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Although ultra-high-performance concrete (UHPC) is one of the promising materials for precast bridge girder applications due to its advanced properties and durability, its implementation in the precast industry is subject to several potential concerns. To support implementation, this paper presents the development of nonproprietary UHPC mixtures for precast, pretensioned UHPC bridge girder applications. The nonproprietary UHPC mixtures were developed using materials commonly available in the Texas precast industry, with the additional requirement of obtaining a compressive strength of 12 to 14 ksi (83 to 97 MPa) within 24 hours without any heat treatment while maintaining the current precast, pretensioned bridge girder fabrication practices. The fresh, hardened, and durability properties of both laboratory- and plant-made UHPC mixtures were investigated. The research results show that the selected nonproprietary UHPC mixture developed in a laboratory setting can be successfully produced in a precast plant setting with comparable properties. [ABSTRACT FROM AUTHOR]

In light of the effort for decarbonization of the energy sector, it is believed that common geopolymer binding materials such as fly ash may eventually become scarce and new geological aluminosilicate materials should be explored as alternative binders in geopolymer concrete. A novel, tension-hardening geopolymer concrete (THGC) that incorporates high amounts of semi-reactive quarry wastes (metagabbro) as a precursor, and coarse quarry sand (granite) was developed in this study using geopolymer formulations. The material was optimized based on the particle packing theory and was characterized in terms of mechanical, physical, and durability properties (that is, compressive, tensile, and flexural resistance; Young's modulus; Poisson's ratio; absorption; drying shrinkage; abrasion; coefficient of thermal expansion; and chloride-ion penetration, sulfate, and salt-scaling resistance). The developed THGC, with an air-dry density of 1940 kg/m³ (121 lb/ft³), incorporates short steel fibers at a volume ratio of 2%, and is highly ductile in both uniaxial tension and compression (uniaxial tensile strain capacity of 0.6% at an 80% post-peak residual tensile strength). Using digital image correlation (DIC), multiple crack formation was observed in the strain-hardening phase of the tension response. In compression, the material maintained its integrity beyond the peak load, having attained 1.8% compressive strain at 80% post-peak residual strength, whereas upon further reduction to 50% residual strength, the sustained axial and lateral strains were 2.5% and 3.5%, respectively. The material exhibited low permeability to chloride ions and significant abrasion resistance due to the high contents of metagabbro powder and granite sand. The enhanced properties of the material, combined with the complete elimination of ordinary portland cement from the mixture, hold promise for the development of sustainable and resilient structural materials with low CO2 emissions, while also enabling the innovative disposal of wastes as active binding components. [ABSTRACT FROM AUTHOR]

Ultra-high-performance concrete (UHPC) is considered a sophisticated concrete construction solution for infrastructure and other structures because of its premium mechanical traits and superior durability. Fibers have a special effect on the properties of UHPC, especially as this type of concrete suffers from high autogenous shrinkage due to its high cementitious content, so the properties and volume fraction of fibers are more important in UHPC. This study will describe previous related works on the mechanical behavior of UHPC specimens reinforced with micro- and nanoscale fibers, and compare of the behavior of UHPC reinforced with microfibers to that reinforced with nanofibers. The compressive strength, flexural behavior, and durability aspects of UHPC reinforced with nanoand/or microscale variable types of fibers were studied to highlight the issues and make a new direction for other authors. [ABSTRACT FROM AUTHOR]

Several incidents of early deterioration of structures have been reported in literature; such incidents have a negative impact. Insufficiencies in the durability design may result from a possible absence of explicit guidelines in design codes and standards that establish a standardized language for building design, construction, and operation. Most design codes and standards, while providing a robust framework for structural capacity and serviceability, do not address durability design to a desirable degree. This study examines and critically reviews the durability design in three international codes: the American, British, and Eurocodes. The study revealed that the European and British standards have comparatively more precise and comprehensive durability provisions, whereas the American code has a larger scope for development. The study introduces a proposal for the improvement of durability design provisions in codes to provide beneficial examples that can assist in the update of upcoming editions of these codes. [ABSTRACT FROM AUTHOR]

The penetration of chloride ions causes degradation of reinforcing bars, which directly affects the service life of the element. In this study, four different alternatives for the construction of a reinforced concrete (RC) caisson parapet beam are investigated: conventional RC, the addition of a corrosion inhibitor to concrete, and the use of glass fiber-reinforced bars (GFRP) and galvanized steel instead of steel bars. The durability of the RC element under marine environment was studied based on measurements performed both in-place and in well-controlled laboratory conditions on specimens prepared in the laboratory, as well as specimens taken from the actual structural element. It was concluded that the exposure of fresh concrete to seawater splash has no effect on mechanical properties. In addition, galvanized rods were found to be a less effective protection strategy compared to the other alternatives studied. GFRP bars, however, provide better protection than the other tested alternatives, although chloride ion penetration in these bars was found to be more accelerated in an alkaline environment compared to a chloride environment. In contrast to the prevailing approach, which considers plain concrete and according to which the electrical resistance of the concrete decreases because of chloride penetration, this study found that electrical resistance in the reinforced element is increased due to an increase in the amount of corrosion products formed between steel and concrete if no cracks occur. Furthermore, it was found that the potential measured using the half-cell method in all the alternatives slowly increased with time, as well as the corrosion risk in the three alternatives with reinforcing steel. The remaining question is whether this change of potential is a direct characteristic of the corrosion risk. Therefore, more research in this direction is needed. [ABSTRACT FROM AUTHOR]

This research examines the performance of quality-controlled recycled concrete aggregates (QRAs) with fly-ash-based cement. Compared to concrete made from untreated recycled concrete aggregates (URC), quality-controlled recycled aggregate concrete (QRC) has superior physical, mechanical, and durability prop)erties. Except for sorptivity, the physical, mechanical, and dura)bility properties of QRC are almost identical to those of natural aggregate concrete (NC). The compressive strength, splitting tensile strength, flexural strength, fracture energy, and modulus of elasticity of QRC are higher than those of URC by 18.0%, 16.8%, 60.0%, 27.17%, and 43.46%, respectively. The abrasion resistance of QRC is approximately 60% higher than URC. Scanning electron microscope (SEM) image and energy-dispersive X-ray (EDX) anal)ysis prove that quality control produces denser old interfacial tran)sition zones (OITZ) with fewer microvoids. The QRA improves not only the pore structure but also the weak mortar structure attached to the aggregate. There is also a strong correlation between the compressive strength and splitting tensile strength, flexural strength, fracture energy, and modulus of elasticity of QRC. QRA can be used to compute the mixture proportions for concrete (certainly up to medium-strength concrete) according to either the Indian standard or the international standard. It is challenging to improve the sorptivity of recycled concrete aggregates closer to NC. In addition, QRC has an initial sorptivity of two times (initial) and a final sorptivity of 1.8 times higher than NC, whereas URC has an initial sorptivity of 3.5 times (initial) and a final sorptivity of 2.35 times higher than NC. [ABSTRACT FROM AUTHOR]

