ASTM C1202 Research Articles

New machine learning prediction models for compressive strength of concrete modified with glass cullet

PurposeRecycled waste glasses have been widely used in Portland cement and concrete as aggregate or supplementary cementitious material. Compressive strength is one of the most important properties of concrete containing waste glasses, providing information about the loading capacity, pozzolanic reaction and porosity of the mixture. This study aims to propose highly nonlinear models to predict the compressive strength of concrete containing finely ground glass particles.Design/methodology/approachA robust machine leaning method called genetic programming is used the build the compressive strength prediction models. The models are developed using a number of test results on 50-mm mortar cubes containing glass powder according to ASTM C109. Parametric and sensitivity analyses are conducted to evaluate the effect of the predictor variables on the compressive strength. Furthermore, a comparative study is performed to benchmark the proposed models against classical regression models.FindingsThe derived design equations accurately characterize the compressive strength of concrete with ground glass fillers and remarkably outperform the regression models. A key feature of the proposed models as compared to the previous studies is that they include the simultaneous effect of various parameters such as glass compositions, size distributions, curing age and isothermal temperatures. Parametric and sensitivity analyses indicate that compressive strength is very sensitive to the curing age, curing temperature and particle surface area.Originality/valueThis study presents accurate machine learning models for the prediction of one of the most important mechanical properties of cementitious mixtures modified by waste glass, i.e. compressive strength. In addition, it provides an insight into the effect of several parameters influencing the compressive strength. From a computing perspective, a robust machine learning technique that overcomes the shortcomings of existing soft computing methods is introduced.

An Accelerated Test Method to Evaluate Cementitious Mixtures Subjected to Chemical Sulfate Attack

Abstract External sulfate attack continues to be a major threat to the long-term durability of concrete structures. Soil or water containing sufficient levels of sulfates can penetrate and chemically react with the hydrated cement compounds, leading to volumetric expansion, and in severe cases, softening of the hardened cementitious paste. While ASTM C1012, Standard Test Method for Length Change of Hydraulic-Cement Mortars Exposed to a Sulfate Solution, is the most widely accepted performance test method used to access the sulfate resistance of cementitious binders, the test requires at least six months and often up to twelve months to perform. This article presents a new accelerated method that places mortar bar specimens under high-vacuum while immersed in sulfate solution to accelerate the penetration and diffusion of sulfates in the specimens and therefore, the degradation and measured linear expansion of the specimens. Expansion, mass change, and visual degradation were assessed over time on mortar specimens immersed in a 5 % and 0.89 % sodium sulfate solution (Na2SO4) and subjected to the vacuum saturation procedure. Expansion results are compared with companion mortar bars that followed the ASTM C1012 method without vacuum saturation. When compared with the current ASTM method, the new test method showed a significant acceleration in the rate of expansion with severe visual deterioration observed two to three times quicker. Visual degradation and measured expansion occurred more rapidly for specimens subjected to the accelerated method and immersed in 5 % Na2SO4; however, mixtures subjected to the accelerated method and immersed in 0.89 % Na2SO4 still showed much faster expansion than companion specimens tested according to ASTM C1012 in 5 % Na2SO4.

Thermal properties of lightweight concrete incorporating high contents of phase change materials

Abstract This research investigated the latent heat and energy storage of lightweight concrete containing high contents of phase change material (PCM) (up to about 7.8% by weight of concrete). PCM – Polyethylene Glycol (PEG) with a fusion temperature of approximately 42–46 °C was impregnated into porous lightweight aggregates up to 24% by weight. The PCM aggregates were then used to replace normal lightweight aggregate at a rate of 0, 25, 50, 75 and 100% by volume. The samples were subjected to series of experiments such as compressive strength (EN12390-3 2002), flexural strength (ASTM C78 ), thermal conductivity (ASTM C518 ) and the thermal storage of phase change materials examined using a heat flow meter apparatus (ASTM C1784 ) at the age of 28 days. Results show that the existence of PCM aggregates affects both mechanical and thermal properties of concrete to different degrees. The mechanical properties appear to improve with increasing PCM aggregate content. For thermal properties such as thermal conductivity and specific heat, the state of the PCM (liquid or solid state) as well as the testing temperature during the test, show significant influence on the obtained results. The latent heat was found to increase proportionally with the increasing PCM aggregate replacement rate.

