Wet Environment Research Articles

Self-healing and rebar corrosion performance of cracked engineered cementitious composites exposed to wet coral sand environment

Wet coral sand environment on islands and reefs features high humidity and abundance in aggressive fluids and gases, thus posing a great threat to the durability of reinforced concrete structures. In this study, engineered cementitious composites (ECCs) with strain-hardening and self-healing characteristics are proposed as a potential cover material in wet coral sand exposure. The autogenous self-healing capability of cracked ECCs was evaluated by the visual crack morphology as well as water permeability, and their rebar corrosion performance over a period of one and a half years was investigated based on electrochemical tests. The results show that cracks with initial width up to 70 μm are able to completely close within one day, probably due to the efficient precipitation of calcium carbonate and further hydration of cement. Compared with the uncracked control, the 0.4 %, 1.0 % and 1.6 % strained ECCs can be healed up to 100 %, 93.4 % and 60.5 % at 30 days, respectively. The water permeability coefficient of the strained ECC decreases rapidly in the first 30 days, and then stabilizes in the later stages. Moreover, the load-carrying capacity of preloaded ECC beams is recovered, exhibiting comparable performance to the uncracked controls after the same exposure periods. The corrosion current densities of steel bars suggest an active corrosion conditions. Both of the corrosion current densities and mass losses of rebar show lower values at decreased strain level, which is closely related to the width and number of cracks that reach the reinforcement.

Bioactive citrate-based polyurethane tissue adhesive for fast sealing and promoted wound healing.

As a superior alternative to sutures, tissue adhesives have been developed significantly in recent years. However, existing tissue adhesives struggle to form fast and stable adhesion between tissue interfaces, bond weakly in wet environments and lack bioactivity. In this study, a degradable and bioactive citrate-based polyurethane adhesive is constructed to achieve rapid and strong tissue adhesion. The hydrophobic layer was created with polycaprolactone to overcome the bonding failure between tissue and adhesion layer in wet environments, which can effectively improve the wet bonding strength. This citrate-based polyurethane adhesive provides rapid, non-invasive, liquid-tight and seamless closure of skin incisions, overcoming the limitations of sutures and commercial tissue adhesives. In addition, it exhibits biocompatibility, biodegradability and hemostatic properties. The degradation product citrate could promote the process of angiogenesis and accelerate wound healing. This study provides a novel approach to the development of a fast-adhering wet tissue adhesive and provides a valuable contribution to the development of polyurethane-based tissue adhesives.

Corrosion protection effect of rust and scales: A “metal protects metal” perception by considering the examples of hematite and magnetite

AbstractThe present report proposes a contradictory remark on the idiom “Iron cuts Iron” that could be synonymized as “Metal cuts Metal” using the example of hematite and magnetite. Most metals and alloys are highly reactive, forming rusts and scales primarily consisting of metal oxides. The formation of metal oxide layers is known as passivation. Generally, passivated metallic surfaces provide anticorrosive protection by avoiding the attacks of corrosive species on the fresh metal surface; therefore, “Corrosion is a Necessary Evil (CNE).” Most passive films are protective, but not all, and their actual nature can be determined using the Pilling–Bedworth ratio (PBR). In dry conditions, passivation occurs spontaneously by the oxidation of metal atoms, but in aqueous media, some external additives, called passivators, are added to build the passive films. Herein, by considering examples of hematite and magnetite, the anticorrosive properties of rusts and scales are described in dry and wet (solution and coating) environments.