This study clarifies the effects of moisture (expressed as percentage saturation degree of permeable pore voids, PSD) on water ingress properties of concrete and establishes a region where PSD does not affect the quantitative water absorption. Experimental measurements and finite element model (FEM) simulation results for ordinary portland cement (OPC) concretes preconditioned to equilibrium moisture formed plateaus between 21 and 58% PSD. Non-continuous finer capillary pores (ϕ10 nm [3.937 × 10-4 mil, thou] to ϕ100 nm [3.937 × 10-3 mil, thou]) constitute the empty pores within the plateau region before tests. Water sorptivity of OPC and slag cement concrete blocks at several degrees of surface moisture with internal moisture gradients validate the existence of the plateau within the PSD range. Measuring short-term water absorption within this plateau region eliminates the effects of initial surface moisture content on the measured properties and evaluates the continuity and connectivity of pores, which is the major indicator of the durability of concrete. [ABSTRACT FROM AUTHOR]

This study proposed using carbon dioxide (CO2) as an indirect admixture for calcined clay blended pastes. By injecting CO2 gas into limewater, solid nano-CaCO3 particles were synthesized and used to partially replace the binder at ratios of 2, 4, and 6%. Various tests and analyses were performed on the calcined clay blended pastes. After adding nano-CaCO3, the strength, ultrasonic pulse velocity, hydration heat, and electrical resistivity were improved; monocarboaluminate and hemicarboaluminate were formed; and CO2 emissions were lowered. The electrical resistivity was improved more significantly than the strength. The reduction ratio in CO2 emissions was higher than the replacement ratio of nano-CaCO3. In summary, based on the transformation of gaseous CO2 to solid nano-CaCO3 particles, the proposed technique shows a similar concept to limestone calcined clay cement (LC3) concrete and can overcome the limitations of carbonation curing. [ABSTRACT FROM AUTHOR]

The current paper investigates the effects of partial cement replacement with nano-titanium dioxide (nano-TiO2 [NT]) in varying weight proportions in concrete. In the C20/25 grade of concrete, NT was added by weight of cement with partial replacement of 0, 0.5, 1.5, 2.0, 2.5, and 3.0% using portland pozzolana cement. The physical and mechanical properties of the resulting concrete were assessed, as well as aspects of durability such as sorptivity and nondestructive tests (NDT) such as ultrasonic pulse velocity (UPV). Compared with the control mixture, the fresh concrete produced showed a drastic reduction in slump with increasing percentage of replacement, with a 54% reduction at a 3.0% replacement. Furthermore, for 1.5% NT, the compressive, flexural, and splitting tensile strengths peaked at 7, 28, 56, and 90 days, after which the values decreased. The addition of NT improved the homogeneity and integrity of the resulting concrete based on the UPV values. As the percentage of NT increased, chloride penetration decreased. From microstructural studies, it can be concluded that NT acts as a filler material and can be used as a partial replacement for cement in concrete up to 2% by weight. [ABSTRACT FROM AUTHOR]

This study aims to investigate the possibility of using Linz-Donawitz (LD) slag as one of the cementitious materials for preparation of composite slag (having 8 and 15% LD slag), which will subsequently be used for manufacturing portland slag cement (PSC). PSC samples (having overall 4 to 9% LD slag) were prepared using LD slag from two sources in a laboratory ball mill. PSC samples were analyzed for various chemical characteristics and physical properties. Studies were conducted on concrete mixtures prepared at water-cement ratios (w/c) of 0.65 and 0.40. Fresh, hardened, and durability properties of concrete mixtures prepared using PSCs made with composite slag having up to 15% LD slag were found to be comparable to their corresponding control mixtures. Based on results, it was observed that composite slag having LD slag up to 15% of total slag can be used up to 60% for manufacturing PSC along with clinker and gypsum. The 3-, 7-, and 28-day compressive strength of PSC samples containing LD slags in different proportions were found to be comparable to control PSC samples and meeting the requirements of IS 455:2015. Even though the free lime content in LD slags was significantly higher (free lime content of 3.03 and 3.48%) in comparison to granulated blast-furnace slag (GBFS), it had almost a negligible effect on the PSC prepared using LD slag and soundness of experimental and control PSC was comparable because the maximum amount of LD slag added in overall PSC was restricted to 9%. The addition of LD slag in different proportions up to 9% in overall PSC does not seem to have any detrimental effect on performance of concrete in terms of sorptivity, carbonation depth, chloride penetration, and diffusion, which indicates its suitability for application in reinforced concrete structures. [ABSTRACT FROM AUTHOR]

An important part of improving the embodied carbon of the built environment is reducing carbon emissions associated with concrete. The long-term limitations around the availability of supplementary cementitious materials (SCMs) to replace portland cement have driven the search for additional innovative approaches. The beneficial use of carbon dioxide (CO2) in ready mixed concrete production has been developed and installed as retrofit technology with industrial users. An optimum dose of CO2 added to concrete as an admixture leads to the in-place formation of mineralized calcium carbonate (CaCO3) and can increase the concrete compressive strength. The improved performance can be leveraged to design concrete mixture proportions for a more efficient use of portland cement, along with the use of CO2 to reduce the carbon footprint of concrete. One producer has used the technology, starting in 2016, at over 50 plants. More than 3 million m3 of concrete have been shipped with an estimated net savings of 35,000 tonnes of CO2. The concrete produced with carbon dioxide is discussed in terms of the fresh and hardened performance, durability performance, and life cycle impacts. [ABSTRACT FROM AUTHOR]

