Alkaline Attack Research Articles

Effect of nickel containing mixing water on the properties blended cement mortar

Influence of Nickel(Ni) present in the water which is used for mixing of blended cement was experimentally evaluated. The properties investigated were setting times, soundness, compressive strength, and durability aspects like acid attack, alkaline attack and sulphate attack. Specimens were prepared by using the de-ionized as well as Nickel(Ni) spiked de-ionized water for reference and the test samples respectively. The concentrations of Nickel(Ni) tested for different samples are 10, 50, 100, 500, 1000, 2000, 3000, 4000 and 5000mg/L. It is observed that on comparison with reference specimens, the setting process of cement of test specimens has increased with increase of Nickel proportion in de-ionized water. Increase of initial setting time was insignificant up to 100 mg/L concentration whereas the same for final setting time was significant for all concentrations. Change in expansion of cement mortar is insignificant up to 3000 mg/L concentrations of the Nickel(Ni). The change in strength was noticed to be insignificant at all the concentrations of Nickel(Ni). However, there is an increase in strength with higher Nickel proportion up to 2000 mg/L. This proportion of 2000 mg/L was considered as the reference mix for conducting durability tests. The strength as well as weight loss for the specimen mortar cubes placed in acidic medium are severe compared to that of alkaline and sulphate solutions with increase in age.

Modification of hemp fibers through alkaline attack assisted by mechanical milling: effect of processing time on the morphology of the system

This paper reports the possibility of functionalizing hemp fibers (HF) through a mechano-chemical treatment assisted by an easily scalable top-down technology. The mechanical action was able to remove non-cellulosic material and to cause exposure of the cellulose microfibrils. Its influence on structure, morphology, and properties of hemp fibers has been analyzed by means of the scanning electron microscopy, X-Ray, FTIR and Raman spectroscopy. The milling process induced a change in crystalline content of hemp fibers, which decreased after a treatment time of 30 min. The crystallinity index and cellulose chain arrangement influence the thermal stability of hemp fibers. In order to compare the improved properties of mechanochemically treated HF respect to the HF modified with conventional alkalization, they were introduced, as green reinforcement, into a pectin matrix. Thermal and mechanical properties demonstrated the effectiveness of milling treatment in improving the considered physical properties of the pectin matrix.

Generation of Porous Scaffolds from Cacao Mesocarp for Biomedical Applications Using Surface Response Methodology

Tissue engineering is the area where cells are applied in combination with biomaterials that induce the proliferation of these cells, in order to regenerate different types of tissues in an organism. Different cytocompatible biomaterials have been developed for this application; however, there is no production of this type of materials in Ecuador. A viable alternative, to produce biomaterials that help cellular regeneration is the use of lignocellulosic material which can be found in agroindustrial waste, due to its high biocompatibility. Therefore, the present study evaluates the use of waste from the pod shell of cacao type CCN-51, which is abundant in Ecuador, for the production of porous scaffolds by alkaline treatments applying a response surface design (Central Composite Designs). Scaffolds were produced by means of an alkaline attack using NaOH, varying operating conditions such as reactant concentration, biomass concentration, operating time, temperature, and mesocarp dimensions to generate a prediction model through the implementation of a central composite design (CCD). It was found that temperature and NaOH concentration were the most influential variables in the model. The CCD analysis allowed to partially predict the behavior of each output variable (lignin content, cellulose, ash and yield) with respect to the input variables mentioned before, obtaining maximum values of yield and cellulose content of 7.91% and 63.77%, respectively. A physicochemical analysis by scanning electron microscopy (SEM), thermogravimetry, and Fourier transformed infrared spectroscopy (FTIR) showed important morphological and structural changes depending on the composition of the scaffold.

Effect of the Partial Replacement of Cement with Microsilica and Coarse Aggregate with Crushed Ceramic Tiles on the Properties of Concrete