Tillage Methods Change Nitrogen Distribution and Enzyme Activities in Maize Rhizosphere and Non-Rhizosphere Chernozem in Jilin Province of China

The tillage method in farming systems is essential to develop strategies to increase fertilizer uptake by plant roots and to avoid environmental pollution. The field study aimed to investigate the characteristics of nitrogen and enzyme activities in rhizosphere soil with different tillage methods. Four treatment plots applied with fertilizers were established: continuous rotary tillage (CR), plowing-rotary tillage (PR), continuous no-till (CN) and ploughing-no-till (PN). The total content of nitrogen in chernozem was high during early stages of plant growth, and then it decreased with the maize growth. In the rhizosphere soil, the total N accounted 1314.45, 1265.96, 1120.47, 1120.47, 1204.05 mg·kg−1 of CR, PR, CN, and PN, respectively, which were markedly greater than that of non-rhizosphere soil (1237.52, 1168.40, 984.51, 1106.49 mg·kg−1 of CR, PR, CN, and PN, respectively). At first growth stages, content of NH4+-N and NO3−-N in two soil regions was low, then increased gradually, which followed the order of CR < PR < PN < CN. The rhizosphere soil showed slightly higher concentration of NH4+-N and NO3−-N than non-rhizosphere. The soil enzymes were more active in the rhizosphere soil than that of non-rhizosphere during the whole maize growth stages. Due to minimal damage to the soil environment and optimal soil moisture and temperature, the urease and catalase activities were greatest in the rhizosphere for CN treatment. Therefore, CN was recommended to be used by farmers for the improvement of macronutrient availability and soil enzyme activities in the soil.

Past and present biomass consumption by herbivores and fire across productivity gradients in North America

Herbivores and fire are important consumers of plant biomass that influence vegetation structure, nutrient cycling, and biodiversity globally. Departures from historic biomass consumption patterns due to wild herbivore losses, livestock proliferation, and altered fire regimes can have critical ecological consequences. We set out to (i) understand how consumer dominance and prevalence responded to spatial and temporal moisture gradients in Holocene North America and (ii) examine how past and present consumer dominance patterns in North America compare to less altered consumer regimes of modern Sub-Saharan Africa. We developed long-term records of bison abundance and biomass burning in Holocene midcontinent North America and compared these records to reconstructions of moisture availability and vegetation structure. We used these reconstructions to characterize bison and fire prevalence across associated moisture and vegetation gradients. We found that bison herbivory dominated biomass consumption in dry settings whereas fire dominated in wetter environments. Historical distributions of herbivory and burning in midcontinent North America resemble those of contemporary Sub-Saharan Africa, suggesting disturbance feedbacks and interactions regulate long-term consumer dynamics. Comparisons of consumer dynamics in contemporary North America with Holocene North America and Sub-Saharan Africa also reveal that fire is functionally absent from regions where it was once common, with profound ecological implications.

Multifunctional packaging film with sustained release behavior triggered by pH microenvironment for efficient preservation of pork

To tackle microbial contamination and spoilage during pork storage, transportation, and sales, a novel packaging film with exogenously driven controlled release behavior was designed through the demand-directed preparation of the emulsion of shellac-encapsulated cinnamaldehyde nano-capsules (SNCs) and the ingenious integration of chitosan (CS) film matrix. Among them, the SNCs were synthesized using the solvent exchange method, allowing controlled release of cinnamaldehyde (CA) in response to volatile alkaline substances present in the meat. The electrostatic interaction between SNCs and CS molecules improved the thermal stability, water resistance, tensile strength, and viscosity of the film-forming solution, while the CA in SNCs enhanced UV resistance and antimicrobial properties of the film. Notably, the CS film with SNC-100 loaded (CSNCs-100 film) achieved 99% inhibition against both E. coli and S. aureus, regulated environmental moisture, and prolonged the freshness duration of pork by an impressive six days.

