Applications of clinker microscopy for approaching a special case study in cement production.

Within this article the importance of the optical light microscopy for the investigation of cement clinker is illustrated by three examples: (a) Ono's method plays an important role in the case of the production of oil well clinker where the reactivity of alite and additionally the melting phase influences strongly the properties of the later cement; (b) the use of secondary fuels can lead to unexpected phenomena in the clinker matrix accompanied by strange changes in colour; (c) for the interpretation of CSA clinkers, the combination of light and scanning electron microscopy can give important information about the formation of clinker phases depending on the burning conditions which can hardly be detected by other methods. However, in case of CSA clinker, there is still little knowledge about the relationship between production and hydraulic properties of the clinker and therefore no systematic documentation is available.

Interpersonal Firearm Injury and Death in Portland, Oregon: 2018 Through 2021.

The annual number of firearm injuries in Portland, Oregon has been higher in the years since 2020 than in any prior year in the city's history. This descriptive study analyzed data from Gun Violence Archives (GVA) from January 1, 2018, to December 31, 2021. All incidents in GVA of interpersonal firearm injury that occurred in Portland during this period were analyzed for location, number of people injured or killed, and demographic information for those injured or killed. Comparisons in firearm injury rates were made with Seattle and San Francisco. Interpersonal firearm injuries began to rise after the first COVID-19 case in Oregon; July 2020 had the most injuries in the four-year period. Black men suffered the highest rate of interpersonal fatalities, with more than 11-fold higher rate per 100,000 than White men in every year studied. Portland had a higher rate of total interpersonal firearm injuries and a higher rate of firearm fatalities from 2018 through 2021 compared to Seattle and San Francisco. Neighborhoods near Downtown and those on the Eastside of the city had the highest rates of interpersonal injuries and deaths from firearms, whereas those in the Southwest had the lowest. Defining the burden of disease from interpersonal firearm injuries is a fundamental step in designing future public health research and implementing interventions to curb the trauma brought by interpersonal firearm injury.

Experimental Analysis of Various Blockage Performance for LiDAR Sensor Cleaning Evaluation.

Autonomous driving includes recognition, judgment, and control technologies, and is implemented using sensors such as cameras, LiDAR, and radar. However, recognition sensors are exposed to the outside environment and their performance may deteriorate because of the presence of substances that interfere with vision, such as dust, bird droppings, and insects, during operation. Research on sensor cleaning technology to solve this performance degradation has been limited. This study used various types and concentrations of blockage and dryness to demonstrate approaches to the evaluation of cleaning rates for selected conditions that afford satisfactory results. To determine the effectiveness of washing, the study used the following criteria: washer, 0.5 bar/s and air, 2 bar/s, with 3.5 g being used three times to test the LiDAR window. The study found that blockage, concentration, and dryness are the most important factors, and in that order. Additionally, the study compared new forms of blockage, such as those caused by dust, bird droppings, and insects, with standard dust that was used as a control to evaluate the performance of the new blockage types. The results of this study can be used to conduct various sensor cleaning tests and ensure their reliability and economic feasibility.

First historical cements in France from Boulogne sur Mer: Investigations on 19th century's manufactured cement-based monuments.

The Boulogne-Sur-Mer area in the North of France is one of the cradles of the French cement industry (the other main one is Grenoble region due to Joseph Vicat's first cement works). From fast setting (Roman) to Portland, those cements were famous in France and have been used throughout the entire country. The main objective of this study is to give a preliminary insight of the type of binders used since there is currently few and scattered data on those specific structures and to assess the efficiency of traditional analytical techniques [X-ray diffraction (XRD), optical (OM) and scanning electron microscopy (SEM) observations, coupled with EDS analysis] used to differentiate natural and artificial cements.

Ab initio calculations of CO2 adsorption on ß-C2S(100) and M3-C3S(001) surfaces: An exploration of early CO2 sequestration pathways.

