Strength Activity Index Research Articles

Evaluation of Pozzolanic and Alkali-Activated Reactivity of Low-Purity Calcium Bentonite.

Alkali-activated cement (AAC) is a sustainable building material with low carbon emissions, but it has a growing demand for raw materials. In this study, the potential of low-purity modified calcium bentonite (CB) as a raw material for AAC was evaluated. The thermodynamic changes and pozzolanic properties of calcined CB were determined using X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (TG-DTA), zeta potential, and a strength activity index (SAI) test. The compressive strength test, scanning electron microscopy-energy dispersive spectrometer (SEM-EDS), and Fourier-transform infrared (FTIR) spectroscopy were performed to examine the compatibility between CB and AAC. It was revealed that CB is a low-purity clay with low-pozzolanic activity. Calcination enhanced its pozzolanic activity, and the optimum temperature is 750 °C. The incorporation of modified CB improved the mechanical properties of AAC, and low-temperature modified CB had better compatibility with AAC than the high-temperature modified CB. Calcination at 150 °C had little effect on the structure of CB, and the water absorption of montmorillonite increased the ion concentration, increasing the rate and degree of hydration. Furthermore, low-temperature calcination had a dissolution-precipitation effect, resulting in leaf-like CaO·SiO2·H2O (C-S-H) gels, whereas the high-temperature calcination of CB was very reactive, resulting in flower-like C(N)-S-H gels.

Anhydrous ethanol as a medium used to grind soda-lime glass for cement-based materials preparation: Evaluating its rheological behavior by the Herschel–Bulkley and Modified–Bingham models

This study reports a method that solid waste grinding with anhydrous ethanol, and waste glass is taken as an example. The waste glass was ground in anhydrous ethanol for 60 min, and the ground powder was added to cement by 3 wt%, 5 wt%, 7 wt%, and 10 wt%, and then mixed with quartz sand to prepare cement mortar. In this study, the rheological properties, self-shrinkage, and mechanical properties of samples of waste glass cement (NWGC) were investigated, and the hydration heat, mass loss, chemical composition, and pore structure of the noted samples were analyzed. The results show that the particle size of WG can be ground to 0.1 μm by the technology of grinding with anhydrous ethanol, which is conducive for WG particles to contact with cement particles, thus promoting the hydration reaction. The Modified-Bingham model is suitable for fitting the rheological properties of the NWGC group, and the fitting coefficient reaches 0.98. The addition of WG after grinding improves the strength of the NWGC group. Especially the sample NWGC6-10 when curing for 1 day, whose strength activity index is about 200% higher than that of sample Control. At 192 h, the autogenous shrinkage of the NWGC group decreases by 6–8 mm3/g compared with that of the sample Control. Meanwhile, the ground WG effectively fills the pore in cement mortar, which improves the compactness of cement mortar. This provides a new treatment method for waste utilization.

Mechanical performance and environmental potential of concrete with engineering sediment waste for sustainable built environment

The extensive use of underground space has led to an increasing amount of engineering sediment waste, which occupies about 60% of construction waste in China. At present, most of the engineering sediment waste is randomly dumped, occupying a lot of land resources and hindering sustainability of built environment. To solve these problems, this work proposes the recycling of engineering sediment waste via calcination and subsequent use as a cement substitute in concrete for construction. The optimal calcination condition is evaluated through strength activity index method. The mechanical properties, environmental and economic benefit of the concrete prepared with various substitution rates of calcined engineering sediment waste are determined using mechanical tests and the life cycle assessment. A multi-criteria analysis method is employed to comprehensively estimate the performance of concrete in terms of compressive and flexural strengths, global warming potential, energy consumption, and economic cost. The effect of calcined engineering sediment on the pozzolanic activity, cement hydration, CH content and microstructure of concrete has been quantitatively evaluated to reveal the mechanism behind the variation of mechanical properties. The concrete with 50% substitution of calcined engineering sediment showed superior environmental performance and economic benefit than those of reference concrete. This work contributes to an effective method for converting sediment waste into valuable resources to prepare concrete with low environmental impact and good mechanical performance, thereby promoting resource conservation and contributing to sustainability of built environment.