High-output moisture-enabled electricity generator for fully self-powered wearable physical and biochemical monitoring

Spontaneous conversion of environmental moisture energy to high-output electricity can help meet the massive electricity demand of wearable electronics. However, low power density and inefficient energy harvesting are the main challenges to power electronics currently. Herein, we developed a flexible moisture-enabled electricity generation (MEG) membrane with high output power. The asymmetrical structure of the moisture-enabled flexible units is composed of a bilayer of polyanion and polycation. The single device produced a sustained voltage of 0.8 V and can be customized by an aligned stacking strategy for scale integration on demand. Enhanced by increasing the diffusion speed of carriers with the metal-air reaction, the output power reached 286.5 μW/cm2, which is enough for long-term wearable health monitoring. Meanwhile, to solve the power supply challenge of the wearables, a fully self-powered system with an energy harvester, a power management module, and a wireless and wearable sensing module was developed. Biochemical indicators and body motion were detected and monitored by the sensor array, demonstrating the promising application in wearable health management, including harvesting energy from giant moisture and powering wearable electronics.

Impacts of Climate Change on Vegetation in Kenya: Future Projections and Implications for Protected Areas

Climate change will cause substantial vegetation shifts across the world. Africa may face varying dynamics such as tree decline, savannization, and woody encroachment due to rising temperatures and rainfall changes. This study examines the potential effects of climate change on Kenyan vegetation and vegetation shifts for 2050 and 2100, employing a statistical model to predict vegetation state as driven by environmental variables, including temperature, soil moisture, livestock density, and topography. We evaluate the model by hindcasting it from 2020 to 2000 and then project future vegetation states for 2050 and 2100 under SSP 2–4.5 and SSP 5–8.5. In response to moderate emissions, a notable increase in arid-associated shrubland vegetation (53–58%) is forecasted, leading to the expansion of drylands at the expense of savannas, grasslands, and forests. Under high-emission scenarios, savannas are forecasted to expand (52–65%) at the expense of forested areas. Overall, dense forest cover declines across scenarios, affecting protected areas by promoting increased savanna cover and reducing forest area (40% to 50%). These projected shifts in major vegetation types would likely alter ecosystem functioning and associated services, impacting pastoralists and wildlife and raising biodiversity concerns. Protected areas in Kenya could lose 50% of their forests, highlighting the urgency of climate change mitigation. These findings offer a crucial foundation for future research and action on Kenya’s vegetation.

Determining Allometry and Carbon Sequestration Potential of Breadfruit (Artocarpus altilis) as a Climate-Smart Staple in Hawai‘i

Breadfruit (Artocarpus altilis) is an underutilized Pacific tree crop that has been highlighted as having substantial potential to contribute to global food security and climate-smart agriculture, including adaptation to and mitigation of climate change. To explore the carbon sequestration potential of breadfruit production, we characterize tree volume, wood density, carbon density, foliar biomass, and growth rates of breadfruit in Hawai‘i. Strong relationships to trunk or branch diameter were displayed for wood density (r2 0.81), carbon density (r2 0.87), and foliar biomass (r2 0.91), which were combined to generate an allometric prediction of tree volume (r2 0.98) based on tree diameter at breast height. Growth rates, as measured by diameter at breast height, were well predicted over time when trees were classified by habitat suitability. We extrapolate potential breadfruit growth and carbon sequestration in above-ground biomass to the landscape scale over time. This study shows that breadfruit is on the low end of broadleaf tropical trees in moist and wet environments, but in an orchard can be expected to sequester ~69.1 tons of carbon per hectare in its above-ground biomass over a 20-year period.

Microstructure and tribological performance of Co-B intermetallic compounds under water environment

Cobalt-boride (Co-B) alloys, as promising wear resistant materials, can form different intermetallic compounds. In this work, supercooling treatment is applied to control the microstructures and compounds in the alloys, and the related mechanical and tribological properties have been investigated systematically. The results suggest that besides FCC-Co and HCP-Co, it forms Co3B and minor Co2B in the as-cast samples, Co3B, Co2B and Co23B6 under different supercooling degree. Tribological experiments of these alloys under distilled water environment demonstrate that the Co-B alloy containing Co23B6 has the best tribological performance, followed by Co2B and Co3B. The coefficient of friction and wear rate of alloy containing Co23B6 are about 0.2 and 1.6 × 10−6 mm3/Nm, respectively, which are reduced by 60 % and one magnitude lower compared to the as-cast sample containing Co2B and Co3B. The promising tribological result of Co23B6 is attributed to the formation of tribolayer, which is rich in Co(OH)2, silicate, SiO2 and possibly H3BO3. This work provides guideline for tuning phases of Co-B alloys when using as rubbing parts in moisture environment.