Normality of Post-Crack Performance Data for Fiber-Reinforced Concrete

Abstract With the increasing use of fiber-reinforced concrete (FRC) for civil infrastructure projects, challenges have become apparent in quality control (QC) testing for this material. The most common problem is high variability, but a secondary problem is identifying the most appropriate probability distribution function (PDF) for post-crack performance data. This article has examined the second of these challenges. It is widely assumed that the normal PDF most reliably describes the distribution of outcomes for many stochastic processes. Most of the conventions underlying probabilistic modeling of engineering processes are therefore predicated upon a normal distribution of material properties. However, evidence exists that other functions, such as the Weibull, lognormal, or gamma distribution functions, may be more appropriate representations of the distribution of test results for some post-crack performance parameters related to FRC, such as fatigue life. The present investigation has examined a large body of QC data to identify the most reliable function describing the probability distribution of post-crack performance of FRC as obtained from ASTM C1550, Standard Test Method for Flexural Toughness of Fiber Reinforced Concrete (Using Centrally Loaded Round Panel), and ASTM C1609/C1609M, Standard Test Method for Flexural Performance of Fiber-Reinforced Concrete (Using Beam with Third-Point Loading). The results demonstrate that the normal and lognormal functions model the distribution of post-crack performance data obtained for FRC equally well. However, the normal function produces the best fit for data assembled from multiple specimen sets, thereby confirming the validity of the central limit theorem. Moreover, a derivative of the normal function also reliably predicts the distribution of variances for data sets comprising a small number of replicate test results.

Compressive strength measurement for cement replacement with recycled glass in concrete

The most important environmental constraints at the present timeis the accumulation of glass waste (transparent glass bottles). A lot ofexperiments and research have been made on waste and recyclingglass to get use it as much as possible. This research using recyclingof locally waste colorless glass to turn them into raw materials asalternative of certain percentages of cement to save the environmentfrom glass waste and reduce some of the disadvantages of cementwith conserving the mechanical and physical properties of concretemade. A set of required samples were prepared for mechanical testwith different weight percentage of waste glass (2%, 4%, 5%, 6%,8%, 10%, 15%, 20% and 25%). American standard for calibration(ASTM C109 / C109M-02) to measure the compressive strengthwhere the results showed that the Maximum compressive strengthwas obtained at the low weight percentage replacement 2%, 4% and5% 6% which is 67.12, 69.24, 62.56 and 59.96 Mpa respectively. fororiginally mix recorded bending resistance (54.16) Mpa.

Ultra-High Performance Concrete Overlays for Concrete Bridge Decks

With much of the world’s infrastructure needing rehabilitation, new and more effective methods of repair are required to ensure that concrete structures can continue to perform adequately. This work investigates the potential for using locally produced ultra-high performance concrete (UHPC) as an overlay material to rehabilitate existing normal strength concrete (NSC) bridge decks. Bond strength tests were conducted using NSC substrate with four different textures seven days after casting the UHPC overlay. Depths of the different textures determined in accordance with ASTM E965 were 0.05, 0.90, 1.6, and 2.8 mm. Results from slant shear, split cylinder, and split prism tests indicate good bond even when inadequate texturing was provided. Average shear strengths from slant shear (ASTM C882) specimens increased from 7.1 MPa for the 0.05 mm texture to 19.8 MPa for the 2.8 mm texture. Similarly, bond strengths from split cylinders (ASTM C496) increased from 1.8 MPa for the 0.05 mm texture to 2.4 MPa for the 2.8 mm texture. Bond strength testing of split prisms specimens was conducted using a modified version of ASTM C496 and produced results of 1.5 MPa for the 0.05 mm texture and 3.7 MPa for the rough texture. Direct tensile strength testing was performed in accordance with ASTM C1583 and produced a bond strength of 1.08 MPa for chipped texture with a depth of 1.00 mm. Testing of chloride permeability (ASTM C1202) of the UHPC indicated negligible charge passing through the specimens. Free shrinkage measurements initiated 90 minutes after placement resulted in a total shrinkage of 1800 micro-strain in the UHPC after seven days. Results from these tests indicate the potential of locally produced UHPC to serve as an alternative to traditional overlay materials.