Investigating the potential of trass-cement binary blend for enhancing microscopic properties, macroscopic performance, and sustainability of cement paste

• Effects of trass on micro- and macro-level properties of cement paste were evaluated. • Blending cement with trass accelerated the C 3 S and C 3 A hydration. • Higher nonevaporable water contents were detected in blended sample compared to plain one. • The values of compressive strength activity index fluctuated between 106.7 and 124.6%. • Incorporating trass into cement can lead to a cleaner, cheaper, and less energy consumer construction. Due to some physical or chemical incompatibility issues between supplementary cementitious materials (SCMs) and cement, it is necessary to investigate the microscopic properties and macroscopic performance of cement composites containing such blends before their incorporation in construction. Hence, in this study, the hydration kinetics, degree of hydration, microstructural morphology, and pore structure of cement paste blended with trass, as well as its mechanical and transport properties, were profoundly evaluated. Moreover, the potential of trass for enhancing the sustainability of construction was also assessed. The physical properties of trass accelerated the C 3 S hydration, while its chemical composition led to the reduction of induction period, in addition to the acceleration of C 3 A hydration. Significant refinement of pore structure characteristics was found in blended sample after 90 days, when the threshold and critical pore diameters were reduced by respectively 27.7 % and 10.7 %, compared to those of the plain sample. This denser microstructure was reflected in superior electrical resistivity of the blended sample, which was 2.1 times of the plain one at 90 days. Furthermore, the inclusion of trass through refining the morphology of CH crystals in the microstructure, besides lowering the calcium hydroxide (CH) content by 12.1–63.3 % and increasing the nonevaporable water content by 2.1–8.0 %, led to 6.7–24.6 % higher compressive strengths in blended sample. Regarding the sustainability, at a similar 90-day compressive strength of 40 MPa, using trass results in an approximately 21.7 % less energy consumer, 20.3 % cleaner, and 15.8 % cheaper construction. Moreover, at equal levels of energy consumption or CO 2 emission, the blended sample has greater compressive strength and electrical resistivity than the plain one, which can be indicative of an extended service life. Accordingly, the utilization of trass is recommended since it has the potential to improve the sustainability both directly and indirectly.

Effects of Glass Wool Residue Recycled Admixtures on the Properties of Portland Cement-Based Composites

In this study, the effects of a recycled mineral admixture based on glass wool residue (GWR) in microstructural and mechanical properties of ordinary portland cement (OPC)-based composites are examined. The GWR was dried and milled into a fine powder, whereby it was physicochemically characterized. Physicomechanical tests, quantitative X-ray diffraction, and scanning electron microscope observation were performed in pastes and mortars at 28, 56, and 90 days of age. Moreover, the potential application of the GWR was evaluated by determining the pozzolanic activity and the fiber reinforcement effect. The results showed that the partial replacement of cement by 25% by weight of GWR presented no reductions in flexural strength at 28 and 56 days of curing, whereas the long-term flexural strength increased by 17%. This replacement also increased the long-term compressive strength of the composites—reaching a strength activity index of 1.06. The results also showed that GWR presented some fiber reinforcement effect—depending on the particle size. Promising properties were observed for samples blended with GWR, yielding technical, environmental, and economic benefits.

Bio-modification and application of coal fly ash in cementitious composites

Coal fly ash (CFA), an industrial solid waste, has been predominantly used a substitute for material in the concrete industry. Its reactivity is usually a crucial factor for use in cementitious composites. Conventionally physical and chemical treatments have been used to modify CFA for improving reactivity, but there still are some limitations such as easy agglomeration of particles, high cost, high energy-consumption, environmental pollution, etc. Herein, a feasible bio-modification treatment on CFA using Paenibacillus mucilaginosus is proposed. Adhesion and desilication of the bacteria & metabolites change the morphology, size distribution and surface properties of CFA. Compared with CFA, the bio-modified CFA (BCFA) has coarser surface, finer particle size, larger specific surface area (SSA), higher surface calcium content and lower surface Si/Al ratio. The characteristic changes contribute to enhancing the reactivity of BCFA relating to morphological, pozzolanic, micro-aggregate and interfacial effects in cementitious composites. The strength activity index (SAI) of BCFA reaches 90.8% at 28 d and increases 27.7% compared to that of CFA. Soluble silicon content in the bioleaching system shows significantly positive correlations with the SSA and SAI of BCFA (P < 0.05). The cementitious composites containing 30% BCFA show higher mechanical properties, lower early hydration heat and denser microstructure compared to those containing 30% CFA. This work could provide a promising green and low-carbon way to produce highly active BCFA for concrete industry and other fields.

