Background

F1000Research

2046-1402

F1000 Research Limited

London, UK

10.12688/f1000research.175541.2

Research Article

Articles

Performance of Polypropylene Fiber-Reinforced Mortar Exposed to Elevated Temperatures

[version 2; peer review: 1 approved, 1 approved with reservations]

Alshijlawi

Murtatha

Investigation Writing – Original Draft Preparation Writing – Review & Editing https://orcid.org/0009-0009-5185-064X 1 Mahmoud Hama

Sheelan

Methodology Supervision Writing – Original Draft Preparation Writing – Review & Editing https://orcid.org/0000-0001-7265-583X a 2 Abdulhamed

Musab A.

Investigation Writing – Original Draft Preparation 1 Aidan

Ibraheem A

Investigation 3 Rajab

Noor A

Writing – Review & Editing 2 Hameed Fayyadh

Aymen

Writing – Review & Editing https://orcid.org/0009-0004-8814-9738 2 1Anbar Technical Institute, Middle Technical University, Baghdad, Baghdad Governorate, Iraq 2Department of Civil Engineering, University of Anbar, Ramadi, Al Anbar Governorate, Iraq 3Department of Civil Engineering, University of Al Maarif, Ramadi, Anbar, Iraq

a drsheelan@uoanbar.edu.iq

No competing interests were disclosed.

19 3 2026

2026

9 3 2026

2026

This is an open access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Background

Lake Titicaca underpins the livelihoods, culture, and ecosystems of high Andean Aymara and lakeside communities in Peru and Bolivia. Recent multi-year declines in lake level, rising temperatures, and greater climate variability threaten water supply, agriculture, fisheries, tourism, and public health. This study characterizes climate change impacts and local perceptions in lakeside sectors to inform adaptation and cross-border management.

Methods

A multidisciplinary, participatory approach combined: (1) exhaustive document review of physical and cultural drivers; (2) fieldwork (November 2024 and June 2025) in Quehuaya (Cohana Bay, Bolivia), Capachica (Puno Bay, Peru), Guaqui (Bolivia), and Puno urban area; and (3) participatory methods including community workshops with social mapping and surveys, six in-depth interviews, and a MINCETUR ecotourism seminar survey (n = 26). Data were triangulated with institutional meetings and synthesized quantitatively.

Results

Eighty-five percent of respondents reported observed climate change indicators; seventy-four percent noted decreased rainfall, and fifty-eight percent reported hotter days. Sectoral impacts included agriculture (61% affected; reduced yields and altered planting calendars), fishing (52% decline in species or volumes), livestock (50% impacts on pasture and water; 42% increased disease), and tourism (27–29% affected by reduced navigability and pollution). Fifty-three percent reported local adaptation actions (e.g., tolerant crops, water reservoirs, traditional practices), while external support from government or NGOs was limited (~18–19%). Primary needs were financing (76%), improved climate information (52%), and organizational strengthening (26%). Participatory mapping documented shoreline retreat and cultivation of exposed lakebeds. High perceived urgency and reported migration increases (53%) highlight socioeconomic vulnerability.

Conclusions

Communities around Lake Titicaca face a chronic water-deficit syndrome driven by climatic and local stressors, producing cascading ecological, economic, health, and cultural impacts. Reactive localized adaptations exist but are insufficient. Effective response requires integrated binational strategies: improved water storage and irrigation, wetland restoration, pollution control, real-time climate information, targeted financing, and strengthened institutional coordination.

load-deflection toughness residual strength high temperatures polypropylene fibers and mortar

The author(s) declared that no grants were involved in supporting this work.

Revised Amendments from Version 1

This revised version of the manuscript incorporates several improvements in response to the reviewers’ comments to enhance clarity, transparency, and scientific rigor. The Materials section has been expanded to include detailed technical specifications of the superplasticizer used in the mixtures. Additional explanations have been added in the Results and Discussion section to clarify the interpretation of compressive strength results and ensure consistency with the reported data tables. A new subsection reporting Ultrasonic Pulse Velocity (UPV) test results has been introduced to provide supplementary non-destructive evaluation of internal damage caused by thermal exposure and to support the mechanical performance trends. Furthermore, minor typographical and presentation errors have been corrected throughout the manuscript, and figure labels have been standardized for clarity. A numerical table corresponding to the flexural toughness results has also been added to facilitate quantitative interpretation of the data. Finally, a brief Limitations and Future Work statement has been included to acknowledge the scope boundaries of the present study and outline directions for further research, including microstructural characterization and expanded testing conditions.

Abbreviations

ALT

Binational Authority of Lake Titicaca

CONCYTEC

National Council of Science, Technology and Innovation of Peru

IIGEO-UMSA

Institute of Geographic Research

MINCETUR

Ministry of Foreign Trade and Tourism of Peru

PROCIENCIA

National Program for Scientific Research and Advanced Studies

1. Introduction

Climate change has emerged as one of the main factors transforming ecosystems and altering socio-environmental systems, affecting both nature and human communities. Recent research (2020–2024) evidences various impacts, such as ecological degradation and socio-environmental vulnerability, linked to ecosystem alterations and a decline in ecosystem services. ^{1–
5} In socially exposed contexts, climate risk exacerbates economic and social inequalities, increasing the vulnerability of populations dependent on natural resources. ^{6–
9}

Climate variability, which affects precipitation patterns, temperature, and water balances, stands out as a critical dimension of climate change, necessitating predictive models and adaptation strategies based on hydrometeorological evidence. ^{10–
13} It also leads to alterations in biodiversity, characterized by changes in species distribution and abundance, where a loss of ecological functionality can also be observed. ^{14–
16}

A review of studies from the last five years confirms that the effects of climate change manifest in multiple dimensions, including climate variability, ecological degradation, habitat loss, and increased socio-environmental vulnerability. ^{17–
30} These impacts transcend ecological concerns, affecting social and territorial structures and demanding integrated approaches to environmental management and territorial planning.

Lake Titicaca, the center of a vast ecological, economic, and cultural network in the high plateau region, has faced a marked and concerning decline in water levels for years. This phenomenon, explained by a combination of global and regional climatic factors alongside local resource management practices, poses a structural threat to the lakeside communities that depend on the lake for water, food, income, and cultural significance. The current research, funded by the PROCIENCIA program of CONCYTEC (Peru) in 2024, aims to identify and characterize the main impacts of climate change on the populations inhabiting the lakeside sector of Titicaca, focusing on the Bay of Cohana (Bolivia) and the Bay of Puno (Peru), and to provide elements to guide policies for adaptation and integrated cross-border management.