Investigating CO2 sequestration in cement-based materials is significant for achieving carbon neutrality in the cement and concrete industries. The early CO2 sequestration pathways on cement-based materials are fundamental for CO2 sequestration, which is not clear. Towards this, the adsorption behavior of CO2 on ß-C2S(100) and M3-C3S(001) was investigated at the atomic level using density functional theory calculations, which were then compared with water adsorption results. The molecular adsorption configurations of CO2 on both ß-C2S(100) and M3-C3S(001) were tilted from their initial configurations due to the influence of surface Ca and O atoms. The CO2 adsorption energy on M3-C3S(001) and ß-C2S(100) were -0.458 eV and -0.426 eV, respectively, indicating adsorption on M3-C3S(001) was more energetically favorable. After CO2 adsorption, electrons were transferred from the surface to the CO2 molecule. Furthermore, the Ca-O bond orders of ß-C2S(100) and M3-C3S(001) after CO2 adsorption were maximally decreased by 2.79% and 6.99%, respectively. A more significant adsorption influence on surfaces was found for H2O, with more negative adsorption energy, more evident electron transfer, and a greater decrease in bond order. The CO2 adsorption on ß-C2S(100) and M3-C3S(001) were still spontaneous at 298 K and 1 atm. This study provides important theoretical insights into early CO2 sequestration at the atomic level, which has practical implications for the design of efficient CO2 sequestration technologies.

Tooth discoloration induced by apical plugs with hydraulic calcium silicate-based cements in teeth with open apices-a 2-year in vitro study.

OBJECTIVES: To assess tooth discoloration induced by different hydraulic calcium silicate-based cements (HCSCs), including effects of blood and placement method. MATERIALS AND METHODS: Eighty bovine teeth cut to a length of 18 mm (crown 8 mm, root 10 mm) were randomly assigned to 10 groups (n = 8), receiving orthograde apical plug treatment (APT). Apical plugs were 4 mm in length and made of ProRoot MTA (Dentsply), Medcem MTA (Medcem), TotalFill BC RRM Fast Set Putty (Brasseler), or Medcem Medical Portland Cement (Medcem) plus bismuth oxide (Bi2O3) with and without bovine blood. Further, orthograde (with or without preoperative adhesive coronal dentin sealing) and retrograde APT were compared. Teeth were obturated with gutta-percha and sealer, sealed with composite and stored in distilled water. Tooth color was measured on apical plug, gutta-percha/sealer, and crown surface before treatment versus 24 h, 1, 3, 6, 12, and 24 months after treatment by spectrophotometry. Color difference (ΔE) values were calculated and analyzed by Shapiro-Wilk test, ANOVA with post hoc tests, Friedman test, t test, and post hoc tests with Bonferroni correction (α = .05). RESULTS: Tooth discoloration occurred in all groups with no significant differences between HCSCs (p > .05). After 24 months, color changes were prominent on roots but insignificant on crowns. Blood contamination induced a significantly decreased luminescence (p < .05). Blood had a stronger impact on tooth color than Bi2O3. No relevant effects of retrograde placement (p > .05) or preoperative dentin sealing (p > .05) were detected. CONCLUSIONS: Apical plugs of the tested HCSCs cause discoloration of bovine roots, but not discoloration of bovine tooth crowns within a 24-month period. CLINICAL RELEVANCE: APT should be performed carefully while avoiding direct contact with the coronal dentin, and in that case no aesthetic impairments occur.

Citizens' preferences on green infrastructure practices and their enhancement in Portland, Oregon.