Pozzolanic Potential and Mechanical Performance of Wheat Straw Ash Incorporated Sustainable Concrete

The pozzolanic potential, mechanical strength, and stress-strain behavior of a locally available wheat straw ash (WSA) as a partial substitute of cement was evaluated in this study. Various samples of a locally available wheat straw were burnt to ashes at three distinct temperatures and characterized through X-ray powder diffraction and energy dispersive X-ray spectroscopy. The WSA obtained from burning at 550 °C was found highly amorphous and possessed suitable chemical composition to be used as pozzolanic material. The burned WSA was grounded to achieve the desired fineness and mortar cubes and concrete cylinders were cast by substituting 15%, 20%, 25%, and 30% cement with it. The strength of mortar and concrete decreased with increasing amounts of WSA except for those containing 15% WSA, where it slightly increased than the respective control samples at later ages, i.e., 28 and 91 days. Despite reduced strength at high replacements (20%, 25%, and 30%), the strength activity index values met ASTM C618 requirements for pozzolanic materials. Moreover, the compressive strength of concrete containing 20% WSA exceeded to that of control concrete at 91 days. The stress-strain relation of concrete containing 15% to 20% WSA also showed comparable stiffness and toughness to those of control samples at all ages. Particularly, the concrete containing 15% WSA showed significant improvement of strength, stiffness, toughness, and ductility at 91 days. Lastly, the results of mechanical strengths and pozzolanic reactivity were successfully validated indirectly by measuring the porosity of mortars and thermo-gravimetric analysis of cement pastes, respectively. Based on current findings and their validation, WSA can be used as a substitute of cement up to 20% in the production of sustainable normal strength concrete for their application in common domestic building projects.

Investigation of Flexural Toughness for Steel-and-Synthetic-Fiber-Reinforced Concrete Pipes

Mechanical responses of steel-and-synthetic-fiber-reinforced pipes (FRCPs) are discussed in this paper. The energy absorption, post-cracking strength (PCS), and toughness were analyzed based on the results obtained from the three-edge bearing (3EB) experimental tests conducted on the FRCPs in accordance with ASTM standard C497. A dry-mixed concrete material was used to manufacture the FRCPs, with variations in the fiber volume fractions (Vf): steel - 0.15%, 0.20%, 0.30%, and 0.40%; and synthetic - 0.15%, 0.20%, 0.30%, and, 0.40%. A total of 40 full-scaled tests were carried out on the synthetic FRCPs by incorporating different fiber volume fractions, and a total of 22 steel FRCPs full-scaled tests were conducted with the referenced fiber volume fractions. Based on the analyzed results from the 3EB tests, it was concluded that steel fiber reinforcement of concrete pipes shows higher energy absorption than synthetic one, and the increase of the steel and synthetic fiber volume fractions do not consistently improve the FRCP's load-carrying capacity. The ideal percentage of fiber for the highest load-carrying capacity is between 0.15% and 0.20% for dry-mixed concrete; however, the increase of the fiber volume fraction tends to increase the mechanical properties of toughness and PCS values. Based on 49.0% and 46.0% higher toughness and PCS values, respectively, it is concluded that steel fibers absorb energy more effectively than synthetic fibers when used as reinforcement. In addition, the steel-FRCP shows the higher ductility rather than the synthetic-FRCP in terms of the toughness index in accordance with ASTM C1018.

The influence of lithium compounds on alkali – silica reaction in calcium aluminate cement mortars subjected to the deicing salts attack

Paper presents the results of research on the effect of the lithium nitrate and carbonate addition on the alkali – silica reaction in calcium aluminate cement mortars, subjected to the a deicing salts attack. Mortars with the addition of quartz glass as the reactive aggregate were immersed in 4.5 molar sodium acetate, chloride and hydroxide solutions according to the modified ASTM C1260 method. In all cases, the mortars exhibited expansion, the highest for samples immersed in the acetate solution, and the lowest in the hydroxide solution. The addition of 1% of lithium carbonate in respect to the cement mass slightly reduces the expansion of mortars immersed in sodium acetate and hydroxide solutions. The addition of 1.86% and 3.73% of lithium nitrate increases the expansion of mortars immersed in both solutions. The addition of 1.86% lithium nitrate reduces the expansion of the mortar stored in sodium hydroxide solution, while 3.73% of this addition increases the expansion of this mortar. Changes in the microstructure were also presented.