Effect of glass powder on the mechanical and drying shrinkage of glass-fiber-reinforced cementitious composites

Ordinary Portland concrete (OPC) is characterized by low tensile strength and low toughness. These properties can be improved by adding glass fiber (GF). However, the alkaline environment of the pore solutions adversely affects the durability of GF. First, the effect of GF addition on the mechanical properties and fluidity of cement mortar was investigated. It was found that the fluidity decreased, and the flexural strength increased with an increase in the GF content. The incorporation of GF had little effect on the compressive strength of mortar. The optimal volume dosage of GF was 2 %. Then, Experiments were conducted to study the effects of glass powder (GP) characterized by different particle sizes and dosages on the fluidity, mechanical properties, and strength activity index (SAI) of glass-fiber-reinforced cementitious composites (GFRC). The results revealed that the fluidity, flexural strength, and compressive strength of GFRC containing GP increased with a decrease in the GP particle size. The flexural and compressive strength of GFRC first increased and then decreased with an increase in the GP content. The SAIs values of all GFRC specimens were more than 75 %, except GPI-25. Finally, the effect of the GPIV (GP of the optimal particle sizes) content on the drying shrinkage and pore structure of GFRC was studied. It was observed that the addition of GP into GFRC resulted in a reduction in the drying shrinkage, and the drying shrinkage of GFRC decreased with an increase in the GPIV content. The pore volume (0.5–50 nm) of GFRC decreased with an increase in the GPIV content. GP in GFRC consumed calcium hydroxide (CH) to produce calcium silicate gel. This helped reduce the extent of corrosion of GF by CH. Waste glass is processed into GP and added into mortar or concrete to replace parts of cement to reduce cement consumption and carbon dioxide emission. This helps protect the environment. GP is a promising agent for the fabrication of glass-fiber-reinforced cementitious composites.

Diatomaceous Earth-Lightweight Pozzolanic Admixtures for Repair Mortars-Complex Chemical and Physical Assessment.

The presented research is focused on the complex assessment of three different types of diatomaceous earth and evaluation of their ability for application as pozzolana active admixtures applicable in the concrete industry and the production of repair mortars applicable for historical masonry. The comprehensive experimental campaign comprised chemical, mineralogical, microstructural, and physical testing of raw materials, followed by the analyses and characterization of pozzolanic activity, rheology and heat evolution of fresh blended pastes, and testing of macrostructural and mechanical parameters of the hardened 28-days and 90-days samples. The obtained results gave evidence of the different behavior of researched diatomaceous earth when mixed with water and Portland cement. The differences in heat evolution, initial and final setting time, porosity, density, and mechanical parameters were identified based on chemical and phase composition, particle size, specific surface, and morphology of diatomaceous particles. Nevertheless, the researched mineral admixtures yielded a high strength activity index (92.9% to 113.6%), evinced their pozzolanic activity. Three fundamental factors were identified that affect diatomaceous earth’s contribution to the mechanical strength of cement blends. These are the filler effect, the pertinent acceleration of OPC hydration, and the pozzolanic reaction of diatomite with Portland cement hydrates. The optimum replacement level of ordinary Portland cement by diatomaceous earth to give maximum long-term strength enhancement is about 10 wt.%., but it might be further enhanced based on the properties of pozzolan.

Enhancement of the pozzolanic activity of natural clays by mechanochemical activation

• The pozzolanic activity of natural clays was improved by mechanochemical activation (MCA) in a planetary ball mill. • Strength activity index (SAI) and Frattini test confirmed the increased pozzolanic reactivity after MCA. • XRD and SEM-EDX investigations confirmed the ability of the MCA-clays to act as pozzolans. • Mechanochemical activation can be considered a feasible and alternative method to enhance the pozzolanicity of poorly reactive clays. Replacement of cement with supplementary cementitious materials (SCMs) is a proven method to reduce clinker in cement and contribute to decreased CO 2 emissions. Natural clays are commonly occurring materials that do not possess pozzolanic activity in their original state. Mechanochemical activation (MCA) can be an alternative and sustainable method to enhance their reactivity. In this study, the pozzolanic reactivity of three natural clays, originating from Sweden, was analyzed after the application of MCA in a planetary ball mill. Strength activity index (SAI), Frattini test, and conductivity test were used to evaluate the pozzolanic reactivity. All processed clays by MCA have achieved a SAI greater than 100%, while the Frattini test indicated an improved pozzolanic activity of samples containing a higher amount of clay minerals. The obtained results show that MCA could improve the pozzolanic reactivity, but the effect depends on the mineralogical composition and particle size of the clays.

