Control Mortar Research Articles

Improvement of High-Volume Fly Ash Cementitious Material Using Single Alkali Activation

This research aimed to present the improvement of the cementitious material in high-volume fly ash using only one alkali activator. Fly ash was used as a partial replacement for Portland cement type I, varying from 0 to 60% by weight of the binder. Concentrations of NaOH varying from 0.00 to 1.25 molar were used as alkali activator. Paste properties and mortar compressive strength at the ages of 3, 7, 14, 28, 60, and 90 days of water curing were investigated. The results reveal that fly ash paste with an alkali activator provides shorter initial setting time when compared to control paste without alkali activator. The use of 0.50 molar NaOH concentration in mortar containing fly ash not exceeding 50% by weight of binder provides the highest compressive strength at any age of curing. At that concentration, there is a significant increase in the 28-day compressive strength of up to 45% over that of the control mortar. In addition, higher NaOH concentration (not exceeding 1.00 molar) has a significant positive effect on the compressive strength of mortar with higher fly ash content, especially over longer curing periods.

Synthesis, application and unique effects of RGOEP on properties of alkali-activated slag binders

A highly-dispersed reduced graphene oxide/epoxy resin (RGOEP) composite was synthesized and used to improve related properties of alkali-activated slag (AAS) binders. This study scrutinizes the effects of epoxy resin and RGOEP composite on the hydration products, microstructure and mechanical properties (especially fracture toughness) of the AAS binders activated by water glass or NaOH solutions. The experimental results showed that RGOEP (3 wt%) is able to significantly improve the fracture toughness of the AAS mortars activated by water glass and NaOH, with more than 42.3 and 13.3 times greater, respectively, compared to the pure AAS counterpart. A peony flower-like hydration product was detected when RGOEP was used which is believed to result from the modification of AAS binding matrix by RGOEP at a nanoscale level. Besides, bonding tensile strength was also improved remarkably when 7 wt% GROEP was added into the BFS binders activated by water glass, almost up to 4.8 and 2.9 times as that of the control mortar and the one enhanced by 5 wt% EP, respectively. Thus, a unique advantage of reduced graphene oxide over epoxy resin in enhancing AAS binders was discovered. Considering a very low content of reduced graphene in epoxy resin (only 0.3 wt%), this research indicates great potential for wider industrial applications of this type of RGOEP in the AAS binders.

Comparative study on the performance of sand-based mortars from marble, floor tile and cinder block waste

This paper presents a comparative study of the role played by sands extracted from marble, floor tile and cinder block wastage on the properties, mechanical performance and durability aspects of a siliceous sand-based mortar. The main purpose is to appreciate the recovery of these sands in the composition of the mortar and to look for the best substitute for natural sand. Three series of mortar mixes were manufactured and compared to the formulation of the control mortar, which was based on a constant quantity of cement and a constant ratio of water/cement equal to 0.56. The various waste sands were used to substitute the dune sand in the reference mortar, at rates of 5%, 10%, 15% and 20%. Several tests were carried out on mortar specimens, namely: density, consistency, air content, mechanical strength tests, water absorption tests, and resistance tests against acid attacks. The results obtained, show a favourable effect of all sands on the properties in the fresh, hardened states and on the durability of the mortars. The mortar at 20% of marble sand waste is the one with the best performance of all the mortars, in terms of consistency, air content, flexural strength, water absorption and resistance to attack by acetic acid solution. However, the mortar with 20% of floor tile sand exhibits the highest compressive strength. Furthermore, the mortar-based 15% of cinder block sand is more resistant to attack by sulphuric acid. Thus, the use of ‘waste’ sand with appropriate dosages lowers the consumption of natural aggregates and contributes to improving the environment by reducing original waste.

