Fine Aggregate Content Research Articles

Mix Design and Mechanical Properties of High-Performance Pervious Concrete.

The mechanical properties of traditional pervious concrete are insufficient, which limits its application. In view of the imperfections of traditional permeable concrete in mechanics, this paper aimed to find a suitable material composition that can be used as a feasible mix design of high-performance pervious concrete, to essentially improve its mechanical properties. Based on the view that concrete is a two-phase material, in order to understand the rheological properties of the matrix, it was subjected to a rheological test, and then the filler aggregate was uniformly incorporated into the aforementioned matrix to further explore the composition and properties of the resulting pervious concrete. For the matrix, the orthogonal array employed was L16(45), which consisted of five factors, each with four levels. Base on the fluidity and compressive strength of the tested matrix, three groups of suitable matrixes mix proportions were selected to serve as the matrix type for pervious concrete mix proportion design. Then, an orthogonal array L9(34), which consisted of four controllable three-level factors, was adopted in the pervious concrete. The parameters investigated included the coarse aggregate size, fine aggregate content, matrix type, and aggregate-to-binder ratio. The test results demonstrate that the key factors affecting the compressive strength of the matrix and the pervious concrete were closely related to the cementitious material. In the matrix, the proportion of the cementitious material was the most important factor, while in the pervious concrete, the type of matrix was the most important factor.

Evaluating the Role of Aggregate Gradation on Cracking Performance of Asphalt Concrete for Thin Overlays

Thin asphalt concrete overlays are a maintenance technique that mainly restore the functional properties of pavements. One of the main issues in thin overlays is reflective cracking that can cause early deterioration and reduce their service life. For this reason, the purpose of this investigation is to evaluate the effect of material selection on cracking performance of asphalt concrete mixtures for thin overlays. In particular, this paper evaluates the role of aggregate skeleton gradation. The study of the effect of aggregate gradation was divided into two stages: (1) fine fraction content and (2) maximum nominal aggregate size. Based on this, up to seven asphalt mixture gradations were designed and evaluated through the Fénix test at different test temperatures. The results showed a significant correlation between the fine fraction content, and maximum nominal aggregate size, and the cracking performance of the asphalt concrete mixtures. Mixtures manufactured with a low content of fine aggregates, as well as small nominal maximum size, experienced a further improvement of their toughness. These results reflected the importance of considering not only the effect of asphalt binder and environmental conditions but also aggregate gradation in the design of asphalt concrete mixtures in order to achieve a desirable cracking performance.

Effects of pretreated fine lightweight aggregate on shrinkage and pore structure of ultra-high strength concrete

In this paper, effects of fine lightweight aggregate (LWA) contents and their pretreatment methods on mechanical performance, shrinkage and pore structure of ultra-high strength concrete (UHSC) were investigated. Two pretreatment methods, namely, normal soaking and vacuum saturation were applied to study their effect on internal curing performance of LWAs as compared with un-treated LWAs. In general, the pretreated fine LWA effectively enhanced the flexural strength of UHSC specimens especially at later ages, while no significant improvement was observed for the compressive strength. Pretreated fine LWA using normal soaking and vacuum saturation provided internal curing water for progressive hydration, and enhanced the microstructure at the interface of LWA and the bulk paste. The pretreated fine LWA reduced the autogenous and drying shrinkage. The maximum efficiency was obtained when 10 to 15% fine LWA was used. Pretreated fine LWA under the vacuum condition was the most effective method. This method helped to maintain the internal RH of UHSC for a longer period and decreased the mass loss by reducing the total porosity of the UHSC.

The Nature-Inspired Metaheuristic Method for Predicting the Creep Strain of Green Concrete Containing Ground Granulated Blast Furnace Slag

The aim of this study was to develop a nature-inspired metaheuristic method to predict the creep strain of green concrete containing ground granulated blast furnace slag (GGBFS) using an artificial neural network (ANN)model. The firefly algorithm (FA) was used to optimize the weights in the ANN. For this purpose, the cement content, GGBFS content, water-to-binder ratio, fine aggregate content, coarse aggregate content, slump, the compaction factor of concrete and the age after loading were used as the input parameters, and in turn, the creep strain (εcr) of the GGBFS concrete was considered as the output parameters. To evaluate the accuracy of the FA-ANN model, it was compared with the well-known genetic algorithm (GA), imperialist competitive algorithm (ICA) and particle swarm optimization (PSO). Results indicated that the ANNs model, in which the weights were optimized by the FA, were more capable, flexible and precise than other optimization algorithms in predicting the εcr of GGBFS concrete.

