ASTM C1202 Research Articles

Characterization of poultry litter ashes as a supplementary cementitious material

In the present work, the possibility of using poultry litter ash (PLA) as a supplementary cementing material (SCM) is presented. Its physicochemical and microstructural parameters were determined and correlated to compressive strength. Thermogravimetric analysis (TGA) determined three suitable treatment temperatures and its training products. XRF analysis showed CaO, P2O5 and SiO2 as the main components. XRD confirmed the presence of calcite, anhydrite and quartz at 600–700 °C, and weddellite formation at higher temperatures (800 °C). SEM results corroborated the formation of crystals, favoring the formation of weddellite and the presence of ettringite at higher temperatures. Pozzolanic activity was evaluated through the Strength Activity Index (SAI). PL calcined at 800 °C showed a SAI 60.71% higher than the rest studied. Cement substitutions for PLA calcined at 800 °C were tested at 10%, 15% and 20% by evaluating compressive strength at 90 days of curing. The best performance was observed for the 10% replacement. All three percentages of substitution, exceeded a SAI value of 75%, according the ASTM C-618 standard.

Assessment of Alkali-Silica Reaction Potential in Aggregates from Iran and Australia Using Thin-Section Petrography and Expansion Testing.

The alkali–silica reaction can shorten concrete life due to expansive pressure build-up caused by reaction by-products, resulting in cracking. Understanding the role of the aggregate, as the main reactive component, is essential for understanding the underlying mechanisms of the alkali–silica reaction and thereby reducing, or even preventing, any potential damage. The present study aims to investigate the role of petrographic studies along with accelerated tests in predicting and determining the potential reactivity of aggregates, including granite, rhyodacite, limestone, and dolomite, with different geological characteristics in concrete. This study was performed under accelerated conditions in accordance with the ASTM C1260 and ASTM C1293 test methods. The extent of the alkali–silica reaction was assessed using a range of microanalysis techniques including optical microscopy, scanning electron microscopy, energy-dispersive X-ray analysis, and X-ray powder diffraction. The results showed that a calcium-rich aggregate with only a small quantity of siliceous component but with a higher porosity and water adsorption rate can lead to degradation due to the alkali–silica reaction, while dolomite aggregate, which is commonly considered a reactive aggregate, showed no considerable expansion during the conducted tests. The results also showed that rhyodacite samples, due to their glassy texture, the existence of strained quartz and quartz with undulatory extinction, as well as the presence of weathering minerals, have a higher alkali-reactivity potential than granite samples.

Potential use of Algerian natural diatomite as pozzolanic and insulator material in cement mortar

The aim of this article is to valorize the use of Algerian diatomite as natural pozzolan and insulator material in mortars manufacturing. The diatomite was characterized using X-ray fluorescence, X-ray diffraction, and SEM analysis. The pozzolanic activity of the diatomite was assessed by strength activity index according to ASTM C618 standard specification. The mechanical strength and thermal conductivity were investigated on mortar mixtures prepared by replacing cement by 10, 20, 30 and 40% of diatomite. The experimental results indicated that: X-ray fluorescence, X-ray diffraction and pozzolanic activity index tests confirmed the suitability to use the Algerian diatomite as natural pozzolans. The compressive and flexural strengths of mortars containing up to 20% diatomite decrease slightly compared than mortar without diatomite. Finally, the decreasing of thermal conductivity indicates an improvement on thermal insulation of diatomite mortars.

Belitic calcium sulfoaluminate cement subjected to sulfate attack and sulfuric acid

Belitic calcium sulfoaluminate (BCSA) cement is a hydraulic rapid-setting cement with a different composition and properties compared to portland cement. There is currently limited information about its sulfate resistance and its resistance to sulfuric acid is not known. The ASTM C1012, Standard Test Method for Length Change of Hydraulic-Cement Mortars Exposed to a Sulfate Solution and a modified ASTM C1012 accelerated method were used to compare the sulfate resistance of BCSA cement, portland cement (PC), and PC-fly ash blends. BCSA cement, citric acid dosages in BCSA cement mixes, PC, and PC-fly ash blends were examined through mortar bar expansion. The most sulfate-resistant mixes contained BCSA cement or a blend of PC and class F fly ash. Citric acid dosage did not appear to affect resistance of BCSA cement to sulfate attack. Resistance of PC, PC-fly ash blends, and BCSA cement to a sulfuric acid solution was also compared. Compressive strength and volumetric changes were measured after prolonged immersion in sulfuric acid. Water to cementitious material (w/cm) ratios and curing time for BCSA were also analyzed to establish if these factors influenced resistance to sulfuric acid attack. The most acid resistant mix contained a blend of PC and class F fly ash. A higher w/cm (0.56) was found to be more resistant against sulfuric acid attack when using BCSA, while differing cure times did not clearly indicate sulfuric acid resistance.

