Influence Of Aggregate Type Research Articles

Study of characteristic specification on mixed mode fracture toughness of asphalt mixtures

Low temperature cracking is one of the main deterioration and failure modes for pavements. Hence, in this paper the effect of asphalt characteristic on its mixed mode I/II low temperature fracture toughness is investigated experimentally. A large number of edge cracked semi circular bend specimens subjected to asymmetric three-point bend loading were tested for different hot mix asphalt mixtures made of various compositions. The influence of aggregate type and size, binder type and air void content were studied on the critical stress intensity factors of four mode mixtures ranging from pure mode I to pure mode II. The fracture toughness results showed the noticeable influence of asphalt characteristic specifications on the low temperature cracking behaviour of mixtures subjected to mixed mode loading.

Effect of Coarse Aggregate Types on the Microstructure of the ITZ and Durability of Concrete

Influence of aggregate types on the impermeability and frost-resistance of concrete with different water/cement ratios were investigated, as well as the pore structure and hydrates of the ITZ. The results show that, concrete prepared with a high water/cement ratio and using granite aggregate, presents the highest values of chloride diffusion coefficient and the lowest numbers of freeze-thaw cycles. Whereas concrete prepared with a low water/cement ratio and using limestone aggregate, obtains the similar durability results. The limestone aggregate with a rough surface and higher water absorption, has a tight bonding with the cement paste. However, the granite and basalt aggregate that formed by magma eruption, have higher activity. The XRD results demonstrate that more clinkers participate in the hydration of cement, therefore, resulting in a denser ITZ. In order to improve the concrete durability, the basalt aggregate both with higher activity and rough surface is consider optimal.

X-ray radiation shielding properties of cement mortars prepared with different types of aggregates

The types of aggregate used play an important role in determining the effectiveness of X-ray radiation protection of cement mortars. Cement mortars were prepared using fine aggregates obtained from six different sources. The influence of aggregate type on X-ray shielding properties was studied. The results showed that mortars prepared with barite and lead-laden recycled cathode ray tube funnel glass provided better shielding properties than mortars prepared with natural sand, natural crushed fine stone or crushed beverage glass. This is attributed to the use of dense aggregates being able to interact with X-ray radiation, thus reducing the depth of penetration. Due to the superior shielding properties of the mortar containing barite, it can be used to replace traditional sand mortar for applications as rendering or plastering materials for the construction of medical diagnostic and CT scanner rooms.

Effectiveness of the traditional parameters for specifying carbonation resistance

This paper presents data on carbonation measurements taken from a range of test specimens stored outside but protected from rainfall. A wide range of concretes were tested that were representative of UK ready-mixed concrete production at ages of between 3·5 and 5·7 years. None of the traditional specification parameters (maximum water/cement (w/c) ratio, minimum cement content and compressive strength class) on their own or in combination give a consistent carbonation resistance. When compared at a fixed w/c ratio of 0·55, there was no clear influence of cement content on carbonation resistance. The measured carbonation depths of the Portland cement concretes were too low to show any influence of aggregate type. When extrapolated to 35 years, in a conservative manner, the data provide no grounds for concern with the BS 8500-1 recommendations with respect to carbonation resistance. There is some indication that the BS 8500-1 recommendations with respect to CEM I concretes may be too conservative. The predicted performance of concrete containing 40% or more fly ash indicates that the particular recommendations set out in BS 8500-1:2006 are justified.

Influence of aggregate type on workability of self-consolidating lightweight concrete

In this study, the effects of aggregate type on the workability of self-consolidating concrete produced with lightweight aggregate (self-consolidating lightweight concrete – SCLC) were investigated. In experiments, three coarse lightweight aggregate (LWA) types, namely pumice, volcanic tuff and diatomite, were used. Different combinations of water/powder ratio and superplasticiser dosage levels were prepared for the self-consolidating lightweight concrete mixtures. The total powder content (cement and mineral additives) was constant in the experiments. Workability tests such as slump flow, restricted slump flow, filling-box, V-funnel, GTM screen stability, L-box and U-box were performed to characterise accurately the flow ability, passing ability and segregation resistance of self-consolidating lightweight concrete in fresh condition. The results, in general, showed that self-consolidating lightweight concrete with lightweight aggregate in low unit weight has higher flow ability and passing ability. The segregation of self-consolidating lightweight concrete was prevented by use of air-entraining admixture in high water/powder ratios. As a result, it was observed that the aggregate type and water/powder ratio has significant influence on the workability properties of self-consolidating lightweight concrete.