Recycle of large amount cathode ray tube funnel glass sand to mortar with supplementary cementitious materials

Utilizing acid treated CRT funnel (T-CRTF) glass sand in mortar is a feasible option to lower natural resource consumption and protect the environment. In this study, T-CRTF glass sand replaces river sand in mortar at four levels (0, 25 %, 50 %, 75 %). The inclusion of T-CRTF glass sand improves the fluidity properties of mortar. At the initial curing period (3 days), T-CRTF glass sand mortar exhibits the larger hardened density, mechanical strength than river sand-based mortar. After all mortars cured in water for 90 days, the hardened densities and the mechanical strength of mortars with 25 %, 50 % T-CRTF glass sand are the slightly higher than control mortar. The use of the excessive T-CRTF glass sand can no increase anyway the long-term hardened density and mechanical strength of mortars. The recycle of T-CRTF glass sand to mortars reduces the water absorption, the chloride ion penetration, enhances the drying shrinkage, the alkali-silica reaction (ASR) expansion and the lead leaching amount. FA, GGBS mortars with 75 % T-CRTF glass sand have the lowest water absorption, chloride ion penetration in all mortars. The introduction of large amount T-CRTF glass sand to FA, GGBS mortars is more easily to induce the drying shrinkage, the ASR expansion and the long-term lead leaching from mortar. Considerations from the long- term mechanical strength, durability behaviors and environmental compatibility of mortar mixture, the application of 50 % T-CRTF glass sand in FA mortar is the sustainable method to dispose CRT funnel glass.

The effect of content and fineness of natural pozzolana on the rheological, mechanical, and durability properties of self-compacting mortar

Mineral admixtures are used in ordinary and self-compacting mortar to reduce carbon dioxide emission and enhance the performance of mortar at the fresh and hardened states. This paper reports the effect of the content and the fineness of natural pozzolana (NP) on rheological, compressive strength, total and autogenous shrinkage properties of self-compacting mortar. Capillary water absorption of self-compacting mortar was also investigated. Natural pozzolana was used as a partial cement replacement with two levels (15%wt. And 30%wt.) and ground to three specific surface Blaine (SSB) fineness measurements 350 m2/kg, 420 m2/kg and 500 m2/kg. Cement content, water to-binder ratio and superplasticizer content were kept constant for all self-compacting concrete mixtures. Rheological tests were conducted by measuring slump flow and V-funnel flow tests as well as using a rheometer to measure plastic viscosity and yield stress. Compressive strengths of self-compacting concretes were determined at 1, 7, 28, 56, 90 and 180 days of curing. Total and autogenous shrinkage were measured during three months and capillary water absorption of self-compacting mortar was also investigated after 90 days of water curing. The results indicated that the increase of replacement level of natural pozzolana affects negatively the rheological properties of self-compacting mortar. The same tendency is observed as the specific surface Blaine fineness increased. However, in the long-term (beyond 28 days of curing), the compressive strength of NP mixes exceeds that of control mortar. The increase of the fineness of natural pozzolana enhances compressive strength at later age but increases both the total and autogenous shrinkage compared with control mortar. It was observed that increasing the percentage of natural pozzolana generates an increase in water capillary absorption. However, increasing the fineness of natural pozzolana results in slightly lower water absorption of mortar.

Debonding of rubberised fibre-reinforced cement-based repairs under fatigue loading: experimental study and numerical modelling