Influence of Jordanian Bentonite as Partial Replacement of Cement and Fine Aggregate on the Workability, Mechanical Properties and Impermeability of Concrete

In recent decades, concrete prepared with bentonite clay has evolved as an accepted substitute of natural aggregate concrete due to the increasing focus on the development of sustainability and the environmental issues. In this research, the evaluation of possible and suitable use of Jordanian bentonite as a partial replacement of Ordinary Portland Cement (OPC) or fine aggregate in the production of concrete mixtures has been investigated. Bentonite has been used as 0, 5%, 10% and 15% by weight replacement of OPC or fine aggregate passing sieve No. 50 to conduct and compare the fresh properties, the mechanical strength and the permeability of concrete mixtures. Elemental compositions and crystalline phases of bentonite clay have been tested by using X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD), respectively. The test results have revealed that the compressive and flexural strengths have decreased as bentonite level has increased beyond 5% with substitutions of fine aggregate, whereas the compressive strength has decreased at every increased dosage of bentonite replacing partially the OPC. The strength activity indices have been higher than the ASTM C618 specified limit of 75%, except for the concrete mixture containing 15% bentonite replacing OPC. The incorporation of bentonite improves the permeation resistance of concrete and the enhancement is more pronounced at higher bentonite increments, especially when replacing the fine aggregate partially with bentonite.

Influence of carbon nanotubes on properties of cement mortars subjected to alkali-silica reaction

This research investigates the impact of carbon nanotubes (CNTs) on the expansion, mechanical properties, and microstructure of cement mortar subjected to alkali-silica reaction (ASR). A total of eight compositions were cast to investigate the influence of CNT surface condition, concentration and aspect ratio, and ultrasonication energy. Two types of CNTs were used as reinforcement: pristine CNTs with an aspect ratio of 800 (Type I) and COOH-functionalized CNTs with an aspect ratio of 2500 (Type II). CNTs were incorporated at concentrations of 0.1c-wt.% and 0.3c-wt.%. The results indicated that certain combinations of mix proportions could significantly mitigate the ASR-induced damages in the mortar bar test (ASTM C1260). Specimens reinforced with 0.1c-wt.% of Type I CNTs exhibited the highest resistance to alkali-silica reaction. While specimens reinforced with 0.3c-wt.% of Type II CNTs had marginal improvements. More specifically, specimens reinforced with 0.1c-wt.% of Type I CNTs reduced the 14-day ASR expansion by 73% against control, and increased the 28-day compressive strength, flexural strength, static and dynamic elastic moduli by 22%, 36%, 54%, and 22%, respectively. Finally, scanning electron microscopy and X-ray energy-dispersive spectroscopy revealed that CNTs resist ASR with three main chemo-mechanical mechanisms: 1) restrain crack propagation, 2) refine the pore structure of the composite, and 3) reduce the alkalinity of the pore solution by altering the ASR gel compositions.

Recycled Untreated Rubber Waste for Controlling the Alkali-Silica Reaction in Concrete.

Recycled rubber waste (RW) is produced at an alarming rate due to the deposition of 1.5 billion scrap tires annually around the globe, which causes serious threats to the environment due to its open land filling issues. This study investigates the potential application of RW in concrete structures for mitigating the alkali–silica reaction (ASR). Various proportions of RW (5%, 10%, 15%, 20%, and 25%) partially replaced the used aggregates. RW was procured from a local rubber recycling unit. Cubes, prisms, and mortar bar specimens were prepared using a mixture design recommended by ASTM C1260 and tested for evaluating the compressive and flexural strengths and expansion in an ASR conducive environment for specimens incorporating RW. It was observed that the compressive and flexural strength decreased for specimens incorporating RW compared to that of the control specimens without RW. For example, an 18% and an 8% decrease in compressive and flexural strengths, respectively, were observed for specimens with 5% of RW by aggregates volume at 28 days. Mortar bar specimens without RW showed an expansion of 0.23% and 0.28% at 14 and 28 days, respectively, indicating the potential ASR reactivity in accordance with ASTM C1260. A decrease in expansion was observed for mixtures incorporating RW. Specimens incorporating 20% of RW by aggregate volume showed expansions of 0.17% at 28 days, within the limit specified by ASTM C1260. Moreover, specimens incorporating RW showed a lower reduction in compressive and flexural strengths under an ASR conducive environment compared to that of the control specimen without RW. Micro-structural analysis also showed significant micro-cracking for specimens without RW due to ASR. However, no surface cracks were observed for specimens incorporating RW. It can be argued that the use of RW in the construction industry assists in reducing the landfill depositing issues with the additional benefit of limiting the ASR expansion.