Effective utilization of textile industry waste-derived and heat-treated pumice powder in cement mortar

A justifiable replacement for pozzolana that utilizes industrial wastes is needed due to the growing concern on CO2 emissions associated with cement. The effect of heat treatment of pumice powder (PP) on mechanical and durability properties of cement mortar was investigated in this study. Nine different mixes of mortars with varying cement replacement levels (10 %, 20 %, 30 %, and 40 %) by weight of PP were prepared. The PP was treated at 100 ℃ (P-100) and 700 ℃ (P-700). Strength activity index (SAI), water demand, setting time, and flow characteristics were determined. Mechanical properties and porosities were also measured and determined at the age of 7, 28, 56, and 90 days. Moreover, mortar samples were exposed to acidic media for 120 days to assess durability. Results of the SAI showed that the high pozzolanic potential of P-700 is attributed to amorphous silica (SiO2) and detected in the X-ray diffraction test. The PP content showed a positive effect on setting times and flowability of mortars. Moreover, 20 % replacement at all ages achieved maximum mechanical properties while 30 % replacement at later ages improved the mechanical properties compared with the control mix. Notably, high replacement levels of PP enhanced the resistance against acidic attack. The SEM-EDX analysis along with Thermogravimetric Analysis (TGA) test verified the better performance of P-700 over P-100.

Comparison of mechanical, chemical, and thermal activation methods on the utilisation of recycled concrete powder from construction and demolition waste

Recycled concrete powder (RCP) poses a considerable challenge with respect to effective utilisation of construction and demolition waste (CDW) resources due to its low activity, high water demand, and potential to cause dust pollution during storage. A suitable activation method is necessary for stimulating the potential activity of RCP and enhancing its utilisation. Therefore, the effect of mechanical, chemical, and thermal activation methods on the properties of RCP were investigated in this study. Mechanical and thermal activation were helpful for the activity of RCP due to the modification of particle size and distributions. RCP exhibits a higher content of SiO2 and a lower content of CaO as well as the main crystal phases of quartz, calcite, gismondine, and dolomite. After 400–800 °C thermal activation, dolomite is not observed while the RCP shows new active components (such as larnite, calcium silicate, and calcium oxide). The chemical activation test highlights that CaO (3%) is the most optimal, followed by CaSO4 (1%) and Na2SO4 (2%), while Ca(OH)2 (4%) has the least optimal activation effect on the strength activity index (SAI) of RCP mortar. For combined activation, Ca(OH)2 and CaSO4 with 1:1 ratio has the most optimal activation effect, and the SAI reaches 80.27%. Based on the mechanical performance, SAI, and micro-characteristics, the most feasible and effective activation method is thermal activation (800 °C), followed by chemical activation (Ca(OH)2+CaSO4), and mechanical activation (75 min). This study proposes a useful combined activation method for RCP that verifiably contributes to the application of CDW.

Modelling and Optimization for Mortar Compressive Strength Incorporating Heat-Treated Fly Oil Shale Ash as an Effective Supplementary Cementitious Material Using Response Surface Methodology.

Fly oil shale ash (FOSA) is a waste material known for its pozzolanic activity. This study intends to investigate the optimum thermal treatment conditions to use FOSA efficiently as a cement replacement material. FOSA samples were burned in an electric oven for 2, 4, and 6 h at temperatures ranging from 550 °C to 1000 °C with 150 °C intervals. A total of 333 specimens out of 37 different mixes were prepared and tested with cement replacement ratios between 10% and 30%. The investigated properties included the mineralogical characteristics, chemical elemental analysis, compressive strength, and strength activity index for mortar samples. The findings show that the content of SiO2 + Al2O3 + Fe2O3 was less than 70% in all samples. The strength activity index of the raw FOSA at 56 days exceeded 75%. Among all specimens, the calcined samples for 2 h demonstrated the highest pozzolanic activity and compressive strength with a 75% strength activity index. The model developed by RSM is suitable for the interpretation of FOSA in the cementitious matrix with high degrees of correlation above 85%. The optimal compressive strength was achieved at a 30% replacement level, a temperature of 700 °C for 2 h, and after 56 days of curing.

Influence of Mechanical Grinding on Particle Characteristics of Coal Gasification Slag.