The Aymara communities and other lakeside populations maintain a close, multisectoral relationship with the lake: artisanal fishing and small-scale agriculture form the basis of food security and economic sustenance; lake water is used for human consumption, irrigation, and productive activities; and the landscapes and practices associated with the lake support a cultural heritage that includes traditional knowledge, rituals, and community organization. The sustained reduction in water volume and variability—particularly the recurrence of drought episodes—alters local hydrological regimes, deteriorates the productivity of agricultural and fishing systems, and jeopardizes the provision of environmental and tourism services. ^{31–
34}

To address this complexity, the research aimed to determine the impacts of climate change on lakeside communities around Lake Titicaca, adopting a multidimensional approach that combined a documentary review of studies on the physical, socioeconomic, historical, and cultural environment; participatory fieldwork in representative communities of the bays of Cohana and Puno (community workshops developing participatory social mapping, surveys, semi-structured interviews with residents and local authorities, and dialogues with institutional actors).

The multifaceted effects identified at the community level include: a decrease in crop production and variety due to reduced irrigation water availability; loss of biomass and fishing habitats affecting fish catch and quality; degradation of wetlands and lakeshore areas that reduce water regulation capacity and biodiversity ^{34,
35}; and an increase in concentrated pollutants due to lower water volumes, with implications for public health. ³⁶ These productive and health impacts are accompanied by profound sociocultural consequences: a breakdown of traditional collective water management practices, erosion of knowledge related to fishing and agriculture, and disruption of rituals linked to the lacustrine cycle. Finally, the deterioration of livelihoods drives internal and cross-border migration processes that reconfigure demographic, economic, and family dynamics, creating additional vulnerabilities for communities remaining in the territory.

2. Materials and methods

To comprehensively address the perception of climate change impacts on lakeside communities around Lake Titicaca, this research adopted a multidisciplinary and participatory approach, integrating both qualitative and quantitative techniques. The methodology was designed in alignment with the objectives of identifying the main impacts on selected communities from the bays of Cohana (Bolivia) and Puno (Peru), along with other areas of interest (see Figure 1), and to provide elements that can guide adaptation and mitigation policies in response to climate change impacts.

Figure 1. Location of the study areas for this research.

The development of this work was structured into three fundamental phases, described below:

First Phase: Document Review

An exhaustive review of scientific literature, institutional reports, and historical studies related to the physical, socio-economic, and cultural environment of Lake Titicaca and its communities was conducted, along with an analysis of climate change, climate variability, and their main impacts. This review allowed for contextualizing the observed changes in the lake system, understanding long-term trends, and identifying factors contributing to modifications in hydrological and social regimes.

Second Phase: Fieldwork

Fieldwork was conducted in two periods: in November 2024 (at the end of the dry season) and in June 2025 (at the beginning of the dry season). The fieldwork took place in the communities of Quehuaya in the Bay of Cohana and Capachica in the Bay of Puno, chosen for their representativeness and vulnerability to changes in the lake. Additionally, work was done in the Bolivian sector in Guaqui, a locality and municipality in the Ingavi province within the La Paz department, located on the shores of Lake Titicaca. In the Peruvian area, the study focused on an area of the city of Puno where the main sewage drains flow into the lake.

The activities included participatory workshops with residents to gather traditional knowledge, perceptions of changes in the lake, and existing adaptation strategies. This involved working with community members in strict compliance with the “Code of Ethics in Research of the National University of San Marcos,” approved by Rectoral Resolution No. 012648–2023-R/UNMSM of November 21, 2023 ( https://letras.unmsm.edu.pe/wp-content/uploads/2023/11/2023_Codigo-de-etica-del-investigador.pdf).

For this study, informed verbal consent was obtained from the communities where the research was conducted. In these communities, consent is traditionally given verbally; it was obtained after presenting, explaining, and reaching an agreement with community leaders on the purpose of the project, the main activities, and the expected benefits before starting the project, through a preliminary visit to the study area. The communities’ tacit and practical confirmation of that consent was evidenced by the participation of their members and leaders in the various workshops and field visits in the study area. In summary, the only valid reason for using verbal informed consent is that the communities in this study do not customarily provide written, signed consent; oral communication and personal word carry greater weight in these populations.

Surveys were applied to all workshop participants (see Appendix A), and non-structured interviews were conducted with community leaders, farmers, fishermen, and local authorities to identify the most relevant threats and community responses to climate alterations and their consequences on ecosystems and inhabitants.

Participatory social mapping was developed during the workshops, viewing the map as a dynamic social message, a “collectivized film” in constant evolution, moving away from positivism while prioritizing dialogue and lived experiences. ^{37,
38} This approach operates on the principle that those who inhabit a territory know it best ³⁹ and gives voice to local knowledge through accessible expressions like drawings and iconography, ⁴⁰ promoting self-recognition and the strengthening of sociocultural heritage. ³⁹ It is especially useful for communities vulnerable to climate change as it incorporates local knowledge in identifying issues and formulating mitigation and adaptation strategies, facilitates the visualization of changes, encourages participation in decision-making, fosters the creation of collective plans, and enhances communication and community commitment in climate research. ^{41–
44}

Additionally, we attended a training seminar organized by MINCETUR, which convened a significant group of residents from the surrounding lake communities actively engaged in ecotourism. At the conclusion of the seminar, participants were asked to complete a survey (refer to Appendix B).

Furthermore, we conducted meetings with governmental institutions, NGOs, and water resource management organizations to gain insights into existing policies and explore opportunities for enhanced coordination.

Third Phase: Data Processing and Analysis

The data collected during the workshops, seminars, and field visits were carefully processed to identify patterns and emerging categories related to impacts and adaptation strategies. Ultimately, all information was systematically integrated and interpreted, resulting in the findings and conclusions presented in this article.

3. Results

Below is a summary of the main results obtained and their interpretation.

3.1 Community workshops in Quehuaya and Capachica

In November 2024, two participatory community workshops were held—one in the Cohana Bay Sector of Quehuaya district, La Paz, Bolivia, and the other in the Puno Bay Sector of Capachica district, Puno, Peru. Additionally, participation took place in the seminar-workshop organized by MINCETUR in Puno, which involved key promoters of ecotourism and experiential tourism around Lake Titicaca and its surroundings.

3.1.1 Surveys

The main results from the survey conducted among 62 residents of the studied communities are summarized in Appendix C-Table C1.1, categorized by gender. The sample consisted of 33 women and 29 men, all over the age of 16, with an average age of 48. Regarding education, 66% of the respondents have not exceeded primary education, 24% have completed secondary education, and only 13% have pursued technical or university studies.

Among the group, 66% are engaged in agriculture, 44% in livestock, 26% in fishing, as well as tourism activities, while the rest are involved in crafts and other activities. It’s important to note that many participants practice more than one activity, such as agriculture, livestock, and fishing.

