Varying Cement Contents Research Articles

Influence of Laboratory Compaction Method on Compaction and Strength Characteristics of Unbound and Cement-Bound Mixtures

During road construction, granular materials for the unbound base course (UBC) and cement-bound base course (CBC) are mostly compacted by vibratory rollers. A widespread laboratory test for determining the optimal moisture content (OMC) and maximum dry density (MDD) of the mixture for installation in UBC and CBC is the Proctor test. Considering that the Proctor test does not produce any vibrations during compaction, this paper compares the Proctor test and the vibrating hammer test. The examination was conducted on UBC and CBC with varying cement content and aggregate types. All mixtures were compacted by both methods with the aim of determining the compaction and strength characteristics. The results indicated the high comparability of the two test methods for mixtures with natural aggregate in terms of MDD, OMC, density and strength characteristics (California bearing ratio (CBR) for UBC and 28-day compressive strength for CBC). For mixtures with higher cement content, the OMC difference depending on the laboratory compaction method used can be significant, so the laboratory compaction method should be chosen carefully, particularly for moisture-susceptible materials. This paper also reveals that by increasing the proportion of rubber in the mixture, the compaction and strength characteristics differ significantly due to the compaction method. Therefore, when using alternative and insufficiently researched materials, the compaction method should also be chosen carefully.

Influence of additives on the structural performance of cement-stabilised rammed earth

The influence of additives on the structural behaviour of cement-stabilised rammed earth was investigated through an experimental programme based on 13 different mixes with varying cement contents (6, 8 and 10% by earth weight) and three different types of additives (superplasticiser, air-entraining agent (AEA) and hardening accelerator). In total, 156 specimens were fabricated and tested at 7 and 28 days in order to compare their compressive strength and other properties such as stress–strain relationships, shrinkage and workability. The results highlighted the essential role of cement in increasing the compressive strength of the material. Specifically, cement contents of 6%, 8% and 10% corresponded, respectively, to strength increases of 41%, 80% and 92% compared with the reference mix with a mean compressive strength of 1.15 MPa. The AEA was found to be the most effective additive for increasing the compressive strength, with obtained strengths of up to 2.93 MPa (an increase of 155% compared with the reference mix). The efficiency of each mix was evaluated through a strength/cost ratio. In addition, an overall comparison of compressive strength, shrinkage, deformation, cost and workability was performed using an analytic hierarchy process. Finally, the experimental results were compared with the mechanical requirements of various codes.

Durability properties of modified ultra-high performance concrete with varying cement content and curing regime

Cement based fibre reinforced composite material has made advancements into Ultra-High Performance Concrete. Concrete is the most widely used man made material used in construction. Ultra High Performance Concrete (UHPC) gives better mechanical and durability properties. Mechanical and durability properties of UHPC can be influenced by various types of curing treatments and amount of cement used. This research focuses on the effect of cement content and different types of curing conditions in strengthening Ultra-high performance concrete. Initially the amount of cement content used in strengthening UHPC was varied from 10 to 25%. Subsequently the compressive strength and durability behaviour of various mixes as per ASTM codal provisions was found after 28 days of heat, steam and normal curing. The temperature maintained was 200°c for heat curing and 90°c for steam curing for about 24 h. The main objective to this study is focused on the mechanical and durability behavior of UHPC. Test results show that a maximum compressive strength of 180.9 MPa is attained with accelerated curing regime, which denotes a 30% incremental in compressive strength attainment. In 28 days of sulphate attack, it is found that the thickness of the concrete increases from 0.2% to 1% in steam curing when compared to other two curing regimes.

Experiment Investigation and Physical Performance of Geopolymer Fly Ash Bricks

In India an approximate 400-500 million metric tons of fly ash are generated annually from thermal power plant. Maximum use of fly ash is necessary for the sustainable development. In this research, an attempt has been made to develop a method for manufacture of bricks using fly ash geopolymer technology. The influence of cement content in geopolymer fly ash based bricks has been studied. The fly ash, cement, silica fumes mixed with 2 molar of alkaline solution with varying cement content from 0% to 15% and heat curing at 100°C for 24 hours. Bricks were tested for compressive strength, flexure strength, water absorption, efflorescence. The compressive strength, flexure strength of the bricks increases with increase in with cement content up to certain limit then decreases. Efflorescence of bricks are slight as per IS1077:1992. Water absorption of geopolymer fly ash bricks are within limit as per IS1077:1992.