Green infrastructure (GI) has been gaining increasing attention due to its efficiency in controlling and purifying urban stormwater runoff, creating environmental amenities, and biodiversity conservation. Nevertheless, the existing knowledge of people's preferences for GI is not yet sufficient for evidence-based policymaking for enhancing GI. This study analyzes citizens' perceptions of the relative importance of six GI practices and estimates their willingness to pay (WTP) to enhance them. To this end, the study applies two types of stated preference methods (best-worst scaling and contingent valuation) to citizen survey data collected in Portland, Oregon. We found that GI practices that are more likely to lead to private benefits (e.g., rain barrels, urban trees) received relatively higher ratings, whereas the ratings of practices that do not offer such benefits (e.g., bioswales, rain gardens) were relatively lower. However, the diversity of preferences was large, as the relative importance varied widely among respondents. Heterogeneous preferences were also found in terms of citizens' WTP for hypothetical GI enhancement. Our comparison of uniform and variable payment schemes revealed that variable payment outperformed uniform payment because of the significant variation in citizens' WTP. The difference was large when the annual household payment was small.

Porewater compositions of Portland cement with and without silica fume calculated using the fine-tuned CASH+NK solid solution model.

The CASH+ sublattice solid solution model of C-S-H aims to predict the composition of C-S-H and its ability to take up alkalis. It was originally developed for dilute systems with high water-solid ratios, and thus in this paper further optimized and benchmarked against measured pore solution compositions of hydrated Portland cement (PC) and PC blended with silica fume (SF) at realistic water-binder ratios. To get an improved agreement with the pore solution data, the stability of two CASH+ model endmembers, TCKh and TCNh, has been fine-tuned with standard Gibbs energy corrections of + 7.0 and + 5.0 kJ·mol-1, respectively (at 1 bar, 25 °C). The agreement was maintained with the experiments used to originally parameterize the CASH+ model for the uptake of K and Na in dilute systems. The K and Na concentrations predicted using the fine-tuned CASH+NK model are in a good agreement with the measured values for PC and PC + SF system at different water to binder ratios, silica fume additions, and at temperatures up to 80 °C. Supplementary Information: The online version contains supplementary material available at 10.1617/s11527-022-02045-0.

Comparative Evaluation of Physicomechanical Properties and Antimicrobial Activity of White Portland Micro- and Nanoparticulate Peruvian Cement, Mineral Trioxide Aggregate, and Neomineral Trioxide Aggregate.

AIM: To compare the surface microhardness, compressive strength, and antimicrobial activity of white Portland nanoparticle and microparticle Peruvian cement, mineral trioxide aggregate (MTA), and neomineral trioxide aggregate (NeoMTA) at 24 hours and 28 days. MATERIALS AND METHODS: Twenty specimens were prepared for each group of cement microparticulated powder (PCm), nanoparticulated cement (PCn), MTA, and NeoMTA to be evaluated at two different times, 24 hours and 28 days for the surface microhardness test and compressive strength. For the antimicrobial activity tests, another 20 specimens were prepared for each group of cement where they were subdivided into two subgroups according to the different periods at 24 hours and 48 hours. For the surface microhardness and compressive strength, the specimens, and the cement groups were mixed according to the manufacturer's instructions and transferred to a cylindrical polyethylene mold of 6-mm diameter and 4-mm height. The compressive strength test was conducted using a universal testing machine. Moreover, the agar diffusion technique was to evaluate the antibacterial and antifungal activity of the American Type Culture Collection (ATCC) Enterococcus faecalis and Candida albicans. Finally, the data were statistically analyzed. RESULTS: The highest microhardness values for the 24-hour subgroup were recorded for NeoMTA cement (16.99 ± 2.02), followed by MTA, PCn, and PCm, respectively. As for the 28-day subgroup, PCn cement (41.64 ± 3.20) presented the highest microhardness, followed by NeoMTA, PCm, and MTA, respectively, with statistically significant differences among them. The compressive strength of both subgroups 24 hours and 28 days exhibited the highest mean for PCn (41.3 ± 4.29, 65.74 ± 3.06), followed by PCm, NeoMTA, and the lowest value for MTA cement. Finally, for the antimicrobial activity, the highest mean for the 24-hours and 48-hours subgroup was recorded for NeoMTA cement (17.6 ± 1.26, 17.8 ± 1.44), followed by PCn, PCm, and the lowest value for MTA, with significant differences between them. CLINICAL SIGNIFICANCE: It is highly recommended, Portland cement (PC) as a viable substitute since it has very similar components and properties, but at a lower cost. CONCLUSION: Regardless of the evaluation time, PCn produced higher surface microhardness and compressive strength; however, NeoMTA showed higher antimicrobial activity.

