Days Of Water Curing Research Articles

Effect of D-Galacturonic Acid on Hydration of Cementitious Materials

The extent of modification of the hydration process in a cementitious material by external agents depends on its mix components. In this study, the effect of D-galacturonic acid on the hydration of fiber-reinforced engineered cementitious composites (ECC) and ordinary mortar was investigated. The final setting time was monitored as well as the flexural or compressive strengths during and after 28 days of curing. It was observed that D-galacturonic acid retarded the setting of both materials, and the presence of D-galacturonic acid in the curing water slightly modified their strength attainment. However, in both cases, the extent of the retardation or modification was more severe for the ordinary mortar than the ECC. Moreover, the acid had an insignificant effect on the strength of either hardened ECC or mortar after 28 days of water curing. Therefore, the hydration and resulting modification of ECC by D-galacturonic acid was more tenacious than that of ordinary mortar

Interaction between Engineered Cementitious Composites Lining and Foundation Subsurface Drain

The effect of cyclic loads on the surface profiles of ECC linings cast on foundations comprising crushed stone and compacted soil was investigated. A geotextile was embedded between the crushed stone and ECC lining for some of the samples. After 28 days of water curing, the hardened surfaces were loaded and monitored for roughness and crack development by measuring surface levels and crack widths, respectively. Neither cracking nor significant variations in the lateral profiles were observed on all the samples for all the loads applied. However, significant variations which depended on the foundation types were observed in the vertical profiles. It was concluded that while ECC can resist cracking due to its high strain capacity, its flexibility causes ECC linings to assume the shape of the foundation material, which can increase the surface roughness at certain loading configurations.

Permeability of Steel Fibre Reinforced Concrete Influence of Fibre Parameters

An extensive laboratory investigation was undertaken to study the effects of different fibre parameters on the permeability of steel fibre reinforced concrete. The effects of fibre content, fibre aspect ratio and curing age were studied. Crimped fibres in varying weight fractions of 1.0%, 2.0% and 4.0% and having aspect ratios of 65, 85 and 105 were used. The concrete grade was kept the same throughout. Samples were cast and tested for water permeability after 7, 14, 28 and 60 days of water curing. Plain concrete samples were also cast and tested for reference purposes. Results of the study indicated a significant decrease in the permeability of concrete with the addition of steel fibres. The permeability decreased significantly with increasing fibre content and increasing curing age. The water permeability was observed to increase with increasing aspect-ratio of fibres but the decrease was not very significant. The Analysis of Variance (ANOVA) statistical method was used to evaluate the effects of these factors on the permeability of SFRC. A α level (probability of error) of 0.05 was used for ANOVA test.

Effect of elevated temperature on physico-mechanical properties of blended cement concrete

Pozzolanas are readily available for use in concrete in the local markets for strength and/or durability enhancement. Although safety and security against disasters are not new, they still presuming a challenge. For instance, the fire resistive properties of concrete are of prime interest. Through this work, the effect of different kinds of pozzolana on the fire resistive properties of concrete was studied. Four types of pozzolana were incorporated into the concrete mixtures, i.e. metakaolin (MK), silica fume (SF), fly ash (FA), and ground granulated blast furnace slag (GGBS). Each of the employed pozzolana was used in two ratios: 10% and 20%, either in the form of cement replacement or as an addition without affecting the cement content. A total of 17 mixes were cast. For all mixtures, compressive strength is evaluated after 28 days of water curing. The mixtures’ compressive strengths were also evaluated after exposure to elevated temperatures: 200 °C, 400 °C, 600 °C, and 800 °C. The residual compressive strengths after heat exposure are evaluated. The formed cementitious phases after incorporation of pozzolana and the heat-induced transformations are investigated via the X-ray diffraction technique (XRD). Test results demonstrate the impact of each type of the employed pozzolana on the heat resistive properties of concrete in addition to their influence on the strength development of the investigated mixes. Therefore, a decision could be made regarding optimizing the benefits specific to each type of pozzolana and their employment method.

Correlation between compressive strength and certain durability indices of plain and blended cement concretes

In this study, plain, silica fume and fly ash cement concrete specimens prepared with varying water to cementitious materials ratio and cementitious materials content were tested for compressive strength, water permeability, chloride permeability, and coefficient of chloride diffusion after 28 days of water curing. The data so developed were statistically analyzed to develop correlations between the compressive strength and the selected durability indices of concrete. Very good correlations were noted between the compressive strength and the selected durability indices, particularly chloride permeability and coefficient of chloride diffusion, irrespective of the mix design parameters. However, these correlations were observed to be dependent on the type of cement.