Recycling of waste glass powder and tyre fiber in the development of eco-efficient concrete for high-performance structural application

Concrete suffers from several drawbacks due to the pollution associated with cement production, low tensile strength and low strain capacity that result in low resistance to cracks. Several attempts have been made to utilize waste materials for economical, sustainable construction and to improve concrete characteristics. This paper aims to investigate the effect of waste glass powder (WGP) as a partial replacement of cement and waste tyre fibre (WTF) as fibre reinforcement in the production of high performance concrete (HPC). ACI 211.1 was used to design a grade 50 HPC. At the first stage, WGP was introduced at a replacement level of 0 to 25 at a 5% interval by weight of OPC increment. Compressive strength at 3, 7, 28, 56, and 90 days of curing and slump flow was investigated, as well as establishing the optimum WGP content. WTF was then added to the optimal WGP-HPC in varying percentage addition of 0 to 2% at an increase of 0.4% by weight in the second stage. The compressive, splitting tensile, and flexural strengths at 3, 7, 28, 56, and 90 days were investigated. Slump flow was also investigated. It was discovered that the WGP is a suitable material for use as a pozzolana as it satisfied the minimum requirement given in ASTM C618. The compressive strength of HPC increased up to a 10% OPC replacement level by WGP before it starts declining. This signifies that the highest compressive strength was obtained at 10% WGP replacement level. It was also shown that adding the WTF decrease the slump flow and enhanced the compressive, splitting tensile and flexural strengths of WGP-HPC up to 1.2% and then dropped. Overall, an optimal HPC mix with 10% OPC replacement by GWP and 1.2% WTF addition outperforms all other mixes.

Evaluation and beneficiation of high sulfur and high alkali fly ashes for use as supplementary cementitious materials in concrete

Coal-fuel power plants with semi-dry or dry flue gas desulfurization (FGD) systems produce high sulfur and/or high alkali fly ashes due to comingling of fly ash with FGD products. Such fly ashes do not meet the SO3 content limit (5.0% max.) of ASTM C618 or are unable to mitigate the alkali-silica reaction. The mineralogy of the sulfur present in these ashes can vary significantly (e.g., CaSO4, CaSO3, Na2SO4) based on the FGD technology used and this affects the performance of these fly ashes in concrete. Thus, the single SO3% limit of ASTM C618 is unable to capture the complexity and performance of fly ash, and this results in elimination of potentially viable pozzolans for concrete. This study performs a systematic investigation of the effect of SO3 type and content in fly ash on various performance parameters of cement-fly ash pastes and mortars, including workability (flow and flow retention), pore fluid pH, setting time, strength development, and potential for deleterious expansion. To better quantify and understand these effects, the study considers both real and doped fly ashes (i.e., a blend of specification-compliant fly ash with target sulfur compounds). The poor performance observed in the case of setting time and pore fluid pH was successfully mitigated using chemical admixtures.

Effects of Taheri Consciousness Fields on Concrete (ASR)

The Alkali-silica reaction of concrete is known as one of the destructive reactions. There are many studies in this area. Taheri Consciousness Fields (TCFs) were founded and introduced by Mohammad Ali Taheri as new Fields. These Fields are neither matter nor energy, therefore, they do not possess a quantity, but they have direct effects on both matter and energy. In other words, although TCFs cannot be directly measured, we can investigate their effects indirectly through various controlled experiments. In this study, cement mortar samples were examined by using the ASTM C1260 standard and under the effect of a type of TCF known as TCF(H). Additional experiments, aggregate petrography, L.O.I (Loss on Ignition), SEM (Scanning electron microscopy), XRD (X-ray Diffraction), XRF (X-Ray Fluorescence), and FT-IR (Fourier-transform infrared spectroscopy) were performed to further investigate the effect of TCF(H). It was found that the TCF (H) was able to reduce the expansion and improve the cement mortar function by up to 10% (average ̴̴ 7% P-value=0.008) and make observable changes in chemical and elemental compositions.