Bentonite replacing part of cement concrete for resistance to chloride ion attack

Bentonite is known as a kind of natural pozzolan that can improve the mechanical properties of cementitious materials and reduce the overall CO2 output of cement production. This study is designed to evaluate the feasibility of using bentonite as a substitute for cement in concrete and analyze the effect of bentonite on resisting chloride ion penetration. The concrete was replaced by equal-quality bentonite for 0%, 5%, 10%, 15% and 20% cement respectively, and the water-cement ratio, fine and coarse aggregate content remained constant. The results indicated that as the bentonite content increased, the compressive strength of the mixes increased first and then decreased. The sample containing 10% bentonite got a higher compressive strength than the other samples. The rapid chloride migration (RCM) tests showed that the samples containing bentonite had better resistance to chloride ion attack than samples without bentonite against chloride, especially the sample containing 10% bentonite. It can be concluded that the concrete with 10% bentonite can improve the resistance to chloride ion diffusion with high compressive strength.

Production and optimization of eco-efficient self compacting concrete SCC with limestone and PET

This study aims to produce and optimize Eco-efficient self-compacting concrete (SCC) mixes using multi-waste substitutions. The main input parameters of mixes were total binder, fine aggregate and water contents whereas slump flow and compressive strength were the two main operational responses of produced concrete. Limestone powder (LP) and waste Polyethylene Terephthalate (PET) were used in concrete as parts of cement and fine aggregate respectively with high range water reducing admixture (SP) as part of water. Response Surface Methodology (RSM) and multi-objectives optimization using Minitab 17 statistical software were employed for this purpose.Twenty SCC mixes were designed and checked experimentally using Central Composite Design (CCD) concept in RSM. Mathematical models were established and evaluated using analysis of variance test (ANOVA) according to the experimental results. This is in order to define the effectiveness degree of design parameters on the properties required and to adjust the derived mathematical models. Multi-objectives optimization process was adopted to determine the optimum values of the input parameters. The optimization revealed that the optimum values of the input factors, LP, PET and SP were 20.1%, 2.4% and 1.16% by weight respectively. These theoretical values were checked experimentally and the achieved responses were quiet similar or higher than the best proposed mix.It was deduced that the developed models can be used to ensure a speedy mix design process by achieving maximum tested properties of eco-efficient SCC.

Reliable Neural Networks for Proportioning of Concrete Mixes Containing Cement Replacement Materials

Abstract Artificial neural network (ANN) is one of the most suitable analytical methods used for modeling complex relationships between concrete properties and concrete mix ingredients. In the present study, common ANN is first trained to predict concrete mix proportions using experimental data sets. Experimental data sets include the content of water, cementitious materials (cement, silica fume, rice husk ash, and natural pozzolanas), coarse and fine aggregates, superplasticizer and the compressive strength, the slump, and the maximum size of the aggregates. Also, statistical analyses are used to correlate the results and the acceptable error. Then, the neural network is retrained using experimental data sets together with analytical data sets that are produced using the Iranian national concrete mix design method, empirical relationships, or both. Finally, the performance of the retrained neural networks is compared with the first one. The results show that the neural networks, which are trained using both analytical and experimental data sets, are more reliable and can be reliably used for modeling of complex relationships.

Microstructure Analysis and Study on Mechanical Property of Cement Compound Based on Constitutive Relation

Cement compound is an important component of building materials. Its microstructure and physical and mechanical properties are affected by admixture. Taking cement compound as the object of study, this study explores the effect of cement compound on the microstructure of cement concrete by adding different contents of coal gangue fine aggregates, as well as reveals the action mechanism of active coal gangue on cement concrete. When the content of coal gangue fine aggregate is 20%, the microstructure is compact. The relationship between compressive strength and axial compressive strength of coal gangue cement concrete is established by testing the compressive property of coal gangue cement compound (CGCC). The stress-strain curve of spontaneous combustion and non-spontaneous combustion of CGCC is obtained, and the compression constitutive model of CGCC is proposed.