Exploring the Reuse Potential of Chemical Sludge from Textile Wastewater Treatment Plants in India-A Hazardous Waste

Problem statement: This study was conducted to explore the reuse potential of the chemical sludge (considered as hazardous waste as per Indian Government Hazardous Waste Management Rules) generated from combined effluent treatment in textile clusters. These textile clusters mainly cover the cotton dyeing and printing operations. Approach: Therefore, treatability studies of chemical sludge were conducted using solidification/stabilization treatment to examine the possibility of its reuse in construction materials. The sludge was characterised for its physico-chemical parameters and heavy metals. Standard blocks of dimensions 70.6×70.6×70.6 mm were prepared, in which chemical sludge was used as a partial replacement of cement by mixing 30-70 % of sludge in cement. After the experimental curing, the blocks were evaluated for physical engineering properties such as hardening time, block density, unconfined compressive strength. The chemical properties were determined in terms of concentrations of heavy metals in the TCLP leachate. Results: The hardening time ranged between 30-45 h. The compressive strength in the sludge cement blocks ranged from 2.63-22.54 N mm-2 after 14 days of water curing and 6.48-24.89 N mm-2 after 28 days of water curing for 30, 40, 50, 60 and 70 % sludge replacement in cement. The block density varied between 1361. 3408-1813.8992 Kg m-3 after 14 days and 1386.3953-1842.3446 Kg m-3 after 28 days of water curing. The concentrations of heavy metals were negligible in the TCLP leachate and thus below USEPA regulatory limits. Conclusion/Recommendations: As far as structural applications is concerned, it is fulfilling the criteria of some of the classes (C to K) as per the BIS standards of the bricks upto a strength of 25 N mm-2. The use of sludge can definitely be explored for other structural and nonstructural applications depending upon strength requirement. Other applications of textile sludge in the construction materials to be explored by conducting more bench scale studies.

Heat Enduring Cement-Glass Mortar

The present work is an experimental investigation concerned with developing plastering cement mortar characterized by an enhanced heat endurance to act as a heat barrier to rather sensitive materials like Advanced Composite Materials (ACM). For this purpose, finely ground waste glass and finely ground granulated blast furnace slag were introduced into the mortar mixtures. A total of eleven mixtures were cast, each of which comprises six groups of mortar cubes. For all mixtures, compressive strength is evaluated at ages extending from one week to three months. After 28 days of water curing, their compressive strengths were evaluated after exposure to elevated temperatures ranged from 200°C to 800°C. The retained strength after heat exposure is regarded as the heat endurance measure. A mineralogical study was conducted on the mortar specimens before and after exposure to 800°C. As a consequence, the formed cementitious phases and the heat induced transformations are clarified. Test results show that by utilizing either ground glass or ground slag a remarkable enhancement in strength and heat endurance can be achieved. This is due to their pozzolanic nature and superior thermal stability.

Utilization of Basic Oxygen Furnace (BOF) slag in the production of a hydraulic cement binder

Basic Oxygen Furnace (BOF) slag is a major waste product generated during the steelmaking process. In India and in most industrial countries, the use of BOF slag as a road ballast and land filler has had a very long history. This being a low end use, a study was conducted to examine the possibility of converting the slag into a hydraulic binder. This paper describes the effect of cooling rate on mineralogy and cementing characteristics of normal BOF slag as well as iron oxide-devoid BOF slag. Specifically, the mineralogy and compressive strengths of heat-treated slags were compared with a conventional ordinary Portland cement. It was found that the slowly cooled slags did not show any cementing properties. The iron oxide-devoid slag, on slow cooling, disintegrated into fine powder. The water-cured cubic specimens of quenched slag products were tested for their compressive strengths. The cementing properties of the quenched slag products were improved by formation of hydraulic phases and showed considerable strength after 28 days of water curing.