Re-use of waste, otherwise deemed to be of no use, in concrete will lead to green environment. The concrete made so is called sustainable concrete which can also be called as Green concrete. The main focus of this research is to study the strength of concrete with crushed waste ceramic tile and silica fume as partial replacement of coarse aggregate and cement respectively. Rapid construction and total reliance on conventional materials of making concrete are leading to dearth of the materials and increased construction cost. In this research an attempt is being made to find the sustainability of waste ceramic tile as coarse aggregate and silica fume as a possible replacement for conventional aggregate and cement in concrete. In this study we replace the micro silica for cement partially in the percentage of 5%,10%, 15%, 20%, and 20% of coarse aggregate is replaced with crushed waste ceramic tiles. The replaced concrete is compared with the normal concrete. Tests are done following codes of Bureau of Indian Standards. Mix design of M30 grade of concrete is designed by following the specification given in the IS 10262:2009. For all the materials, physical properties shall be determined and fresh concrete is prepared. Concrete is then tested for determination of physical properties in fresh state. In hardened concrete, mechanical properties such as compressive strength & split tensile strength of concrete and durability properties like resistance against acid and alkaline attack would be examined and compared with conventional concrete.

Durability and mechanical properties of seashell partially-replaced cement

This research investigates the possibility of grinding and burning bivalve clam seashells to produce seashell ash powder. This ash is used to partially replace cement by 5, 10, 15 and 20% by weight. These mixes are tested and compared with a SC0 that has 0% seashell ash powder (SC0). The fresh and hardened properties of all mixes are studied through a variety of tests, including: slump, unit weight, compressive strength and splitting tensile strength. The durability of seashell concrete cubic specimens is studied by immersion in 5% NaOH(aq) and MgSO4(aq) solutions. The addition of thermally treated seashells increased the calcium hydroxide content. The results also show that the compressive strength of the 5% replacement is slightly higher than the SC0 at 28 and 90 days of age, while the tensile strength is higher than the standard for the 5% and 10% of replacement at 7 and 28 days. Furthermore, the slump test value generally increases with increasing the percentage of replacement. The highest durability against sulfate and alkaline attacks is obtained with 5% replacement of cement with seashells which reported the lowest decrease in weight and the highest compressive strength after immersion in 5% NaOH(aq) and MgSO4(aq) solutions. The 5% replacement mix is the optimum percentage of replacement. Therefore, this study recommends replacing cement with 5% seashell cement.

Durability of chemically modified sisal fibre in cement-based composites

The degradation of sisal fibre in a cement-based matrix due to the highly alkaline environment reduces the strength of the composite. In this research, to avert this degradation, alkaline treatment and acetylation were respectively performed with sodium hydroxide (NaOH) and Acetic Acid or Acetic Anhydride to improve the resistance of the fibre to alkaline attack. In addition, single fibre pull-out (SFP) tests were performed to evaluate the influence of chemical treatment on fibre strength, fibre-matrix interaction and also determine the critical fibre length. Specimens were tested in indirect tension (flexure) at 28 days to determine the strength of the composite. Additional ageing tests by extended curing in water at 24 °C, lime saturated hot water at 70 °C, and alternate cycles of wetting and drying were done. Aged samples were further tested at 90 days to evaluate the durability of the fibre. It was found that a combination of alkali treatment and acetylation was the most effective treatment condition, followed by that of alkali treatment at low concentrations of sodium hydroxide. At higher concentrations of sodium hydroxide, a significant reduction in strength was observed. Chemical treatment improves the durability of sisal fibres in concrete, albeit slight degradation still occurs.

Alkaline Attack on Cement or Lime Mortar and Glass Fiber-Reinforced Polymer Rods

Alkaline Attack on Cement or Lime Mortar and Glass Fiber-Reinforced Polymer Rods

The Environmental Friendly Route to Obtain Sodium Silicate Solution from Rice Husk Ash: A Comparative Study with Commercial Silicates Deflocculating Agents

Sodium silicate solutions were synthesized treating Rice Husk Ash (RHA) with sodium hydroxide solutions at low molar concentrations (1–4 M). During the study the operative conditions were optimized. Raman spectroscopy was used to check the chemical nature of the silicates solutions obtained by comparison with commercial ones. The deflocculating efficiency of the synthesized solutions was checked by rheological measures on clay suspensions (solid content 60 and 65 wt%). Some findings of the study permit to confirm that the extraction of SiO2 increases by increasing NaOH concentration. The alkaline attack (NaOH solution) at 1.5 and 2 M show the best results for SiO2/Na2O ratio close to 2, this ratio is widely used as deflocculating agents in ceramic sector using commercial silicates. The 0.5wt% content resulted the optimum dosage for all additives. In particular, the viscosity values obtained using the silicates synthetized from RHA are lower than those corresponding to the commercial products. The deflocculating capability behaves similar, or even better, than commercial ones. This valorization of matter from RHA allows the obtainment of high added value products that can play role of “green” substitutes of commercial ones.