ABSTRACT This study presents experimental and numerical studies of the initiation and propagation of interface debonding between the substrate and thin-bonded cement-based overlay under fatigue testing. The overlay material is mortar incorporating amorphous metallic fibres (30 kg/m) and/or rubber aggregates (30%), while the substrate is a plain mortar. Uniaxial tensile tests were carried out on overlay materials and substrate-overlay interface to obtain a residual normal stress-crack opening relationship (σ-w law) and residual normal stress and substrate-overlay interface debonding relation respectively. Three-point bending fatigue tests were carried out on the composite beam to analyse the structural behaviour of repaired beam. The propagation of debonding along the substrate-overlay interface was monitored by using the Digital 3D Image Correlation (DIC) technique. Three-point bending fatigue test was modelled by finite element method (FEM) using CAST3M, developed by French Atomic Energy Commission. Direct tension test results show reduction in tensile strength and improvement in strain capacity (1.5 times of control mortar) for rubberised mortars. For fibre-reinforced mortars, post-peak residual tensile strength is significantly enhanced. Rubberised fibre-reinforced mortars show positive synergetic effects both in the improvement of residual post-peak strength and strain capacity (3.5 times than control mortar). Results show that the rubberised fibre-reinforced thin-bonded cement-based overlay proved to be very effective in restraining crack opening, by transferring stresses through the crack, and enhancing the fatigue resistance of repair system, by limiting interface debonding propagation upto 50%. Experimental results of composite beams are in good agreement with modelling results.

Experimental Analysis of Changes in Cement Mortar Containing Oil Palm Boiler Clinker Waste at Elevated Temperatures in Different Cooling Conditions

Changes in cement-based materials containing waste after exposure to elevated temperatures are an important aspect that should be studied in developing sustainable construction materials. Modified cement-based materials obtained using the industrial waste present robust engineering properties can lead to sustainable development. This work evaluated the capacity of oil palm boiler clinker (OPBC) waste that had been produced during the palm oil extraction process as partial and full substitutions for natural sand to produce cement mortar. The mortar materials were cured under three different curing conditions and were then tested at a room temperature of approximately 27 °C and elevated temperatures of 200 °C to 1000 °C using an electric furnace. The specimens were maintained in the electric furnace under maximum temperatures for 2 h and were then cooled down with water or under ambient temperature. The changes in the forms of colour, weight, compressive strength, microstructure, mineralogical composition, and thermal conductivity were investigated. Test results showed that the compressive strength of OPBC mortars was generally higher than the strength of the control mortar after heat exposure. Water cooling exerted less damage to samples compared to air cooling. The results from field emission scanning electron microscopy–energy-dispersive X-ray spectroscopy demonstrated that the mineral composition varied at different temperatures. In conclusion, this work provides an extensive report and can be used as a guide in utilising OPBC as cementitious materials for future cement-based applications.

Design and experimental study of a blended cement containing high-volume solid waste activated ultrafine powder

To improve the utilization efficiency of industrial solid waste and reduce the cost of cement production, a blended cement containing high-volume solid waste activated ultrafine powder (AUP) is designed and prepared. The experimental works are divided into two parts. In the first part, steel slag (SS), blast furnace slag (BFS), fly ash (FA), and desulfurized gypsum (DG) are separately ground and mixed properly to prepare a solid waste AUP, and the effect of the mixture properties on the activity index of the AUP is evaluated. The AUP with the highest activity index is selected in the second part to replace the cement at levels of 95%, 90%, 85%, 80%, and 75%, and the properties of the blended cement containing high-volume AUP (C-AUP) are analyzed. The C-AUP mortar is shown to exhibit higher compressive strength and lower heat of hydration than the control mortar. Compared with pure cement, the hydration degree of the C-AUP has a large gap. However, the C-AUP has fewer harmful pores and lower porosity, resulting in a high-strength mortar with a dense microstructure. In addition, carbon footprint analysis is conducted, the results of which show that the amount of CO2 released during C-AUP production is 270 kg/t less than that of pure cement.

