Static Modulus Research Articles

Effect of initial temperature damage on the static and fatigue performance of all-lightweight shale ceramsite concrete

The effects of initial temperature damage on the static and compressive fatigue properties of LC30 all-lightweight shale ceramsite concrete (ALWSCC) were studied. The curing conditions ranged from -5 °C to -30 °C without antifreeze, with an elevated temperature range of 100 °C to 400 °C applied after 28 days of standard curing. We tested the static strength, elastic modulus, and stressstrain curves of ALWSCC, as well as its uniaxial compression fatigue life and ƐN curves under different stress levels. The credibility of data from only three test samples per condition was statistically analyzed, and we explored how temperature, aggregate properties, and concrete pore structure affect performance. The results indicate that the impact of temperature on the static and fatigue performance of ALWSCC can be described by a unified damage model. The Hillerborg characteristic length effectively captures the brittleness induced by temperature changes. Using the two-parameter Weibull equation and various fatigue equations that account for failure probability and temperature, the fatigue life predictions were accurate. Although low and high temperatures affect ALWSCC differently, temperature effects combined with static and fatigue loads further accelerate its deterioration.

Mechanical properties of recycled aggregate concrete reinforced with conventional and recycled steel fibers and exposed to high temperatures

The widespread use of concrete has significantly impacted the environment, resulting in substantial greenhouse gas emissions and strain on natural resources. This study investigated the mechanical properties of concrete made with recycled aggregate, conventional steel fibers and recycled steel fibers subjected to high temperatures. This is a crucial consideration in practical applications, such as structures exposed to fires or high temperature environments, and it is an integral part of assessing the durability and safety of alternative construction materials. The following variables were studied: three percentages of recycled aggregate substitution (0, 50 and 100 %), three quantities of conventional and recycled fibers (0, 40 and 80 kg/m3), four temperature steps (20, 200, 400 and 600 °C). The recycled steel fibers came from used tires. The studied variables were the consistency, the hardened density, the compressive strength, the dynamic and static elasticity modulus, the thermal conductivity, the flexural strength and the stress-strain behavior. Besides, scanning electron microscopy photographs were taken to analyze in detail the concrete structure. The main result obtained is that concrete with all recycled aggregate and recycled fibers underwent, in general, the same mechanical properties as a conventional concrete (without fibers and without recycled aggregate) for any temperature step.

Machine learning based prediction for bulk porosity and static elastic modulus of Yungang Grottoes sandstone

In this work, four mainstream machine learning (ML) techniques are used to evaluate the bulk porosity and static elastic modulus of weathered Yungang Grottoes sandstone. Datasets are gathered from the experiments, which includes 432 groups effective experimental data including 8 inputs features. bulk porosity and static elastic modulus were considered as outputs to determine the weathering degrees of Yungang Grottoes sandstone. The 4 performance criteria were used to evaluate the ML models. Results demonstrate that the Artificial Neural Network (ANN) is the best-fitted models for estimating the bulk porosity and static elastic modulus compared to Multiple Linear Regression (MLR), Support Vector Regression (SVR), Gaussian Process Regression (GPR). The accuracy of the trained model for static elastic modulus is slightly higher than that of bulk porosity. The GPR and ANN model can accurately predict the bulk porosity and static elastic modulus in training stages. The ANN with multi-hidden layers developed is competent with high degree of precision and generalization ability for bulk porosity and static elastic modulus compared to other selected regression-based ML models (MLR, SVR, and GPR). The coefficient of determinations of ANN in the range of (0.9537–0.9641) during the testing stages is more stable and higher than that of (0.8883–0.9453) other built ML models. The prediction efficiency of pretrained ANN model was well adjusted for the actual and forecast datasets at the training and testing stages, and the error range was no more than 0.7% and 0.15 GPa at both stages of prediction for bulk porosity and static elastic modulus respectively. And the ANN based static elastic modulus prediction model’s error proportions significantly decreased and were confined to a modest range between + 10% and − 10%. The proposed surrogate models are valid for the bulk porosity ranging from 7 to 14% and the static elastic modulus ranging from 0.7 to 1.4 Gpa, which can be utilized for the accurate and fast prediction of the weathering degrees of Yungang Grottoes sandstone.