Lime activated flyash-phosphogypsum blend as a low-cost alternative binder.

This study investigates the potential of a blended binder formulated from two industrial solid wastes viz. phosphogypsum and fly ash in combination with lime. Three mix proportions of phosphogypsum and fly ash were investigated, and the minimum lime contents required for activation were determined using the Eades and Grim pH test. The lime-fly ash-phosphogypsum blends were then cast into cubes, both in their paste form as well as mortar form, mixed with sand in the ratio of 1:3. They were cured for a period of seven days, and afterwards, their compressive strength was determined. Ordinary Portland cement and lime mortar blocks were also cast as control specimens for comparative evaluation of the strength. The optimal lime-fly ash-phosphogypsum blend was identified and used to construct a masonry prism, and the strengths of the masonry prisms were also evaluated. The optimal lime-fly ash-phosphogypsum blend mortar was also subjected to an X-ray diffraction analysis to determine the reaction products formed during hydration. The study revealed that 5% lime mixed with fly ash:phosphogypsum in the ratio of 3:1 was the optimal proportion which gave the maximum strength to the cubes. The optimal lime-fly ash-phosphogypsum blend mortar developed strength that was higher than conventional Portland cement and lime mortar. The optimal lime-fly ash-phosphogypsum blend mortar masonry prisms developed strength that was comparable to that of Portland cement mortar masonry. The X-ray diffraction analysis revealed the formation of calcium silicate hydrate minerals as well as ettringite and portlandite which were responsible for strength gain.

Microbial effect on water sorptivity and sulphate ingress by Bacillus megaterium on mortars prepared using Portland Pozzolana cement.

AIMS: To determine the effect of direct embedment of Bacillus megaterium into Portland pozzolana cement mortars on water sorptivity and diffusivity coefficient of sulphate ions. METHODS AND RESULTS: Prisms with a water/cement ratio of 0·5 were prepared by blending Portland Pozzolana cement with the requisite volume of a B. megaterium (microbial) solution whose concentration was 1·0 × 107 cells per ml. Mortar prisms of 160 mm × 40 mm × 40 mm were fabricated for this study. Mortars cured for 28 days were exposed to 0·2465 mol l-1 Na2 SO4 solution using accelerated ion migration test method for 36-h session using a 12V DC power source. Sulphate ion concentration was then determined through the ingressed mortar at 10 mm interval. A minimum water sorption gain of 0·61% was observed on the prism prepared with and cured in microbial solution. A maximum of 0·0289 and a minimum of 0·0093 water sorptivity coefficients were exhibited by the control prism and microbial prisms, respectively. The microbial prisms exhibited the lowest apparent diffusion coefficient (Dapp ) of 4·5179 × 10-11  m2  s-1 . CONCLUSIONS: Direct incorporation of B. megaterium in mortar preparation, curing or both regimes significantly retarded water sorption and lowered sulphate ion ingress. The inclusion of this bacterial in the mortar further complements the pozzolana pore structure benefits. SIGNIFICANCE AND IMPACT OF THE STUDY: This novel B. megaterium bacteria which can survive and cause biocementation within hydrating cement mortar when not encapsulated would result in a green innovation. Once adopted and applied in real-life scenario, it would promote construction of durable, safe, resilient and affordable shelter.

Dynamic Panel Data Modeling and Surveillance of COVID-19 in Metropolitan Areas in the United States: Longitudinal Trend Analysis.