Unveiling the pitting corrosion mechanism of borated stainless steel in the wet storage environment of spent nuclear fuels

Borated stainless steels (BSSs) with high neutron absorbability are promising alloys for the wet storage of spent nuclear fuel. However, consensus on the underlying mechanisms for the effects of B content in BSS and H3BO3 in wet storage environment on the pitting corrosion resistance of BSSs is still lacking. To determine the mechanisms, we designed three hypoeutectic BSSs containing 0.6, 1.2 and 1.8 wt.% B and systematically investigated their electrochemical behavior in solutions with various Cl−/H3BO3 ratios through experimental and computational studies. Results revealed that the pitting corrosion resistance of BSS was dependent on the synergistic effect of the pit initiation induced by localized Cr depletion and the pit stable growth caused by microgalvanic effect, causing the pitting corrosion preferentially occurred at the (Cr, Fe)2B/matrix interface. A higher B content increased the density and width while reduced the Cr contents of the Cr-depleted regions, enhancing the susceptibility to pitting initiation. Meanwhile, the strengthened micro-galvanic effect between the (Cr, Fe)2B phase and γ matrix further facilitated the stable pit growth. For the H3BO3 effect, the first-principles calculations indicated that the competitive adsorption of B(OH)4− to Cl− inhibited pitting initiation in solutions with lower Cl−/H3BO3 ratios. However, as the Cl−/H3BO3 increased, the inhibition effect of the H3BO3 was weakened, and the acidizing effect became the dominant factor deteriorating the corrosion property. Ultimately, based on the Cr depletion-microgalvanic synergetic mechanism, the corrosion resistance of the BSS was significantly improved by tailoring the size and distribution of the (Cr, Fe)2B phase.

Janus polyurethane sponge as an antibiofouling, antibacterial, and exudate-managing dressing for accelerated wound healing.

The non-fouling condition, bacteria-free environment and suitable moisture at wound site are crucial for chronic wound healing. However, it remains highly meaningful yet challenging to develop wound dressings that can simultaneously achieve these desirable functions. In this work, a kind of multifunctional Janus polyurethane sponge (Janus-PU) was designed and fabricated by coating near-infrared (NIR)-responsive and superhydrophobic nanoparticles (F-ZnO@Ag NPs) on one surface of sponge. The nano-functionalized outer layer can endow Janus-PU with superhydrophobic antifouling property for preventing bacterial colonization and broad-spectrum antibacterial activity due to the presence of Ag NPs. Especially, the synergistic combination of asymmetric structure and strong NIR photothermal effect can impart Janus-PU with NIR-controlled unidirectional exudate removal, thus achieving an optimal wetting environment for wound healing. The mice full-thickness skin acute wounds treated with Janus-PU under NIR irradiation showed superior anti-infection and healing effect compared to the commercial dressings. Significantly, the treatment using Janus-PU with NIR irradiation can accelerate the recovery of methicillin-resistantStaphylococcus aureus(MRSA)-infected diabetic chronic wounds due to the synergistic effect of antibiofouling, antibacterial and exudate-managing. The Janus-PU as a promising multifunctional dressing can prevent bacterial invasion and create an appropriate environment for wound healing, providing an effective solution for intractable wounds and infections. STATEMENT OF SIGNIFICANCE: The development of advanced wound dressings to ensure non-fouling condition, bacteria-free environment and suitable moisture is crucial for chronic wound healing. However, it remains a considerable challenge to simultaneously integrate antibiofouling, antibacterial and exudate-managing properties into a single dressing. In this work, we developed a kind of multifunctional Janus polyurethane sponge (Janus-PU) by a single-sided superhydrophobic modification strategy, which can simultaneously achieve superhydrophobic antifouling property, effective broad-spectrum antibacterial and near-infrared controlled exudate removal. The Janus-PU designed herein can not only create an optimal environment for accelerated wound healing, but also avoid frequent dressing replacement, thus providing an ideal material system for intractable wounds and infections.