Enhancing Water Resistance of Cement and Gypsum-Cement Materials

In recent years silica fume, a by-product in the production of metallic silicon or ferrosilicon, has gained acceptance for use as a mineral admixture in cementitious materials. The principal areas of application of silica fume include producing high strength concretes and improving concrete resistance to aggressive chemicals. A new application of silica fume for enhancing water resistance of cement and gypsum-cement materials is reported. As a characteristic of water resistance the wet/dry strength ratio of the material was used. The values of strength and the wet/dry strength ratio for hardened cement pastes of various ages, with water to cementitious material ratio varying from 0.33 to 0.50, were obtained. It is shown that, despite the low value at 3 days, the wet/dry strength ratio of cement-silica fume paste rises significantly after 28 days of water curing, achieving the value of pure portland cement paste having the same water to cementitious material ratio, and at 200 days exceeds it, approaching a value of 1. However, the most pronounced improvement of water resistance was fixed for the gypsum-cement materials with 5% addition of silica fume, where the value of the wet/dry strength ratio after 200 days of water immersion increased twice as much, compared with the ratio after 3 days of water immersion. The physical and chemical mechanisms of this improvement are discussed.

Strength and water absorption for gypsum—cement—silica fume blends of improved performance

The present work describes results of testing gypsum—cement—silica fume blends having gypsum binder contents of 65, 75 and 85% at various silica fume/Portland cement ratios: 1/4, 2/3, 3/2 and 4/1. Cases of extra expansion and cracking due to ettringite formation were not revealed. It is shown that the hydraulic properties are developed in time in a diflerent manner for various compositions. Some of the blends achieved a high wet/dry strength ratio exceeding 0·6 after 200 days of water curing. This is explained by the development of a microstructure in which gypsum crystals were engulled by C-S-H. The optimum compositions were revealed by high absolute values of compressive strength in the water-saturated state, as well as low values of water absorption. The high values of water absorption for some compositions together with the low values of strength in the wet state are due to the extra content of silica fume, which is not needed for pozzolanic reaction and can be freely removed from the structure by washing.

Influence of Na 2SO 4 solutions on the capillary absorption and shrinkage of mortars made with cement containing silica fume

Mortars containing cement with silica fume (sf) replacements of 0, 10, 20 and 30% were produced. Following 28 days of curing in water at 20 °C ± 2 °C, the mortars were kept in water, Na 2SO 4 solution of pH = 6 and in laboratory atmosphere at 20 ± 2 °C and 65 ± 5% R.H. The specimens kept in water and sulfate solution were tested for absorption and unit mass, and those stored in air were tested for shrinkage. The coefficient of capillary absorption of 0% sf mortar exposed to sulfate increased up to 3.07 times that of the mortar cured in water while the value for the 30% sf mortar was 0.48; indicating a reduction when exposed to sulfate. The water absorption decreased by 12% at sf replacement of 30%. Shrinkages of the 20% and 30% sf were close to each other and were about 1.5 times that of the 0% and 10% sf, starting with the age of 7 days.

Performance and Correlation of the Properties of Fly Ash Cement Concrete

Abstract This investigation was conducted to evaluate the performance of fly ash cement concrete specimens made by cement replacement levels of 0, 10, 20, 30, and 40% with Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Concrete (ASTM C 618) Class F fly ash. Compressive strength, pulse velocity, porosity, and water permeability were determined after 28, 90, 180, and 360 days of water curing. Reinforced concrete specimens were used to assess the corrosion-resistance of plain and fly ash cement concretes in chloride environments. The corrosion potentials on steel were measured at periodic intervals to determine the time-to-initiation of reinforcement corrosion. The data generated was statistically analyzed to ascertain the relationship between the various properties of plain and fly ash cement concretes. Results indicated a better performance by the 20% fly ash cement concrete than plain cement concrete and those made with other cement replacement levels. A good correlation between porosity, compressive strength, permeability, and porosity was observed.

Effect of grain size on the strength characteristics of cement-stabilized lateritic soils

Lateritic soils are readily available all over Nigeria and as such have attracterd several research studies in recent times, the obvious aim being its utilization in the construction industry. This paper gives an account of the work done to further classify the usefulness and limitations of lateritic soils. Cement was used as the stabilizer and the lateritic soils used were obtained from the Ifewara deposits located about 10 km along Ife-Ifewara Road. A sieve analysis of the sample was made. Five different grain size ranges, from coarse to fine, were extracted from the samples. Cubes were moulded by mixing each grain size range with cement in five different proportions, the optimum water/cement ratio of each mix proportion being determined beforehand. The compressive strengths of the cubes were determined after 7, 21, and 28 days of curing in water, respectively. It was established that the higher the laterite/cement ratio, the lesser the compressive strength, and that the finer the grain size range, the higher the compressive strength. Finally, it was observed that cubes made using laterite/cement mix proportions 1:1 and 3:1 kept gaining strength with age while the others were losing strength.