The built environment is facing an increasing challenge of reducing emissions regarding both embodied and operational carbon. As an ultra-durable concrete, engineered cementitious composites (ECC) reduce the need for repair, thus resulting in a prominent reduction of life-cycle footprints. Herein, a new version of low-carbon ECC was developed for cast-in-place applications by sequestering CO2 through mineralization. Two waste streams were pre-carbonated and incorporated into ECC as fine aggregate and supplementary cementitious material, respectively. At 28 days, the CO2-sequestered ECC exhibited a compressive strength of 32.2 MPa (4670 psi), tensile strength of 3.5 MPa (508 psi), and strain capacity of 2.9%. Multiple fine cracks were distinctly identified, with a residual crack width of 38 µm (0.0015 in.) and a selfhealing behavior comparable to that of conventional ECC. The new ECC sequestered 97.7 kg/m3 (164.7 lb/yd3) CO2 (equivalent to 4.7 wt% of final mixture) and demonstrated a 42% reduction in cradle-to-gate emissions compared to conventional concrete at the same strength level. This study demonstrates the viability of turning waste CO2 gas into durable construction materials and proposes a potential path towards carbon neutrality. [ABSTRACT FROM AUTHOR]

Chloride diffusivity and steel corrosion are two major factors in the durability characteristics of concrete structures. It is possible to use the electrical resistivity (ER) of concrete as a measure of concrete's ability to resist the movement of ions within the material. In this study, surface electrical resistivity (SR) and bulk electrical resistivity (BR) of concrete cylinders were measured from 3 to 161 days for concrete mixtures with four varying water-cement ratios (w/c) (0.45 to 0.60) and three distinct cement types. The study investigated the influence of important durability parameters such as cement type, long-term curing period, and w/c on concrete electrical resistivity. In addition, the impact of cylinder size on SR of concrete was observed. The findings show that both SR and BR of concrete decrease with increasing w/c, except for concrete with cement Type-I/II, which showed a minor increase in resistivity with a w/c of 0.55. Concrete with Type-V cement showed the highest electrical resistance. Moreover, a strong linear relationship between the two types of resistivity was established, and a new equation was introduced in terms of cement type, w/c, and long-term curing period. The correlation between SR and BR was validated by determining the mean absolute error (MAE) of the proposed equation for the three types of cement, which were 0.41 (Type-I/II), 0.65 (Type-III), and 0.35 (Type-V). For all three cement types, the mean absolute percentage error (MAPE) and coefficient of variation (COV) were within acceptable limits, and the 95% confidence interval (CI) indicated a small error margin for the proposed equation when estimating BR from SR using experimental data. Statistical analysis showed that the new equation was less reliable for Type-III cement than the other two types, possibly due to its rapid strength increase property. [ABSTRACT FROM AUTHOR]

Studies have revealed that kaolinite-containing marine clay (MC) exhibits pozzolanic reactivity after thermal activation, making it a sound supplementary cementitious material for concrete production. In this study, calcined MC with two different finenesses was used to substitute cement in the mortar at 0, 10, 20, and 30% replacement ratios. The pozzolanic activity of calcined MC was confirmed by the reduced portlandite content in hydration products (by quantitative X-ray diffraction [QXRD]) and the formation of the calcium-silicate-hydrate (C-S-H) and calcium-aluminumsilicate-hydrate (C-A-S-H) gels (by scanning electron microscopy/energy-dispersive X-ray spectroscopy [SEM-EDS]). The microstructural, mechanical, and transport properties of mortar were investigated. The pore volume increased with the incorporation of calcined MC, while obvious pore refinement was noted. Due to the cement dilution effect and higher pore volume in the mortar, the strength and modulus of elasticity generally decreased with higher MC content. Chloride transport in the mortar was greatly inhibited due to the reduced pore sizes and higher chloride-binding capacity of calcined MC. With the addition of 10% fine calcined MC, the low-carbon mortar exhibits an earlier and increased heat release, similar strength, 8% lower water absorption, 14% lower water sorptivity, 44% lower chloride migration coefficient, and 12% loss in modulus of elasticity. [ABSTRACT FROM AUTHOR]

Ultra-high-performance concrete (UHPC) is a cement-based material whose superior mechanical and durability features are ascribed to its enhanced microstructure. Nonetheless, large amounts of cement and other expensive components are usually necessary to achieve that particular microstructure, leading to higher costs and carbon footprint than standard concretes. Even though several pieces of research have focused on the employ of mineral admixtures as partial replacement of cement and silica fume while maintaining a compressive strength of over 150 MPa, there is a lack of knowledge on how these additions affect other properties of UHPC. This research paper aims to fill that gap in the Colombian case by analyzing the mechanical properties (compressive strength, modulus of elasticity) and durability (ultrasonic pulse velocity, volume of permeable voids, and chloride ion penetration) of two optimized, cost-efficient, and eco-friendly UHPC dosages containing locally available and low-cost mineral admixtures, encompassing two economically viable milled waste glass powders with an average particle size of 7 and 28 microns, and limestone powder. The results were compared with those obtained for a control mixture, which contained high amounts of cement and silica fume as cementitious materials. The conclusions showed that limestone and recycled glass powders reduce both the high-range water-reducing admixture (HRWRA) and the time of the mixing procedure, leading to a relevant decrease in the production costs. Cost-efficient and eco-friendly UHPCs' mechanical and durability properties were minor but in the same range as the reference mixture. However, the UHPC dosage incorporating limestone and 28-micron glass powders implied a reduction in cement by 31% and material costs by 32.5% from the reference. In comparison, the dosage in that addition contained 7 microns of glass powder which led to a lessening of 29% in cement and 33.5% in final costs. These outcomes endorsed using limestone and recycled glass powders to develop low-cost and eco-friendly UHPC in Colombia. [ABSTRACT FROM AUTHOR]

Cement concretes modified with hydrothermal nanosilica and basalt microfiber were developed. The compressive strength Fcom, flexural strength Fflex, and characteristics of impact viscosity were determined: the number of blows before the first fracture Nff and before ultimate failure Ncd, the coefficient Niv = Ncd/Nff, and the specific energy of impact destruction Eim/Sc. The strong effect of SiO2 action and synergistic effect of the combined action of nanoparticles and microfiber on Ncd and Eim/Sc was revealed. Statistical correlations with high R2 values were obtained between the characteristics of mechanical strength and impact viscosity at different doses of SiO2 nanoparticles. Correlations obtained can be used for reduction of the cross section of concrete structures and cement consumption. The mechanism of the strong synergistic effect of the combination is explained by the enlargement of the volume fraction of the high-density (HD) phase of calcium-silicate-hydrate (C-S-H) gel with more packed nanogranules and an increase in the shear stress of C-S-H gel relative to the lateral microfiber surfaces inside the HD-phase volume. The reduction of the coefficient of water filtration Kf and an increase in the frost resistance were achieved. [ABSTRACT FROM AUTHOR]

