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To ensure equitable development for all the regions of Rwanda and to limit migration into and prevent congestion of Kigali, the capital city of Rwanda, the Rwandan government has embarked on the development of secondary cities. Consequently, there is the need to provide affordable and safe buildings in the proposed secondary cities. This study investigated the feasibility of using reinforced masonry bricks (RBM) for constructing buildings in the Rwandan secondary city in Muhanga District as an alternative to using reinforced concrete (RC) presently in use in the Kigali based on the availability of clay as the raw material for the production of masonry bricks needed for RBM. Questionnaires were administered and interviews were conducted to establish the level of acceptance of RBM for constructing building in Muhanga. The comparison of the costs of construction building using RBM and RC and the other advantages of RBM over RC for constructing buildings the Rwandan secondary city in Muhanga District are presented.

Seismic isolation has been widely accepted as one of the techniques that can be used to protect structures during earthquake ground motions. However, some challenges still exist such as the optimal control of excessive isolator shear strains imposed by some ground motions. The main purpose of this study was to assess the effects of building height variation and earthquake ground motion type on the optimal performance of the seismic isolation using lead core rubber bearing (LCRB). Nonlinear time history analysis for building models of various storeys isolated by LCRB and exposed to different real earthquakes was performed. To achieve this, the equations governing the motion of the isolated three different building models were presented, and an approach for solving the equations while taking into consideration of the optimized mechanical properties of the LCRB was developed. The LCRB performance was measured in terms of elastomer shear strains, derived after an optimal criterion leading to reliable substructure and superstructure responses was reached. The results showed that the combined effects of the earthquake type and building height significantly affect the substructure responses (maximum isolator displacement, energy dissipation capacity, maximum isolator force) and the superstructure responses (storey shear forces, storey drifts, floor displacements, and floor accelerations), which in some cases lead to a need for adding a fluid damper. In this regard, an attempt to couple the LCRB with nonlinear fluid viscous damper was made, and the performance of the hybrid was assessed. It was generally found that the hybrid can positively improve the substructure responses, thereby reducing the unwanted large elastomer shear strains without adversely affecting the superstructure responses.

Different weather conditions, like temperature and humidity influence on the performance of concrete structures to which they are normally subjected, especially at earlier stage of their service life. One of practical measures has been the regulation of the setting time of fresh concrete. Some admixtures are used in concrete to regulate the setting time and therefore increase structures performance under given situation. Almost all admixtures used in Rwanda are being imported from outside the country and this is one of factors affecting the construction cost. A big quantity of basalt powder at different sites in the country is left without being used and has been negatively impacting the environment. This study aimed at analyzing the potentials of basalt powder waste used in concrete as admixtures in different percentages, e.g. 0%, 5%, 10%, 15% and 20%. Different investigations on concrete incorporating basalt powder as admixture, such as the setting time, workability and compression tests were conducted. The results showed that the gradual incorporation of basalt powder waste as admixture up to 20%, accelerated the setting time more than 13 times, but decreased the compressive strength of concrete by around 24.5%, with comparison to normal concrete strength. The application of basalt waste in concrete would contribute not only to the reduction of environmental pollution but also to the provision of more affordable admixtures for mortar and concrete.

It is generally accepted that having a proper river crossing point has a positive effect on rural inhabitants. Such crossing points would increase the ability of communities to access their social services, markets, jobs, and thereby lead to raising their standard of living. In line with this objective,Rwanda has been promoting the construction of pedestrian footbridges in rural areas, and with different partners, different pedestrian footbridges have already been constructed. It is very crucial that all institutions involved in the construction of pedestrian footbridges, both public and private, consider the financial benefits of pedestrian footbridges and some significant direct and indirect effects on the rural communities.The Objective of this study was to identify all possible benefits that may be generated by pedestrian footbridges to understand the potential range of their impacts in rural areas and the likely responses from those people impacted by the project. The study also proposed a comprehensive approach for estimating the economic impacts of a pedestrian footbridge in rural areas. The methodology involved community interviews conducted during site visits to identify and predict possible impacts due to the lack and availability of safe access via pedestrian footbridges.

Adobe or mud brick building technique is an ancient technique dating back at least to 8300 BC. The oldest continually inhabited structures in the world are made in adobe. Adobe brick have revealed many advantages such as low cost, simple construction, excellent thermal and acoustic properties. Dispute these advantages, adobe buildings experience many problems, like water effect and low brick strength, among others. The objective of this study was to assess the strength of adobe brick made from natural soils and stabilized using laterite, fine sand and fibrous grass. The study first checked the quality of all used materials components, and then with reference to the USCS, the classification and quality of those materials were determined. Afterwards, the controlling brick sample made of natural soil, and the stabilized brick made of natural soils with stabilizers were manufactured using the mix ratio of 50% natural soil, 30% of laterite, 15% of fine sand and 5% of fibrous grass. After the bricks curing, the compressive strength test was performed. It was observed that the adobe brick strength was improved from 1.04 N/mm2 to 2.128 N/mm2 after its stabilization. Further studies were recommended regarding the improvement of adobe bricks performance using other soils mixture content, or other types of stabilizers with target to achieve the strength of stabilized soil bricks with cement or even the strength of burnt bricks.