Suitability of stabilized copper slag and fly ash mix for road construction

PurposeIndustrial wastes such as copper slag and fly ash are being generated in tons every year and disposed mainly by land fillings, resulting in wastage of useful land. Copper slag in itself is a granular cohesionless sand-like material, while fly ash is highly pozzolanic. The purpose of this paper is to investigate copper slag and fly ash mixes with cement as stabilizer for their proper use in road construction.Design/methodology/approachDifferent trial mixes of copper slag and fly ash were tested for obtaining the optimum mix having maximum dry density. Cylindrical specimens were prepared using optimum mix with different proportion of cement (3, 6 and 9 per cent) and cured for period of 7, 14 and 28 days in desiccator. Several tests such as proctor test, unconfined compressive strength test, splitting tensile strength test and soaked CBR test were carried out.FindingsAfter analyzing the variation of test results with varying cement content and curing period, maximum compressive strength of 10 MPa and maximum tensile strength of 1.5 MPa was found for specimen having 9 per cent cement content cured for a period of 28 days. It was concluded that copper slag and fly ash when mixed in optimum proportion and stabilized with 6 and 9 per cent cement can be effectively used as granular material in sub base and base layer of road pavement.Originality/valueA typical flexible pavement section was designed and checked using IITPAVE software which gave desired results. This paper may add value in the areas of pavement design, waste utilization, etc.

INVESTIGATION OF THE EFFECTS OF DIFFERENT NATURAL FIBERS ON THE STRENGTH OF COMPRESSED STABILIZED EARTH BLOCKS (CSEB)

This study investigates the most effective combination of natural fibers (namely coconut coir,abaca, and maguey) used as reinforcement for Compressed Stabilized Earth Blocks (CSEB). Portland cementand 0.25% fibers by weight were used to stabilize and reinforce CSEB, respectively. The blocks were madeprimarily with Manila soil and were formed using hand-pressed machine. CSEB without fibers were firsttested with varying cement contents of 6%, 8%, 10%, and 12% by weight. This was examined to determinethe practical cement content (PCC). Three strength tests namely dry compressive strength, wet compressivestrength, and flexural strength were conducted on CSEB at PCC with different fiber combinations of coir,abaca, and maguey fibers to determine the mix producing maximum strength. The highest dry compressivestrength was obtained with 100% maguey fiber; the highest wet compressive strength was obtained with100% abaca fiber; while the highest flexural strength was obtained with 17% coir fiber, 17% abaca fiber, and67% maguey fiber. Using the Response Surface Methodology (RSM), the maximum strengths were predictedas follows: 100% maguey for dry compressive strength, 100% abaca for wet compressive strength, and38.4% abaca and 61.6% maguey for flexural strength. However, the optimal mix of CSEB for three thestrength tests consists of CSEB with 42.5% abaca and 57.5% maguey. The fibers were found to improve theperformance of the block such as the strength and post-crack behavior. Furthermore, the performances of awall made of fiber-reinforced and unreinforced CSEB were investigated. The test results showed a 33.79%increase in load carrying capacity of the fiber-reinforced wall compared to unreinforced wall.

A practical method for estimating maximum shear modulus of cemented sands using unconfined compressive strength

The composition of naturally cemented deposits is very complicated; thus, estimating the maximum shear modulus (Gmax, or shear modulus at very small strains) of cemented sands using the previous empirical formulas is very difficult. The purpose of this experimental investigation is to evaluate the effects of particle size and cement type on the Gmax and unconfined compressive strength (qucs) of cemented sands, with the ultimate goal of estimating Gmax of cemented sands using qucs. Two sands were artificially cemented using Portland cement or gypsum under varying cement contents (2%–9%) and relative densities (30%–80%). Unconfined compression tests and bender element tests were performed, and the results from previous studies of two cemented sands were incorporated in this study. The results of this study demonstrate that the effect of particle size on the qucs and Gmax of four cemented sands is insignificant, and the variation of qucs and Gmax can be captured by the ratio between volume of void and volume of cement. qucs and Gmax of sand cemented with Portland cement are greater than those of sand cemented with gypsum. However, the relationship between qucs and Gmax of the cemented sand is not affected by the void ratio, cement type and cement content, revealing that Gmax of the complex naturally cemented soils with unknown in-situ void ratio, cement type and cement content can be estimated using qucs.