Alkaline stability of model anion exchange membranes based on poly(phenylene oxide) (PPO) with grafted quaternary ammonium groups: Influence of the functionalization route

We study the effect of pendent methyl groups on the alkaline stability of model anion exchange polymers based on poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) with grafted trimethylammonium groups. The polymer backbone is modified varying the synthesis procedure: by the bromination route, the ionomeric ammonium groups are inserted on the structural methyl group of PPO (Br-PPO-TMA), while by the chloromethylation route the ammonium groups are attached in the ortho-position to the methyl group of PPO (Cl-PPO-TMA). The properties of the membranes are studied by NMR and FTIR spectroscopy, thermogravimetry, water uptake, mechanical tensile tests, small-angle X-ray scattering (SAXS) and impedance spectroscopy. SAXS analysis indicates a better nanophase separation for Cl-PPO-TMA, which is consistent with a slightly larger water uptake and ionic conductivity. The properties of the two polymers are also compared before and after the aging in 2 M NaOH at 80 °C for different times. The thermogravimetric analysis shows the loss of the ammonium groups and the backbone ether cleavage after alkali treatments. The samples prepared by the bromination route show a higher stability of ionic conductivity, presumably due to a reduced alkaline attack of the ammonium groups, although DFT calculations do not show major differences of thermodynamic and kinetic reaction parameters. After alkaline treatment, the mechanical properties are more degraded for the Br-PPO-TMA compound. The decreased mechanical properties can be attributed to a reduction of the average chain length of PPO by alkaline scission of the ether links. Both synthesis routes have advantages and disadvantages, but the higher reproducibility and the better mechanical properties of samples prepared by chloromethylation are considered preponderant benefits.

Strength and Durability Characteristics of Coconut Fibre Reinforced Earth Cement Blocks

ABSTRACT The study investigated the improvements in post-peak resistance induced by the introduction of coconut fiber in earth cement blocks. Earth cement blocks reinforced by coconut fiber of various fiber weight fractions were tested under axial compression and flexural loading to examine the response of the material in terms of peak load-carrying capacity, post-peak residual strength and toughness. It was observed that the coconut fiber reinforcement greatly improved the residual strength, ductility and energy absorption of the earth cement blocks. For durability, against the alkaline attack and the acid attack was reduced by the addition of coconut fiber in the mortar. Similar durability improvement shows against freeze-thaw and wet-dry cycle.

Efflorescence Processes in Exterior Wall Surface of Buildings

Alkali hydroxide and alkali salt possessing high solubility are considered to be one of main reasons for efflorescence occurrence in exterior walls of buildings made from solid masonry units. Analysis of alkaline attack on efflorescence processes in the surface of exterior walls of buildings is presented herein. Volumetric changes in solid phase materials in the course of alkali hydration and carbonation reactions under efflorescence are calculated by the proposed procedure. The indicated processes are confirmed by laboratory simulation and by field studies of ceramic block and lime brick masonries, and vibropressed concrete blocks within the Republic of Bashkortostan.

Study on the Properties of Concrete Made with Sugar Cane Bagasse Ash under Acid and Alkaline Attack

Study on the Properties of Concrete Made with Sugar Cane Bagasse Ash under Acid and Alkaline Attack

Partial Replacement of Cement Concreete with Biological Green Waste

Bagasse ash (BA), the residue obtained after the burning of sugarcane bagasse as a fuel, has pozzolanic properties with potential use as a supplementary binding material (SCM). Use of Bagasse ash (BA) as a mineral admixture needs to be established, especially in India, where sugarcane cultivation is widespread, to reduce land required for its disposal and cement consumption in construction industry. Hence, to encourage commercial use ofBA with minimum processing, an evaluation of the physical, chemical and morphological characteristics of a locally available BA and its effect, as SCM on properties of structural concrete was taken up.This research work describes the feasibility of using the Fly Ash (FA) Rice Husk Ash (RHA) and Sugarcane Bagasse Ash(SCBA) waste in concrete production as a partial replacement of cement. This present work deals with the effect on strength and mechanical properties of concrete using Triple blending of cement concrete using FA, RHA and SCBA instead of cement. The cement has been replaced by rice husk ash, accordingly in the range with 0%, 10%, 20% and 30% by weight. Concrete mixture of M20 and M25 and M30, were produced, tested and compared in terms of compressive strengths with the Conventional concrete. These tests were carried out to evaluate the mechanical properties for the test results of7, 14, 28, 56 and 90 days for Compressive strengths and Tensile & Flexural Strengths at 28 days. The durability aspect of the samples for Acid attack, Alkaline attack and Sulphate attack was also tested. The result indicates that the FA, RHA and SCBA improve the Compressive Strength and durability of concrete.