Experimental Study On Acoustic Emission Characteristics of SAP Mortar Self-Healing Process

Self-healing properties of super absorbent polymer (SAP) concrete can reduce the harmful effects of concrete cracking in structures. This study examines the self-healing process of mortars with different SAP content under dry and wet conditions through acoustic emission testing (AE) and elastic wave velocity testing. Findings indicate that the SAP mortar healing process has three stages: rapid water absorption, smooth water absorption, and drying. In a dry environment, increasing SAP content enhances AE activity, indicating internal crack self-healing via further hydration of unhydrated cement particles. In a wet environment, AE activity increases with increasing SAP content during the second healing cycle, indicating self-healing of the mortar matrix. These results suggest the use of SAP concrete could potentially mitigate future structural damage.

Environmental Controls on the Tropical Island Diurnal Cycle in the Context of Intraseasonal Variability

Abstract The mechanisms regulating the relationship between the tropical island diurnal cycle and large-scale modes of tropical variability such as the boreal summer intraseasonal oscillation (BSISO) are explored in observations and an idealized model. Specifically, the local environmental conditions associated with diurnal cycle variability are explored. Using Luzon Island in the northern Philippines as an observational test case, a novel probabilistic framework is applied to improve the understanding of diurnal cycle variability. High-amplitude diurnal cycle days tend to occur with weak to moderate offshore low-level wind and near to above average column moisture in the local environment. The transition from the BSISO suppressed phase to the active phase is most likely to produce the wind and moisture conditions supportive of a substantial diurnal cycle over western Luzon and the South China Sea (SCS). Thus, the impact of the BSISO on the local diurnal cycle can be understood in terms of the change in the probability of favorable environmental conditions. Idealized high-resolution 3D Cloud Model 1 (CM1) simulations driven by base states derived from BSISO composite profiles are able to reproduce several important features of the observed diurnal cycle variability with BSISO phase, including the strong, land-based diurnal cycle and offshore propagation in the transition phases. Background wind appears to be the primary variable controlling the diurnal cycle response, but ambient moisture distinctly reduces precipitation strength in the suppressed BSISO phase and enhances it in the active phase.

Petrographic and geochemical analysis of Barmer Basin Paleogene lignite deposits: Insights into depositional environment and paleo-climate

The current study attempts to characterize the samples from Kapurdi, Giral and Sonari lignite mines of Barmer Basin within Rajasthan Tertiary Lignite deposits using petrographic and geochemical techniques. The data generated has been studied in order to better understand the geochemical properties, hydrocarbon potential, depositional environment and paleo-climatic condition of the paleo-mires of these lignites. The proximate analysis of the samples reveals that the average ash content of the Barmer Basin is 11.93 %, the average moisture content is 14.08 %, average volatile matter yield is 42.03 % and the average fixed carbon is 31.95 %, which suggesting that the physical properties of lignite are dominated by volatile matter on dry basis. The ultimate investigation reveals the chemical properties of the lignite with the average carbon content found to be 58.79 wt%, hydrogen value 3.83 wt%, nitrogen percentage 1.60 wt% and sulphur content 2.75 wt%. This clearly indicates high sulphur concentration in Barmer lignite deposits, based on dry basis. The lignite samples subjected to FTIR studies identified aliphatic CH group, aromatic CO group, hydroxyl OH and Aldehyde HCO group. The Rock-Eval pyrolysis studies have been carried out to know the coalification profile of the deposits and hydrocarbon source rock potential. The varying behaviour between brown coal lithotype are primarily reflected by changes in oxygen index values, whereas hydrogen index values demonstrate a more pronounced correlation with coal type rather than the level of maturation. The results show the average total organic carbon (TOC) 47.29 %, S1 peak 2.18 mg HC/g, S2 peak 88.70 mg HC/g, S3 peak 19.22 % mg CO2/g, Tmax 410.53 °C, hydrogen index 219.2 mg HC/g TOC and oxygen index 46.33 mg CO2/g TOC. According to petrographic investigations, the huminite macerals dominate followed by liptinite and inertinite maceral groups in mineral matter-free basis. In all the three different lignite mines, the huminite group dominates with preserved sub-maceral ulminite indicating less transformation of structured plant matter. Reconstruction of depositional environment and paleo-climatic condition of the paleo-mires has been attempted by using organic petrographic indices. The high gelification index (GI) and low tissue preservation index (TPI) values suggest a prolonged wet environment during the decomposition of organic material, accompanied by a gradual subsidence process. The ground water influence index (GWI) and vegetation index (VI) denote ombrotrophic to mesotrophic hydrological conditions of basin at the time of deposition.