Influence of Taheri Consciousness Bond Field on the Alkaline Reaction of Concrete

Some natural aggregates used in concrete contain activated silica and react with the alkalis in the concrete, the product of which is an expansion gel that eventually destroys the concrete. The aim of this study was to investigate the effects of the Consciousness Bond Field on concrete. Consciousness Bond Field is one of many Taheri Consciousness Field (TCFs) that were founded and introduced by Mohammad Ali Taheri as new Fields. These Fields are neither matter nor energy; therefore, they do not possess a quantity, but they have direct effects on both matter and energy. In other words, although TCFs cannot be directly measured, we can investigate their effects indirectly through various reproducible experiments. To achieve the goal of this study, alkaline reaction stimulus aggregate was selected, and the aggregate and cement reactivity was tested. Three series of cement mortar were prepared under the ASTM C1260 standard. Tow series were subjected to the TCF, and one series was considered the control. The reactivity of concrete increased ( 5%) under the influence of the Consciousness Bond Field.

Hydration and compressive strength of Portland cement blended with kamafugites and carbonatites: Effect of Physical Properties

Kamafugites and carbonatitic tuffs, though not common natural pozzolans, are the main option for supplementary cementitious materials in regions surrounding the Western part of the East African Rift valley system. The tuffs are silica undersaturated, carbonatitic and largely ultrapotassic. The current study sought to characterise their physical and chemical properties and compare them with those of published works on natural pozzolans. Two samples, a carbonatite and a kamafugite, from the Toro-Ankole geological region of East Africa are investigated for their effect on specific properties of pastes and mortars when used as natural pozzolans in Portland cement. The volcanic tuffs milled to three fineness levels and blended with Portland cement at 0%, 5%, 10%, 20% and 35% replacement levels are tested for effects on hydration and compressive strength. Results show a time dependent variation in heat of hydration which increases for the first 14 hours before decreasing. The variation seems dependent on level of replacement. Compressive strength results show dependence on level of replacement and fineness which was pronounced until 90 days, peaking at 28 days. Increase in replacement level resulted in a general reduction in compressive strength. A compressive strength conversion process that peaks at 10% replacement level is observed in all blended samples leading to compressive strength results at 180 days being lower than those at 90 days of curing. Compressive strength test results, however, sustain the ASTM C618 and BS 3892 minimum requirement for pozzolanic Portland cements indicating that the carbonatites and kamafugites can be gainfully applied in cement production from the resource and energy economy perspectives.

Taguchi-based interval multi-criteria decision-making method for optimisation of alkali activators

The main purpose of this study is to assess the optimal condition with multiple responses using the Taguchi method in the presence of conformity assessment. For this purpose, all possible arrays, including orthogonal and non-orthogonal arrays, were included in the analysis. The experimental data in the form of interval numbers were directly derived from experimental results for orthogonal arrays, and were computed using the Taguchi prediction method for non-orthogonal arrays. A new pattern of conformity assessment was introduced that eliminates arrays that do not meet the criteria or modifies the interval number of non-orthogonal arrays that meet a part of the criteria. Finally, each accepted array was specified as an alternative, and interval multi-criteria decision-making methods were finally deployed to rank the alternatives. A case study was carried out to find the optimal mixture of sodium silicate activators with strict criteria of ASTM C150 based on the proposed method. To this end, three factors, including the weight percentage of sodium oxide (Na2O) in slag, silicate modulus (SiO2/Na2O), and water to slag (W/S) ratio, each at three levels, were investigated by examining the compressive strength and drying shrinkage of the mortar, along with the setting time and mini-slump cone tests on the fresh paste. Results revealed the effectiveness of the proposed approach and indicated that the Na2O, SiO2/Na2O, and W/S values of 6%, 0.8, and 0.42, respectively, were a reasonable choice for the activator.

Investigating Optimum Conditions for Developing Pozzolanic Ashes from Organic Wastes as Cement Replacing Materials.