Fatigue Assessment of Cement-Treated Base for Roads: An Examination of Beam-Fatigue Tests

AbstractThis paper presents an examination of the fatigue characteristics of cement-treated base (CTB), a cement-stabilized material for use in road pavement construction based on CTB beam test specimens prepared and tested under laboratory conditions. The beam fatigue protocol for asphalt concrete, following the Austroads standard test method of AG:PT/T233, were adapted to examine the fatigue characteristics of the CTB test specimens. Standard road base (Granite/Diorite) from the local quarry in Western Australia was employed as the parent material of CTB. The beam-fatigue tests were conducted under the strain-controlled (constant strain) and stress-controlled (constant stress) testing conditions with varying cement contents (3–10%) of CTB test specimens. Two different loading waveforms of sinusoidal and haversine load curves were also investigated. The results show that for the strain-controlled testing condition, the fatigue characteristics of the CTB test specimens were not affected by the difference ...

Critical State Parameters of Dredged Chennai Marine Clay Treated with Low Cement Content

The present article discusses the stress–strain behavior and critical state parameters of the dredged Chennai marine clay stabilized with low cement content (2.5–10%). A series of one-dimensional consolidation tests and consolidated undrained tri-axial tests are performed on the cement stabilized dredged Chennai marine clay to evaluate the critical state parameters (λ, κ, M, Г, N) for varying cement contents and curing days. The results show that the slope of the critical state line M increases with an increase in the cement content. The parameter λ for the treated marine clay increases up to a cement content of 7.5% followed by a reduction. The parameter κ decreases with the addition of cement content. Finally, empirical formulations are proposed to predict the critical state parameters as the functions of the cement's contents and curing days.

BRIEF EVALUATION OF MASS LOSS INDEX, WATER ABSORPTION AND COMPRESSIVE STRENGTH REVERTIBILITY COEFFICIENTS OF PAPERBRICKS IMMERSED IN WATER

With the need to develop alternative, lightweight cheaper bricks for masonry which will be durable, paperbrick produced with varying cement content of 3 – 18 wt. % and fixed sand content of 20 wt. % were immersed in water for seven days, it was observed that with increasing cement content and curing ages, compressive strength revertibility increased. Weight loss index also reduced with higher cement content and longer curing days and concluded that higher cement content and longer duration periods produce more water durable paperbricks.

Performance Studies on Cement Stabilized Gravelly Soil Exposed to Sulfate Environment

Soil is being used as construction material worldwide since decades for construction of flexible pavements, embankments and brick making. Many methods have been tried for improving the characteristics of soil to make it suitable for intended purpose. Stabilization of soils in order to improve strength and durability properties often relies on additives such as cement, lime, fly ash, and asphalt emulsion. These materials are low-priced, relatively easy to apply and provide benefits to different soils. In the present study, comprehensive laboratory work is carried out on the durability characteristics of cement stabilized gravelly soils exposed to three sodium sulfate solutions with sulfate concentrations of 1, 3 and 5 %, with exposure periods up to 6 months. Two types of soils, namely clayey gravel (GC) and silty gravel (GM) are stabilized with varying cement content ranging from 4 to 14 % by dry weight of the soil in increments of 2 %. As per the results, the compressive strength gain of CSGM cubes with age continued with addition of cement whereas compressive strength gain of CSGC cubes with age increased with increase in cement content up to 6 % and thereafter decreased.

Underground void filling by cemented mill tailings

Underground mining always create voids. These voids can cause subsidence of surface. So it is always a demand to fill the void in such a manner that the effect of underground mining can be minimized. Void filling using mill tailings especially in metal mining is one of the best techniques. The tailings produced in milling process have traditionally been disposed in tailing ponds creating a waste disposal and environmental problems in terms of land degradation, air and water pollution, etc. This disposal practice is more acute in the metal milling industry where the fine grinding, required for value liberation, results in the production of very fine tailings in large percentage. This paper includes discussions on the effectiveness of different paste mixes with varying cement contents in paste backfilling operations. The results revealed that material composition and use of super plasticizer strongly influenced the strength of cemented backfill.