An impressive 85% identified various indicators of climate change impacts, highlighting a decrease in rainfall (74%), hotter days (58%), increased cold and snow (29%), and heavier or irregular rains. They also acknowledge that these changes have affected agriculture (61%), fishing (31%), tourism (29%), and livestock (24%) significantly. In agriculture, the main impacts include reduced production of various crops (56%), such as potatoes, quinoa, broad beans, and valde, as well as the need to change traditional planting calendars (48%).

Livestock has also been affected, with impacts on pasture areas and water availability (50%), an increase in livestock diseases (42%), and consequently a decrease in the number of livestock (40%). For the fishing sector, a decrease in fish availability regarding species and volumes has been reported (52%), especially affecting species like carachi, pejerrey, umanto, ispi, suche, and boga. Some fishers have reported needing to move to areas with better availability within Lake Titicaca.

The tourism sector, like the previous ones, shows significant impacts acknowledged by 27% of the surveyed individuals. Among these impacts, the loss of lake water stands out, which primarily hinders navigation and communication on Lake Titicaca, jeopardizing excursions and experiential activities included in the region’s tourism offerings. Additionally, alarming levels of lake pollution and loss of water volume threaten the survival of this important aquatic ecosystem. When compounded by severe issues often caused by social protests, tourism activities are considerably affected.

In response to these direct and indirect impacts of climate change, the communities are developing adaptation and/or mitigation measures. In the case of the studied communities, 53% of surveyed residents report implementing some measures, such as introducing new climate-resistant crop varieties (23%), constructing water reservoirs, using traditional practices mainly in agriculture and livestock (19%), participating in climate change training (18%), diversifying activities like tourism and crafts (15%), among others.

Moreover, in response to this crisis, many community members have started cultivating Andean products along the lake’s shores, taking advantage of soil moisture and the space created by receding waters. This illustrates their resilience in the face of drought and underscores the community’s adaptation to new living conditions ( Figure 2).

Figure 2. Example of a section of the lake that has become exposed due to decreasing water levels and is being utilized for the development of new crops.

In the development of these activities to combat climate change, communities have received support from various entities and organizations. This study shows that government entities and NGOs contribute almost equally (18% and 19%, respectively), followed by the National Lake Authority (16%) and universities (13%).

Lastly, respondents expressed the main needs of the communities to better address climate change. The most significant need, highlighted by 76% of participants, is for funds or loans to develop various tasks aimed at improving infrastructure resilience, building new water reservoirs, and creating more efficient irrigation systems, among others. Similarly, 52% called for improved and more comprehensive information about climate issues, which would enhance their preparedness for different weather phenomena. Additionally, 26% emphasized the importance of organizational strengthening, both within communities and in their relationships with various levels of government, civil society, academia, and the private sector.

A significant 87% of respondents consider climate change a critical issue, recognizing its effects on 63% of agricultural activities. Additionally, 53% report increased migration, particularly among young men, which poses a direct threat to community survival. Furthermore, 47% emphasize the health problems associated with climate change, 40% cite its impacts on livestock, while a smaller portion, 24%, notes its effects on tourism, and 15% on crafts.

When analyzing the survey results, based on the opinions of the groups by economic activity (Appendix C—Table C2.1), interesting information emerges that is summarized below according to each of the main topics.

The characteristics of the interviewees reveal an average age of 48 years for the Fishing group, 35 years for the crafts group, and 36 years for Tourism, which are notably younger than the Agriculture and Livestock groups, both at 55 years. This suggests a possible generational difference in participation in these activities. The crafts activity is predominantly male (80%), with only 20% female participation, while the tourism sector shows perfect gender balance (50% women, 50% men). The Agriculture, Livestock, and Fishing groups have a slight male majority but significant female participation (between 41% and 46%). In terms of education levels, the crafts and Tourism groups have the highest levels, with no community members lacking education or only having completed primary school. Secondary education (40–44%) and technical training (38–60%) are the most common. This aligns with their lower average age. Agriculture and Livestock members primarily have primary education (56–59%), followed by secondary education, while the Fishing group has an intermediate educational level, with primary education being the most common (44%), but also significant participation in secondary (25%) and technical education (31%).

There is a high diversification of productive activities across nearly all groups, indicating that community members do not engage exclusively in one activity. The Fishing, crafts, and Tourism groups display the greatest diversification, with a high percentage of members involved in multiple activities (e.g., fishermen also engaging in agriculture and livestock). Notably, 100% of community members in both the Livestock and Fishing groups also participate in Agriculture, suggesting a strong interdependence or combination of these activities.

Regarding perceptions of Climate Change, there is an overwhelming consensus on the occurrence of such changes in the last 10–20 years. The crafts (100%), Tourism (94%), and Fishing (88%) groups perceive these changes most broadly, although Agriculture (78%) and Livestock (74%) also show a high perception.

The perception that climate change impacts productive activities is very high across all groups. The crafts (100%) and Tourism (94%) groups report the most widespread impacts, with each group tending to report the greatest effect on their main activity (e.g., 75% of the Tourism group reports impacts on tourism). However, there is also notable cross-impact: agriculture is frequently mentioned as affected even by non-agricultural groups (e.g., 81% of fishermen perceive impacts on agriculture).

When analyzing the impacts on each main activity, the effects on potato, quinoa, and broad bean crops are the most consistently reported by community members across all groups. For the Fishing activity, the Fishing group reports 100% impact on various species, with carachi (100%) being the most affected, followed by pejerey (81%) and umanto (75%). Other activities are perceived to have impacts on these species, with carachi being the most mentioned by everyone.

Other activities, like Crafts are only perceived as highly impacted by their own group. The other groups report a significantly lower perceived impact. In terms of tourism, impacts are strongly felt within the Tourism (94%) and crafts (80%) groups, with the main causes of impact being lake water loss (50%) and water pollution (50%), followed by strikes due to social protests (38%).

Regarding adaptation strategies, a significant portion of all groups (between 40% and 74%) has implemented adaptation measures. The use of new climate-resistant crop varieties, the construction of water reservoirs, and the adoption of traditional practices are the most common. Overall, support for adaptation is relatively low, with an average of 25–38% of community members receiving it, and the Fishing and Tourism groups receiving the most (38% each), with the main sources of support being the government, NGOs, and for the Tourism group, also universities. The vast majority of community members (between 60% and 81%) perceive the need to take action to address climate change, with the Tourism group feeling the strongest urgency (81%). There is a general emphasis on the need for funding/loans and timely, accurate weather information.

There is a near-universal consensus (between 80% and 94%) when considering climate change as a major problem, particularly among the Tourism (94%) and Fishing (88%) groups. Reasons vary but center around direct impacts on their livelihoods and broader social issues, with migration being a significant concern for several groups—especially the main reason for the Tourism group (75%) and very relevant for crafts (60%), Livestock (59%), and Agriculture (51%). Public health is a major concern for the crafts group (80%) and also significant for the Tourism group (56%).