This paper presents the finite element (FE) analysis of double-bolt shear-out (DBSO) fracture failure. The DBSO fracture shape consists of two oppositely: inclined outer main shear fractures, inner main shear fracture, outer shear lips, and curved inner curved fractures. The DBSO begins with two outer main shear fracture initiations under shear, vertical compressive bending, and sideways bending deformations/stresses followed by the two inner main shear fracture initiations under shear and vertical compressive bending deformations. The outer shear lips occurred under vertical compression bending, shear, and sideways tensile bending stresses/deformations while the two inner curved fractures occur under rotational deformation.

The footbridges in rural areas have been crucial as the only mean to overcome the rural isolation and allow breaking the cycle of poverty by providing access to such development facilities like education opportunities, markets, medical clinics and other basic services. In Rwanda, under collaboration with Engineers without Borders from German, and International Non-Government Organization Bridge to Prosperity (B2P, some footbridges are already built. In line with the agreement with B2P around 355 bridges are also planned in 5 years. The key challenge is to optimally allocate resources in order to maintain this number of bridges, especially under the current financial constraints. The purpose of this paper was to investigate and propose a pedestrian footbridge management system for Rwanda (PFBMS) which should allow the efficient bridge management, through the analysis of condition data, determination of the ranking and priority of bridge maintenance activities, as well as evaluation of the alternatives of preservation or replacement. The methodology comprises of the use of interview and discussions with district engineers in charge of bridge management, local community using the constructed footbridges as well as bridge builders from B2P. Microsoft Excel analysis tool has been used to developing the deterioration model, and therefore the PFBM was proposed. It is concluded that this system can accurately predict optimal maintenance planning as well as bridge rating.

The building industry has been one of the fast-growing sectors in Rwanda, and multiple residential houses with amazing pitched roofs are being implemented in different cities. As the country is very hilly, the influence of wind loads on the buildings is high and therefore the selection step of roof slopes needs to be carefully undertaken, in order to ensure not only the structure safety, but also the economy. Available international and national guidelines give details about safety and functionality requirements, but don’t talk much about economic aspect, and this was the purpose of the given study. Using a well elaborated methodology, the influence of the roof slope on its cost was checked, and it was established that the slope’s increase of one degree would raise the roof cost by 3.6%. Therefore, during the roof slope selection and design process, economic requirements need more attention.

The consumption of natural resources like sand and stones for concrete production has resulted not only in their scarcity but also in environmental degradation associated with their extraction, and air pollution due to the generated quarry dust as result of the rock crushing. Also, with increase of mining sites in Rwanda, the amount of mine tailings has extremely increased, and their dumping is becoming a big challenge. The purpose of this study was to search for an engineering solution to the above dual problem, analyzing the performance of both mine-tailings and quarry dust as potential replacements for ordinary aggregates in concrete. The methodology consisted of evaluating the properties of the two materials, and then the analysis of strength characteristics for the new concrete manufactured using the two new aggregates. Concrete preparation was done by keeping constant the mine tailings portion as coarse aggregate, while partially replacing river sand by quarry dust at different fractions as 0%, 10%, 30% and 50%. It was established that, comparatively to normal concrete at 28 days, the compressive and tensile strengths of concrete with mine-tailings and river sand increased from 27MPA to 37.5 MPA, and from 1.9 to 3.1 MPA respectively on one hand, and on the other hand the compressive and tensile strengths decreased with partial replacement of river sand by quarry dust from 37.5 to 27.9MPA and from 3.1 to 2.3 MPA at replacements from 0% to 50% respectively. It was concluded that mine tailings and quarry dusty can be used together as concrete new aggregates in replacement of ordinary aggregates, with a due attention to concrete workability and its area of application.

The waste generation from old rubber tires has been increasing and causing environmental degradation with the escalation of vehicles number especially in the cities. Bitumen is extensively used in flexible pavement construction and as its manufacturing industries were still growing, the cost has not been much affordable. This study aimed at evaluating the possibility of a partial replacement of ordinary bitumen by tire rubber waste, with the purpose to reduce not only the amount of rubber wastes dispersed in the nature, but also the material cost, while keeping or improving the bitumen product performance. The study used rubber waste powder as partial replacement to ordinary bitumen by 5%, 10%, 15%, and 20% of its weight and, with adequate samples, properties of the bitumen product were investigated, after checking the standard quality of used bitumen 60/70 grade. It was established that more adequate results were achieved at 5% of replacement, which showed the penetration value of 61.66 tenths mm, the softening point value of 52.750C, and the viscosity of 134 sec. Regarding the cost estimation of this new bitumen, a cost reduction of around 5.3% was realized. Therefore, the use of rubber waste powder would contribute not only to the reduction of the quantity of respective waste in the environment, but also influence on the material affordability. The use of other grades of bitumen than 60/70, as well as the strength and durability performance may be a good scope for further studies.