Based on the test results of laser particle size analyzer, specific surface area analyzer and infrared spectrometer, the grinding kinetics of coal gasification slag (CGS) was systematically described by using Divas–Aliavden grinding kinetics, Rosin–Rammler–Bennet (RRB) distribution model and particle size fractal theory. The influence of grinding time and particle group of CGS on the strength activity index of mortar was studied by using the strength activity index of mortar and grey correlation analysis. The results show that the particles are gradually refined before mechanical grinding of CGS for 75 min. When the mechanical grinding time is greater than 75 min, the “agglomeration phenomenon” of fine CGS particles led to the decrease in various properties. Divas–Aliavden grinding kinetics, the RRB model and fractal dimension can characterize the change of CGS particle size in the grinding process quantitatively. The strength activity index of CGS at different curing ages is positively correlated with grinding time, and the influence on the later strength activity index is the most obvious. The relationship between CGS particle size distribution and strength activity index were probed using grey correlation analysis. The CGS particle groups with the particle size of 20~30 μm and 10~20 μm have the greatest impact on the early and late strength activity index, respectively. Therefore, the optimal grinding time of CGS as auxiliary cementing material is 75 min, considering factors, such as economy and performance, and the specific surface area (SSA) is 4.4874 m2·g−1.

Pozzolanic activity and environmental risk assessment of water-based drilling cuttings of shale gas

• The pozzolanic activity of WDC was comprehensively studied. • A systematic study of human carcinogenic risk and ecological security risk assessment were carried out. • The risk control values of heavy metals were presented In order to evaluate the application potential of water-based drilling cuttings (WDC) as cementitious materials for building material admixtures, the physical and chemical properties of WDC were studied, and the environmental risk and human health risk of heavy metals in WDC were also systematically studied. The results showed that the particle pitch diameter is 26.70 µm, mineral types of WDC are mainly limestone, calcium hydroxide and quartz. The 28-day compressive strength of WDC is 27.6 MPa. The strength activity index of WDC cement mortar is 58.3 %, and the amorphous phase content is 23 %. At 80 °C, the weight loss rate and bound water content of “ WDC-CaO-H 2 O ” hydrate were 5 % and 0.13, respectively. It is found that WDC has certain pozzolanic activity, can not only participate in the secondary reaction of the system as active mineral admixtures, but also reduce harmful holes in the system by filling compaction. According to the calculation and analysis, only Hg reached moderate pollution in WDC, As and Cr had carcinogenic risks to human health, so Hg, As and Cr were used as characteristic heavy metal pollutants in WDC. As well as, under the analysis results of characteristic heavy metals and the limits of relevant standards, the risk control values of heavy metals in different exposure scenarios were obtained. The expected existence of arsenic ions, chromium ions and mercury ions in XPS spectra and their corresponding binding energy and orbital state were analyzed. After analysis and fitting, these values are basically consistent with the reference values cited in the document, and the resource utilization direction and environmental safety control measures of WDC were proposed. The above research results will further promote the basic technical support of shale gas WDC resource utilization, and ensure the ecological environment safety and human health safety in the process of resource utilization.

Study on SO42-/Cl- Erosion Resistance and Mechanism of Recycled Concrete Containing Municipal Solid Waste Incineration (MSWI) Powder.

In this paper, the strength characteristics and erosion resistance of solid waste incineration (MSWI) powder were studied. Firstly, the optimum process for the preparation of regenerated powder from MSWI bottom slag by ball milling was determined as follows: rotational speed 350 r/min, time 45 min. The strength activity index of regenerated powder reached the maximum when the substitute content of powder was 30%. Secondly, the semi-erosion method was used to study the strength variation rule of mortar with different content of MSWI powder in semi-immersion of salt solution. It was found that the higher the content of MSWI powder, the greater the anti-erosion coefficient of mortar specimen. Finally, the capillary rise test, crystallization test and capillary pore water absorption test were used to study the total porosity, coarse capillary-pore porosity and fine-capillary pore porosity of concrete containing MSWI powder. The results showed that, with the increase in MSWI powder content, the above pore structure properties were improved. The results revealed the transport and crystallization process of salt solution in concrete mixed with MSWI powder and the mechanism of corrosion resistance.

Assessment of Pozzolanic Activity of Ground Scoria Rocks under Low- and High-Pressure (Autoclave) Steam Curing.