There is a general trend where each group prioritizes the impact on their main activity (e.g., crops for Agriculture, fishing for Fishing, livestock for Livestock).

3.1.1.1 Interviews

To better understand the survey results, the findings from the non-structured interviews conducted with four community leaders and two regular community members are presented, all of whom have lived in the community for a long time. Below is a summary of the main points discussed.

Most interviewees agree that the most significant changes in the climate have been droughts, lack of rainfall, and rising temperatures, which they attribute to global warming. They also point out that climate change has negatively impacted their community, leading to a decrease in totora (a local plant), loss of fish, and droughts that reduce agricultural production, affecting crop planting and livestock feeding. Pollution has harmed aquatic wildlife, while a decline in tourism has reduced their income, limited access to food, and affected their daily lives, including health and economic activities.

All six interviewees agree that the quantity and quality of water in the lake have diminished and worsened, mainly due to contamination from garbage, sewage, and mining waste, resulting in increased algae presence.

They consider the most pressing environmental issues for their community currently to be drought, loss of fish, declining lake levels, garbage accumulation, global warming, and lack of community communication. Additionally, they have adopted traditional adaptation practices, such as seeking help from their gods for rain, preserving food during droughts, adjusting their planting schedules, and incorporating previously submerged land into new cultivation areas.

Among the most significant rituals is the one performed by the Yumani community on the Island of the Sun to invoke rain. The ceremonial procession begins with dancers adorned in traditional attire, singing chants and playing instruments as they carry a clay pot to the Peruvian side, where they must find a frog. The climax occurs on the Bolivian side of the island, at the top of the “Pallasca” viewpoint. There, the amphibian is placed inside the pot with the belief that its croaking will attract precipitation; once the water fills the container, the frog will be allowed to escape. ⁴⁵ They hope for new rainfall to address these challenges and recognize the need to improve water quality, secure financial support, implement investment projects, conduct community clean-ups, and provide seeds and irrigation systems to strengthen their resilience against climate adversity.

In this way, their prayers in Aymara plead with God to send rain for their crops. They hope for new rains to tackle these challenges and acknowledge the need to improve water quality, receive financial support, implement investment projects, carry out community clean-ups, and provide seeds and irrigation systems to strengthen themselves against climate adversity.

Finally, the interviewees mention that they confront environmental challenges through traditional practices and prayers, without incorporating new techniques. They feel they need more financial support, better environmental education, resources such as water and productive projects, as well as greater coordination with authorities to tackle the effects of climate change. They foresee a future of continuous migration for community members (mainly men and youth) to other regions of the country or abroad due to the impacts of climate change. ^{46,
47}

This is reflected in the words of community member Ismael Sillero from the Bay of Cohana, who expressed, “We live from livestock and cheese, but there’s no forage, no rain, nothing. So, one starts selling their animals. What can you do? There’s nothing left but to take another path”. ⁴⁸

3.1.2 Participatory social mapping

The event took place in the Quehuaya community, which, due to its geographical location relative to the lake, is one of the areas most affected by decreasing water levels. The activity involved participation from all community members, including men, women, and young students from the local school.

Upon arrival, a motivational talk was given, highlighting climate change, historical data from the Binational Authority of Lake Titicaca, and a quick training session on how to create a “speaking map” organized by four groups formed for this purpose.

Before starting, the participants were shown a satellite image of the area, where they marked zones of drought, flooding, reduced agricultural, fishing, and livestock production, and affected tourist areas, noting the overall impact of climate change on their community. This collaborative work involved all participants ( Figure 3), who used different colors to indicate the areas impacted and the types of climate effects experienced. After completing the map, a secretary or spokesperson was chosen to explain the drawn map ( Figure 4).

Figure 3. Participation of community leaders and women in the development of talking maps in the Quehuaya Community.

Note: Persons shown have been de-identified.

Figure 4. Example of a talking map created by the community leaders group.

Based on the maps created ( Figure 5), the community members shared their experiences of overcoming these adverse phenomena and the strategies they have implemented to face them. They also discussed how they have mitigated these effects or how they are adapting to these challenges.

Figure 5. Systematization and synthesis of talking maps of the Quehuaya community.

As a result, all the information depicted in the participatory maps has been systematized and summarized into a single map ( Figure 4). This map highlights the areas of the lake’s recession, cultivated areas, and land reclaimed from Lake Titicaca for growing tubers, along with previous tourist zones and areas of decreased fishing, among others. This cartography has also been printed and provided to the community members so they can identify their future intervention spaces for new projects.

3.2 Workshop with promoters and agents of ecotourism and experiential tourism in Puno

As a result of conducting 26 surveys with participants at the workshop organized by MINCETUR, which included eco-tourism promoters and agents from the lakeside communities around Lake Titicaca, several key findings emerged (Appendix D).

All respondents reported experiencing significant climate changes that have impacted their tourism activities in recent years. Specifically, 92% identified a decrease in rainfall as one of the most notable changes, alongside rising temperatures and fluctuations in the lake’s water level. The sustained decline in Lake Titicaca’s water level particularly affects access and the operation of boats and floating accommodations, ultimately reducing the space available for tourism activities. Additionally, 81% noted an increase in seasonal rainfall, which involves intense downpours that damage infrastructure and alter tourist routes. Furthermore, 42% reported experiencing stronger winds and frosts, especially during winter, complicating transportation and safety for both tourists and locals.

When asked about the impact of these changes on their businesses or jobs, 96% indicated that the primary consequence is a decrease in visitors during adverse weather conditions, leading to a reduction in economic income for local communities and tourism enterprises. A similar percentage mentioned increased operational costs, necessitated by the need to reinforce vulnerable infrastructures such as boats and accommodations to withstand extreme weather conditions. A significant concern raised by 88% of respondents was the limitation of their service offerings; certain outdoor products and experiences become unfeasible under specific weather conditions, affecting both tourist satisfaction and the competitiveness of local communities. Additionally, 73% reported that safety is compromised as transportation routes and traditional itineraries become unsafe or unmanageable, forcing modifications or cancellations of scheduled activities.

In response to these challenges, 96% of participants indicated that communities and entrepreneurs have implemented various adaptation and mitigation measures. Notably, they have adjusted tourism seasons to promote activities during more favorable weather periods. Furthermore, 81% highlighted the diversification of tourism offerings, incorporating cultural, artisanal, and educational activities that are less dependent on the weather. This strategic shift allows for sustained activity under various conditions, alongside initiatives to build resilient infrastructure, such as retaining walls and boats modified for the shallower lake conditions. Finally, 77% supported the alteration of routes and itineraries to mitigate vulnerability to adverse weather phenomena.