BIODENTINE V/S BIOSTRUCTURE MTA- THE BETTER ROOT END FILLING MATERIAL- CLINICAL CASE REPORT

An ideal root end filling material is the one which is biocompatible, easy to handle, dimensionally stable ,radio opaque, set in the presence of wet environment, have good compressive strength, non staining, have adequate working time and must be antibacterial in nature. Newer materials have been introduced over the years and two such materials are Biostructure MTA and Biodentine. Both of them fulfil the criteria of an ideal root end filling material. So this case report compares the two materials and the post operative healing following the placement of the material.

PLANT COMMUNITY CHANGE ACROSS THE PALEOCENE–EOCENE BOUNDARY IN THE GULF COASTAL PLAIN, CENTRAL TEXAS

Abstract Long-term global warming during the early Paleogene was punctuated by several short-term ‘hyperthermal’ events, the most pronounced being the Paleocene–Eocene Thermal Maximum (PETM). During this long-term warming, tropical climates expanded into extra-tropical areas, creating a widespread band of thermophilic flora that reached into the paratropics, possibly as far north as mid-latitude North America in some regions. Relatively little is known about these paratropical floras, despite distribution across the North American Gulf Coastal Plain. We assess floras from the Gulf Coastal Plain in Central Texas before and after the Paleocene–Eocene boundary to define plant ecosystem changes associated with rapid global warming in this region. After the Paleocene–Eocene boundary, these floras suggest uniform plant communities across the Gulf Coastal Plain, but with high turnover rate and changes in community composition. Paleoecology and paleoclimate assessments from Central Texas Paleocene and Eocene floras suggest a warm and wet environment, indicative of tropical seasonal forest to tropical rainforest biomes. Fossil evidence from the Gulf Coastal Plain combined with the Bighorn Basin, Wyoming data suggest that early Paleogene warming helped create a paratropical belt that extended into mid-latitudes. Evaluating the response of fossil plant communities to rapid global warming has important implications for understanding and preparing for current global warming and climate change.

Exploring the potential of biologically active phenolic acids from marine natural products as anticancer agents targeting the epidermal growth factor receptor