Influence of Powder and Paste on SCC Using Recycled Concrete Aggregate

The use of recycled concrete aggregate is an important issue for preserving the natural resources, protecting the environment, saving of energy and for sustainable development. In this study, a unique simple mixture proportioning method was successfully adopted for developing SCC based on the absolute volume concept, starting with a volume of paste with maximum aggregate size of 20 mm. The method involved very few trials with different types of aggregate that can be advantageously used in field practice. The volume of paste chosen was 0.38 to 0.43 fraction of the total mix. Natural crushed angular granite and recycled demolished concrete waste were used as aggregate for making SCC with fly ash as filler. SCC and vibrated normal concrete mixes were made for varying cement contents of 300 kg/m 3 to 450kg/m 3 and for a constant water content of 185 l/m 3 . Cubes of 150 mm size were cast and tested for compressive strength at different ages of 7, 28 and 60 days. The results indicate that higher paste content not only makes the mix more cohesive with better lubrication of aggregates, but also increases the slump flow (reduces yield stress) and compressive strength. The 28 day compressive strength of SCC with both natural and recycled concrete aggregate showed higher compressive strength than vibrated normal concrete and significant increase at later age, possibly due to pozzolanic activity of the filler material (fly ash). However, the compressive strength of SCC mixes with recycled concrete aggregate has a lower value, when compared with SCC mixes of natural crushed angular granite aggregate at the same age. The study clearly shows the importance of paste in SCC and the advantage of using recycled concrete aggregate with better performance than the vibrated normal concrete with natural crushed aggregate and can go a long way in conserving the natural resources by the use of recycled concrete aggregate for sustainable development.

Evaluation of the effect of marine salts on urban built infrastructure

This paper presents the results of a study that evaluated the effects of marine salts on built infrastructures at the Port city of Chittagong in Bangladesh. Specimens made from five different types of mortars (normally used as external renders in built infrastructures such as buildings and bridges) with varying cement contents were exposed to atmospheric environment at 12 sampling stations scattered around the metropolitan area of Chittagong. The performance of the specimens was evaluated based on marine salt deposition and resistance to marine salt penetration. The study also monitored the deposition of chlorides and sulfates in wet candle sensors located at 12 stations. The type and amount of salts captured in powdered samples extracted from the mortar specimens as well as from wet candle sensors were determined using ion chromatography. The study showed that the marine salt deposition is significant up to a distance of about 200 m from the seashore. The analysis of deposition and subsequent penetration of marine salts in exposed specimens identified the mortar types that are more resistant to the aggressive potential of the region's marine aerosol. The results of this study can be very useful for local authorities engaged in selecting protective measures (in terms of external renderings) to improve the durability of infrastructures exposed to marine salts.

Evaluation of the aggressive potential of marine chloride and sulfate salts on mortars applied as renders in the Metropolitan Region of Salvador – Bahia, Brazil

In recent years, growing interest has focused on determining the performance of materials and evaluating the service life of structures exposed to various environmental forces. In this context, the determination of the aggressive potential of marine salts on mortars used as external renders is critical. The present study aimed to evaluate the spatial distribution of marine salts relative to distance from the sea. This was done by monitoring the deposition rate of chlorides and sulfates in wet candle sensors, located at nine stations scattered around the Metropolitan Region of Salvador, state of Bahia, Brazil. The study also determined the effectiveness of water-soluble salts at penetrating three different types of mortars of varying cement content via deposition and diffusion. The methodology employed enabled an evaluation of the efficiency of the monitoring sensors' measurement of the aggressiveness potential of local marine aerosol, and determination of the comparative performance of the three mortars tested, from the standpoint of resistance to salt penetration. The type and amount of salts captured both in solution and in powder samples extracted from the mortars were determined by ion chromatography. The analysis of the various types of mortars tested indicated which types are more resistant to the aggressive potential of the region's marine aerosol and the distance from the shore where local buildings are liable to be most strongly affected.