This research was performed to investigate the optimum conditions for developing pozzolanic ashes from organic wastes to be used as cement replacement materials. The organic wastes explored in the research are rice husk ash (RHA), wheat straw ash (WSA), and cow dung (CDA). When the organic waste is turned into ash, it develops a pozzolanic character due to the presence of silica. However, the presence of reactive silica and its pozzolanic reactivity depends on the calcination temperature, duration, and grinding. In this research, the organic wastes were calcined at three different calcination temperatures (300 °C, 400 °C, and 800 °C) for 2, 4, 6, and 8 h duration. The obtained ashes were ground for 30 min and replaced by 20% with cement. The samples containing ashes were tested for compressive strength, X-ray diffractometry (XRD), weight loss, and strength activity index (SAI). It was observed that the RHA calcinated at 600 °C for 2 h showed better strength. However, in the case of WSA and CDA, the most favorable calcination condition in terms of strength development was obtained at 600 °C for 6 h duration. The highest SAI was achieved for the mortar samples containing CDA calcinated at 600 °C for 6 h duration (CDA600-6H). The other two ashes (RHA and WSA) did not qualify as pozzolan according to the ASTM C618 classification. This was due to the presence of silica in crystalline form and lower surface area of the ash material. In this research, the ash was ground only for 30 min after calcination which did not contribute to an increase in the specific surface area and thus the pozzolanic activity. The materials ground for the higher duration are recommended for higher SAI.

Evaluation of Alternative Sources of Supplementary Cementitious Materials for Concrete Materials

This study characterized and evaluated the use of reclaimed fly ash (RFA) and reclaimed ground bottom ash (GBA) as alternative sources of supplementary cementitious materials (SCMs) for the production of concrete mixtures. Conventional Class F fly ash (FA) was also evaluated for comparison. The effects of SCM content on fresh and hardened properties of concrete were investigated by replacing 10%, 20%, and 30% of cement by mass. Characterization results showed that all three ashes met ASTM C618 chemical requirements (i.e., sum of SiO2 + Al2O3 + Fe2O3, CaO, SO3, moisture content, and loss of ignition) and 7- and 28-days strength activity index (SAI) requirements for Class F FA. In addition, RFA exhibited slightly higher SAI at 28 days of curing, followed by GBA and FA. In relation to fresh concrete properties, FA increased the concrete slump compared with the control mixture, whereas RFA and GBA decreased the concrete slump. However, GBA produced more significant slump decrements than RFA, which was attributed to the irregular angular particles of GBA. Generally, all the coal ashes produced decrements in air content compared with the control mixture. Comparatively, among the three ashes, GBA exhibited the highest 28- and 90-days compressive strength and surface resistivity (SR) at all cement replacement levels. Furthermore, at 90 days of curing, RFA and GBA concrete mixtures outperformed the FA concrete mixtures in relation to compressive strength and SR. Consequently, both RFA and GBA are promising SCMs for concrete materials.

Portland-Limestone Cement’s Implementation into Mississippi’s Concrete Market

Abstract In recent years, the use of ASTM C595 Type IL portland-limestone cement (PLC) has continued to gain momentum in the concrete industry. In the Southeast United States, PLC ground to fineness levels exceeding 500 m2/kg have demonstrated useful synergies with some fly ash sources. In 2014, the Mississippi Department of Transportation (MDOT) approved use of PLC and they have a specification that allows up to 35 % fly ash with PLC but only up to 25 % fly ash with ASTM C150 Type I ordinary portland cement (OPC). The primary objective of this paper is to assess the use of PLC in Mississippi in the context of MDOT’s new specification for both MDOT and non-MDOT projects. The authors documented several case study projects including residential-light commercial, highway barriers, slabs, a multistory hotel, and a wastewater facility with sulfate exposure conditions, in addition to evaluating data from several dozen laboratory-produced concrete mixes to make assessments. Class C and Class F fly ashes were considered, mostly at 20–35 % replacement rates. Overall, Type IL PLC was found to be a better cement for use in the marketplace for Mississippi than Type I OPC, and MDOT’s existing specifications were successfully vetted.

Assessment of Reactive powder concrete subjected to three different sodium sulfate Concentrations: Compressive Strength, Absorption, Porosity, Microstructure, and durability

Reactive Powder Concrete (RPC) is a relatively new type of concrete material characterized by very low water-to-binder ratios (w/b), the addition of supplementary cementitious materials like silica fume (SF), and the presence of very fine aggregates instead of conventional coarse aggregates. The durability of RPC with various w/b (0.18, 0.22, and 0.26) and SF content (15%, 20%, and 25%) against external sulfate attack (ESA) at various sodium sulfate (Na2SO4) concentrations (0.35 M, 0.7 M and 1.4 M) was investigated in this study through examinations of compressive strength, expansion and mass change, microstructural characteristics, mineralogy, porosity, and sorptivity. The results indicated that: 1) owing to its improved microstructure, RPC could accommodate expansive products of ESA reactions, which can provide additional strength; 2) RPC showed very high resistance to Na2SO4 attack under the ASTM C1012 criteria; 3) considerable sulfate ingress did not result in significant expansion and strength reduction for RPC mixtures at early stages of exposure, especially for the mixtures with high initial sorptivity and high interparticle connectivity; 4) considering the coupled effect of w/b and SF content on the number of RPC characteristics, mixture with w/b = 0.22 and 20% SF content showed the best performance upon exposure to ESA.