External sulfate attack ("sulfate attack" hereafter) is one of the most important factors that influences the long-term durability of concrete structures when exposed to aggressive environments. Concrete can expand, crack, and lose strength as a result of sulfate attack. This paper presents the results from an experimental investigation on nano-CaCO3-modified concrete under sulfate attack. The specimens were exposed to a partially submerged condition in 10% Na2SO4 solution. The mechanical and durability performance were evaluated based on durability evaluation parameters. Eventually, the Birnbaum-Saunders (B-S) life prediction model was used to assess the long-term performance of the tested mixtures. The results show that when the content of nano-CaCO3 is 1%, the resistance of concrete to sulfate attack is greatly increased, and the service life of concrete structures is increased significantly. Moreover, using a reliability approach, the proposed model can effectively describe the degradation process of concrete under sulfate attack. [ABSTRACT FROM AUTHOR]

The main purpose of this research was to verify non-expandable powdered perlite (PP) for suitability as a Type II addition for use in concrete. The tests were carried out using CEM II/A-S 42.5 N. Pozzolanic reactivity was verified by the Frattini test. The suitability for use in concrete was assessed by considering the criteria of EN 450-1 as the limits of individual results necessary to be fulfilled for fly ash. If a standard is not issued for a pozzolan, it must be evaluated by the most closely related standard. Following this request, the k-value for PP required by EN 206+A2 and prescribed in TNI CEN/TR 16639 was determined. The k-value concept is based on the comparison of the durability performance for the relevant exposure class of a reference concrete with cement "A" against a test concrete, in which a part of cement "A" is replaced by an addition. This concept permits a defined range of combinations of cement conforming to EN 197-1 with a pozzolanic addition that may count fully toward requirements for the maximum watercement ratio (w/c) and minimum cement content, which are specified for concrete. The TNI provides more detailed information on the principles of the equivalent performance concept and on the application of this concept in 12 European Committee for Standardization (CEN) member countries. This paper reveals the methodological and experimental procedures for the k-value determination for PP as well as the resistance to carbonation, which includes one important aspect of durability related to the exposure class XC--corrosion induced by carbonation. The novelty of this investigation consists of the presentation of the Slovak national procedure for determination of the k-value and the resistance to carbonation alongside those elaborated by Technical Committee CEN/TC 104, Concrete and Related Products. The results point to the fact that the unexpanded PP is a Type II addition suitable for use in concrete. [ABSTRACT FROM AUTHOR]

The durability of three repair materials was investigated under two exposures: freezing-and-thawing cycles in the presence of deicing salts, and substrate undergoing expansion due to alkali-aggregate reaction (AAR). The bond strength of the repairs under freezingand- thawing exposure was evaluated using slant shear, splitting tensile, and pulloff tests. Additionally, the pulloff test was implemented to investigate the bond strength of repairs undergoing expansion due to AAR. Under freezing and thawing, the substrate surface roughness was evaluated and resulted in a higher bond strength under combined shear and compression forces (slant shear test). The results for both exposures showed that the efficacy of a repair could not only be explained based on the net unrestrained length change between the repair and the substrate. While significant autogenous shrinkage of ultra-high-performance concrete (UHPC) can increase the net unrestrained length change, the strength, fibers, and high paste content of such material enhance the bond strength. [ABSTRACT FROM AUTHOR]

Alkali-activated slag/fly ash concretes were tested regarding their resistance to freezing-and-thawing cycles and deicing salt scaling. Different fly ash contents, added water dosages, and air-entraining admixture (AEA) dosages were tested. The deicing salt-scaling resistance tests were conducted on different types of surfaces (troweled, formed, saw cut). The tested alkali-activated slag/fly ash concretes showed excellent performances to freezing and thawing (300 cycles) with statistically identical values of relative dynamic modulus of elasticity averaging 100%. The performance was also good for specimens tested without addition of AEA. However, they exhibited poor scaling resistance to deicing salts with only one mixture satisfying the 0.50 kg/m2 (0.102 lb/ft2) limit of the Bureau de normalisation du Québec (BNQ) test procedure, with a value of 0.49 kg/m2 (0.100 lb/ft2). Finished surfaces underwent more scaling than formed or saw-cut surfaces. The curing of the specimens and the scaling test itself may not be suitable to test alkali-activated concrete. [ABSTRACT FROM AUTHOR]

In alkali-activated slag/fly ash systems, autogenous shrinkage represents the dominant type of shrinkage. Increasing contents of added water and fly ash contents both reduce the importance of autogenous shrinkage. For a constant added water content (AW/B = 0.14), increasing the fly ash content from 20 to 40% resulted in an autogenous shrinkage reduction on paste specimens (from 5644 to 2168 μm/m at 28 days). The autogenous shrinkage of control ordinary portland cement (OPC) paste (water-cement ratio [w/cm] of 0.50) reached 505 μm/m. Alkali-activated slag/fly ash mixtures of this study had average pore radius values ranging between 3.40 and 3.55 nm, compared to 8.25 nm for the OPC paste control specimen. Smaller pores and high sodium concentrations result in higher internal pressure during the process of selfdesiccation and could be the main causes for the very high autogenous shrinkage values recorded. [ABSTRACT FROM AUTHOR]

The American Concrete Institute (ACI) provides guides, specifi- cations, and code documents related to concrete durability. The authors reviewed two code documents from ACI Committees 318 and 350, two guidance documents from ACI Committees 201 and 222, and a specification document from ACI Committee 350, and observed that several discrepancies exist in terms of providing uniform durability requirements for freezing and thawing and chemical sulfate attack of concrete, and allowable chloride limits for new construction. By analyzing existing concrete durability data from published literature, laboratory testing, and field exposure sites, recommendations on unified durability requirements and exposure class descriptions are made for potential adoption by ACI Committees 201, 222, 318, and 350. [ABSTRACT FROM AUTHOR]