Adhesive properties of laminated veneer lumber poles for use in temporary soil nailing: bonding performance of curved structures in a high-alkaline environment

Circular hollow sections of beech-laminated veneer lumber (LVL) for the use as temporary geotechnical soil nailing systems are currently being developed. Due to their permanent subsoil cement embedment, investigations of the bond line quality of the timber sections are essential. This paper presents the bonding properties of flat and curved beech LVL after cyclic conditioning in a water–cement grout solution aimed at inducing short- and long-term alkaline attack of the timber. In total, 409 and 69 samples were tested in tensile shear tests after short-term and long-term conditioning, respectively. Three different adhesive systems, a one-component polyurethane adhesive, a melamine–urea–formaldehyde adhesive and a melamine–urea–formaldehyde adhesive modified by means of (polyvinyl)-acetate adhesive were investigated and compared. Short-term conditioning by submersion in boiling cement suspension was found to be a reliable method for testing the bonding performance rather than long-term conditioning. In the case of tensile shear tests of samples subjected to long-term treatment, wood material strength was the decisive criterion. Generally, tensile shear test samples of all investigated adhesives achieved reliable bonding for a pressing force up to 1.0 MPa. No relationship was recognised between the determined bonding failure and the wood properties tensile shear strength, wood failure percentage, fracture pattern and bulk density of veneers adjacent to the bond line. For the determination of the bond line integrity of curved veneer poles, it was necessary to test bonding quality in a combined test using curved and flat samples and to compare tensile shear strength with data determined on reference samples in the same veneer population without bond line.

Short-term lime solution-kaolinite interfacial chemistry and its effect on long-term pozzolanic activity

Abstract Soils stabilization with lime addition is a widespread technique in geotechnical field. Better understanding of interaction mechanism is central for optimization of the technique. In the present work, the short-term kaolinite-lime solution interfacial chemistry and the effect on the dissolution and long-term reaction has been investigated. Calcium adsorption from saturated lime solution (i.e. simulated alkaline pore solution ([Ca] = 22 mmol/l and pH = 12.63)) characterized by initial fast uptake followed by slower adsorption rate curves, whereas only initial fast uptake is identified from chloride solution ([Ca] = 22 mmol/l and pH = 7). Species of calcium available for adsorption are strongly dependent on the pH conditions (i.e. Ca2+ at pH 7 and CaOH+ at pH 12.63). The adsorption increased with increasing initial concentration of calcium. On the other hand, the more the quantity of calcium adsorbed, the less the measured concentration of silicon and aluminum in the supernatant. The adsorbed calcium distribution has been mapped using μ-XRF. Regardless of the quantity of calcium adsorbed, homogeneous distribution has been identified suggesting coating of kaolinite particle by adsorbed calcium. The coating in turn prevented the kaolinite particles from alkaline attack and retards long-term pozzolanic reaction.

An innovative FRP fibre for concrete reinforcement: Production of fibre, micromechanics, and durability

An innovative FRP fibre is proposed for concrete reinforcement as an alternative to the corrosion-susceptible steel fibres and to fill in the performance gap in the polymer fibre reinforced concretes. Vacuum infusion technique was employed to produce glass- and carbon-fibre-reinforced FRP which was cut to produce FRP fibres with strengths ranging from 194 to 953 MPa. The interface between the FRP fibre and cementitious matrix was assessed by studying the reinforcing mechanisms and failure patters in single fibre pullout tests. The durability of the fibres was investigated in terms of changes in tensile- and bond strength following their exposure to an alkaline environment. Further, SEM images were also obtained to observe any morphological changes on the surface of the FRP fibres due to potential alkaline attacks. A greater pullout resistance of FRP fibres over traditional straight and some of the hooked steel fibres was observed. Overall, FRP fibres showed good alkaline resistance. While the GFRP fibre revealed small reductions in strength, the CFRP fibre showed no such decline. There was likewise no reduction in bond strength involving either of the types of fibre. In both cases, no morphological or chemical changes could be observed under the SEM-EDX either.