During the seminar with MINCETUR, 73% of respondents indicated that several communities have received governmental assistance in the form of funding for resilient infrastructure projects and the modernization of tourism services, as well as training on risk management, sustainability, and community capacity building. The additional primary external support sources for tourism development included NGOs (35%), universities (27%), and the private sector (15%).

When asked about additional support deemed essential for strengthening tourism resilience in their region, 100% of participants emphasized the need for greater financial investment in resilient infrastructure, including protective walls, suitable boats, and improvements to sanitation systems. Furthermore, 88% called for enhanced coordination between public and private institutions and communities to enable more integrated and effective responses, alongside the provision of adequate, systematic, and updated technical assistance. Meanwhile, 73% emphasized the significance of access to real-time climate information and accurate forecasts for effective planning and informed decision-making. Regarding barriers to accessing these supports, 23% highlighted the need for streamlining permits and regulations to facilitate the swift implementation of improvements without encountering excessive bureaucratic obstacles.

4. Discussion

The results confirm that climate change is manifesting in the surrounding area of Lake Titicaca as a socio-ecological syndrome with multiple stressors: a sustained decline in lake levels, ^{49,
50} increased intra-annual rainfall variability, rising temperatures, ⁵¹ intensified winds, and extreme events. In line with recent literature, these changes operate cumulatively on fragile ecosystems and water-sensitive livelihoods, amplifying historical vulnerabilities and pre-existing inequalities. ^{9,
17,
35}

Firstly, the generalized perception of water level loss of Titicaca (100%), along with contamination, confirms a structural rather than a temporary water crisis. The perceived drought and the community prioritization of irrigation and storage highlight a gap between water supply and productive demand, leading to declining yields and the shifting of crops to newly exposed soils.

Secondly, tourism findings confirm a “domino effect” between the declining lake level, operational restrictions (access, navigability), and falling demand, resulting in increased costs and risks. Diversifying offerings and adjusting seasons are emerging as early adaptive responses, but they remain reactive and limited in scope unless accompanied by resilient infrastructure, accessible insurance, and timely and useful alert systems.

Thirdly, participatory social mapping reveals an accelerated reconfiguration of the territory: retreating water surfaces, expansion of crops on newly exposed soils, and contraction of riverine habitats. This “advance on the banks” demonstrates short-term resilience but may compromise ecological functions (wetlands as buffers, water quality) and increase future exposure to floods or socio-environmental conflicts. ⁵²

In summary, the evidence indicates that the system has entered a state of chronic water deficit, necessitating a shift from reactive responses to integrated management: technical irrigation and decentralized storage, restoration of regulatory wetlands, ⁵³ pollution control, ⁵⁴ and binational agreements for allocation and early warning to sustain water and productive security.

5. Conclusions

Research on the impacts of climate change on communities around Lake Titicaca has revealed and confirmed a complex and concerning reality. The findings indicate that climate change is causing a chronic water deficit in the region, as evidenced by declining lake levels, increasing droughts, and climate variability affecting various productive activities, including agriculture and fishing. This situation not only threatens the food and economic security of the Aymara communities and other lakeside groups, but also interferes with public health and exacerbates existing socio-economic vulnerabilities.

Through a participatory approach, there is a high level of community awareness regarding climate change and a willingness to adapt to the new reality through traditional practices. However, the responses observed are reactive and limited, highlighting the urgent need to implement more integrated and sustainable adaptation policies. The importance of promoting efficient water management, restoring critical ecosystems like wetlands, and establishing transboundary coordination mechanisms to ensure water security is emphasized.

Adaptation strategies must be accompanied by significant resources, continuous training, and greater integration between communities, governments, and organizations. The creation of resilient infrastructure and early warning systems is essential to mitigate the effects of climate change and enhance the resilience of the communities surrounding Lake Titicaca.

This study integrated a social component based on knowledge exchange workshops and participatory mapping. It has been compared with climatological and aerospace information, highlighting the gap between Western knowledge and ancestral practices rooted in direct observation of nature. These traditional practices involve strong community participation led by the Pachayatiri, a local expert responsible for forecasting the weather and preventing risks (such as droughts or frosts) using bioclimatic, astronomical, and atmospheric indicators. ^{45,
55} However, the project revealed that these indicators are being altered due to climate change, as the occurrence of extreme and irregular events disrupts natural signals, making it more difficult to predict their effects through traditional knowledge and practices. ⁵⁶

In conclusion, the findings of this research stress that Lake Titicaca, as an integral socio-ecological system, requires a holistic approach that considers not only adaptation to environmental changes but also the promotion of equitable and sustainable development that preserves its cultural and ecological value.

Data availability

The following information presents the primary and intermediate processed data that support the results of this article. These data are hosted in the Zenodo repository, which can be freely accessed at Primary data from an article in the journal 1000Research [Data set]. https://doi.org/10.5281/zenodo.18521682. ⁵⁷

File	Content
Survey results in the Communities.xlsx md5:101ab9c54bf70683d2ee10845adc57cd	Excel spreadsheet with the results of the surveys administered to participants in the community workshops.
Survey results from MINCETUR Seminar.xlsx md5:fdf17daba5fc5865c9d7e624f61ba41d	Excel spreadsheet with the results of the surveys administered to participants in the MINCETUR workshop in Puno.
APENDIX-A.docx md5:e60422e87a44c6f07877db1a5ecd2455	Appendix A. Questionnaire for Community Workshop Participants
APENDIX-B.docx md5:298c2322ce688e953146d59f26d9e751	Appendix B. Questionnaire for participants in the MINCETUR seminar in Puno
APENDIX-C1.docx md5:043aa43182f3f7b62a5b9e0dc865aa2a	Appendix C1.1. Table of the behavior of the variables measured in the study according to gender
APENDIX-C2.docx md5:f506da88a3dc7bce1b6fa651e13029d5	Appendix C2.1. Table of the behavior of the variables measured in the study according to economic activities
APENDIX-D.docx md5:9d67f2f90482b82363e9fab19fc22348	Appendix D. Summary of the results (averages and percentage values) of the application of the surveys to the participants in the MINCETUR Seminar in Puno.

Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).

Acknowledgments

The authors thank the management of the Institute of Geographic Research (IIGEO-UMSA) for the support provided for fieldwork, as well as the Binational Authority of Lake Titicaca (ALT), the directives, and the population of the communities and district governments involved in this study.

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10.5256/f1000research.197465.r469065

Reviewer response for version 2

Biricik

öznur

1 Referee 1Bursa Uludag University, Nilüfer-Bursa, Turkey

Competing interests: No competing interests were disclosed.

28 3 2026

2026

This is an open access peer review report distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

recommendation

approve

The revisions are sufficient for indexing .

Is the work clearly and accurately presented and does it cite the current literature?