This paper investigates the structural performance of large-scale lightweight self-consolidating concrete (LWSCC) and lightweight vibrated concrete (LWVC) beams made with expanded slate coarse aggregates (ESCAs) and expanded slate fine aggregates (ESFAs) under flexural loads. Nine large-scale concrete beams were cast with different types of lightweight aggregate (either ESCA or ESFA), coarse-to-fine aggregate ratios (0.5 to 1.5), and total binder contents (550 and 600 kg/m3 [34.3 and 37.5 lb/ft3]). The structural performance of the tested beams was assessed based on the characteristics of the load-deflection response, cracking pattern, displacement ductility, energy absorption, cracking moment, and ultimate flexural strength. The reliability of code-based expressions in predicting the cracking and ultimate moment capacity of the tested beams was also investigated in this study. The results indicated that using ESFA better improved the beam's cracking moment capacity, deformability, ductility, and energy absorption capacity compared to using ESCA. Although LWSCC exhibited a lower modulus of elasticity than normalweight SCC, the deflection values observed in the LWSCC beams under service loads were well within the allowable limit provided by BS 8110. The measured crack widths at the service loads for all tested beams ranged from 0.20 to 0.26 mm (0.008 to 0.01 in.), satisfying the limits proposed by ACI 318, CSA A23.3, and BS 8110 design codes for durability aspects. [ABSTRACT FROM AUTHOR]

Herein, the first trial to investigate the possibility of using one type of sugar beet waste, named carbonation lime residue after calcination (CCR), as an additive for alkali-activated slag (AAS) cement was explored. For this reason, typical AAS cement was prepared, then slag was partially replaced with CCR at levels ranging from 2.5 to 15% by weight. To explore the effect of CCR on the properties of AAS pastes, typical traditional tests such as flowability, setting time, and compressive strength at various ages were measured. In addition, different types of durability such as accelerated aging, water-air cycles, water-hot air cycles, HCl attack, and cyclic wetting in 5% Na2SO4 and drying at 80°C (176°F) were explored. The results were analyzed with different advanced devices. The results showed that it is possible to use CCR as an additive, similar to CaO, for AAS cement. The flowability and setting time decreased with the inclusion of CCR. The inclusion of 5% CCR in AAS cement was the optimal content, which proved the best compressive strength, microstructure, and durability. On the contrary, the inclusion of 15% CCR showed a negative effect. The pronounced outcomes of this investigation may be the solution for sugar beet waste landfills and improving the properties of AAS cement. [ABSTRACT FROM AUTHOR]

Ultra-high-performance concrete is a milestone of both durability and mechanical performance; nevertheless, its high consumption of clinker generates a large carbon footprint, and a large quantity of this clinker remains anhydrous due to the very low water availability in the compound. Studies of back-scattered electrons, X-ray diffraction, and quantitative energy-dispersive spectroscopy were done to propose that the cement replacement by inert fillers having a hardness between the limestone and quartz powder is possible due to a higher dissolution of both cement and silica fume that allows the formation of lower Ca/Si ratio C-S-H if enough silica fume is present to keep porosity next to the aggregate constant. Finally, the replaced mixtures had a 37% lower carbon footprint than the reference. The results showed no difference between quartz and limestone systems—both with an adequate silica fume dosage, where able—to keep both compressive strength and bulk resistivity performance at a 37.5% cement replacement. [ABSTRACT FROM AUTHOR]

The use of calcined clays in cement (kaolinitic and common calcined clays) introduces challenges due to the high alumina content, large specific surface area, and high-alkali content. This paper examines the performance against sulfate attacks, alkali-silica reactions, and chloride penetration in mixtures with calcined illitic shale (CIS). Replacement of high and moderate alkali content cement with 25% CIS significantly reduces the expansion in the alkali-silica reaction (ASR) test, as the pozzolanic reaction contributes to the combination of alkalis. Replacing 20% white portland cement with CIS allows the formulation of sulfate-resistant cement by limiting the formation of gypsum and ettringite. The incorporation of 25% CIS in concrete does not significantly increase chloride ingress. Therefore, blended cements with replacement levels of 20 to 25% of portland cement by CIS reduce or maintain the performance against ASR, sulfate attack, and chloride penetration. [ABSTRACT FROM AUTHOR]

The improvement of durability and service life of reinforced concrete structures in the marine environment with the incorporation of corrosion inhibitors has attracted significant attention in recent years. The present study aims to evaluate the performance of a commercially available organic corrosion inhibitor in protecting the steel reinforcement of concrete structures in marine conditions. The study was performed on a control mixture and a test mixture with water-cement ratios (w/c) of 0.4 and 0.6, providing aggressive laboratory and field environments following the recommendation of international standards for corrosion inhibitors assessments. Corrosion monitoring methods and visual inspection of reinforcing bars confirmed the effectiveness of migrating corrosion inhibitor in mitigating chloride-induced corrosion. The migratory properties of the corrosion inhibitor and its ability to densify the matrix microstructure were confirmed through scanning electron microscopy and X-ray photoelectron spectroscopy analyses. [ABSTRACT FROM AUTHOR]

Mortar cubes containing different addition levels (0, 1.5, 4, 8, 42, and 95%, by water mass replacement concentration) of Opuntia ficus-indica (OFI) mucilage were exposed for a 14-year (5110-day) period in a natural CO2-laden environment. Physical characterization tests were performed on the mortar cubes, such as saturated electrical resistivity (ρS), percent total void content (%TV), water capillary absorption (εEFF), and compressive strength (fc). Changes in pH due to carbonation were also determined, and carbonation rates (KCO2) were recorded. Findings suggest that the addition of OFI mucilage concentrations between 4 and 8% (by water mass replacement) may be suitable for durability-enhancing applications in cement-based mortar exposed to carbonation-induced environments. [ABSTRACT FROM AUTHOR]

Blast-furnace slag (BFS) has been increasingly used in cement production and has shown great influence on the electrical resistivity of concrete. The objective of this paper is to compare the theoretical values of electrical resistivity obtained through a mathematical model with experimental values for concrete with BFS. Reference concrete mixtures with ordinary portland cement were also studied. Results indicate higher electrical resistivity and smaller porosity for concretes with CEM III/A. The electrical resistivity of the CEM III/A concrete does not have a well-defined correlation with the water-binder ratio (w/b) or with the compressive strength, unlike CEM I concretes. The correlation between calculated and experimental resistivity requires a correction factor for the CEM III/A concretes. In this study, the correction factor was obtained empirically by reducing the theoretical tortuosity of concrete by 15%. Therefore, the model should be used in cements with BFS with the application of a correction factor. [ABSTRACT FROM AUTHOR]