Experimental studies on the utilization of kaolinite amalgamated in cement mortar

Objective: To investigate the physical and strength properties of mortar using locally available mineral admixture. Methodology: The compressive strength of the mortar at different temperatures was found. Setting time, consistency, and porosity were also studied by blending natural kaolinite and metakaolinite (MK) with cement in different proportions. An experimental work was carried out using control mix and adding kaolinite from 5% to 20% in ordinary Portland cement (OPC) at 5% equal intervals. Findings: The test results revealed that the use of natural admixtures such as Natural kaolinite (NK) and MK in OPC enhances the performance of the binder in mortar. The compressive strength enhancement of natural kaolinite cement–blended binder was comparatively lower than that of control mortar for all percentages whereas the mortar added to MK had increased strength. MK mortar with a 15% mix proportion was the optimum one to yield maximum compressive strength. Novelty: The present research work is focused on the partial replacement of metakaoline with temperature variant and the percentage of dosage used as a double variant parameter. Keywords: Natural kaolinite; Metakaolinite; Calcination; Apparent porosity; Compressive strength

Finite Element-Based Numerical Simulations to Evaluate the Influence of Wollastonite Microfibers on the Dynamic Compressive Behavior of Cementitious Composites.

This paper investigates the dynamic compressive behavior of wollastonite fiber-reinforced cementitious mortars using multiscale numerical simulations. The rate dependent behavior of the multiphase heterogeneous systems is captured in a multiscale framework that implements continuum damage towards effective property prediction. The influence of wollastonite fiber content (% by mass) as cement replacement on the dynamic compressive strength and energy absorption capacity is thereafter elucidated. An average compressive strength gain of 40% is obtained for mortars with 10% wollastonite fiber content as cement replacement, as compared to the control mortar at a strain rate of 200/s. The rate dependent constitutive responses enable the computation of energy absorption, which serves as a comparative measure for elucidating the material resistance to impact loads. Approximately a 45% increase in the dynamic energy absorption capacity is observed for the mixture containing 10% wollastonite fibers, as compared to the control case. Overall, the study establishes wollastonite fibers as a sustainable and dynamic performance-enhanced alternative for partial cement replacement. Moreover, the multiscale numerical simulation approach for performance prediction can provide an efficient means for the materials designers and engineers to optimize the size and dosage of wollastonite fibers for desired mechanical performance under dynamic loading conditions.

Absorption and Strength Properties of Short Carbon Fiber Reinforced Mortar Composite

This paper presents the water absorption and strength properties of short carbon fiber reinforced mortar (CFRM) composite. Four CFRM composites with 1%, 2%, 3%, and 4% short pitch-based carbon fibers were produced in this study. Normal Portland cement mortar (NCPM) was also prepared for use as the control mortar. The freshly mixed mortar composites were tested for workability, wet density, and entrapped air content. In addition, the hardened mortar composites were examined for compressive strength, splitting tensile strength, flexural strength, and water absorption at the ages of 7 and 28 days. The effects of different carbon fiber contents on the tested properties were observed. Test results showed that the incorporation of carbon fibers decreased the workability and wet density, but increased the entrapped air content in mortar composite. Most interestingly, the compressive strength of CFRM composite increased up to 3% carbon fiber content and then it declined significantly for 4% fiber content, depending on the workability and compaction of the mortar. In contrast, the splitting tensile strength and flexural strength of the CFRM composite increased for all fiber contents due to the greater cracking resistance and improved bond strength of the carbon fibers in the mortar. The presence of short pitch-based carbon fibers significantly strengthened the mortar by bridging the microcracks, resisting the propagation of these minute cracks, and impeding the growth of macrocracks. Furthermore, the water absorption of CFRM composite decreased up to 3% carbon fiber content and then it increased substantially for 4% fiber content, depending on the entrapped air content of the mortar. The overall test results suggest that the mortar with 3% carbon fibers is the optimum CFRM composite based on the tested properties.