BACKGROUND: The COVID-19 pandemic has had profound and differential impacts on metropolitan areas across the United States and around the world. Within the United States, metropolitan areas that were hit earliest with the pandemic and reacted with scientifically based health policy were able to contain the virus by late spring. For other areas that kept businesses open, the first wave in the United States hit in mid-summer. As the weather turns colder, universities resume classes, and people tire of lockdowns, a second wave is ascending in both metropolitan and rural areas. It becomes more obvious that additional SARS-CoV-2 surveillance is needed at the local level to track recent shifts in the pandemic, rates of increase, and persistence. OBJECTIVE: The goal of this study is to provide advanced surveillance metrics for COVID-19 transmission that account for speed, acceleration, jerk and persistence, and weekly shifts, to better understand and manage risk in metropolitan areas. Existing surveillance measures coupled with our dynamic metrics of transmission will inform health policy to control the COVID-19 pandemic until, and after, an effective vaccine is developed. Here, we provide values for novel indicators to measure COVID-19 transmission at the metropolitan area level. METHODS: Using a longitudinal trend analysis study design, we extracted 260 days of COVID-19 data from public health registries. We used an empirical difference equation to measure the daily number of cases in the 25 largest US metropolitan areas as a function of the prior number of cases and weekly shift variables based on a dynamic panel data model that was estimated using the generalized method of moments approach by implementing the Arellano-Bond estimator in R. RESULTS: Minneapolis and Chicago have the greatest average number of daily new positive results per standardized 100,000 population (which we refer to as speed). Extreme behavior in Minneapolis showed an increase in speed from 17 to 30 (67%) in 1 week. The jerk and acceleration calculated for these areas also showed extreme behavior. The dynamic panel data model shows that Minneapolis, Chicago, and Detroit have the largest persistence effects, meaning that new cases pertaining to a specific week are statistically attributable to new cases from the prior week. CONCLUSIONS: Three of the metropolitan areas with historically early and harsh winters have the highest persistence effects out of the top 25 most populous metropolitan areas in the United States at the beginning of their cold weather season. With these persistence effects, and with indoor activities becoming more popular as the weather gets colder, stringent COVID-19 regulations will be more important than ever to flatten the second wave of the pandemic. As colder weather grips more of the nation, southern metropolitan areas may also see large spikes in the number of cases.

Predicting why people engage in pro-sustainable behaviors in Portland Oregon: The role of environmental self-identity, personal norm, and socio-demographics.

This study aims to identify factors influencing people's participation in frequent and effective pro-sustainable behaviors (PSB) in Portland, Oregon, using value-belief-norm theory and a modified value-identity-personal-norm (VIP) model. Drawing from a resident survey (n = 484) and applying a series of regression and mediation analyses, we tested the power of the VIP model in our sample to examine the influence of values, environmental self-identity, and personal norms on PSB while adjusting for socio-demographic factors. Our study revealed participants who held altruistic values (i.e., cared for the community, valued diversity and gender equality, and made decisions based on cooperation) had stronger environmental self-identity characterized by a belief that reflects biocentrism, ecofeminism, ecospirituality, or deep ecology. These identities were significantly associated with participation in more effective PSB after adjusting for personal norms. Participants with egoistic values had stronger anthropocentric identity and weaker personal norms which translated into lower participation in more effective PSB. Also, education increased PSB, with master's degree holders participating more than other groups. Overall, values, environmental self-identity, and higher education predicted participation in effective PSB. Our refined theoretical model is, therefore, promising for assessing multiple PSB at once, especially those that significantly reduce carbon footprint on the planet.

Potential risk of exposure to heavy metals from co-processing of secondary wastes in the Republic of Korea.

