginning of the pozzolanic reaction, during which is consumed the extinguished CaO. If there is also present high temperature fly ash in cement composite, it could be accelerated his pozzolanic reaction in the same manner using a fluidized bed combustion fly ash. In this experiment was tested a synergy effect in the use of fluidized bed combustion fly ash with high temperature fly ash as an additive. The experiment was carried out on cement pastes that have been studied in particular the progress of hydration processes, pointing to a possible acceleration of pozzolanic reactions of both types of fly ash.

Stabilization of carbon nanotubes with superplasticizers based on polycarboxylate resin ethers

The mechanism of stabilization of carbon nanotubes by ultrasonic treatment in the presence of a superplasticizer of new generation, based on polycarboxylate resin ethers, is analyzed. The main factors determining the stability of lyophobic systems as applied to solutions of stabilized carbon nanotubes are considered. The plots illustrating the efficiency of using solutions of stabilized carbon nanotubes in production of cement composites are presented. The solutions of stabilized carbon nanotubes preserve their properties for a long time. This feature allows preparation of repair mixes with required properties for performing various building works.

Effect of halloysite nanoclay on mechanical properties, thermal behavior and microstructure of cement mortars

Many studies have targeted the application of clay in cement composites and declared some enhancement on the properties of concrete. However there is little knowledge on nanoclays and their effect on the mechanical properties and durability of cement composites. Halloysite nanoclay is one of the subcategories of nanoclay that has been undeservedly ignored in the production of cement composites. Chemically, the outer surface of the halloysite nanotubes has properties similar to SiO2 while the inner cylinder core is related to Al2O3 which together may improve the cement matrix. In this study the mechanical properties, flowability, thermal behavior and durability of mortars containing 1, 2, 3% halloysite nanoclay were studied. Compressive strength and gas permeability of samples with 3% and 2% nanoclay were improved up to 24% and 56%, respectively. SEM, XRD, DSC tests were carried out to investigate the microstructure and chemical composition change in samples with halloysite nanoclay.

Avaliação dos efeitos da acetilação nas propriedades das fibras de caroá

As fibras de vegetais são altamente higroscópicas, característica que se apresenta como um dos principais problemas em sua aplicabilidade na produção de fibrocimentos, induzindo a variações dimensionais sob a influência da umidade, deposição dos produtos da matriz em seus poros e a degradação. Visando encontrar alternativas para minimizar os impasses gerados nos compósitos cimentíceos com relação às fibras de caroá objetivou-se, neste trabalho, avaliar a aplicação do tratamento de acetilação em diferentes níveis. Sua eficiência foi determinada considerando-se a redução da hidrofilicidade, a manutenção do desempenho mecânico das fibras e as modificações na composição química, avaliadas por meio de ensaios de determinação das propriedades físicas, químicas, mecânicas e térmicas. Os tratamentos de acetilação conduzidos a 120 °C e/ou por 3 h, apresentaram reduções de 42 a 47% na hidrofilicidade. Na acetilação a 120 °C, durante 1 h o incremento nas propriedades mecânicas foi superior a 110%. O tratamento também promoveu modificações na composição das fibras com a implantação de grupos acetil, aumentou a estabilidade térmica e reduziu consideravelmente a cristalinidade da celulose, sem gerar degradações que comprometessem sua superfície de adesão.

KOMPONEN KIMIA DAN FISIK ABU SEKAM PADI SEBAGAI SCM UNTUK PEMBUATAN KOMPOSIT SEMEN

This research aimed to determine chemical and physical component of rice husk ash as supplementing cement material to manufacture cement composite products. Charcoal of rice husk ash obtained by burning rice husk conventionally in kiln drum and burned again in furnace 1400 Barnsted Thermolyne Type at temperature 600o C for 2 hours. Analysis of chemical and physical component refer to SNI 15-2049-2004. Major chemical compound of rice husk ash was 72.28 % of silica and 21.43 of LOI. Density of rice husk ash was 760 kg/m3. Key words: SCM, rice husk ash, chemical and physical component, cemet composite

Pultruded Fabric-Cement Composites

The use of reinforcement in thin cement-based elements is essential to improve the tensile and flexural performance. The reinforcements can be either short fibers or continuous reinforcements, in a fabric form. Practical use of fabric-cement composites requires an industrial, cost-effective production process. The objective of this study was to develop the pultrusion technique as an industrial, cost-effective production method of prefabricated thin-sheet fabric-reinforced cement composites. Woven fabrics made from low-modulus polyethylene and glass meshes were used to produce the pultruded cement composites. The influence of fabric type, cell opening, application of pressure during casting, and cement-based matrix modification were examined. The tensile strength and ductility of the pultruded fabric-cement components were found to be relatively high, exhibiting strain hardening behavior even for fabrics with low modulus of elasticity. The best performance was achieved from glass fabric composites with a high content of fly ash. The mechanical properties were significantly affected by the matrix formulation, rheology of the matrix, and the intensity of the pressure applied after the pultrusion process. The promising combination of fabric reinforcement in cement composite products using the pultrusion process is expected to lead to a new class of high-performance fabric-cement composite materials.