The presence of cracks in concrete is a concern because they can reduce the mechanical properties and durability of concrete. The presence of a single crack in concrete and its effect on strength and durability has been studied extensively, but the influence of multiple small cracks or microcracking density as it relates to serviceability is not as well understood. An experimental study was conducted to quantify the relationship between cracking parameters (width, depth, and density) and the strength, stiffness, and durability of concrete. It was found that the density of microcracks is an important factor to take into account for durability, as it can impact serviceability. [ABSTRACT FROM AUTHOR]

The climate emergency requires the adoption of strategies and technologies that effectively reduce CO2 emissions in the short to midterm to keep the global temperature rise below 2°C above pre-industrial levels. Concrete is the substance most consumed by humanity after water. The blended cements in which supplementary cementitious materials replace part of the energy-intensive clinker are the most realistic means to obtain large-scale CO2 reductions. Limestone calcined clay cements (LC³)--blended cements produced by the combination of limestone, calcined clays, and portland cement (OPC)--provides a solution that achieves equivalent mechanical performance to OPC, better durability against chloride, and alkali-silica reaction reduction of CO2 emissions by approximately 40%. Furthermore, it is cost-effective compared to OPC currently on the market. Due to the similarities with OPC, it is a material that can be adopted today using the same construction equipment and workforce worldwid [ABSTRACT FROM AUTHOR]

The main purpose of this work is to evaluate which parameters obtained from the characterization of metakaolins (MKs) (physical, chemical, and mineralogical parameters) have greater relevance in terms of positive impact on concrete durability properties related to chlorides, and which scientific arguments support these results. In parallel, a comparative study between three different MKs was carried out to statistically evaluate the ability that each of these materials must modify and eventually improve concrete durability properties associated with chlorides (electrical resistivity and chloride migration). A discussion of the results was carried out considering evaluations of the microstructure, emphasizing the cementitious systems' porosity (by mercury intrusion porosimetry [MIP]). It was found that MKs contributed to reduced porosity and refined pores, which made the transport of chlorides significantly more complex, and that some characteristics of MK, especially its amorphous content, have been more decisive for that. [ABSTRACT FROM AUTHOR]

Corrosion performance of reinforced pervious concrete was evaluated through field and laboratory evaluations. Two reinforced pervious cemetery walls in Chicago, IL, were visually evaluated, and samples were investigated through petrographic examination. Corrosion performance of two-layered concrete samples, with an outer layer of conventional concrete and an inner layer of pervious concrete, was evaluated in the laboratory. Results indicated that pervious concrete around the reinforcement can significantly delay the cracking and spalling of samples compared to conventional concrete. Chloride profiles of samples and instantaneous corrosion rate measurements showed that corrosion of reinforcement embedded in two-layered samples was similar to conventional concrete although two-layered samples provided a longer time to cracking. Laboratory results are in agreement with long service life performance observed in the field and with prior pervious concrete corrosion studies. [ABSTRACT FROM AUTHOR]

Reliability-based durability design of reinforced concrete structures requires a probabilistic service life modeling approach. Probabilistic service life modeling of chloride-induced corrosion should consider the statistical distributions of key parameters that influence corrosion initiation and subsequent damage. For typical reinforced concrete structures (such as bridge decks), these are chloride exposure, chloride penetration resistance of the concrete, chloride-induced corrosion threshold, depth of concrete cover, and corrosion propagation time. Assessing the impact of the use of corrosion-resistant reinforcement, such as epoxy-coated reinforcing bars (ECR), is typically performed through a selection of the chloride threshold and/or propagation time. This paper provides recommendations for statistical distributions for the chloride threshold to be used in service life modeling for structures containing carbon steel and ECR based on both experimental work reported in the literature and field investigations of existing structures conducted by the authors. [ABSTRACT FROM AUTHOR]

This experimental study evaluated the influence of delayed ettringite formation (DEF) on physical and mechanical properties and also microstructural characteristics of concretes cast in laboratory for 6 months. The results show that DEF can generate high expansions, in the order of 1%, and reduce mechanical properties, such as compressive strength, tensile strength, and the modulus of elasticity by more than 50%. Already in the 28th day, the presence of ettringite could be identified in the concrete matrix. The results of the study indicate high premature deterioration of the concrete and, consequently, its disqualification for use after the thermal cure adopted. [ABSTRACT FROM AUTHOR]

The water-to-cement (w/c) ratio is one of the most important parameters determining the quality of cement-based materials. Currently, there is no practical way to accurately determine this ratio after all the ingredients of concrete have been mixed, posing a significant quality control problem for the construction industry. A new method has been developed to address this challenge whereby an electrical resistivity probe is immersed in fresh concrete, providing an instantaneous and accurate measure of a concrete’s water-to-cement ratio. Experiments were conducted on eight concrete mixtures designed according to the ACI 211.1 procedure, with varying w/c ratios (0.30, 0.40, 0.50, and 0.60) and fly ash percentages (0% and 25%). The results demonstrate a strong direct correlation between the resistivity of fresh concrete and the water-to-cement ratio. Average w/c ratio estimates based on measurements using the resistivity probe were within ±0.01 of the actual values for all mixes tested.

Physical salt attack (PSA) is a potential deterioration mechanism in porous materials, including concrete, exposed to salt-laden environments. Damage occurs as salt crystals grow in the nearsurface pores causing tensile stresses on the pore walls higher than the tensile capacity of concrete, which can lead to surface scaling similar in appearance to that of freezing-and-thawing damage. This paper compiles, synthesizes, and analyzes current knowledge/research on this topic in terms of the mechanisms of damage, test procedures, damage assessment methods, most influential factors, protection against PSA, and code/guideline provisions. Moreover, key aspects that require further investigation are highlighted, along with a proposed classification for the resistance of concrete to PSA and mitigation strategy. [ABSTRACT FROM AUTHOR]

In this study, copper slag and lime-activated fly ash were used for the manufacturing of cold-bonded aggregates. Cold-bonded copper slag fly ash (CSFA) aggregates were manufactured by varying copper slag content. The aggregate type with 37.5% copper slag and 62.5% fly ash showed optimum strength properties and was selected for the production of CSFA aggregate concrete. The strength and durability properties of concrete with a varying replacement ratio of CSFA aggregate from 0 to 100% at normal temperature and at elevated temperatures of 200, 400, and 600°C were investigated. The results show that concrete containing CSFA aggregate can be ideally used as a construction material up to a temperature of 400°C and as 100% replacement for coarse aggregate. A prediction model has been formulated using multiple regression analysis for the mechanical strength properties of concrete at different replacement ratios and exposure temperatures. A mixture design methodology is also proposed for the concrete containing CSFA aggregates. [ABSTRACT FROM AUTHOR]