Partly

If applicable, is the statistical analysis and its interpretation appropriate?

Not applicable

Are all the source data underlying the results available to ensure full reproducibility?

Yes

Is the study design appropriate and is the work technically sound?

Yes

Are the conclusions drawn adequately supported by the results?

Yes

Are sufficient details of methods and analysis provided to allow replication by others?

Yes

Reviewer Expertise:

Concrete technology

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

10.5256/f1000research.193533.r461087

Reviewer response for version 1

Roushan

Kaveh

1 Referee https://orcid.org/0009-0003-3471-8694 1University of Missouri, Columbia, USA

Competing interests: No competing interests were disclosed.

2 3 2026

2026

recommendation

approve-with-reservations

General Evaluation

This study examines the mechanical and thermal properties of cement mortar reinforced with polypropylene (PP) fibers at volume fractions of 0%, 0.5%, 1.0%, and 1.5%, subjected to temperatures of 200°C, 400°C, and 600°C. It is highly relevant for fire-resistant building applications. A key strength is its focus on mortar specifically, clearly distinguishing it from concrete in terms of pore structure, thermal response, and cracking behavior, thus filling an important research gap. Identifying 0.5% PP fiber as the optimal balance between initial strength and residual fire performance offers a practical takeaway. Additionally, making the raw dataset available on Zenodo enhances transparency and reproducibility.

Specific Comments

1. Absence of Microstructural Evidence: The paper's main mechanistic claim — that melting PP fibers form micro-channels that reduce internal vapor pressure and prevent explosive spalling — is reiterated throughout the results and discussion but lacks direct evidence. No SEM images are included, making this key assertion speculative. To support this, SEM images of fractured mortar cross-sections after exposure to 200°C, 400°C, and 600°C should be provided for both the control and fiber-reinforced mixes, with annotations highlighting micro-channel formation, fiber remnants, the fiber–matrix interface, and void distribution. Additionally, quantitative porosity measurements via Mercury Intrusion Porosimetry (MIP) or Ultrasonic Pulse Velocity (UPV) testing would strengthen the existing density and strength data.

2. Superplasticizer Characterization and Workability Methodology: The manuscript mentions '1% superplasticizer type F' but does not specify the manufacturer, product name, code, or chemical base, which are necessary for reproducibility. More importantly, the superplasticizer dosage was kept constant across all mixes while PP fiber content varied from 0% to 1.5%. This caused a 32.4% reduction in flow diameter in the highest fiber mix, potentially affecting casting quality and confounding the interpretation of compressive strength at higher fiber levels. The lower strength might partly result from reduced workability rather than fiber effects alone. The authors should either (a) modify the superplasticizer dosage for each mix to ensure consistent workability before casting strength tests, or (b) clearly state this as a study limitation and estimate its possible influence on the results.

3. Missing Specimen Replication Details and Flexural Testing Setup: The methodology lacks details on the number of specimens used for density measurements, and the overall specimen count for each property–temperature–fiber combination is not summarized. A table should be included, listing specimen counts, dimensions, and related test standards for each measured property. Furthermore, Section 2.2 does not clarify whether flexural testing was conducted under displacement or load control, nor does it specify the crosshead speed (mm/min) or the model and capacity of the testing machine. Since toughness values are obtained from load–deflection curves, knowing the testing rate is essential; without this, the toughness data cannot be independently verified or reproduced.

4. PP Fiber Type and Internal Melting Temperature Inconsistency: The fiber type (monofilament or fibrillated/multifilament) and the manufacturer or product name are not specified. These details affect fiber–matrix bonding, dispersion, and thermal properties, and should be included as standard information. Additionally, there is an inconsistency regarding the melting temperature: the abstract and Section 2.1 report a melting point of 160–170°C, whereas Section 3.4 states that PP fibers 'melt near 320–340°C'. This discrepancy needs clarification and resolution. The 160–170°C range corresponds to the standard melting point of isotactic polypropylene, while the higher temperature likely refers to a different thermal or kinetic condition. Consistent use of the correct values throughout the document is essential manuscript.

5. Curing Conditions: The manuscript states that curing occurred 'in water at 20 ± 2°C until 28 days old," but it does not clarify whether the water was lime-saturated, which is the standard method to prevent calcium leaching from mortar and influences hydration products and final strength. Additionally, it is not mentioned if the curing water was renewed regularly. These details should be included.

6. Novelty Justification and Literature Differentiation: Although the mortar-vs-concrete distinction is presented as the novelty claim, the Introduction lacks a detailed mechanistic comparison to fully justify why this difference merits separate investigation. The literature should be cited to discuss the specific quantitative differences in paste-to-aggregate ratio, pore-size distribution, and thermal cracking mode between mortar and concrete. Additionally, in Sections 3.3 and 3.5, where results are compared with previous studies, it should be clearer whether those studies examined mortar or concrete. Each comparison ought to specify the material system used in the cited work and emphasize the mortar-specific findings of the current study.

7. Internal Inconsistency in Compressive Strength Reporting: In Section 3.3, it states that mortars reinforced with PP fiber 'maintain a comparatively higher strength (33–28%, respectively)' for the 0.5% and 1.5% PP mixes at 600°C. However, Table 3 shows the 1.0% PP mix retains 27.6%, and the 1.5% PP mix retains 26.5%. The 1.5% mix is not the pair being described. The text should be revised to accurately reflect the tabulated values for each mix separately and organize the performance ranking clearly.

8. Dedicated Limitations and Future Work Section: The manuscript lacks a 'Limitations and Future Work' section, which is a notable omission. The following limitations should be explicitly recognized: (a) only one PP fiber geometry was tested; comparing it with basalt, steel, or hybrid systems would enhance the applicability; (b) only a single mortar mix design (w/c = 0.45, 1:3 cement to sand) was studied; (c) the highest temperature tested, 600°C, does not encompass more extreme fire scenarios reaching 800–1000°C; (d) long-term durability aspects such as carbonation, chloride resistance, and creep after thermal exposure were not evaluated; and (e) the influence of different cooling methods (furnace cooling versus water quenching) on residual properties was not addressed, although this is crucial for post-fire structural assessments.

9. Minor Typographical and Presentation Errors: Several typographical and presentation errors need correction. The axis label 'Temretures, 0C' in Figures 5, 6, and 9 should be amended to 'Temperature (°C)'. The term 'formulation' in Section 3.5 should be changed to 'formation' ('pore formation'). The phrase 'control mia' in Section 3.4 should be corrected to 'control mix'. The label 'pp%' in Figure 4 should be standardized as 'PP fiber content (%)'. Lastly, Figure 10 (toughness) would be improved by adding a supplementary data table similar to Tables 2–5, enabling readers to easily access the exact numerical toughness values.

Is the work clearly and accurately presented and does it cite the current literature?