The effect of furnace steel slag powder on the performance of cementitious mortar at ambient temperature and after exposure to elevated temperatures

Induction furnace steel slag is a secondary product obtained when molten steel is separated from the impurities in the steel-producing furnaces. Though numerous studies have been published on the mechanical strength of concrete/mortar made with steel slag as fine aggregate, relatively few studies focus on the shrinkage, durability (i.e., porosity, water absorption, and resistance to chloride penetration) at ambient temperature, and especially the mechanical and durability performances after exposure to elevated temperatures. Within this context, the present study investigates mechanical strength, shrinkage, and durability of mortar made with different contents of steel slag powder (SSP) at two different water-to-cement (w/c) ratios before and after exposure to elevated temperatures (120, 250, 400 and 600 °C). Mortars made with SSP showed significantly higher mechanical strength and better durability than mortar made with 100% natural sand (control mortar). Compressive, tensile, and flexural strength increased by 45%, 72% and 56%, respectively, when SSP entirely replaced natural sand. Porosity, water absorption, and chloride penetration decreased by 42%, 61% and 52%, respectively, for 100% SSP mortar. Furthermore, the shrinkage of the mortar decreased with increasing percentages of SSP. Conversely, residual compressive strength after heat exposure was lower for 100% SSP mortar than for the control mortar. Therefore, this study presents a first step towards the successful utilization of SSP in cementitious mortar.

Mechanical Properties of Tin Slag Mortar

The increased demand for cement mortar due to rapid infrastructural growth and development has led to an alarming depletion of fine aggregate. This has prompted the need for a more sustainable material as a total/partial replacement for natural fine aggregate. This study proposes the use of tin slag (TS) as a replacement for fine aggregate in concrete to bridge this sustainability gap. TS was used to replace fine aggregate at replacement levels of 0%, 25%, 50%, 75%, and 100% in cement mortar. Fresh and hardened properties of TS mortar were obtained. Flow tests showed that, as the TS quantity and the w/c ratio increased, the mortar flow increased. Similarly, the compressive strength increased as the TS replacement increased up to 50% replacement, after which a decline in strength was observed. However, with the TS replacement of fine aggregate up to 100%, a compressive strength of 6% above control was attained. The morphological features confirm that specimens with TS had a denser microstructure because of its shape characteristics (elongated, irregular, and rough), and, thus, plugged holes better than the control mortar. The natural sand’s contribution to strength was a result of better aggregate hardness as compared to TS. Hence, TS can be used as alternative for fine aggregate in sustainable construction.

Development of piezoresistive cement-based sensor using recycled waste glass cullets coated with carbon nanotubes

Different from widely exploring the application of waste glass to replace natural aggregate or cement powder, this study firstly utilized waste glass cullets coated with carbon nanotubes (CNTs) as conductive fillers to develop novel self-sensing cement-based sensors. The coating efficiency of CNTs and self-sensing properties were also investigated in terms of workability, water absorption, mechanical properties, electrical resistivity and microstructure. The results show that CNTs are attached to the surfaces of waste glass particles, especially the small-size waste glass particles with high roughness. Workability decreased significantly with the increased waste glass. Cementitious mortar with sand replaced by CNTs-coated waste glass exhibited the highest flowability when the replacement ratio was 25%. Moreover, the water impermeability continuously increased with the content of waste glass. The compressive strength was higher than that of the control mortar, which reached the highest with 50% waste glass content. Additionally, an excellent piezoresistivity was achieved for cement-based sensors with CNTs-coated waste glass particles for the self-monitoring of stress magnitude and failure. The CNTs are uniformly distributed well in the cement matrix by attaching the surfaces of waste glass particles, thus the conductive passages are formed in cement-based sensors for structural health monitoring.

Bioremediation of mortar made from Ordinary Portland Cement degraded by Thiobacillus thioparus using Bacillus flexus