The Influence of Aggregate Interaction and Aging Procedure on Bitumen Aging

Abstract Bitumen, like many other organic substances, is affected by the presence of oxygen, ultraviolet radiation, and by changes in temperature. These external influences result in the phenomenon known as “aging” and cause changes in the chemical composition and therefore the rheological and mechanical properties of the bitumen. Aging is primarily associated with the loss of volatile components and oxidation of the bitumen during asphalt mixture production (short-term aging) and progressive oxidation of the in-place material in the field (long-term aging). Both factors cause an increase in viscosity (or stiffness) of the bitumen and consequential stiffening of the asphalt mixture. Aging at moderate levels is generally accepted and can even enhance performance, but at significant levels results in embrittlement of the bitumen, significantly affecting its adhesive characteristics and usually resulting in reduced cracking resistance of the asphalt mixture under repeated loading. It has long been recognized that the characteristics of bitumens are affected by the mineral aggregate with which they come into contact and that age hardening is influenced by both the bitumen and the mineral aggregate as reported by Bell and Sosnovske in 1994. This paper investigates the influence of aggregate type and aging procedure on the rheological and chemical fractional properties of aged bitumen. Asphalt mixtures comprising limestone or granite aggregate have been artificially aged in the laboratory and the rheological properties and chemical composition of the recovered bitumen from the mixtures determined after different durations of aging. In addition, the influence of bulk aging versus thin film aging has been assessed on the same bitumen aged in the presence of aggregate.

Influence of Aggregate Type and Size on Ductility and Mechanical Properties of Engineered Cementitious Composites

The influence of aggregate type and size on engineered cementitious composite (ECC) mechanical and ductility properties was investigated and the results presented in this paper. A micromechanically-based high-performance fiber-reinforced cementitious composite, ECC enjoys improved durability and high ductility due to tight crack width. Microsilica sand (200 μm [0.008 in.] maximum aggregate size) is typically used to produce standard ECC mixtures. There was investigation of ECC mixtures containing either gravel sand or crushed dolomitic limestone sand with maximum sizes of 2.38 or 1.19 mm (0.094 or 0.047 in.) in this study. Three different ECC mixtures with 1.2, 2.2, and 4.2 fly ash/portland cement (FA/C) ratios were cast for each aggregate type and maximum aggregate size. There was experimental determination of crack development, drying shrinkage behavior, and the effects of FA/C, aggregate type, and maximum aggregate size on compressive, flexure, and unixial tensile properties. Experimental results show that strain-hardening behavior with strain capacities, provided that the matrix employs a high FA content, can be compared with the standard microsilica sand ECC mixtures, in ECC mixtures produced with gravel sand and crushed dolomitic limestone sand with higher maximum aggregate sizes. Tensile strengths of these mixtures can be 3.57 to 5.13 MPAa (0.52 to 0.74 ksi), and tensile ductility can maintain, at 28 days of age, 1.96 to 3.23%. Material behavior can be further improved by using crushed dolomitic limestone sand and gravel sand, since they can be drying-shrinkage arrestors in the paste.

Long Term Study of 23 Excavatable Tennessee Flowable Fill Mixtures

Abstract Twenty-three different EFF mixtures were placed in trenches simulating utility cuts during March through May of 2001. All EFF mixtures were tested for flow, unit weight, gravimetric air content, suitability for load application, and compressive strength development over time. The trenches were excavated in March 2003. Excavation difficulty was correlated with laboratory compressive strength for non-air-entrained mixtures. Bearing capacity estimates with the dynamic cone penetration apparatus were determined for all trenches. Nine EFF mixtures were used to assess the impact of Portland cement content and ASTM C 618 Class F fly ash content. Portland cement contents of 17.8, 26.7, and 35.6 kg/m3 and ASTM C 618 Class F fly ash contents of 178, 219.5, and 261 kg/m3 were used to evaluate the impact of component proportions. Proportions for the EFF mixtures were chosen using Kentucky Transportation Cabinet and Tennessee Ready Mixed Concrete Association (TRMCA) recommendations as well as a previous Tennessee Technological University research mixture. Six EFF mixtures were used to assess the impact of Portland cement content and high-unburned carbon fly ash content. Portland cement contents of 26.7 and 35.6 kg/m3 and high-unburned carbon fly ash contents of 219.5, 261, and 302.5 kg/m3 were used to evaluate the impact of component proportions. The influence of aggregate type on EFF mixtures was evaluated by using five different aggregate types in the EFF mixture recommended by TRMCA (26.7 kg/m3 Portland cement and 219.5 kg/m3 ASTM C 618 Class F fly ash). In addition, four comparison EFF mixtures were also used in the study (1 Tennessee Department of Transportation (TDOT) and 3 air-entrained EFF mixtures).