Development of sustainable self-compacting concrete: Replacement of sand with municipal solid waste incineration ash molten slag and recycled fine aggregate

The purpose of this study is to develop self-compacting concrete using MSWA and RA as fine aggregates, supplemented with fly ash and GGBS that can modify the workability of the concrete. To evaluate the performance of sustainable self-compacting concrete, its mechanical properties, workability, drying shrinkage, and pore structure were comprehensively analyzed. The results demonstrate the feasibility of producing self-compacting concrete by replacing 50–100 % of sand with MS and RA, as all mixes in this experiment achieved the target slump flow of 600 ± 20 mm. The compressive strength remained unaffected for MS contents below 25 %, but at 50 % MS, it was 10 % lower than that of normal concrete. The drying shrinkage deformation of all specimens was below 700 μ, meeting the requirements for practical engineering applications. Incorporating fly ash increases porosity but transforms micropores larger than 100 nm into those smaller than 100 nm. Incorporating GGBS not only reduces porosity but also converts pores of 10–100 nm into gel pores smaller than 10 nm. Additionally, the suitability of various formulas correlating compressive strength and static elasticity modulus, recommended by American Concrete Institute (ACI 363), European Practice (EN 1992), and the Architectural Institute of Japan (JASS 5), was evaluated, and appropriate formulas were determined through regression analysis.

Measurement of the Static Nonlinear Third‐Order Elastic Moduli of Rocks: Problems and Applicability

AbstractThe third‐order elastic (TOE) model has been used to describe the widely observed nonlinear mechanical behaviors of earth materials. In addition to linear elastic constants (λ, μ), three nonlinear elastic moduli (A, B, C) are required for isotropic rocks. Contrary to previous research on dynamic TOE moduli, this study followed the protocol to measure strain and stress under uniaxial and hydrostatic compressive tests statically, which were later used to invert for the full set of TOE moduli for four standard rock types with differing pore structures of a porous oolitic limestone, quartz‐rich sandstones, and a dense crystalline basalt. The applicability of the TOE model to characterize nonlinearity depends on the fulfillment of path‐independence and small‐strain assumptions. Using the measured static TOE moduli, the finite element model demonstrates that the stress in the vicinity of the wellbore is more amplified than the stress in the linear elastic case, which leads to a wider zone of rock failure around the wellbore. Due to the long‐standing discrepancy between static and dynamic moduli, the rarely reported full set of static TOE moduli is necessary and will benefit future research in understanding the effect of rock nonlinearity on geophysical and geomechanical applications, such as long‐term safe storage of CO2 and generating process of geohazards.

New and Highly Accurate Static Young's Modulus Model Using Machine Learning Techniques.

Static Young's modulus (E s) is a critical property required in numerous petroleum calculations. Various models to forecast E s have been proposed in the literature. However, existing models, by and large, lack precision and are confined to specific data set ranges. This study proposes an alternative approach for E s determination, utilizing different machine learning methods, such as an adaptive neuro-fuzzy inference system (ANFIS). In these proposed methods, the predictor variables include bulk formation density (RHOB), shear wave velocity (DTs), and compressional wave velocity (DTc). The models were trained on a data set comprising 1853 hydrocarbon reservoir rock samples from globally diverse locations. They were evaluated using trend, group error, and statistical error analyses. To test the efficacy of the proposed models, the optimally performing model was identified and used to detect the rock types along with the previously published models. Results indicated that ANFIS is the optimum model and can predict E s with an average absolute percentage relative error (AAPRE) of 5.1% and a correlation coefficient (R) of 0.9602. The ANFIS method has some benefits over other machine learning approaches insofar as its superiority in reaching a quicker decision about the mapped relationship between the inputs and outputs because it combines artificial neural networks and fuzzy logic in one tool. The ANFIS can perform a highly nonlinear mapping and displays a better learning ability. The proposed ANFIS model demonstrates its ability to capture accurate physical relationships between input rock properties and E s through trend analysis, which shows that increasing the RHOB increases the E s. Contrarily, increasing the DTc and DTs reduces the E s. Furthermore, the ANFIS model can accurately detect the rock types based on its E s determinations. This research demonstrates the importance of accurately predicting E s for the proper identification of rock types. Thus, this study offers potential advancements in geological assessments of hydrocarbon reservoirs and improvements in many petroleum engineering applications.