False Positives in ASTM C618 Specifications for Natural Pozzolans

False Positives in ASTM C618 Specifications for Natural Pozzolans

Preliminary Evaluation of Concrete-Rock Interface Behavior Under the Action of Freeze-Thaw Cycles

The most common source of failure for tunnellining occurs at the excavated surface due to a high frequency of freeze-thaw cycles and cold weather that significantly drop the strength of the interface between the rock and the concrete. A preliminary experiment was conducted to confront the problems associated with cold weather effect on concrete and the adhering connection between the concrete and the excavated rock surface. A series of composite specimens made of sandstone rocks and concrete with the three types of surfaces (smooth, semi-rough, and rough) were prepared in the Materials Laboratory of Northern Arizona University. All specimens were undertaken up to 180 Freeze-thaw cycles using an ASTM C666 apparatus with modifications on molds and dimensions of specimens. Tensile splitting tests of the interface between concrete and three types of rock surfaces were performed with respect to the bonding strength. The purpose of the research was to (1) evaluate the effect of freezing and thawing cycles on the bonding strength/interface behavior of the composite specimens and (2) to determine the rate at which adhesion strength is lost when undergoing cold weather environment. Based on the test results, the concrete-rock specimens prepared with rough surface show higher bonding strength than the other two surface treated specimens (smooth and semi-rough surface treatments).

Reinforced concrete corrosion prevention/reduction by hydrophobic impregnation

The prevention of corrosion in reinforced concrete structures can be achieved by different means. The aim of this paper is to present the efficiency of corrosion prevention using silane hydrophobic impregnation, through laboratory investigations as well from long term field studies. The laboratory investigation was carried out in Zürich, is based on modified ASTM C109, where the product was applied on cracked concrete beams (before cracking and before corrosion initiation; after cracking and before corrosion initiation and finally after cracking and after corrosion initiation). The long term field studies were carried out over 12-years exposure to de-icing salts in a Swiss tunnel, and after 10 years exposure to a marine zone simulation in Japan. This paper will show that the use of a silane hydrophobic impregnation can be an effective way to reduce the risk of corrosion for concrete structures, including structures exposed to chlorides in a marine environment, or from the use of de-icing salts in winter time.

Reaktywność alkaliczno-krzemionkowa wybranych krajowych kruszyw drobnych

The paper presents selected information on the quality of the aggregates, especially natural sands, extracted and manufactured in Poland. The sands usually meet the basic quality requirements (e.g. concerning grading and purity) for fine aggregates to be used in road construction. Tests of the alkali reactivity of natural sands and manufactured (by crushing compact rock) sands are described in detail. The results of the reactivity tests carried out in accordance with domestic standards PN-B-06714 show the tests to be poorly reliable. Exemplary abridged petrographic descriptions of selected sands and the results of reactivity tests carried out on mortar beams in accordance with standard ASTM C1260 are presented. The beam linear expansion values were geographically assigned by marking them on a contour map of Poland. The tested fine aggregates were found to greatly vary qualitatively as regards their mineral composition and the likelihood of occurrence of the alkali-aggregate reaction. Over half of the tested sands were characterized by an expansion over 0.1%, which according to the AASHTO R-80 classification means that they are moderately reactive aggregates.

Monitoring of the Impact of Lithium Nitrate on the Alkali⁻aggregate Reaction Using Acoustic Emission Methods.

The study analyzed the possibility of using the acoustic emission method to analyse the reaction of alkali with aggregate in the presence of lithium nitrate. Lithium nitrate is a chemical admixture used to reduce adverse effects of corrosion. The tests were carried out using mortars with reactive opal aggregate, stored under the conditions defined by ASTM C227. The acoustic activity of mortars with a corrosion inhibitor was referred to linear changes and microstructure of specimens in the initial reaction stages. The study found a low acoustic activity of mortars with lithium nitrate. Analysis of characteristic parameters of acoustic emission signals, combined with the observation of changes in the microstructure, made it possible to describe the corrosion processes. As the reaction progressed, signals with different characteristics were recorded, indicating aggregate cracking at the initial stage of the reaction, followed by cracking of the cement paste. The results, which were referred to the acoustic activity of reference mortars, confirmed that the reaction of opal aggregate with alkali was mitigated in mortars with lithium nitrate, and the applied acoustic emission method enabled the detection and monitoring of ASR progress.