Effects of CO2 curing treatment on alkali-silica reaction of mortars containing glass aggregate

In this study, the influence of CO2 curing treatment on the alkali-silica reaction (ASR) of mortar bars containing 100% recycled glass was investigated. The ASR expansion results according to ASTM C1260 demonstrated that a short period (3 h) of CO2 curing could fully suppress the ASR expansion. Apart from mechanical strength enhancement, reduced pH and permeability properties, it is interesting to note that the distribution of ASR gel in the CO2 cured specimen was totally different from traditional glass-induced ASR as reported in the literature. For CO2 curing treated specimen, the ASR gel which formed at the glass-cement interface instead of initiation at microcracks within the glass aggregate is identified as an important reason for the decreased expansion. With the reduction of calcium hydroxide (CH) in the cement matrix caused by CO2 curing treatment, silica could dissolve from glass surface and induced the ASR reaction. The swelling of the surface ASR gel applied inward pressure on the glass aggregate, reducing the aggregate cracking progression. In addition, these surface gels can possibly be partly accommodated by residual space in the interfacial transition zone (ITZ).

Discrete element method to investigate flexural strength of pervious concrete

Pervious concrete (PC) is a sustainable pavement material that has been widely used for low volume roads, walkways, and bicycle paths. Past literature studies have proposed several mix design methods to prepare PC with desired properties. However, the current mix design procedure involves substantial consumption of materials and is labor-intensive iterative process. Several numerical simulation studies used discrete element method (DEM) in simulating PC as a granular material (aggregates) coated with cement paste. Even though several researchers investigated mechanical properties such as compressive, flexural, and tensile strengths in the laboratory, and simulated the behavior of PC under compression and tensile loads, no known study has attempted simulating flexural response of PC. Given the significance of flexural strength in the pavement design process, it is essential to simulate the flexural behavior of PC. Therefore, the objective of this study was to develop a DEM framework to simulate PC mixtures and predict their flexural behavior by simulating the flexural strength test in a DEM based software YADE. A laboratory experimental program was conducted to obtain the experimental data required for calibration and validation of the proposed PC simulation model. In addition, a DEM program was developed to simulate the PC mixtures with the desired gradation and porosity levels, as achieved in the laboratory. A flexural strength test similar to ASTM C78 (1 MPa/s loading rate) was devised to simulate the flexural behavior of the prepared numerical PC specimens. The cohesive particle model in YADE was calibrated using experimental data and then used as the constituent model to simulate the interaction between cement coated aggregates in these flexural strength simulations. Overall, the proposed DEM approach could simulate the PC specimens with specified porosities and was able to predict the flexural response of the PC mixtures at 97% accuracy. It is envisioned that the proposed model could be further used to design PC mixtures with desired porosity and flexural strength properties instead of preparing trial mixtures, which would substantially reduce wastage of materials and human effort.

Thermal and acoustic properties of sustainable structural lightweight aggregate rubberized concrete

This study investigated the effect crumb rubber recycled from wasted tires on properties of structural lightweight aggregate concrete (LWAC). Two types of concrete were tested: control LWAC and rubberized lightweight aggregate concrete (RLWAC). The control LWAC consisted of cement, fine aggregate (river sand), and lightweight coarse aggregate (porous aggregates). For the RLWAC, the fine aggregate was replaced by crumb rubber at the rate of 10, 20, 30, 40, and 50% by volume. The water to cement ratio for both concrete types was set at 0.35. The experiment series consisted of density (ASTM C567), compressive strength (ASTM C39), flexural strength (ASTM C78), thermal conductivity (ASTM C518), and sound absorption coefficient (ISO 10534-2). Results showed the decrease in density of about 10%, compressive strength of 21.4%, and flexural strength of 35.4% with the increasing crumb rubber replacement ratio up to 50%. For thermal and sound properties, the increasing crumb rubber content of up to 50% improved the thermal insulation of concrete, as seen by the decrease in thermal conductivity by about 14.6%. RLWAC also exhibited superior sound insulating properties to LWAC as seen by higher sound absorption coefficient over the working sound frequency range. In order to satisfy the requirements of ASTM C330 and ACI 318, the optimum crumb rubber replacement was recommended at less than 10%.