EVALUATION OF PROPERTIES OF WOOD PLASTIC COMPOSITES MADE FROM SEVEN TYPES OF LIGNOCELLULOSIC FIBERS

This article aims to investigate the characteristics of wood plastic composites (WPC) prepared from polyethylene (PE) reinforced with lignocellulosic fibers derived from the xylem and bark of Masson pine, fir, cypress, as well as from Moso bamboo. The surface polarity and elemental composition of fibers were determined through contact angle measurements and X-ray photoelectron spectroscopy (XPS). The lignocellulosic fiber/PE composites were manufactured through hot-pressing technique, and their water absorption, mechanical properties, and mildew resistance were evaluated. The results revealed that the surface free energy of xylem fibers was higher than that of bark fibers among the three conifer species. XPS analysis showed that the O/C ratio of bark was consistently lower than that of xylem fiber. Among the three conifers, the Masson pine bark had the lowest O/C ratio (22.25%), while its xylem fibers had the highest ratio of 41.64%. WPC made with bark fibers had better water resistance. Additionally, the composites reinforced with xylem fibers showed superior static bending strength, impact strength, and mildew-resistant properties as compared to the composites reinforced with bark fibers. WPC made from bamboo fibers exhibited the best water resistance, with a water absorption rate and thickness swelling rate of 1.83% and 1.42%, respectively. They also had the highest static bending strength, elastic modulus, and impact strength, at 41.31 MPa, 3.82 GPa, and 10.24 kJ/m2, respectively. The WPC made from fir xylem fibers showed the most effective mildew resistance, with the smallest damage (0.50).

Dilatational rheological studies on the surface micelles of Poly(styrene)-[formula omitted]-Poly(4-vinyl pyridine) block copolymer at the air-water interface

A thin film of an amphiphilic block copolymer, poly(styrene)-b-poly(4-vinyl pyridine), is investigated at the air–water interface. The surface pressure - area per molecule isotherm and the static compressional modulus provide evidence of two phases, assigned as L1 and L2, respectively. The surface topography and the phase images of these phases obtained using atomic force microscope reveal the presence of surface micelles of different sizes and densities. The dilatational rheology of these phases was investigated using the oscillatory barrier method for different strain amplitudes (1−5%) and qualitatively assessed using Lissajous–Bowditch curves. It points out the emergence of nonlinearity (asymmetric shape and distorted ellipse) with an increase in strain amplitude. Using a fast Fourier transform, the amplitudes and the phases of different harmonics of the stress–strain curves were extracted, and the total harmonic distortion was determined. In contrast to L1 phase, the total harmonic distortion for the L2 phase increases monotonically with strain amplitude. Fixing the strain amplitude at 1% (small amplitude regime), the temperature as well as frequency dependence studies of the dilatational moduli were carried out. The dynamic storage moduli of the L1 phase is found to be insensitive to temperature while it decreases for the L2 phase suggesting softening. Further, evidence for solid-like viscoelastic response emerges (explained using the Kelvin–Voigt model) for the L1 phase, whereas the L2 phase show a cross-over behaviour.

A novel data-driven model for real-time prediction of static Young's modulus applying mud-logging data

A novel data-driven model for real-time prediction of static Young's modulus applying mud-logging data

A New Correlation for Estimating Static Elastic Properties of Sandstone Formations: Case Study from Rumaila Oilfield

Evaluating the elastic characteristics of reservoir's rocks is crucial for the oil and gas sector to reduce risks throughout drilling and production operations. Elastic parameters are essential for prediction of wellbore stability, estimation of in-situ stresses, optimization of drilling performance and design of hydraulic fracturing. Depending on the type of formation, Elastic parameter is varied dramatically. Thus, a precise way to identify these characteristics is needed. Inaccurate assessment of elastic characteristics can result in excessive expenditure and inappropriate field development plans. Static elastic modulus (Est) can be determined through laboratory testing. Although laboratory measurement is the most precise approach to determine the elastic modulus, it requires a continuous core sample to acquire a complete profile of the formation's elastic characteristics. However, just a portion of the well is typically sampled for cores. On the other hand, wireline log data is applied to determine the dynamic modulus (Edyn), allowing for continuous assessment of elastic properties. Numerous characteristics of the rock, including consolidation, pore pressure and lithology affect the dynamic modulus. Thus, it needs to be converted to Static elastic modulus by empirical formulae. Several empirical equations have been proposed to convert dynamic Young's modulus to static Elastic modulus. Nevertheless, the validity of these relationships is restricted and exclusive to certain areas. This research seeks to establish a relationship between Dynamic modulus and static Elastic modulus for sandstone formation of Rumaila oil field. The suggested correlation provides accurate predictions of the static elastic modulus for the complete sandstone segment. The newly created correlation performed better than the previous correlations in predicting static elastic modulus with average absolute error of 8.69 %, and correlation coefficient of 0.9848. The newly established empirical correlation can assist geo-mechanical engineers in estimating continuous profile of the sandstone formation's static modulus.