Sodium silicate activated slag‐fly ash binders: Part III—Composition of soft gel and calorimetry

AbstractSodium silicate activated, slag‐fly ash binders are potential alternative binders to Portland cement. In this study, the early age properties of slag‐fly ash binders namely, set time, and heats of reaction were investigated. Set time was investigated using a combination of two methods namely, the ASTM C403 penetration testing, and s‐wave ultrasonic wave reflectometry (SUWR). The discrepancy in set time identified by these two methods suggested the presence of a soft gel which eventually hardened with time. The composition of this soft gel was analyzed by suspending the chemical reaction of the binder after the soft gel formed, but before it hardened. In order to analyze the composition of the soft gel, selective chemical extractions were performed on the binder. 29Si Magic Angle Spinning‐Nuclear Magnetic Resonance (MAS‐NMR), and FTIR spectroscopy were performed on binders and extraction residues. The soft gel contained a modified calcium silicate hydrate gel (C–N–S–H where N=Na), with a short mean chain length and no observable Al incorporation. Orthosilicate units were also found to be present in relatively high proportions when compared to hardened binders at later ages.

Suitability study of soybeans husk ash as a mixing material to OPC: Effect of calcination time-preliminary investigation

Soybeans husk was collected from a dump site, dried de-carbonated, separated into six samples and calcined at a temperature of 600 °C, for 1, 2, 3, 4, 5 and 6 hours respectively. Samples were taken for X- ray Florescence (XRF) analysis, Standard Electron Microscopy (SEM) imaging, setting time, standard water of consistency determination and specific gravity test. The result of XRF analysis revealed that the SHA contain less than 70 % SiO2+Al2O3+Fe2O3 stipulated by ASTM C618 for pozzolanas, but has very high CaO content. The SiO2 +Al2O3+Fe2O3 and CaO content though varies slightly with the calcination time of soybean husk. The specific gravity of SHA varies with calcination time of SH and ranges between 2.3 and 2.7 and is less than that of OPC irrespective of the calcination time. Setting times of OPC/SHA pastes at 10 % replacement of OPC with SHA increases with calcination time and is greater than that for OPC paste. The SEM analysis shows that the crystal structure of the SHA changes with calcination temperature. The compressive strength of mortar using OPC/SHA as a binder was determined after 7, 14 and 28 days curing and was found to be less than that for OPC mortars at all ages. However, the percentage reduction in strength decreased with curing age, with SHA calcined at 4 hours having the greater strength (i.e. 87.4 % of OPC strength at 28 days). The percentage gain in strength was more pronounced from 7 to 14 days. In all, SH calcined at 600 °C for 4 hours optimizes the pozzolanic potential of SHA.Kathmandu University Journal of Science, Engineering and Technology Vol. 12, No. I, June, 2016, Page: 13-22

Pozzolanic and hydration properties of kamafugites and carbonatitic lavas as supplementary cementitious materials in Portland cement

Kamafugites and carbonatites, being materials of volcanic origin with carbonates as their primary minerals, are relatively low in silica and alumina saturation. Their silica and alumina under-saturation is considered a limiting factor in pozzolanic reactivity; however, these materials are currently being utilised as supplementary cementitious materials in Portland cement in Uganda. This paper presents the findings of an experimental study into their pozzolanic and hydration properties. Pastes and mortars made from cement samples blended with test kamafugites and carbonatites were studied for water demand, setting time, heat of hydration and strength development. Results show carbonatites and kamafugites, because of their low saturation of silica and alumina phases, to have less pronounced pozzolanic properties. The results also show no dependence on reactive silica content for pozzolanic performance after 28 days of curing. The kamafugites and carbonatites accelerated early heat of hydration, reduced setting time, and increased water demand. Although the carbonatites are currently utilized in blended Portland cement as natural pozzolans under the EN 197-1 and ASTM C618 cement standards, they do not meet the minimum composition requirement and volatile elements (LOI) demanded by these standards.