Influence of Aggregate Type on Mechanical Behavior of Normal- and High-Strength Concretes

Effects of coarse aggregate type on the mechanical properties of both normal- and high-strength concretes (HSCs) were investigated under compressive loading. Basalt, sandstone, and Triassic and Devonian crushed limestone coarse aggregates were used in the concretes. For each coarse aggregate type, 6 concrete mixtures were made with the same portland cement and natural sand. Nominal slump, effective water-cement ratio, and cement content were kept constant in each concrete class. In all mixtures, the grading and maximum particle size were the same. Triassic limestone containing concrete had the highest compressive strength. However, in HSCs, the compressive strength of basalt containing concrete had the highest value. In HSCs, the hysteresis loops of Triassic and Devonian limestone concretes are generally narrower than those of basalt and sandstone concretes. It can be concluded that the irreversible energy up to prepeak stress in compression decreases significantly and the loop becomes narrower with an increase in compressive strength. The brittleness index increases substantially with the compressive strength of concrete.

Aggregates and the Deformation Properties of Concrete

This paper presents results from two comprehensive series of tests spanning a 5-year period that investigated the influence of 23 different aggregate types on the properties of hardened concrete. The information given is concerned with concrete stiffness and deformation. Tables of design values for estimating the elastic modulus of concrete are given. The influence of aggregate type on concrete shrinkage and creep is discussed with reference to the experimental work. Guidance is provided on the adjustment of code values for the effects of aggregates. The results provide evidence that aggregates exert a profound and important influence on the deformation properties of concrete.

Development of Dowel Looseness Prediction Model for Jointed Concrete Pavements

The results of an in-depth study of factors that affect dowel looseness in jointed concrete pavements are presented. The laboratory investigation revealed the influence of aggregate type (in relation to oxide content), aggregate texture and shape, bearing stress (dowel diameter and crack width), load magnitude, and number of load cycles on the magnitude of dowel looseness and the subsequent loss in load transfer efficiency across saw-cut joints. A discussion is included on the development of an empirical-mechanistic dowel looseness prediction model based on the experimental results. Results of the sensitivity analysis of the dowel looseness prediction model (using laboratory data) are also presented. An associated scope of this research was to develop a relationship between dowel looseness and loss of load transfer efficiency. The sequential use of the dowel looseness prediction model and its relationship to load transfer efficiency allows the design engineer to predict load transfer characteristics of a ...

Development of Dowel Looseness Prediction Model for Jointed Concrete Pavements

The results of an in-depth study of factors that affect dowel looseness in jointed concrete pavements are presented. The laboratory investigation revealed the influence of aggregate type (in relation to oxide content), aggregate texture and shape, bearing stress (dowel diameter and crack width), load magnitude, and number of load cycles on the magnitude of dowel looseness and the subsequent loss in load transfer efficiency across saw-cut joints. A discussion is included on the development of an empirical-mechanistic dowel looseness prediction model based on the experimental results. Results of the sensitivity analysis of the dowel looseness prediction model (using laboratory data) are also presented. An associated scope of this research was to develop a relationship between dowel looseness and loss of load transfer efficiency. The sequential use of the dowel looseness prediction model and its relationship to load transfer efficiency allows the design engineer to predict load transfer characteristics of a joint, based on calculated (or measured) dowel looseness. The framework suggested to predict dowel looseness can then be incorporated into a fault prediction model for doweled joints.

The influence of aggregate type on the stability of asphalt mixtures

Abstract Mineral aggregates used in asphalt mixtures become reduced in size during mixing, consolitation and under traffic action. Laboratory and field investigations were made into the factors affecting this process. Each factor in turn was treated as a variable and its influence upon stability evaluated. Five aggregates—norite, dolerite, basalt, dolomite and quartzite—were chosen and are described petrologically. Successive crushing tests on the chosen aggregates show that final gradings were reached, after which there was little further size‐reduction under load and only a small increase in bulk density. This final grading is shown to be influenced by the original grading and the type of stone used. An examination of the crushing characteristics of the aggregates indicates decrease in crushing resistance when flaky particles are present in quantity. The degree of comminution of each aggregate type was tested, and was found to be closely connected with the degree of lubrication given to the aggregate by the binder, which in turn is controlled by its viscosity. Aggregate type influences stability, which usually increases with mix density, but experiments show that strength of an aggregate is not the controlling factor in giving maximum stability; aggregate shape and size are both important. It is concluded that maximum stability results from the use of an aggregate whose physical properties are intermediate between the very hard and the very soft.