The co-processing of secondary wastes during ordinary Portland cement (OPC) can result in high heavy metal concentrations in OPC products. However, earlier studies have not evaluated the concentrations of heavy metals (HMs) in OPC as a function of secondary input materials. Further, the health risk assessment (HRA) model has, thus far, has not been employed to assess the potential health risks associated with secondary raw materials and secondary fuels in OPC. Hence, to address these knowledge gaps, herein, monthly data for six HMs in the input materials and fuels from seven OPC manufacturers in the Republic of Korea were analyzed and modeled. Pb and Cu concentrations were found to be approximately 10-200 and 4-200 times higher than those of the other HMs, respectively. Furthermore, maximum Pb and Cu concentrations were 2-3 and 2-5 times higher than those reported in other countries, respectively. The quantity of input material had a significant influence on the observed patterns, and secondary raw materials, secondary additives, and secondary fuels were also determined to be important. Based on HRA assessment, although the risk levels were within permissible ranges, carcinogenic hazards attributable to Cr and Pb were not negligible. The results can aid in informed decision making and in implementing effective measures for managing risks associated with HMs in the OPC industry, thereby ameliorating threats to human health and environment.

Recycling of lithium slag extracted from lithium mica by preparing white Portland cement.

In recent years, lithium slag (LS) has increased sharply with the development of lithium industry, which has caused serious environmental problems. However, the utilization of this industrial waste residue has been a difficult topic in lithium industry. In this paper, the effects of LS on mineral crystal type, ionic solid solution, decomposition temperature of CaCO3 and strength of white Portland cement clinker were studied by XRD, FT-IR, DSC, SEM-EDS and other means. The results show that LS can stabilize the M1 crystal of C3S, improve the crystallinity of C3A, and reduce the content of ACn. The LS content of 5 wt% can reduce the decomposition temperature of CaCO3 about 10 °C, but increase the low eutectic temperature of materials. Na elements tended to be dissolved in the intermediate phase, while Al3+ dissolved in calcium silicate may replace Ca2+ or Si4+. Sintering white Portland cement clinker with appropriate content of LS can effectively reduce the content of f-CaO and greatly improve the early compressive strength of clinker. Therefore, LS within 5 wt% can be used as high quality raw material of white cement, which can recycle LS.

Mercury-bearing wastes: Sources, policies and treatment technologies for mercury recovery and safe disposal.

Due to the lenient environmental policies in developing economies, mercury-containing wastes are partly produced as a result of the employment of mercury in manufacturing and consumer products. Worldwide, the presence of mercury as an impurity in several industrial processes leads to significant amounts of contaminated waste. The Minamata Convention on Mercury dictates that mercury-containing wastes should be handled in an environmentally sound way according to the Basel Convention Technical Guidelines. Nevertheless, the management policies differ a great deal from one country to another because only a few deploy or can afford to deploy the required technology and facilities. In general, elemental mercury and mercury-bearing wastes should be stabilized and solidified before they are disposed of or permanently stored in specially engineered landfills and facilities, respectively. Prior to physicochemical treatment and depending on mercury's concentration, the contaminated waste may be thermally or chemically processed to reduce mercury's content to an acceptable level. The suitability of the treated waste for final disposal is then assessed by the application of standard leaching tests whose capacity to evaluate its long-term behavior is rather questionable. This review critically discusses the main methods employed for the recovery of mercury and the treatment of contaminated waste by analyzing representative examples from the industry. Furthermore, it gives a complete overview of all relevant issues by presenting the sources of mercury-bearing wastes, explaining the problems associated with the operation of conventional discharging facilities and providing an insight of the disposal policies adopted in selected geographical regions.

The Effect of Silica Fume and Organosilane Addition on the Porosity of Cement Paste.

The present work systematically investigates the influence of silica fume and organosilane addition on the hydration dynamics and the capillary pore formation of a cement paste. The cement samples were prepared with two water-to-cement ratios with increasing amounts of silica fume and of (3-Aminopropyl)triethoxysilane (APTES) organosilane. Low-field 1H nuclear magnetic resonance (NMR) relaxation measurements were performed during the hydration of the samples and after hydration, in order to reveal the dynamics of water molecules and the pore distribution. Increasing concentrations of silica fume impact the perceived hydration dynamics through the addition of magnetic impurities to the pore solution. However, there is a systematic change in the capillary pore size distribution with an increase in silica fume concentration. The results also show that the addition of APTES majorly affects the hydration dynamics, by prolonging the dormancy and hardening stages. While it does not influence the pore size distribution of capillary pores, it prevents cyclohexane from saturating the capillary pores.