Long-term material properties of circular hollow laminated veneer lumber sections under water saturation and cement alkaline attack

ABSTRACTInnovative beech laminated veneer lumber (LVL) circular hollow sections for the use as temporary geotechnical soil nailing systems are currently being developed. Due to the permanent subsoil cement embedment, combined with high water saturation and permanent loading, the timber sections will lose strength and stiffness over time to a degree currently unknown. This paper presents the tensile and bending material properties of flat and curved beech LVL under various periods of immersion in a water–cement grout solution aiming at inducing both water saturation and long-term alkaline attack of the timber. In total, 824 and 279 samples were tested in tension and bending, respectively. Results show that samples manufactured from 3 mm thick veneers result in tensile strength and stiffness 17% and 24% higher, respectively, than samples manufactured from 2 mm thick veneers. A reduction in the initial bending and tensile strength of up to 70% was found after 90 days of water saturation and cement contact. Taking into account a duration of load factor for permanent loading of two years, it is recommended to reduce the short-term tensile and bending strength of beech circular hollow sections to be used as geotechnical anchors by 80%.

Electrochemical Evaluation of the Influence of Surface Treatment Used on the AA6063T5 Alloy

Three AA6063T5 alloy samples were investigated: as received, trimmed and polished mechanically and chemically treated. The mechanical treatment was performed using sandpaper SiC of sizes 320 to 4000 and the chemical was performed using an aqueous solution containing a mixture of hydroxide, sulfate and sodium chloride. All samples were physically characterized by X-ray diffractometry (XRD), hardness measurements, scanning electron microscopy (SEM) and optical microscopy (OM), and by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. The SEM images showed that the presence of intermetallic particles on the alloy surface decreases after the chemical treatment compared to the mechanical treatment. The EIS results showed that the chemical treatment offers higher resistance to corrosion than those submitted to the other treatments, because the alkaline attack used dissolved most precipitates containing Fe or Cu, elements responsible for cathodic sites. Washing with HNO3 through which the chemically treated sample passed probably reinforced the oxide layer, making the surface of the alloy more resistant to attack by chloride.

Comparative study on open air burnt low- and high-carbon rice husk ash as partial cement replacement in cement block production

This study analyzes the feasibility of using high-carbon content rice husk ash waste generated from open air burning of rice husk, as secondary raw materials in the manufacture of cement blocks. Solid masonry blocks having the size of 215mm × 105mm × 65mm, were cast with the mix proportion of 1:5 cement and sand. Blocks were manufactured with two types of rice husk ash (RHA); low-carbon content RHA and high-carbon content RHA. Cement blocks, at four different RHA replacement levels of 5%, 10%, 15% and 20% were prepared for low and high-carbon RHA as partial cement replacement. Testing was included for workability (water/binder ratio and setting time), strength (compressive, flexural bending and splitting tensile) and durability (water absorption, sorption, acid attack resistance and alkaline attack resistance). Results from this test results indicate that the workability, mechanical and durability characteristics of low-carbon RHA cement blocks slightly better than that of high-carbon RHA cement blocks. However, both RHA replacement cement blocks satisfy the limit recommended by standards. Even, high-carbon RHA replacement cement block does not vastly improve the strength or durability properties, the economic and environmental benefits encourage to use high-carbon RHA in cement block production.

Performance of coconut coir reinforced hydraulic cement mortar for surface plastering application

This study was to investigate the effect of coconut coir on the strength and durability properties of cement-lime surface plaster mortar. The purpose of adding coconut coir into the mortar was due to coconut coir had a capacity in controlling cracking in the mortar. In this study, total 115 samples were prepared which were 100 cubes (150mm×150mm×150mm) and 15 beam prisms (100mm×100mm×500mm). Testing was included; water absorption, porosity, sorption rate for physical properties; acid attack resistance, alkaline attack resistance for durability properties; compression and flexural bending for strength properties. The samples were tested with mortar containing 0.125%, 0.25%, 0.50% and 0.75% of coconut coir. The percentage of coconut coir fraction was calculated based on the cement, lime, sand mix by mass. Test results show that, although compressive and flexural bending strength are not improving, but post crack properties such as ductility, residual strength, and toughness are increased with higher coconut coir fraction in the matrix.