Study of Damage Mechanism and Evolution Model of Concrete under Freeze–Thaw Cycles

Researching the mechanical characteristics of concrete subjected to the freeze–thaw cycle is crucial for building engineering in cold climates. As a result, uniaxial compression tests were performed on concrete samples exposed to various freeze–thaw (F–T) cycles, and the measurements of the pore size distribution, porosity, and P-wave velocity of the saturated concrete samples were obtained, both before and after being exposed to the F–T cycles. Concrete’s F–T damage mechanism and damage evolution model were thoroughly examined. Using rock structure and moisture analysis test equipment to observe the T2 spectrum, the results showed that the F–T cycles can cause the internal structure of the samples to deteriorate. Porosity and F–T cycles have a positive correlation, although P-wave velocity has a negative correlation with the F–T cycles. As the F–T cycles increased, the specimens’ peak strength and elastic modulus steadily declined, while the peak strain clearly exhibited an increasing trend. A microscopic F–T damage model that takes into account the pore size distribution was developed, based on the relative changes in the pore structure distribution (PSD), before and after the F–T cycles. The concrete sample damage evolution law under various F–T cycles was examined using the following metrics: total energy, pore size distribution, static and dynamic elastic moduli, porosity, and P-wave velocity. Uniaxial compressive strength (UCS) and peak strain tests were used to evaluate the accuracy of the pore size distribution damage model, as well as that of five other widely used damage models.

An Experimental Investigation on the Effects of Temperature and Confining Pressure on the Static and Dynamic Behaviors of Shale Rocks

Abstract To better understand the associated thermal and mechanical effects on the elastic behaviors of shale rocks, we examine the shale rocks at reservoir stress (static) and elastic conditions (dynamic) at varying temperature (25–110°C) and pressure (5–55 MPa) conditions through coupling dynamic–static experimental measurements. The results illustrate that the shale’s P- and S-wave velocities increase with the increasing confining pressure but decrease with the elevated temperature. For the pressure history, ultrasonic P-wave velocities upon hydrostatic unloading are slightly larger than the loading ones, whereas S-wave velocities are almost overlapping together. Meanwhile, the temperature elevation causes much less velocity reduction at a higher confining pressure than lower confining pressure. The measured data demonstrate that the static bulk modulus is more sensitive to the confining pressure than the dynamic bulk modulus. Moreover, with the elevated temperature, the dynamic bulk moduli separate by showing a decreasing trend in either hydrostatic loading or unloading. The loading–unloading cycle shows that the static bulk moduli present values approaching the dynamic ones at all temperature levels when the confining pressure is initially unloaded from the maximum pressure. Both static and dynamic bulk moduli decrease with the continued unloading, with more decrement for the static bulk modulus. The coupling effects of the pressure and temperature on the static and elastic properties of shale samples imply that, in the practical shale reservoir characterization process, temperature and pressure influences should be considered to characterize the relation of dynamic and static properties of shale rocks. The laboratory investigations on shales imply that the relation of dynamic and static properties is pressure dependent mainly due to the intrinsic behavior of fracture, soft pore, and microstructure in the rock frame.

Moisture Impact on Static and Dynamic Modulus of Elasticity in Structural Normal-Weight Concretes.

In the case of concrete built into a structure, the static secant modulus of elasticity (Ec,s) is often estimated based on its dynamic value (Ed) measured by the ultrasonic pulse velocity method instead of direct tests carried out on drilled cores. Meanwhile, the prevailing equations applied to estimate Ec,s often overlook the impact of concrete moisture. This study aimed to elucidate the moisture impact across two normal-weight structural concretes differing in compressive strength (51.6 and 71.4 MPa). The impact of moisture content was notably more evident only for the weaker concrete, according to dynamic modulus measurements. In other cases, contrary to the literature reports and expectations, this effect turned out to be insignificant. These observations may be explained by two factors: the relatively dense and homogeneous structure of tested concretes and reduced sensitivity of Ec,s measurements to concrete moisture condition compared to Ed measurements obtained using the ultrasonic method. Additionally, established formulas to estimate Ec,s were verified. The obtained modulus results tested under different moisture conditions of normal-weight concretes were also compared with those of lightweight aggregate concretes of identical volume compositions previously obtained in a separate study.