Two sources of natural scoria rocks were procured and ground for use in concrete as natural pozzolans (NP1 and NP2). The evaluation of their pozzolanic reactivity is carried out using different techniques and approaches. The primary goal of employing these techniques is to monitor the amount of portlandite (CH=Ca(OH)2) consumed during steam curing at low or high pressure. The pozzolanicity of NP powders is determined either directly by monitoring CH variation or indirectly by compressive strength and microstructure development. Autoclave curing is known to stimulate the pozzolanicity of the inert siliceous and aluminosiliceous materials under its high-pressure steam conditions. Both steam-curing conditions were applied in this investigation. In this study, X-ray diffraction, scanning electron microscope, thermogravimetric, Fourier transform infrared, and isothermal analyzers were used. It is concluded that the nature and types of minerals in SR determine their pozzolanic reactivity as either low-pressure steam-reactive or high-pressure steam-reactive cementitious materials. Due to the nature of their silicate structures, notably single-chain or 3D-framework structures, plagioclase feldspars (albite-anorthite) minerals are high-pressure steam-reactive minerals, whereas pyroxene (enstatite and diopside) minerals are low-pressure steam-reactive minerals. Using high-pressure steam curing, varied replacement levels of up to 60% were achieved in NP1, with a consistent strength activity index (SAI) of 99%, while an SAI of 79% was obtained with NP2. During low-pressure steam curing, NP1 and NP2 consumed around 72 and 80% of portlandite, respectively, demonstrating their relative pozzolanic reactivity. When compared to the control concrete mix, the strength activity indices of NP1, NP2, and class F fly ash in their normal concrete mixes reached 74.3, 82, and 73.7%, respectively, after 56 days of normal curing conditions.

Robustness of self-compacting concrete incorporating bone china ceramic waste powder along with granite cutting waste for sustainable development

Keeping sustainability at the centre of this work, two solid waste materials have been selected for this study. First is bone china ceramic waste powder (BCCWP) obtained from broken or distorted bone china ceramic waste products, and the second is granite cutting waste (GCW) from the granite cutting and shaping industry. The present study aims at assessing fresh state, mechanical and durability characteristics of the SCC mixes incorporating BCCWP and GCW as cement and fine aggregate replacement, respectively. In a preliminary state, the raw BCCWP was evaluated for various pozzolanic activity tests such as the Frattini test, strength activity index and lime saturation test. SCC mixes were tested for compressive strength, splitting tensile strength, corrosion and chloride resistance tests. SCC mixtures were also tested at elevated temperatures by conducting thermogravimetric analysis (TGA) and differential thermal analysis (DTA) tests. Outcomes of fresh properties were found in the satisfactory limit as per EFNARC standard, except the SCC mix prepared with 30% BCCWP and 40% GCW. SCC mix with 10% BCCWP and 30% GCW showed the maximum strength properties. Moreover, statistical analysis using ANOVA was carried out to find the effectiveness of BCCWP and GCW parameters on various hardened state characteristics. From ecological and economic analysis, lesser embodied energy and embodied carbon dioxide emission, as well as cost reduction, was observed for SCC mixes containing BCCWP and GCW.

The efficiency of recycled glass powder in mitigating the alkali-silica reaction induced by recycled glass aggregate in cementitious mortars

With the potential for a decline in fly ash (FA) production over time, due to the phasing down of coal fired power plants, alternative supplementary cementitious materials need to be identified. The efficiency of pulverised glass powder (PGP) was studied for its reactivity and its capacity for inhibiting alkali-silica reaction (ASR) that results from utilisation of recycled glass as a fine aggregate (sand) replacement. Characterisations of pastes containing PGP reveal that PGP may possess latent hydraulic properties, resulting in a more than 75% strength activity index, together with better strength gain than FA-blended pastes. PGP also offered increased heat of hydration compared to FA, from a combination of the dilution effect, filler effect and early-age reactions of PGP. A comparable efficiency of PGP and FA in ASR expansion mitigation was confirmed with mortar bar expansions of less than 0.10% at cement replacement levels of at least 10%. Both PGP and FA provided alkali dilution and reduced the mass transport in hydrated cement paste from the refinement of larger pores to below 60 nm. The FA mix consumed calcium hydroxide and, thus, performed marginally better than the PGP mix in mitigating ASR. This pozzolanic reactivity is not evident for PGP, whereas in the literature glass powders are often regarded as pozzolanic. Microscopic images confirm that PGP and FA significantly limit the occurrence of ASR gels without altering its composition. It was concluded that PGP is a comparable ASR inhibitor to FA, despite the underlying differences in their mechanisms. The result of this research support the utilisation of recycled glass both as an aggregate, and as an ASR-inhibiting SCM in cementitious systems.

Characterization of poultry litter ashes as a supplementary cementitious material

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

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

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