Partly

If applicable, is the statistical analysis and its interpretation appropriate?

Not applicable

Are all the source data underlying the results available to ensure full reproducibility?

Yes

Is the study design appropriate and is the work technically sound?

Partly

Are the conclusions drawn adequately supported by the results?

Partly

Are sufficient details of methods and analysis provided to allow replication by others?

Partly

Reviewer Expertise:

Soil stabilization, soil improvement, fiber reinforcement, novel stabilizer, durability cycles, energy engineering, geothermal energy, shallow geothermal energy, energy piles, energy micropiles, energy helical piles, numerical simulation, FEM.

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.

Hama

Sheelan

Civil Engineering, University of Anbar, Ramadi, Al Anbar Governorate, Iraq

Competing interests: No competing interests were disclosed.

5 3 2026

Specific Comments

Response to reviewer comment: While Scanning Electron Microscopy (SEM) observations would indeed provide direct microstructural visualization, SEM analysis was not performed in the present experimental program due to laboratory limitations. Nevertheless, in response to the reviewer’s suggestion, Ultrasonic Pulse Velocity (UPV) testing has been conducted and incorporated into the revised manuscript to provide additional quantitative insight into the internal damage and microstructural deterioration of the mortar specimens after thermal exposure.

A new subsection entitled “3.7 Ultrasonic Pulse Velocity (UPV) Analysis” has been added to the Results and Discussion section. The UPV results show a progressive reduction in wave velocity with increasing temperature and fiber content, which indicates the development of internal microcracks, pore expansion, and increased internal voids within the mortar matrix. These observations are consistent with the reductions observed in density and mechanical strength.

The authors acknowledge that future work will include detailed microstructural characterization using SEM and pore structure analysis techniques such as Mercury Intrusion Porosimetry (MIP) to further investigate the micro-channel formation and pore evolution in heated mortar.

Response to reviewer comment: The Materials section has been revised to clearly describe the type and technical properties of the superplasticizer used in this study. The manuscript now specifies that a polycarboxylate-based high-range water-reducing admixture, Sika ViscoCrete-180 GS, conforming to ASTM C494 Type F, was used. Additional information regarding its specific gravity (1.07), pH range (4–6), color (light brownish), and dosage (1% by weight of cement) has been added to improve the clarity and reproducibility of the experimental methodology.

“A polycarboxylate-based high-range water-reducing admixture (HRWR), Sika ViscoCrete-180 GS, conforming to ASTM C494 Type F, was used to improve the workability of the mortar mixtures. The superplasticizer has a specific gravity of approximately 1.07, pH value ranging from 4 to 6, and a light brownish liquid appearance. The admixture is based on modified polycarboxylate ether technology and was added at a constant dosage of 1% by weight of cement for all mixtures to maintain comparable workability conditions while isolating the effect of polypropylene fiber content on the fresh and hardened properties of the mortar.”

Response to reviewer comment: A new summary table has also been added to the manuscript to clearly present the specimen count, specimen size, and relevant test standards used for density, compressive strength, flexural strength, and UPV measurements, see Table 2.

Also, Section 2.2 has been expanded to clarify the flexural testing procedure and loading conditions. The manuscript now specifies that the flexural tests were performed using a three-point bending configuration on prism specimens (50 × 50 × 160 mm) in accordance with ASTM C348. The tests were conducted using a universal testing machine with a capacity of 300 kN, and the loading was applied under load control at a constant rate of 50 ± 10 N/s, as specified in the standard. During testing, the load–deflection response was recorded to evaluate post-cracking behavior and flexural toughness.

Response to reviewer comment: The authors thank the reviewer for this important observation. In response to this comment, the manuscript has been revised to clarify both the type and manufacturer information of the polypropylene fibers and to resolve the inconsistency regarding the reported melting temperature. First, the fiber type has now been clearly specified in Section 2.1. The polypropylene fibers used in this study are monofilament polypropylene fibers with a length of 12 mm and a diameter of approximately 18 μm. These fibers were selected due to their effectiveness in improving crack resistance and reducing spalling in cementitious composites exposed to elevated temperatures. Second, the inconsistency related to the melting temperature has been corrected throughout the manuscript. The correct melting temperature of polypropylene fibers is approximately 160–170°C, which corresponds to the melting point of isotactic polypropylene reported in the literature. The previously stated value of 320–340°C in Section 3.4 was incorrect and has been removed from the revised manuscript to maintain consistency. The text in Section 3.4 has been revised accordingly to state that polypropylene fibers soften and melt at approximately 160–170°C, forming micro-channels within the cementitious matrix that facilitate vapor release and reduce internal pore pressure during heating.

These revisions ensure consistency and improve the clarity and accuracy of the material description in the manuscript.

Response to reviewer comment: In the present study, the specimens were cured in tap water maintained at 20 ± 2°C until the age of 28 days. Although lime-saturated water is sometimes recommended to minimize calcium leaching, the use of tap water for curing cementitious specimens is a common laboratory practice and has been widely adopted in many experimental studies on mortar and concrete.

To maintain stable curing conditions, the curing water was periodically renewed, and the temperature of the curing tank was maintained within the specified range (20 ± 2°C). These details have now been clarified in Section 2.1 of the revised manuscript to improve the transparency and reproducibility of the curing procedure.

Response to reviewer comment: The novelty of this study lies in providing a comprehensive experimental evaluation of polypropylene fiber–reinforced cement mortar exposed to elevated temperatures up to 600°C. While most previous studies have focused primarily on fiber-reinforced concrete, the present work specifically investigates mortar systems, which exhibit different behavior mechanisms. In addition to conventional strength measurements, this study systematically examines residual compressive strength, flexural strength, load–deflection behavior, and flexural toughness after thermal exposure. The work also identifies the best polypropylene fiber dosage for improving post-fire mechanical performance of mortar and provides detailed insights into the role of fiber melting in reducing thermal damage and enhancing residual structural integrity.

Response to reviewer comment: The authors appreciate the reviewer for carefully identifying this inconsistency in the description of the residual compressive strength results. The statement in Section 3.3 has been revised to accurately reflect the values reported in Table 3.

According to the experimental results, at 600°C, the residual compressive strength values were 33.4% for the 0.5% PP mix, 27.6% for the 1.0% PP mix, and 26.5% for the 1.5% PP mix, compared with 19.1% for the control mixture. Therefore, the 0.5% PP mixture exhibited the highest residual strength, followed by the 1.0% PP and 1.5% PP mixtures, respectively. The manuscript text has been corrected to clearly present this ranking and ensure consistency with Table 4.

