Papers by Keyword: Indirect Tensile Strength

Abstract: With the rapid development of ferrous metallurgy, the production of iron tailings as waste after beneficiation is increasing. Due to the shortage of natural stone in road construction, iron tailings can be used as an alternative material to natural stone in semi-rigid bases. In order to study the feasibility of application of cement stabilized iron tailings (CSIT) in semi-rigid base, unconfined compressive strength (UCS), indirect tensile strength (ITS) and cyclic freeze-thaw tests were carried out on cement stabilized iron tailings (CSIT). The gradation composition and cement content were selected as influencing factors. The results show that under the condition of the same cement content, the UCS and ITS of CSIT are proportional to the particle size in the mixture. In CSIT with the same gradation, the mechanical properties increase with the increase of cement content; CSM-40(B) has a higher UCS and CSM-40(C) has a higher ITS, the frost resistance coefficient of CSIT increases with the increase of cement content and the tendency of frost resistance coefficient decreases with the increase of cement content. The frost resistanceofCSM-40 (B) is better than that of CSM-40 (C) for the same cement content. Therefore, for the use of iron tailings in CSM, a suitable gradation composition and cement content should be selected.

Abstract: Through a series of experimental studies on the unconfined compressive strength, indirect tensile strength (ITS) and freeze-thaw stability of cylindrical specimens, the feasibility of cement-stabilized iron tailings for semi-rigid bases in road construction is determined.Three variables, including the genesis of the materials from which cement stabilized macadam (CSM) are composed, the granulometric composition of the mineral part and the content of cement, were taken as influencing factors. The experimental study shows that with the increase of cement content, the unconfined compressive strength (UCS) , indirect tensile strength (ITS) and frost resistance all increase. Studies have shown that the content of coarse aggregate affects the strength properties and frost resistance of cement-stabilized macadam materials.

Abstract: Demolition of any structure is costly, and simultaneously there is non-accessibility of land or disposal sites in nearby areas. Recycling such demolished concrete material and converting it into an appropriate size of aggregates can be further used for the following construction cycle. Prior exploration showed utilization of Steel Fibers (SF) and Styrene Butadiene Rubber (SBR) latex in Recycled Concrete (RC) independently for various strength and durability improvements. This experimental work cast RC as M25 & M40 grade to satisfy reinforced concrete and rigid concrete pavement concrete demand. Total 132 cubes, 198 cylinders, and 198 beams of Normal Concrete (NC), RC, and RC reinforced by SF with SBR latex cast and termed as Polymer Modified Steel Fiber Reinforced Recycled Concrete (PMSFRRC). The objective was to evaluate the properties due to SF and SBR latex blending and obtaining the optimum dosages of SF and SBR latex. A strength and durability study was carried out to find out cube compressive strength, indirect tensile strength, flexural strength, chloride attack, and sulfate attack. The concrete was modified with the SBR latex dosage range of 2.5% –7.5% by cement weight. SF was added as 0.5% – 1.5% by concrete mix volume at the average length of 25 mm and 0.5 mm in diameter. Experimental findings of PMSFRRC for grade M25 with SF 1% volume fraction of concrete and SBR latex 5% of cement weight improve NC in indirect tensile strength by 9.93% and 8.58%, flexural strength by 10.01% and 8.99% at 28 and 91 days, respectively. Similarly, there was an enhancement in indirect tensile strength by 13.18 % and 11.11 % and flexural strength by 12.88 % and 10.78 % at 28 and 91 days, respectively, for PMSFRRC of grade M40 compared to NC. Durability analysis shows that a combined dosage of SF 1.5% volume of concrete mix and SBR latex 7.5% of cement weight seemed to be excellent concrete additives for good resistance to acid and sulfate attack for both mixtures. The results exhibited improved hardened properties of modified concrete due to the combined addition of SF and SBR latex, improved cracking resistance, flexure resistance, and reduced acid and sulfate attack rate into the specimens. The study also demonstrated an effective way of preparing sustainable concrete with SF and SBR latex to improve strength and durability.

Abstract: Currently, application of industrial waste or by-product in road construction industrials is a major interest by researchers, government officers and engineers. Coal ashes by-product from industrial parks negatively impact environment, costly in treatment, and require large ground for disposing areas. Therefore, this paper proposes on using the coal ash from furnace products of an industrial park in South of Vietnam to be incorporated into dense graded asphalt concrete using Nominal Maximum Aggregate Size 12.5mm. Laboratory performance tests including Marshall stability, indirect tensile strength, Cantabro loss, and dynamic fatigue test were conducted. The effects of coal ash contents in replacement of fine aggregate which is passing 4.75mm sieve from asphalt mixture into laboratory performance of mixture is also discussed in detail.

Abstract: Brick as a material is of vital importance in the construction industry, however, the burning processes for its preparation contribute to environmental pollution and the generation of greenhouse gases; for this reason, the present research has as aims to propose quality traditional materials for sustainable buildings through the design of soil-cement mixtures in making brick using raw materials from the amazon region of Ecuador: Centza mine (MC) and Quiringue mine (MQ) and improve the mechanical properties of the brick by incorporating carbon nanotubes, which have been dispersed in two aqueous media, sodium naphthalene sulfonate (NSS) and calcium chloride (CC) in percentages of 0.5%, 1% and 1.5%. The characterization of the raw material (analysis: physicochemical and mineralogical) was of great help. The optimum percentage of cement and water was determined through simple compression tests and soil compaction respectively. The different combinations were tested at indirect traction strength at ages 7, 14 and 28 days, determining an optimal mixture for each group of combinations, in this way the simple compressive strength of bricks has been estimated using the Griffith criterion and validation of results by finite element method applying the CivilFEM software, obtaining a resistance of 4 MPa in mixtures of SC-Ar1, 6.3 MPa in combinations of MWCNTs NSS-9 and 5.3 MPa in mixtures of CC-4 MWCNTs, increasing resistance by 57.5% and 32.5% with respect to soil-cement bricks and qualifying them as suitable for use in construction according to standars.