The present study concerns a testing methodology to investigate the permeability of cracked concrete based on oxygen permeability testing. The methodology was applied to study self-healing; thus, concrete specimens were preliminarily subjected to mechanical compression and successively exposed to water. The aim was to assess any change in the conditions of the oxygen flow respect to the corresponding plain specimens. Different concrete types were used--that is, ordinary concrete and high-performance concrete. It was found that both the oxygen permeability as well as the type of oxygen flow were affected by the presence of cracks even partially filled in with hydration products. In particular, the intrinsic permeability was determined. In addition, it was possible to assess the relative proportions of viscous and inertial flows. On those bases, the critical velocity was identified as a parameter to permit a consistent comparison between different specimens under similar flow types. [ABSTRACT FROM AUTHOR]

Corrosion in reinforced concrete (RC) represents a serious issue in steel-reinforced concrete structures; therefore, finding an alternative to replace steel reinforcement with a non-corrosive material is necessary. One of these alternatives is glass fiber-reinforced polymer (GFRP) that arises as not only a feasible solution but also economical. The objective of this study is to assess the durability of GFRP bars in concrete bridges exposed to a real-time weather environment. The first bridge is Southview Bridge (in Missouri) and its GFRP bars have been in service for more than 11 years; the second bridge is Sierrita de la Cruz Creek Bridge (in Texas State) and its GFRP bars have been in service for more than 15 years. To observe any possible mechanical and chemical changes in the GFRP bars and concrete, several tests were conducted on the GFRP bars and surrounding concrete of the extracted cores. Carbonation depth, pH, and chlorides content were performed on the extracted concrete cores to evaluate the GFRP-surrounding environment and see how they influenced certain behaviors of GFRP bars. Scanning electron microscopy (SEM) was performed to observe any microstructural degradations within the GFRP bar and on the interfacial transition zone (ITZ). Energy dispersive spectroscopy (EDS) was applied to check for any chemical elemental changes. In addition, glass transition temperature (TA) and fiber content tests were carried out to assess the temperature state of the resin and check any loss in fiber content of the bar after these years of service. The results showed that there were no microstructural degradations in both bridges. EDS results were positive for one of the bridges, and they were negative with signs of leaching and alkali-hydrolysis attack on the other. Fiber content results for both bridges were within the permissible limits of ACI 440 standard. Carbonation depth was found only in one of the bridges. In addition, there were no signs of chloride attack in concrete. This study adds new evidence to the validation of the long-term durability of GFRP bars as concrete reinforcement used in field applications. [ABSTRACT FROM AUTHOR]

This paper presents the durability performance of ultra-highperformance concrete (UHPC) exposed to a marine environment for up to 21 years. Concrete specimens (152 x 152 x 533 mm [6 x 6 x 21 in.]) were cast using a water-cementitious materials ratio (w/cm) in the range of 0.09 to 0.19, various types and lengths of steel fibers, and the presence of conventional steel reinforcement bars in select mixtures. Laboratory testing included taking cores from each block and determining the existing chloride profile, compressive strength, electrochemical corrosion monitoring, and microstructural evaluation. Regardless of curing treatment and w/cm, the results revealed that UHPC exhibits significantly enhanced durability performance compared with typical high-performance concrete (HPC) and normal concretes. UHPC prisms exhibited minimal surface damage after being exposed to a harsh marine environment for up to 21 years. Chloride profiles revealed penetration to a depth of approximately 10 mm (0.39 in.) regardless of exposure duration. Electrochemical corrosion monitoring also showed passivity for reinforcement at a cover depth of 25 mm (1 in.) following 20 years. [ABSTRACT FROM AUTHOR]

The use of seawater as mixing water in reinforced concrete (RC) is currently prohibited by most building codes due to potential corrosion of conventional steel reinforcement. The issue of corrosion can be addressed by using noncorrosive reinforcement, such as glass fiber-reinforced polymer (GFRP). However, the long-term strength development of seawater-mixed concrete in different environments is not clear and needs to be addressed. This study reports the results of an investigation on the effect of different environments (curing regimes) on the compressive strength development of seawater-mixed concrete. Fresh properties of seawater-mixed concrete and concrete mixed with potable water were comparable, except for set times, which were accelerated in seawater-mixed concrete. Concrete cylinders were cast and exposed to subtropical environment (outdoor exposure), tidal zone (wet-dry cycles), moist curing (in a fog room), and seawater at 60°C (140°F) (submerged in a tank). Under these conditions, seawater-mixed concrete showed similar or better performance when compared to reference concrete. Specifically, when exposed to seawater at 60°C (140°F), seawater-mixed concrete shows higher compressive strength development than reference concrete, with values at 24 months being 14% higher. To explain strength development of such mixtures, further detailed testing was done. In this curing regime, the seawater-mixed concrete had 33% higher electrical resistivity than the reference concrete. In addition, the reference concrete showed calcium hydroxide leaching, with 30% difference in calcium hydroxide values between bulk and surface. Reference concrete absorbed more fluid and had a lower dry density, presumably due to greater seawater absorption. Seawater-mixed concrete performed better than reference concrete due to lower leaching because of a reduction in ionic gradients between the pore solution and curing solution. These results suggest that seawater-mixed concrete can potentially show better performance when compared to reference concrete for marine and submerged applications. [ABSTRACT FROM AUTHOR]

In recent decades, concrete-filled fiber-reinforced polymer tube (CFFT) columns have gained increasing popularity in bridge construction as an alternative to conventional reinforced concrete columns. CFFT columns have excellent structural performance, which is attributed to the superior properties of the fiber-reinforced polymer (FRP) tubes. Furthermore, using FRP tubes eases the construction of CFFT columns. However, one obstacle hindering the greater acceptance of FRP as a common construction material in civil infrastructure application is the susceptibility of FRP to degradation during long-term exposure to a severe environment. The purpose of this study is to investigate the durability of CFFT columns subjected to seawater corrosion, which is the scenario for seashore bridges. CFFT stubs were immersed in simulated seawater with two different elevated temperatures for up to 450 days. Sustained axial loads were also applied to the stubs to simulate the real-life service load. Compression tests and hoop tensile tests were carried out on both pre- and post-conditioned specimens. [ABSTRACT FROM AUTHOR]