The epidermal growth factor receptor (EGFR) dimerizes upon ligand bindings to the extracellular domain that initiates the downstream signaling cascades and activates intracellular kinase domain. Thus, activation of autophosphorylation through kinase domain results in metastasis, cell proliferation, and angiogenesis. The main objective of this research is to discover more promising anti-cancer lead compound against EGRF from the phenolic acids of marine natural products using in-silico approaches. Phenolic compounds reported from marine sources are reviewed from previous literatures. Furthermore, molecular docking was carried out using the online tool CB-Dock. The molecules with good docking and binding energies scores were subjected to ADME, toxicity and drug-likeness analysis. Subsequently, molecules from the docking experiments were also evaluated using the acute toxicity and MD simulation studies. Fourteen phenolic compounds from the reported literatures were reviewed based on the findings, isolation, characterized and applications. Molecular docking studies proved that the phenolic acids have good binding fitting by forming hydrogen bonds with amino acid residues at the binding site of EGFR. Chlorogenic acid, Chicoric acid and Rosmarinic acid showed the best binding energies score and forming hydrogen bonds with amino acid residues compare to the reference drug Erlotinib. Among these compounds, Rosmarinic acid showed the good pharmacokinetics profiles as well as acute toxicity profile. The MD simulation study further revealed that the lead complex is stable and could be future drug to treat the cancer disease. Furthermore, in a wet lab environment, both in-vitro and in-vivo testing will be employed to validate the existing computational results. Communicated by Ramaswamy H. Sarma

The effect of the cyclic hornification on the hygromechanical and surface characteristics of rice stubble agriculture waste

An indiscriminate burning of rice stubble waste in the farms poses a major environmental challenge worldwide. The stubble waste can be utilized to fabricate the natural fibre polymer composites for several mild- to low-load-bearing applications in the civil construction. However, the susceptibility to long-term environmental moisture limits the use of stubble waste. In this work, we analyse the effect of water and alkali hornification as a pre-treatment technique on the moisture uptake, surface roughness, wettability and mechanical strength of rice stubble straw, and the results are compared with untreated stubble straw. The water retention value was reduced by ∼49% and ∼60% after four hornification cycles under the water and alkali mediums, respectively. Preliminary visual and microstructural assessments revealed the reduction in hydrophilic cellulose and lignin contents with both types of pre-treatments. It is observed that in comparison to alkali hornification, the water hornification technique leads to a significant improvement in hygromechanical characteristics of stubble straw. When compared to untreated stubble, one cycle of water hornification leads to approximately ∼16% reduction in the moisture uptake, and ∼42% increase in the tensile strength. On the other hand, the alkali hornification resulted in the improvement in tensile strength by ∼36%, but it led to an increased water uptake. The results indicated that the thinning and surface roughening of the fibres is primarily caused by the removal of amorphous contents during the pre-treatment. For an improved environmental durability with better mechanical strength, it is recommended to do the pre-treatment of the stubble waste using one water hornification cycle before it is used further.

Evaluation of compressive strength of concrete durability degradation in dry and wet environments using destructive and non-destructive testing

To develop an effective non-destructive testing (NDT) method to assess the strength of concrete in dry and wet cyclic environments, concrete compressive strengths were evaluated of six different mix ratios in this study using ultrasonic method, rebound method and quasi-static compression tests indoors. Firstly, the results of concrete indoor quasi-static compressive strength tests were compared with the NDT results and the optimum NDT methods applicable to different concrete strength classes were determined. Subsequently, an in-situ NDT evaluation of concrete gates exposed to dry and wet environments for a long-term period was carried out based on the results of the laboratory indoor tests, and the degradation mechanism of concrete strength under dry and wet cyclic conditions was revealed by rebound method testing, borehole coring, and industrial computerized tomography (CT) scanning. The results show that the concrete strength obtained by the ultrasonic rebound method is closer to the actual value when the initial strength of concrete is less than 30 MPa; When the initial strength of concrete is between 30 and 40 MPa, the concrete strength obtained by the rebound method is closer to the actual value; When the initial strength of concrete is greater than 40 MPa, the concrete strength obtained by the rebound and ultrasonic rebound methods differ greatly from the quasi-static compressive strength. In addition, the compressive strength of concrete increases and then decreases with the number of dry and wet cycles increases. In the early stage of the dry and wet cycle, the main reason for the increase of the concrete strength is that the filling of the pores by the hydration products reduces the porosity of the concrete; As the number of dry and wet cycles increases, the hydration products absorb water to expand and lose water to shrinkage, which leads to microcracks, and this is the main reason for the decrease of the concrete strength in the late stage of the dry and wet cycle.