Autogenous shrinkage and electrical characteristics of cement pastes and mortars with carbon nanotube and carbon fiber

The autogenous shrinkage and electrical characteristics of cement pastes and mortars incorporating carbon nanotube (CNT) and carbon fiber (CF) were investigated in this study. The dispersion agents for the CNT and CF were polycarboxylate-type superplasticizer and silica fume, respectively. The electrical characteristics of the pastes and mortars were investigated by means of the two-probe method, while the autogenous shrinkage characteristics of the cement pastes and mortars were discussed in the light of the reaction characteristics of cement particles. The effects of the replacement ratio of the CF to CNT, the length of CF, and the fine aggregate content on the autogenous shrinkage and electrical characteristics of the cement pastes and mortars were examined. The test results showed that the CNT addition inhibited the hydration reaction at an early stage of curing, thereby reducing the autogenous shrinkage of the pastes and mortars. The addition of CF mitigated an adverse effect of the addition of fine aggregates on the electrical resistivity of the mortars.

The Performance of Controlled Low-strength Material Base Supporting a High-volume Asphalt Pavement

A lack of proper base and subbase materials in pavement construction is one of the common problems in the tropical region worldwide. In many countries such as Thailand, cementitious materials are usually used for ground improvement. Controlled Lowstrength Material (CLSM) was considered in this study as a pavement base material. The CLSM mixes were prepared by varying cement, fly ash and fine aggregate content. Each mixed component was studied for their physical and chemical properties. After mixing, properties of the CLSM were investigated based on the standard testing of fresh concrete and cement-treated base material. The flowability, setting time and bleeding were checked to ensure that the CLSM were self-compacting. The mechanical properties of hardened CLSM were determined by means of CBR, unconfined compressive strength and resilient modulus tests. The resilient modulus results were used in the analytical design of flexible pavement with CLSM base. The critical traffic data under high-volume road collected by the Thailand Department of Highway was adopted in this study. Results show that the CLSM base considerably increased the performance as well as design life of asphalt pavement compared with the conventional crush rock base pavement.

Design of self-compacting high-performance concrete: Study of mortar phase

The design of self-compacting high-performance concrete (SCHPC) materials, to be applied in marine environments, demands for an adequate selection and combination of constituent materials. In the current study, a ternary mixture of white Portland cement + limestone filler + metakaolin was selected to produce a white SCHPC. Design of experiments approach was employed to investigate the effect of design variables, and their coupled effects, on the relevant mortar properties. Statistical models were developed to predict the fresh state properties, maximum temperature rise (under semi-adiabatic conditions), initial and final setting times and shrinkage deformation of mortars. Metakaolin to cement weight ratio was found to exhibit the highest effect (a negative effect) on workability and on initial/final setting time, which is explained by the high reactivity of metakaolin. The fine aggregate content had the highest effect on both the maximum temperature rise and shrinkage of mortars. Finally, the derived statistical models and a numerical optimization technique allowed finding the best combination of constituent materials to reduce the risk of cracking during the first days, which ensures a more impermeable concrete in the final structure.

High-pressure uniaxial confined compression tests of mortars

The paper presents the development of an experimental setup to perform confined compression tests of cementitious paste, mortar, and concrete specimens at high pressures up to 1 GPa as well as the validation of the multi-scale model for the equation of state (EOS) of mortars. The test results for the EOS show that the secant bulk modulus of the loading branch monotonically increases with the content of fine aggregate. The comparison of the loading branches of the EOS for unsaturated specimens of two different specimen sizes indicates that there is negligible size effect for all types of the mixture compositions. Validation of the multi-scale model proposed previously for the EOS of a cement paste shows good agreement with the test results at the high-stress range with slight deviation at the lower stresses. It was demonstrated on mortars with a water to cement ratio of 0.50 that the Hirsch mixture model shows a good agreement with the test results for all levels of fine aggregate content in mortars.