This paper investigates and compares the potential of ureolytic and non-ureolytic bacteria in resisting corrosion due to chloride penetration and carbonation. The concrete specimens with and without reinforcement were treated with ureolytic and nonureolytic bacterial strains and exposed to 3.5% NaCl and 2% CO2, respectively, for 90 days. The bacteria-treated reinforced concrete (RC) specimens showed approximately 32% lower corrosion rate, more positive value of Ecorr, and an approximately 26% increase in pullout strength than the control. Field emission scanning electron microscopy (FESEM) of the treated RC revealed thick mineral deposition by bacteria at interfacial transition zone (ITZ), leading to overall densification of the concrete. Moreover, ureolytic and non-ureolytic bacteria-treated concrete showed approximately 60% less carbonation. X-ray diffraction (XRD) revealed additional formation of hydration products and quantification by thermogravimetric (TG) analysis, validating approximately 40% higher CH in carbonated bacterial concrete. Besides calcite, the bacteria mediated additional formation of hydration product (CH) instead of reduction during carbonation, which is believed to be the definite reason of improved ITZ and thus the durability of treated concrete. [ABSTRACT FROM AUTHOR]

Cracks in concrete are expected to accelerate the degradation of reinforced concrete--mainly reinforcement corrosion. Previous literature studies have shown that the initiation time can decrease due to cracks, whereas the accelerating effect on corrosion propagation has no clear experimental evidence. This paper critically assesses how different common experimental setups may influence the test results. It is found that, particularly, the exposure duration and condition, the water-binder ratio (w/b), and the crack width have an impact on the outcome of the experimental study about corrosion rates in cracked concrete. Hence, these parameters should be carefully considered when designing experiments to study the influence of cracks. Recommendations for future research work are given. [ABSTRACT FROM AUTHOR]

In the last four decades, numerous investigations have been undertaken on abrasion-erosion of concrete using various test methods. These have suggested the existence of different abrasion mechanisms, limitations of existing test methods, and inconsistencies on the importance of compressive strength to abrasion resistance of concrete. The objective of this review is to understand the mechanisms of concrete abrasion-erosion, assess the suitability of existing test methods to simulate field conditions, and investigate the relationship between abrasion resistance and compressive strength. It is found that concrete abrasion mechanisms are dependent on both transport modes of abrasive charge and the ratio of coarse aggregate to matrix hardness. The ASTM C1138 (underwater) test method appears to simulate all the critical modes of sediment-induced abrasion expected in field conditions and specific energy can be used as a framework to correlate ASTM C1138 test results with field measurements. With the exception of concrete with rubber aggregates, abrasion loss is found to fit a simple power function of its compressive strength, and no significant improvements in abrasion resistance can be gained by using concretes with compressive strengths exceeding 60 MPa (8.70 ksi). Also, the influence of cementitious additives and coarse aggregate properties is only significant at compressive strengths below the optimal value of 60 MPa (8.70 ksi). [ABSTRACT FROM AUTHOR]

This paper examines the applicability of a recently developed testing protocol to evaluate the potential of sulfide-bearing aggregate—mainly from Ontario—to oxidize and cause damage when used in concrete. The protocol consists of three sequential tests: total sulfur (St), the oxygen consumption test (OCT), and the oxidation mortar bar test (OMBT). The paper suggests modifications to the OCT, and the expansion criteria of OMBT based on testing aggregates with different total sulfur contents. For OCT, using crushing equipment with cast-iron working surface was found to contaminate the samples and give high values of oxygen consumption. The OMBT showed lower expansion values for carbonate aggregates compared to aggregates with silicate. Exposing siliceous aggregate—whether alkali-silica reactive or not—to the high pH and temperature encountered in the OMBT produces high expansion regardless of the oxidizable sulfide content. As such, new expansion criteria are suggested, which take into consideration the silicate nature of some aggregates. [ABSTRACT FROM AUTHOR]

A comprehensive analysis on the effect that fine fraction of reclaimed asphalt pavement (RAP) aggregates can produce on the fresh properties, strength, and durability characteristics of cementitious mixtures—that is, mortar and concrete—when used as partial or full replacement of natural fine aggregates (NA) is represented in this study. The replacements of NA were done by volume at 25, 50, 75, and 100% catering to the difference in specific gravity between the aggregates. The cement was also partially replaced by volume using silica fume and activated sugarcane bagasse ash (SCBA). To achieve this objective, effect of RAP aggregates was studied in both mortar and concrete. Although recycling is not a novel concept, altering the conventional mixture design and testing methodology whilst using RAP aggregates were looked into. The application of this study was focused upon rigid pavements, where flexural strength is of great importance. The mixtures considered did achieve the design flexural strength and protected the reinforcement from corrosion due to basic pH and absence of carbonation. [ABSTRACT FROM AUTHOR]

33ACI Materials Journal/March 2020ACI MATERIALS JOURNAL TECHNICAL PAPER Because of ordinary reinforced concrete’s poor durability in saline soil areas and Qinghai Salt Lake, magnesium oxychloride-coated steel-cement concrete was adopted in this area. The process of the degradation of coated steel bars’ durability was evaluated according to the actual service situation of magnesium-oxychloride-coated reinforced concrete in saline soil areas and Qinghai Salt Lake. The corrosion parameters of coated steel bars in magnesium oxychloride cement concrete were obtained by the accelerated immersion and natural corrosion tests in a drying environment. Using the Copula function as the connection function, the corrosion current density of the coated steel obtained by accelerated tests and natural rust tests was adopted as the degradation factor of the edge distribution function. The results demonstrated that the Clayton-Copula function reflects the actual process of the degradation in durability of coated steel bars well, and the coated steel bars reached a severe state of corrosion at 18,250 days. [ABSTRACT FROM AUTHOR]

This paper compares biogenic and chemical acid attack for assessing the final stage of microbially induced corrosion of concrete (MICC). Paste specimens were exposed to either biogenic or sulfuric acid solutions. The solutions had an initial pH of 2. Maintaining the pH of the chemical acid solution in the desired range was highly challenging. The pH of biogenic acid solution remained consistent for a longer time. Calcium leaching measurements showed that biofilm on the surface of specimens exposed to biogenic acidification restricted excessive leaching of calcium from the samples. X-ray fluorescence (XRF) results showed that biogenic acid attack caused higher changes in the chemical composition of the specimens. Flexural strength tests did not show a significant difference between the chemical and biogenic acid attack; however, this could be attributed to the short test duration. [ABSTRACT FROM AUTHOR]