Abstract: Flexible pavements deteriorate and crack with time due to the frequent traffic load imposed upon it. Many studies have been done to predict the effects of frequent traffic load and environmental conditions on pavements in the effort to find the best pavement design which resist deterioration and ensure longer pavement service time. This study investigates the effect of mixing asphalt with varying percentages of nano calcium carbonate (CaCO₃), namely 0, 2, 4, and 6 %. The mixtures were designed based on the Superpave mix design criteria. Investigation was done using several tests, namely resilient modulus, indirect tensile strength, moisture susceptibility, and dynamic modulus tests. Samples were subjected to aging to determine their resilient modulus. The results of the investigation show that resilient modulus and indirect tensile strength increased when higher percentages of nanoparticles were added to asphalt mixture, with improvement of 138 and 48.18% respectively. Modified binders showed up to 17% improvement in moisture susceptibility comparison to base asphalt mixture, while the result of dynamic modulus test showed that the stiffness of modified asphalt increased 76.69%. The investigation also found that adding 6% CaCO₃ nanoparticles to asphalt produced modified asphalt with the best performance. In addition, the results show that the modified asphalt with CaCO₃ is suitable for hot and humid regions (tropical countries) in the field of highways construction, as the modifier was able to mitigate the influences of high-temperature rutting and moisture damage.

Abstract: Asphalt mix durability is one of the most important aspects if looking on longer lifetime of pavement structures. It is influenced by several factors whereas one of the most important is moisture susceptibility and the quality of adhesion between bitumen binder and aggregateparticles. If the coating by the bitumen is not fully provided or is affected by strongly hydrophilic aggregate type which easier creates bonds with more polar water then it is immediately attacking the aggregate surface and leads to stripping effects – ongoing loss of bitumen-aggregate bonds, mix cohesion problems, etc. With respect to improve adhesion quality different additives (surfactants) are used, whereas two factors might be critical for them: 1) thermal stability of the additive used in bitumen stored for several days at elevated temperatures; 2) bitumen ageing and the effect on additive activity. Both aspects have been studied as a key objective of an ongoing research looking fora suitable laboratory procedure for simulating the thermal stability and assess the remaining activity of the additive. Further asphalt ageing impact on moisture susceptibility is evaluated by changed ratios of indirect tensile strength values for unaged and differently aged test specimens. Results for one type of mix and different aggregates with application of straight-run bitumen 50/70 and 4 different types of adhesion promoters are summarized in the paper.

Abstract: The foamed bitumen technology is experiencing a global renaissance and rather extensive development of innovative approaches with respect to both, its application and research, is clearly visible. However, the variability of available bituminous binders for utilization within the technology is quite large; therefore, a general methodology of quality parameters determination for foamed bitumen and the requirements for mixes bound by this type of binder must be specified.In general different types of pen grade bituminous binders can be used for producing the foam. Besides the pen grades which are defined by penetration and also its viscosity, the source of the bitumen can have important effect on final foamed bitumen quality given especially by its expansion ratio and stability of the foam as well. Experimental study has been done to compare different types of bitumen from different sources to assess the effects on the foamed bitumen and on cold recycled mixes produced by these binders. In parallel the effect of a suitable foaming agent has been assessed as well. The foamed bitumen was analyzed by its expansion ration, half time defining the stability of the foam and the so called foam index. Cold recycled mixes were produced with one type of reclaimed asphalt material and different foamed bituminous binders. For the mix assessment mainly indirect tensile strength, water susceptibility and stiffness modulus have been considered. Results and comparison of the evaluated effects are presented in this paper.

Abstract: The amount and nature of filler in asphaltic concrete mixes significantly affect its design and performance. The use of Palm oil fuel ash (POFA) as filler in asphaltic concrete has been studied with varying degree of success, this study therefore, evaluates the effect of POFA on the indirect tensile strength of asphaltic concrete AC 14. POFA was grained and passed through 75 μm sieve; a number of trial mixes were prepared using the Marshal Mix design procedure with 5% POFA to arrive at asphalt concrete mixtures that fulfill the Marshal criteria. The effects of POFA on stability, flow, stiffness and indirect tensile strength of asphaltic concrete (AC14) mixtures at their respective optimum binder content were evaluated. The results show that Marshall stability, flow, stiffness and indirect tensile strength values generally improved in the POFA modified mix compared with the control. POFA modified sample shows 16% improvement on the indirect tensile strength compared to the control.

Abstract: An unravelling porous asphalt concrete was developed by adding steel wool and heating it with induction energy. The purpose of this paper is to examine the effects of the steel wool distribution on the properties of this unravelling porous asphalt concrete. The mixture was mixed for 10 min, 12 min, 15 min or 20 min respectively, and then samples were prepared with a gyratory compactor. The steel wool distribution at different mixing time was compared with CT scanning analysis. The electrical resistance, indirect tensile strength and induction heating speed of samples with different mixing time were also studied. It was found that a better distribution of steel wool in porous asphalt concrete increased its indirect tensile strength, but decreased its electrical conductivity and induction heating speed. 15 min mixing is sufficient to disperse steel wool to a homogenous distribution.