Performance of Concrete Using Waste Fiber Reinforced Polymer Powder as a Partial Replacement For Fine Aggregate

Proper disposal of fiber waste products is a major problem faced by the FRP industries and hence needs a sustainable solution for its reuse and recycling. The present paper deals with the performance of concrete using waste fiber reinforced polymer powder (FRP), as a partial replacement for fine aggregate in the concrete. Field emission scanning electron microscopy (FESEM) analysis along with energy dispersive X-Ray (EDX) is carried out to find out the elements present in the FRP powder used in the present study. Partial replacement of 5%, 10% and 15% are carried out in the fine aggregate content of control mixture of M30 grade. The workability, compressive strength, split tensile strength, flexural strength, impact and abrasion resistance are measured to observe the effect of waste FRP powder on the concrete. From the study it is observed that workability decreased with increase in percentage of FRP substitution with a considerable increase in strength properties for 10% replacement of fine aggregate content by waste fiber reinforced polymer powder. Also better performance is observed for impact and abrasion resistance

Physico-chemical and mineralogical study of ancient mortars used in Harran area (Turkey)

Very limited studies have been accomplished concerning the historical structures around Harran area. Collected mortar samples from the historic structures in the area were tested to explore their mechanical, chemical and mineralogical properties. Mortar samples from three different points of each historical structure were taken and specified in accordance with the related standards taking into consideration their mechanical, chemical and mineralogical properties. By means of SEM-EDX the presence of organic fibres and calcite, quartz, plagioclase and muscovite minerals has been examined. Additionally, by means of XRF analysis, oxide (SiO2, Al2O3, and Fe2O3) percentages of mortar ingredients have been specified, also. According to the test results obtained, it was confirmed that the mortars had densities ranging between 1.51-2.10 g/cm3, porosity values ranging between 8.89-35.38% and compressive strengths ranging between 5.02-5.90 MPa. Specimen HU, which has the highest durability and lowest water absorption and porosity, was the mortar taken from the most intact building in the mosque complex. This result is most likely due to the very little fine aggregate content of HU. In contrast, HUC mortars with a small amount of fine particles and brick contents yielded slightly lower compressive strengths. The interesting point of this study is the mineralogical analysis results and especially the presence of ettringite in these historic mortars linked to the use of pozzolanic materials. Survival of these historic structures in Harran Area through centuries of use and, also, having been subjected to many earthquakes can probably be explained by these properties of the mortars.

Method for controlling the absorbed water content of recycled fine aggregates by centrifugation

Accurate determination of the absorbed water content of recycled fine aggregates (RFAs) is necessary for proper proportion cement-based mixtures. However, some current standard methods are time consuming and have high operator error. In this paper, we propose an alternative method to control the absorbed water content of RFAs by centrifugation. The rotation speed, centrifugation time, and initial water content are considered as parameters. Ten commercially available RFAs were tested by a single operator with multiple measurements by the centrifugation method, and the results were compared with those obtained by the cone and volumetric flask methods. In addition, the fluidity of the mortar with RFAs and manufactured sand were compared to evaluate the additional water required for saturation. The experimental results indicate that the pre-wetted RFAs can reach the saturated-surface-dry condition after centrifugation at 2000 rpm for 10 min when the centrifugal radius is 6–10 cm, at which the water content can be defined as absorbed water. By comparing the standard deviations with other methods, the absorbed water content can be more accurately and repeatedly controlled by the centrifugation method. The fluidity of the mortar with RFAs including additional water by centrifugation shows a good relationship with that of manufactured sand. Therefore, the centrifugation method can be used to control the absorbed water content of RFAs and applied to mixture design.

Use of incinerator bottom ash in open-graded asphalt concrete

To observe the effects of the use of incinerator bottom ash (IBA) on open-graded asphalt concrete (OGAC), natural fine aggregates are partially replaced by IBA in OGAC. The results indicate that the use of IBA helps improve the adhesive force between asphalt and aggregates. The stability and indirect tensile strength of OGAC are effectively improved by the use of IBA as a replacement material. The natural fine aggregate content in the OGAC is 25%. The results indicate that 80% of natural fine aggregates could be replaced by IBA and demonstrate the feasibility of using IBA in OGAC in engineering applications.