Self-Healing Properties of Bioinspired Amorphous CaCO3/Polyphosphate-Supplemented Cement.

There is a strong interest in cement additives that are able to prevent or mitigate the adverse effects of cracks in concrete that cause corrosion of the reinforcement. Inorganic polyphosphate (polyP), a natural polymer that is synthesized by bacteria, even those on cement/concrete, can increase the resistance of concrete to progressive damage from micro-cracking. Here we use a novel bioinspired strategy based on polyP-stabilized amorphous calcium carbonate (ACC) to give this material self-healing properties. Portland cement was supplemented with ACC nanoparticles which were stabilized with 10% (w/w) Na-polyP. Embedding these particles in the hydrated cement resulted in the formation of calcite crystals after a hardening time of 10 days, which were not seen in controls, indicating that the particles dissolve and then transform into calcite. While there was no significant repair in the controls without ACC, almost complete closure of the cracks was observed after a 10 days healing period in the ACC-supplemented samples. Nanoindentation measurements on the self-healed crack surfaces showed a similar or slightly higher elasticity at a lower hardness compared to non-cracked surfaces. Our results demonstrate that bioinspired approaches, like the use of polyP-stabilized ACC shown here, can significantly improve the repair capacity of Portland cement.

The use of calcium sulfo-aluminate cement as an alternative to Portland Cement for the recycling of municipal solid waste incineration bottom ash in mortar.

Municipal solid waste incineration generates large quantities of bottom ash that should be recycled. Current use of municipal solid waste incineration bottom ash (MSWI-BA) in cementitious materials is mostly in Ordinary Portland Cement (OPC). This paper considers using MSWI-BA as sand substitution in Calcium Sulfoaluminate Cement (CSA) as an alternative to OPC. A comparison between OPC and CSA mortars containing 0-2 mm MSWI-BA is conducted. The MSWI-BA used was treated to remove the ferrous and non-ferrous metals in order to obtain a better mineral fraction. Different percentages (0%, 25%, 50%, 75%, and 100%) of standard sand were substituted by MSWI-BA based on equivalent volume. Experimental results showed that the compressive strength and porosity of the CSA mortars were superior to OPC after substitution at 1, 7, 28, and 90 days. The compressive strength of OPC mortars with 25% substitution decreased by 40% compared to 11% for CSA mortars at 90 days. This is due to the difference in pH between the two cement pastes as OPC in contact with the MSWI-BA leads to a reaction with the aluminum content which releases hydrogen gas, increases the porosity, and decreases the compressive strength.

Transformation of Construction Cement to a Self-Healing Hybrid Binder.

A new biomimetic strategy to im prove the self-healing properties of Portland cement is presented that is based on the application of the biogenic inorganic polymer polyphosphate (polyP), which is used as a cement admixture. The data show that synthetic linear polyp, with an average chain length of 40, as well as natural long-chain polyP isolated from soil bacteria, has the ability to support self-healing of this construction material. Furthermore, polyP, used as a water-soluble Na-salt, is subject to Na+/Ca2+ exchange by the Ca2+ from the cement, resulting in the formation of a water-rich coacervate when added to the cement surface, especially to the surface of bacteria-containing cement/concrete samples. The addition of polyP in low concentrations (<1% on weight basis for the solids) not only accelerated the hardening of cement/concrete but also the healing of microcracks present in the material. The results suggest that long-chain polyP is a promising additive that increases the self-healing capacity of cement by mimicking a bacteria-mediated natural mechanism.