Response to reviewer comment: The authors appreciate this valuable suggestion. Accordingly, a short “Limitations and Future Work” statement has been incorporated in the revised manuscript. The present study is limited to a single PP fiber geometry and one mortar mix design (w/c = 0.45; cement:sand = 1:3) with a maximum exposure temperature of 600°C under furnace cooling conditions. In addition, long-term durability aspects after thermal exposure were not examined. Future research will investigate alternative fiber systems (e.g., basalt, steel, or hybrid fibers), higher fire temperatures (800–1000°C), different cooling regimes, and microstructural characterization techniques (e.g., SEM and porosity analysis) to provide deeper insight into thermal damage mechanisms.

Response to reviewer comment: The authors thank the reviewer for carefully identifying these typographical and presentation issues. Also, Table 7. Flexural toughness and percentage change relative to the control mix (0% PP) at each temperature, has been added

10.5256/f1000research.193533.r451092

Reviewer response for version 1

Biricik

öznur

1 Referee 1Bursa Uludag University, Nilüfer-Bursa, Turkey

Competing interests: No competing interests were disclosed.

5 2 2026

2026

recommendation

approve-with-reservations

General Evaluation

The study investigates the effects of polypropylene (PP) fiber reinforcement (at 0%, 0.5%, 1%, and 1.5% ratios) on the fluidity and post-high-temperature strength properties of mortar mixtures. While the topic is relevant, several methodological points and technical additions are required to enhance the quality of the manuscript.

Specific Comments

Workability and Casting Methodology: In the study, the superplasticizer dosage was kept constant across all mixtures to compare slump values. However, the significantly reduced fluidity in the 1.5% fiber-reinforced mixture directly impacts the casting quality and, consequently, the compressive strength results. It would have been methodologically sounder to maintain a constant flow/workability by adjusting the superplasticizer dosage for each fiber ratio before preparing the strength specimens. This would ensure that the strength loss is attributed solely to the fiber characteristics rather than poor consolidation.

Reference Timeliness: The manuscript would benefit from a more up-to-date literature review. Incorporating more citations from 2023, 2024, and 2025 will strengthen the current state-of-the-art section and demonstrate the study’s relevance to recent developments.

Material Characterization: The specific properties and technical data of the superplasticizer used in the mixtures should be clearly detailed in the Materials section.

Microstructural Analysis (SEM): The inclusion of Scanning Electron Microscopy (SEM) images is essential to support the macroscopic observations. Specifically, SEM images taken after exposure to high temperatures would provide visual evidence of the "melt-out" effect of the PP fibers and the resulting micro-channels/voids that influence the residual strength.

Porosity and NDT Analysis: To better quantify the internal damage caused by thermal stress, the authors are encouraged to perform Ultrasonic Pulse Velocity (UPV) tests or Mercury Intrusion Porosity (MIP) analysis. These methods would provide a more scientific explanation for the void formation and structural degradation observed after high-temperature exposure.

Is the work clearly and accurately presented and does it cite the current literature?

Partly

If applicable, is the statistical analysis and its interpretation appropriate?

Not applicable

Are all the source data underlying the results available to ensure full reproducibility?

Yes

Is the study design appropriate and is the work technically sound?

Yes

Are the conclusions drawn adequately supported by the results?

Yes

Are sufficient details of methods and analysis provided to allow replication by others?

Yes

Reviewer Expertise:

Concrete technology

Hama

Sheelan

Civil Engineering, University of Anbar, Ramadi, Al Anbar Governorate, Iraq

Competing interests: No competing interests were disclosed.

5 3 2026

Specific Comments

Response to reviewer comment: The authors agree that maintaining a constant workability by adjusting the superplasticizer dosage could help isolate the pure effect of fiber reinforcement on strength. However, in the present study, the superplasticizer dosage was intentionally kept constant for all mixtures to clearly evaluate the direct influence of polypropylene fiber content on the fresh and hardened properties of mortar. As reported in the manuscript, increasing the fiber volume fraction significantly reduced the flow diameter from 185 mm for the control mix to 125 mm for the 1.5% PP mixture, indicating a clear reduction in workability with increasing fiber content.

“To ensure a consistent basis for comparing the influence of polypropylene fiber content on fresh and hardened properties, the dosage of the superplasticizer was kept constant for all mixtures. This approach allowed the study to directly evaluate the effect of increasing fiber volume fraction on workability and mechanical performance. It is well known that fiber addition tends to reduce the flowability of cementitious composites due to increased internal friction and higher surface area of dispersed fibers. Therefore, maintaining a constant admixture dosage enabled the observed changes in flow diameter and strength to be interpreted as a combined effect of fiber inclusion and its influence on the rheological behavior of the mortar. Nevertheless, it is acknowledged that adjusting the superplasticizer dosage to maintain constant workability could be considered in future studies to further isolate the mechanical contribution of fiber reinforcement."

Nevertheless, the reviewer’s suggestion is appreciated, and it has been acknowledged in the revised manuscript as a recommendation for future studies, where maintaining constant workability by adjusting the superplasticizer dosage could provide additional insight into the isolated mechanical contribution of polypropylene fibers.

Response to reviewer comment: The introduction and literature review sections have been revised to incorporate several recent studies published between 2023 and 2025 addressing the behavior of polypropylene fiber-reinforced cementitious materials under elevated temperatures.

Material Characterization: The specific properties and technical data of the superplasticizer used in the mixtures should be clearly detailed in the Materials section.

Response to reviewer comment: The authors agree that microstructural observations using Scanning Electron Microscopy (SEM) would provide direct evidence of the microstructural changes occurring in polypropylene fiber-reinforced mortar after exposure to elevated temperatures. However, SEM analysis was not performed in the present experimental program due to laboratory limitations.

To address the reviewer’s concern, the discussion section has been expanded to include a mechanistic explanation supported by previous SEM-based studies, which reported that polypropylene fibers melt at approximately 160–170°C, leaving behind micro-channels and voids within the cementitious matrix. These micro-channels facilitate the release of internal vapor pressure during heating, thereby reducing pore pressure buildup and mitigating explosive spalling. This mechanism contributes to the improved residual strength and toughness observed in fiber-reinforced specimens compared with the control mixture.

In addition, it has been noted in the manuscript that future work will include detailed microstructural characterization (SEM and porosity analysis) to further investigate the internal morphology of the heated mortar and the role of fiber melting in modifying the pore structure.

Response to reviewer comment: The authors sincerely thank the reviewer for this valuable suggestion. In response to this comment, Ultrasonic Pulse Velocity (UPV) tests were conducted and incorporated into the revised manuscript to provide additional insight into the internal damage and microstructural degradation caused by elevated temperatures.

A new subsection entitled “3.7 Ultrasonic Pulse Velocity (UPV) Analysis” has been added to the Results and Discussion section. The UPV measurements were performed on all mortar mixtures after exposure to 0, 200, 400, and 600°C, and the results are presented in Table 7.