Experimental Study on the Damage of Bridge Concrete in a Fire Environment Based on the Impact Echo Method

Abstract To accurately assess the damage degree of bridge structures in a fire environment, fire damage test studies were conducted on the C30 and C50 concrete specimens at different temperatures (room temperature, 100°C∼700°C) based on the impact echo method. In addition, the variation rules of mass, impact echo signal, dynamic modulus of elasticity Ed, and static and dynamic modulus of elasticity ratios (Ec/Ed) with overfire temperature were obtained. The results show the following: (1) at ablation temperature ≤ 300°C, the main frequency of the impact echo signal is single, the peak value is obvious, the signal attenuation is fast, and the change is uniform; at ablation temperature > 300°C, the main frequency is frequent, there is more than one peak, and the vibration duration of the phenomenon is longer. (2) After fire damage, the specimen’s dynamic modulus of elasticity Ed is in a cubic relationship with the overfire temperature. (3) In engineering practice, the static and dynamic modulus of elasticity (Ec/Ed) ratio is classically based on Lydon and Balendran’s formula, which is usually used for derivation at room temperature. This article found that the formula can be extended to the rough estimation at lower temperatures (≤200°C), and the model proposed in this article can be used for the derivation of the static modulus of elasticity Ec and the dynamic modulus of elasticity Ed at high temperatures. In summary, the impact echo method can be used to quantitatively assess the damage state of bridges after fire. After the signal time-frequency domain conversion, a qualitative assessment of the degree of concrete damage can be made. Furthermore, a quantitative assessment of bridge concrete after fire damage can be made using the model proposed in this article.

Mechanical Properties of LL6 Chondrites Under Pressures Relevant to Rocky Interiors of Icy Moons

AbstractIcy moons in the outer Solar System likely contain rocky, chondritic interiors, but this material is rarely studied under confining pressure. The contribution of rocky interiors to deformation and heat generation is therefore poorly constrained. We deformed LL6 chondrites at confining pressures ≤100 MPa and quasistatic strain rates. We defined a failure envelope, recorded acoustic emissions (AEs), measured ultrasonic velocities, and retrieved static and dynamic elastic moduli for the experimental conditions. The Young's modulus, which quantifies stiffness, of the chondritic material increased with increasing confining pressure. The material reached its peak strength, which is the maximum supported differential stress (σ1 − σ3), between 40 and 50 MPa confining pressure. Above this 40–50 MPa range of confining pressure, the stiffness increased significantly, while the peak strength dropped. Acoustic emission events associated with brittle deformation mechanisms occurred both during isotropic pressurization (σ1 = σ2 = σ3) as well as at low differential stresses during triaxial deformation (σ1 > σ2 = σ3), during nominally “elastic” deformation, indicating that dissipative processes are likely possible in the rocky interiors of icy moons. These events also occurred less frequently at higher confining pressures. We therefore suggest that the chondritic interiors of icy moons could become less compliant, and possibly less dissipative, as a function of the moons' pressure and size.

Research on triaxial compressive mechanical properties and damage constructive model of post-thawing double-fractured quasi-sandstones with different angles

Joints and fractures lead to different failure mechanisms in rock masses under different environments. The mechanical properties and failure mechanisms of rocks with fissures are key problems in rock mass engineering. Parallel double-fracture quasi-sandstone specimens with different dip angles were prepared and subjected to triaxial compression tests after a single freeze-thaw cycle. Pore development, crack propagation, damage evolution, and failure characteristics were analysed. Combined with the strength distribution theory of microelements and the static elastic modulus theory, a damage constitutive model of double-fracture quasi-sandstone under freeze-thaw cycles and loads was established. This study explored the pore development, fracture propagation, damage evolution, and failure characteristics of fractured sandstone after thawing. The results showed that the compression wave velocity of the thawed specimens decreased, the nuclear magnetic resonance (NMR) T2 curve shifted to the right, and the frost heave force promoted the development of the internal porosity in the specimens. With an increase in the crack dip angle, peak stress, expansion stress, cohesion and internal friction angle, the specimen showed a ‘U’ shaped change trend, compression cracks, and rock bridge penetration rate after failure decreased, and mixed failure of tension and shear gradually changed into shear failure. When the dip angles were 30° and 60°, the double fractured quasi-sandstone had larger total damage and more obvious brittle failure characteristics.