Bio-inspired self-healing cementitious mortar using Bacillus subtilis immobilized on nano-/micro-additives

Bio-inspired self-healing strategies are much innovative and potentially viable for the production of healable cement mortar matrix. The present research explores the feasibility of gram-positive “Bacillus subtilis” microorganisms in the effective healing of nano-/micro-scale-induced structural and non-structural cracks. The main concern related to the survival of such microorganisms in cementitious environment has been successfully addressed by devising proficient immobilization scheme coherently. The investigated immobilizing media includes iron oxide nano-sized particles, micro-sized limestone particles, and milli-sized siliceous sand. The effect of induced B. subtilis microorganisms immobilized on nano-micro-additives was analyzed by the quantification of average compressive resistance of specimens (ASTM C109) and healing evaluation. The healing process was mechanically gauged by compressive strength regain of pre-cracked specimens after the healing period of 28 days. The pre-cracking load was affixed at 80% of ultimate compressive stress “[Formula: see text]” while the age of pre-cracking was kept variable as 3, 7, 14, and 28 days to precisely correlate healing effectiveness as the function of cracking period. The healing mechanism was further explored by examining the healed micro-crack using field emission scanning electron micrographs, energy dispersive x-ray spectrographs, and thermogravimetry. The results revealed that B. subtilis microorganisms contribute extremely well in the improvement of compressive strength and efficient healing process of pre-cracked cement mortar formulations. The iron oxide nano-sized particles were found to be the most effective immobilizer for preserving B. subtilis microbes till the generation of cracks followed by siliceous sand and limestone particles. The micro-graphical and chemical investigations endorsed the mechanical measurements by evidencing calcite precipitation in the induced nano-/micro-cracks as a result of microbial activity.

EFFECTS OF ALUMINIUM ADDITION ON INHIBITION OF CONCRETE EXPANSION RESULTED FROM ALKALI SILICA REACTION (ASR)

Alkali-silica reaction (ASR) is one of the major causes of expansion, which ultimately leads to failure in concrete. When reactive concrete is subjected to humidity, alkali silicate hydrate gel (ASR gel) is formed. The swollen ASR gel exerts pressure and creates cracks in the concrete structure. This study, thus, aimed at inhibiting concrete expansion which was caused by the ASR reaction, by creating pores. To achieve pore formation, aluminium powder was used as an air entrainment agent. Mortar bars with aluminium content of 0.05, 0.1, 0.15 and 0.2 weight percent of cement was tested according to the ASTM C1260: Standard Test Method for Potential Alkali Reactivity of Aggregates. The results indicated that a larger quantity of entrained pores was achieved at higher aluminium content. The results also showed that when tested according to the ASTM C1260, concrete expansion was reduced as the aluminium content was increased. Microstructural analysis revealed that the entrained pores accommodated spaces for ASR gel, resulting in the decline of concrete expansion.

Performance-based criteria to assess the suitability of geopolymer concrete in marine environments using modified ASTM C1202 and ASTM C1556 methods

In marine or coastal zones, the most harmful exposure for reinforced concrete structures to chloride ions. The ASTM C1556 chloride diffusion test (or its European equivalent NT BUILD 443) has been widely used as the most reliable testing method to assess the performance of concrete against chloride penetration. However, this test is time demanding and labour intensive. As a result, accelerated test ASTM C1202 (RCPT) is often preferred, providing fast and acceptable assessment of chloride penetrability of Ordinary Portland Cement Concrete. This study aimed to investigate the suitability of RCPT to assess the performance of Geopolymer Concrete (GPC) in chloride environment. The correlation between several GPC properties [i.e. compressive strength, volume of permeable voids (VPV) and sorptivity] and the chloride diffusion coefficient are examined. Results indicate that the compressive strength, the VPV and the sorptivity coefficient are not suitable indicators of the GPC performance. The ASTM C1202 standard RCPT failed to measure the charges passed through most of the GPCs tested. A modified version of RCPT using 10 V (as opposed to 60 V specified by standard ASTM C1202) is proposed in this paper, allowing to successfully measure the charges passed through all GPC samples using a wide range of binders. A good correlation was observed between modified ASTM C1202 and Standard ASTM C1556 test results. Performance-based recommendations are proposed in this paper. Both experimental results from this study and appropriate reference concretes from the literature were used to calibrate the modified ASTM C1202 and ASTM C1556 performance-based requirements for GPCs.