A cement based syntactic foam

In this study, a cement based syntactic foam core was proposed and experimentally investigated for composite sandwich structures. This was a multi-phase composite material with microballoon dispersed in a rubber latex toughened cement paste matrix. A trace amount of microfiber was also incorporated to increase the number of mechanisms for energy absorption and a small amount of nanoclay was added to improve the crystal structure of the hydrates. Three groups of cement based syntactic foams with varying cement content were investigated. A fourth group of specimens containing pure cement paste were also prepared as control. Each group contained 24 beam specimens. The total number of beam specimens was 96. The dimension of each beam was 30.5 cm × 5.1 cm × 1.5 cm. Twelve foam specimens from each group were wrapped with plain woven 7715 style glass fabric reinforced epoxy to prepare sandwich beams. Twelve cubic foam specimens, three from each group, with a side length of 5.1 cm, were also prepared. Three types of testing, low velocity impact test and four-point bending test on the beam specimens and compression test on the cubic specimens, were conducted to evaluate the impact energy dissipation, stress–strain behavior, and residual strength. Scanning electron microscope (SEM) was also used to examine the energy dissipation mechanisms in the micro-length scale. It was found that the cement based syntactic foam has a higher capacity for dissipating impact energy with an insignificant reduction in strength as compared to the control cement paste core. When compared to a polymer based foam core having similar compositions, it was found that the cement based foam has a comparable energy dissipation capacity. The developed cement based syntactic foam would be a viable alternative for core materials in impact-tolerant composite sandwich structures.

Evaluation of paste backfill mixtures consisting of sulphide-rich mill tailings and varying cement contents

Using mill tailings to produce paste backfill is a relatively new technique. The most important way in which paste backfilling is beneficial is through mine reclamation and elimination of adverse environmental effects of the tailings. This article includes discussions on the effectiveness of different paste mixes with varying cement contents and slump values in a paste backfilling operation in a sulphide-rich environment at a copper–zinc underground mine in northeast Turkey. The chemical composition, mineralogy, specific gravity, particle size distribution, and the index rheology tests have been presented. A total of 219 paste samples prepared from mill tailings (tailings samples T1 and T2) were tested at 3, 7, 28, 90, and 180 days for uniaxial compressive strength (UCS). The objective of the study was to determine the rheological properties of the mill tailings with respect to paste production and determine the strength gain of the tailings with the addition of PKC (Portland composite cement)/B-type binder currently used in the pasteplant. Additionally, PKC/A-type binder was chosen to compare the tailings in terms of strength gain. It was found that for high sulphide bearing tailings, neither binder was effective or suitable to provide adequate long-term strength for paste backfilling operations, although paste backfill samples developed high early strength at 28 days of curing. Alternatives such as sulphate-resistant-based binders or desliming of the tailings should be investigated by additional tests for improving paste backfill strength performance.

Effect of varying cement content and curing conditions on the properties of sarooj (artificial pozzolana)

This paper describes research carried out at Sultan Qaboos University on the use of the local pozzolanic material, known as sarooj, with Portland cement. Sarooj was the major constituent and cement was used as an additive with various percentages, as used in restoration of historical monuments around the country. Seven mixes with the proportion of sarooj=1.0, sand=0.4, cement=0.2 and water=0.5 were cured for different durations in air and water to establish the best curing conditions suitable for the hot humid conditions of the Gulf region (28–45°C, R/ H 60–80%). In addition, four groups of mixes (sarooj, sand, cement, water), each containing 11 mixes with cement content varying from 0 to 100% by mass of sarooj were tested to study the effect of varying the amount of cement on the strength characteristics. It was found that curing in the sun produced the highest strength results. The cement/sarooj ratio by mass was about 0.6.

Brazilian tensile strength test of lightly cemented sand

Tensile stress – tensile strain relationships for lightly cemented sand specimens obtained by conducting Brazilian tensile strength tests have been presented. The tensile strain measurement was done by using an optical image analysis technique. In addition to the tensile strength tests, some unconfined compression tests on sand specimens with varying cement contents were also performed. Based on the results of the above tests, a nondimensional tensile stress – tensile strain relationship has been presented. Also the variation of the tensile and compressive strength and strain ratios with varying cement contents have been discussed. Key words : lightly cemented sand, optical image analysis, tensile strain, tensile strength, unconfined compression strength.

Strength characteristics of Portland-limestone cements

Portland-limestone cements have been investigated in which up to 25% limestone has been used to replace the Portland cement clinker. Strength development in standard tests has been compared with that in constant workability concrete at varying cement contents. The latter has been shown to be a more meaningful guide to overall performance. The addition of 5% limestone had little effect on performance although at higher addition rates the properties of the limestone were shown to be significant. The suitability of the cements for use in a range of designed strength concretes has been demonstrated.