Comparison of methods for estimating Young’s moduli of mortar specimens

Precisely estimating material parameters for cement-based materials is crucial for assessing the structural integrity of buildings. Both destructive (e.g., compression test) and non-destructive methods (e.g., ultrasound, computed tomography) are used to estimate Young’s modulus. Since ultrasound estimates the dynamic Young’s modulus, a formula is required to adapt it to the static modulus. For this formulas from the literature are compared. The investigated specimens are cylindrical mortar specimens with four different sand-to-cement mass fractions of 20%, 35%, 50%, and 65%. The ultrasound signals are analyzed in two distinct ways: manual onset picking and full-waveform inversion. Full-waveform inversion involves comparing the measured signal with a simulated one and iteratively adjusting the ultrasound velocities in a numerical model until the measured signal closely matches the simulated one. Using computed tomography measurements, Young’s moduli are semi-analytically determined based on sand distribution in cement images. The reconstructed volume is segmented into sand, cement, and pores. Young’s moduli, as determined by compression tests, were better represented by full-waveform inversions (best RMSE = 0.34 GPa) than by manual onset picking (best RMSE = 0.87 GPa). Moreover, material parameters from full-waveform inversion showed less deviation than those manually picked. The maximal standard deviation of a Young’s modulus determined with FWI was 0.36, while that determined with manual picking was 1.11. Young’s moduli from computed tomography scans match those from compression tests the closest, with an RMSE of 0.13 GPa.

Synergistic effects of nano and micro silica on fresh and hardened properties of self-consolidating concrete

The escalating demand for methods to diminish cement usage without compromising the strength and durability of concrete mixtures has led to an intensified exploration of alternative mixture ingredients. Nano silica has emerged as a prominent supplementary cementitious material, recognized for its capability to partially substitute cement. Despite this potential, there was a gap in the literature on the effects of nano silica on the concrete’s fresh and hardened properties, particularly when used in conjunction with silica fume. This gap motivated the current investigation, aiming to capture and compare the effects of incrementally substituting silica fume with nano silica in self-consolidating concrete (SCC). For this purpose, four nano silica dosages—1%, 2%, 3%, and 5%— were considered as replacements for silica fume. A range of experiments, including slump flow, T50 time, and L-box tests, were conducted to assess the workability of the developed SCC mixtures. Subsequent analyses focused on key mechanical attributes, including the static modulus of elasticity, compressive strength, and tensile strength. The research further encompassed water absorption, penetration depth, and electrical resistivity evaluations to understand the durability characteristics of the developed mixtures. The scanning electron microscopy (SEM) analyses complemented these tests, offering a microstructural perspective to further explain the outcomes. This investigation’s findings offer novel insights into leveraging nano silica’s distinctive properties to achieve the desired SCC properties while reducing the environmental impact of this class of mixtures.

Effect of Corn Stover Ash Reinforced with Cabuya Fiber on the Mechanical Properties of Concrete

Currently, organic wastes are an environmental problem generating pollution, bad odors and accumulation of residues in northern Peru, among these products are corn stover and cabuya, predominant materials in the area. Therefore, this research focuses on determining the effect of optimum temperature and optimum percentage of corn stover ash (CSA) reinforced with different proportions of cabuya fiber (CF) on the mechanical properties of concrete. Two conventional designs of standard concrete called A and B (21 and 28 MPa) were made, to these designs were added percentages of CSA in 7%, 10%, 12% and 15% by substitution of the weight of cement to determine the optimum percentage, which was reinforced with percentages of cabuya fiber in 0.5%, 1%, 1.5% and 2% in volume of the concrete. The results showed that the optimum mix was A/B+7CSA, evidencing an improvement in compressive strength of 2.7% as opposed to the optimum CSA +CF hybrid mix, where it was observed that its mechanical properties of compressive strength, tensile strength, flexural strength and static modulus of elasticity decreased to 15.8%, 11.30%, 5.14% and 10.5%, respectively. It is concluded that corn stover ash reinforced with cabuya fiber does not positively influence the mechanical properties of concrete; however, it is an environmentally sustainable alternative to be used in non-structural concrete.

SOME PHYSICAL PROPERTIES OF LIGHTWEIGHT MORTARS WITH EXPANDED VERMICULITE

<p class="ABSTRACT">Expanded vermiculite was added to the cement-lime mortar at 10%, 20% and 30%, which reduced the density of the hardened mortar (HM) without expanded vermiculite (EV) by an average of 8,3% for the HM with 10% EV, 14,7% for the HM with 20% EV and 24,2% for the HM with 30% EV. Compressive and flexural strength and static modulus of elasticity were investigated and the relationships between these properties were determined. The effect of the added amount of EV on: total porosity, air void content and capillary suction of HM according to SIA 262, Appendix A; capillary water absorption; gas permeability and air permeability; water permeability and internal freeze/thaw resistance up to 200 cycles was investigated and determined.</p>