Cement is widely used as a construction material in the construction industry. However, there are challenges affecting its durability efficacy. Cement mortar/concrete is subject to degradation by aggressive ions such as sulphates and chlorides. Sulphates can be introduced into the concrete or mortar by Sulphur producing bacteria of the species Thiobacilli. Microbiologically induced CaCO3 precipitation (MICP) has found its application in bioremediating cement based materials. It has been found to be environmental friendly. However, no work has been reported on bioremediation of biodegraded cement based materials. This paper presents findings of possible bioremediation of mortars after undergoing biodegradation. Bacillus flexus, a beneficial bacterium was used. The control mortars were prepared using Ordinary Portland Cement (OPC). The test mortars were prepared and cured in a solution of Thiobacillus thioparus, a Sulphur oxidizing bacteria, deleterious bacterium for 14, 28, 56 and 90 days. Compressive strength analysis was conducted on the 14th, 28th, 56th and 90th day of curing. Results showed that the lowest compressive strength was recorded on the 90th day as 31.02 MPa. This was a 34.17 % loss in compressive strength. Another category of mortar cured in Thiobacillus thioparus for 28 days was bioremediated for 28 days using Bacillus flexus solution. Compressive strength and Scanning Electron Microscopy (SEM) analyses were then done. The results show a compressive strength of 45.83 MPa at the 56th day. This represents a 99.91 % strength recovery from biodeterioration. The SEM analysis results revealed a denser material. This was due to massive precipitation of calcium carbonate in the mortar matrix and pores/voids for bioremediated mortars as opposed to the biodegraded mortars. The results further revealed reduced ettringite crystals on the bioremediated mortars. Bacillus flexus could perhaps be used in restoring lost compressive strength as well as in sealing voids in degraded concrete in sewer lines and other cement based materials. This could improve on its efficacy with minimal repair.

Effects of ground basaltic pumice and high temperatures on the properties of HSMs

The mechanical and microstructural properties of high strength mortars (HSMs) containing ground basaltic pumice (GBP) subjected to 25, 300, 600, 900 and 1050 °C temperatures are investigated in this article. The mortars containing GBP employing the replacement ratio up to 25% GBP by weight of ordinary Portland cement (OPC) as well as a control mortar manufactured with OPC are produced. Two different cures, which are steam curing and pochette curing, are applied to the fresh mortars produced. The unit weight (ρ), ultrasonic pulse velocity (Upv), flexural strength (fs) and compressive strength (fc) of mortars containing GBP are investigated at the short/long terms and high temperatures. The microstructural properties of mortars containing GBP at high temperatures are also investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDAX) analyses. The results have shown that GBP can be successfully used instead of OPC in the mortar mixtures. Especially, the steam curing application has improved the mechanical properties of mortars containing GBP better than those of pochette curing.

Impact of Alfa fibers morphology on hydration kinetics and mechanical properties of cement mortars

The Alfa plant is indigenous and spans a large zone throughout North Africa. Recently, Alfa plant has been used in building materials, notably as a reinforcement. This study aims to valorize the Alfa plant into fiber-reinforced mortar based on a cement-glass composite mix design. Two Alfa fiber morphologies are considered herein: different cutting lengths (10, 20 and 30 mm), and ground using a knife mill (shorter than 2 mm). These fibers were added to mortars at various volume ratios: 1, 2 and 3%. The workability and density of these distinct formulations were then measured in their fresh state. In comparison with the control mortar (CM), the introduction of Alfa fibers (either cut or ground), with ratios below 2% vol., leads to a slight decrease in mixture workability. However, Alfa fibers do not significantly alter the fresh material density. It was recorded a delay in setting time of the composites as a function of fiber addition rate. In the hardened state, an improvement in flexural strength is noticed for mortars reinforced with 1% vol. of fibers compared to the CM. However, results show that the increase in either type of fiber (cut or ground) generates a decrease in compressive strength compared to the CM. This outcome can be confirmed by both the decrease in heat released during the hydration reaction and water-accessible porosity inside the matrix.