Influence of Fine Aggregate Content on Low-Temperature Cracking of Asphalt Pavements

Abstract Low-temperature cracking occurs on some asphalt pavements even though the high-performance grade (PG) binders are applied in asphalt mixtures. It is neither realistic nor economic to solve the problems related to low-temperature cracking on asphalt pavements by purely using high PG binders. Other factors need to be investigated so that this type of distress can be further restrained. This study focuses on investigating the effect of fine aggregates on the low-temperature cracking on asphalt pavements. Low-temperature cracking was monitored and recorded on asphalt pavements in a cold, northeast area of China. Cores were drilled on the spots where low-temperature cracking occurred, and the aggregate gradations of the drilled cores were analyzed in the laboratory. An index called the Fine Aggregate Content Deviation Index (FACDI) was defined as the difference between the actual fine aggregate content and the lower limit of fine aggregate content in the designed aggregate gradation. A positive relation was observed between the FACDI and the cracking index of asphalt pavements. It was demonstrated that the fine aggregate content was another important factor that influences low-temperature cracking of asphalt pavement. The increase of fine aggregate content was found to jeopardize the resistance of asphalt mixture on low-temperature cracking. Based on FACDI, fine aggregate's contents in asphalt mixtures of asphalt layers can be recommended to ensure an asphalt pavement with good low-temperature performance.

Predicting the drying shrinkage behavior of high strength portland cement mortar under the combined influence of fine aggregate and steel micro fiber

The workability, 28-day compressive strength and free drying shrinkage of a very high strength (121-142 MPa) steel micro fiber reinforced portland cement mortar were studied under a combined influence of fine aggregate content and fiber content. The test results showed that an increase in the fine aggregate content resulted in decreases in the workability, 28-day compressive strength and drying shrinkage of mortar at a fixed fiber content. An increase in the fiber content resulted in decreases in the workability and drying shrinkage of mortar, but an increase in the 28-day compressive strength of mortar at a fixed fine aggregate content. The modified Gardner model most accurately predicted the drying shrinkage development of the high strength mortars, followed by the Ross model and the ACI 209R-92 model. The Gardner model gave the least accurate prediction for it was developed based on a database of normal strength concrete.

Open Graded Asphalt Mixture Design for Environmentally Friendly Road

The road is an important infrastructure to support various economic development. By increasing the population, the constructions of road infrastructure are obviously required and cover more land use area, consequently narrowed the areas for water absorption into the land. Therefore, it is necessary to improve more environmentally friendly of road constructions, in this case is by using open graded asphalt. Open graded asphalt is the mixture of asphalt with low fine aggregate content to produce a high percentage of air voids, which expected to be able to absorb water into the land underneath. This observation uses laboratory experiment method. Materials that are used are natural gravel and the volcanic gravel, 60/70 asphalt penetration and stone dust filler. The tests performed for the samples are Marshall test, falling head water permeability, indirect tensile strength and unconfined compressive strength. The optimum bitumen content for each type of aggregate have been found to be 2.95% for natural gravel and 4.65% for volcanic gravel. Open graded asphalt porosity is 26.52% for natural gravel, whereas the volcanic gravel is 22.31%. The vertical and horizontal permeability for natural gravel are 1.25 cm/second and 0.92 cm/second, respectively. Whereas, for the volcanic gravel is 1.43 cm/second and 1.10 cm/second, respectively. Indirect tensile strength (ITS) value for natural gravel is 59.49 KPa whereas the volcanic gravel is 74.84 KPa. The unconfined compressive strength (UCS) value for natural gravel is 1070.63 KPa, whereas the volcanic gravel is 1120.69 KPa. It is concluded that the open graded porous asphalt is only compatible for low volume traffic road and need improvement to be able to be used as standard road.

Compressive Strength and Abrasion Resistance of Concretes under Varying Exposure Conditions

The purpose of this study is to comparatively evaluate the wear resistance of concretes under abrasion rates. Five concrete mix proportions of a fixed water-cement ratio of 0.45 were considered in the study, but the constituent materials, age of concrete and exposure contact conditions were varied. The coarse aggregate type employed in the study was crushed granite. The compressive strength and abrasion resistance of concretes were tested between at ages 7 to 70 days and 100 - 500 revolutions of abrasion wheels respectively. The study revealed that the compressive strength and abrasion resistance had the optimal performance when the coarse aggregate content was 45% and the worst performance when the fine aggregate content was 28.7% of the total weight of concrete constituents. There was a remarkable loss of concrete particles to wear between 200 revs and 300 revs of abrasion wheel contact. Concrete grade in excess of 60 N/mm2 is required to resist abrasion beyond 200 revolutions of abrasion wheel contact on concrete specimens. Concretes investigated also showed weak resistance to deep abrasion at and above 300 revolutions of abrasion wheel contact.