Properties of Self-Compacting Mortar Containing Slag with Different Finenesses

It is well established that Self-Compacting Concrete (SCC) contains large amounts of fines including mineral admixtures, such as fly ash and slag, in order to avoid segregation and to increase cohesion. The use of these materials in concrete reduces CO2 emissions and contributes towards sustainable construction. To overcome the negative effect of slag on the strength development slag was ground to three finenesses. Therefore, this paper examines the rheological, compressive strength, total and autogenous shrinkage and capillary water absorption of Self-Compacting Mortars (SCM) containing ground granulated blast furnace Slag (S). A total of seven mortar mixes were prepared. The control mix had a proportion of 1 (cement): 1.8 (sand): 0.38 (water). In the other mixes, the cement was partially replaced with 15% and 30% slag of different fineness of 350, 420, and 500 m2/kg. The other constituents remained unchanged. Testing included slump flow, V-funnel flow time, yield stress and viscosity, compressive strength, total and autogenous shrinkage, and capillary water absorption. The presence of slag was found to reduce the plastic viscosity and yield stress of SCM mixtures as the content and the fineness increase. The higher the fineness (specific surface) of the slag the less the rheological parameters (i.e. slump flow and viscosity). The results show also a reduction in compressive strength of SCM at early ages of curing in the presence of slag. However, in the long-term, the compressive strength of SCM mixtures containing slag was higher than that of control mortar. Generally, there is reduction in the total shrinkage and an increase in the autogenous shrinkage of SCM mixtures as the content and fineness increase. Doi: 10.28991/cej-2021-03091694 Full Text: PDF

Thermophysical Properties of Cement Mortar Containing Waste Glass Powder

This study aims to provide a thermophysical characterization of a new economical and green mortar. This material is characterized by partially replacing the cement with recycled soda lime glass. The cement was partially substituted (10, 20, 30, 40, 50 and 60% in weight) by glass powder with a water/cement ratio of 0.4. The glass powder and four of the seven samples were analyzed using a scanning electron microscope (SEM). The thermophysical properties, such as thermal conductivity and volumetric specific heat, were experimentally measured in both dry and wet (water saturated) states. These properties were determined as a function of the glass powder percentage by using a CT-Meter at different temperatures (20 °C, 30 °C, 40 °C and 50 °C) in a temperature-controlled box. The results show that the thermophysical parameters decreased linearly when 60% glass powder was added to cement mortar: 37% for thermal conductivity, 18% for volumetric specific heat and 22% for thermal diffusivity. The density of the mortar also decreased by about 11% in dry state and 5% in wet state. The use of waste glass powder as a cement replacement affects the thermophysical properties of cement mortar due to its porosity as compared with the control mortar. The results indicate that thermal conductivity and volumetric specific heat increases with temperature increase and/or the substitution rate decrease. Therefore, the addition of waste glass powder can significantly affect the thermophysical properties of ordinary cement mortar.

Correlation Between Ultrasonic Pulse Velocity (UPV) and Compressive Strength of Coal Bottom Ash Mortar

The utilization of coal bottom ash (CBA) as natural sand replacement in mortar is a feasible solution to reduce the environmental issues created due to its disposal. However, strength behavior of CBA mortar varies from conventional natural sand mortar. For design and quality control in the field, there is a need to assess the feasibility of nondestructive test methods in estimating the in situ mechanical properties of CBA mortar. To address this, the present research study elaborates the correlation between compressive strength and ultrasonic pulse velocity to predict the compressive strength of CBA mortar using UPV test. The influence of CBA replacement level and curing age was examined. The experimental program involves two mortar mix proportioned cement-fine aggregate ratios of 1:3 and 1:5 having standard flow of 110–115%. The natural sand replacement with CBA varies from 20 to 100% in increment of 20%. Control mortar mix contains 100% natural sand. Mortar samples were casted, cured at ambient temperature and then tested at curing age of 7 days, 28 days, 56 days, 90 days and 120 days. Workability and density test of mortar specimens have also conducted for reference. Results indicate that the UPV and compressive strength of CBA mortar were lower than those of the control mortar for all replacement levels at all curing age and for all mixes. The empirical relationships obtained between compressive strength and UPV were exponential in nature with high correlation coefficient varying from 0.91 to 0.99. The feasibility of developed empirical equations in predicting the compressive strength was validated by comparing the predicted results with measured test results.