Worldwide, the medium density fiberboard (MDF) materials have been extensively used for furniture as well as a normal building material. The MDF production is based on wood materials that are obtained from the tree cutting, and this process may conduct to gradual deforestation. Different works have shown the advantages of using other renewable biomass sources for MDF manufacturing. This study aimed at assessing the potential of using the African couchgrass, as one of worldwide available grass, and which has been one of the most worrying weeds for agriculture areas. The test with the manufactured MDF checked such material properties like density, moisture content, water absorption, and thickness swelling. The established results were 727.143 kg/m3, 5.81%, 9.18%, and 7.6% respectively. All those results are in the range of standard values recommended by ASTM D1037, and they give optimism for the application of couchgrass in the manufacturing of MDF. This new material was planned to be used as a partition component. Therefore, further studies should evaluate other important properties, like fire and sound resistance, while a proposal for potential replacement of the used industrial wood glue is also welcome.

The development of local construction industry has resulted in the high demand for cement, used not only for structural but also non structural applications, such as finishing. As a consequence cement has been far from being an affordable material for the good part of the population, especially in the rural areas where financial means are still limited. Regarding the finishing exercise, those people have been using soil mortar alone or reinforced with grasses without any strategy about mixture content. The objective of this study was to assess the performance of cohesive soil mortar mixed with cow dung and establish recommended mix content for plastering works. Twelve samples of soil mortar with 10%, 20%, 30% and 40% of cow dung, were prepared and subjected to drying period of 28 days before they were tested for water absorption, shrinkage, weathering resistance, specific gravity and Atterberg limit tests. The tests showed good results for checked properties with 20% of cow dung, and therefore it could be considered as a low-cost alternative plastering material to cement mortar for some structural members under normal weather conditions. In order to avoid the earlier shrinkage and cracks in this mortar due to spontaneous drying by sun, the mortar should be protected and not be left in open area at earlier stage. Keywords: Cohesive Soil, Cow dung, Mortar, Shrinkage, Water absorption, Weathering resistance

With the development of infrastructures in Rwanda, the roads construction has been one of busiest area, and as the country counts thousands hills the design and construction of drainage systems required a great attention. Most of road drainage channels are covered with concrete plates that are reinforced with ordinary steel bars, while others are not covered due to the high cost of reinforced concrete plates. As the majority of these plates are only subjected to light pedestrian loads, they should be reinforced accordingly. This study was intended to check the potentials of sisal fibres from Agave Sisalana’ cactus plant which has shown good results in flexural members, as plates reinforcements. At first the quality of ordinary concrete components was checked. Then some of sisal fibres were prepared, manufactured into ropes of 10 mm diameter and then used as replacements of main steel bars in concrete plates before their tensile capacity was checked. Other pieces of sisal fibres of 5 cm length were mixed in concrete mass with different percentages of 0.5%, 1% and 1.5% of concrete volume. Test results showed that the compressive, tensile and flexural strengths for concrete with 1% of sisal fibres were more adequate for M30 concrete and therefore able of sustaining the real loads applied to the drainage concrete cover plates. As the performance of natural sisal fibres depends on fibres treatment methods, length, and type of required concrete, further studies on the use of sisal fibres should consider those factors. Keywords: Agave sisalana, drainage channel, Reinforced Concrete, Sisal Fibres, Sisal ropes.

Construction materials are increasingly on high demand in the developing world. The construction industry has a challenge of discovering, new alternative construction materials to conventional materials which are locally available materials in environmentally friendly manner. The experimental tests are conducted on volcanic concrete system to analyze its properties especially corrosion resistance potential for its applicability in construction. The major aim is to investigate its suitability and corrosion resistance potential especially when used in construction of structures with embedded steel. The test results of the material show that volcanic concrete system with 30% fly ash and 10% silica fume cementing materials is an alternative green construction material. Permeability properties are reduced by 8% and 24% with 30% fly ash and 10% silica fume respectively. Tests also indicate that Compressive strength, Corrosion potential and polarization resistance in volcanic concrete system with supplementing cement materials has more potential to resist sulfate attack when compared with conventional volcanic concrete systems. The supplementary cementing materials (SCM) reduce the pore system and hence decrease the ingress of corrosive ions an water in concrete. Corrosive ions, moisture and air would initiate corrosion to the embedded steel in concrete leading to reduced service life such structures. Key word: Supplementary Cementing Materials, Sulfate attack, volcanic concrete system, Granite powder, river sand, Corrosion of embedded steel

The construction industry is one of the rapidly growing and the cost analysis suggests that the materials cost is constantly increasing. The continuous extraction of aggregates intensively used in the field is negatively acting to the environment. Therefore research in construction materials should focus not only on discovering new alternative materials but also in appreciating the quality of those locally available for their better application. This research aimed at evaluating the performance of bamboo and mud bricks as two available local building materials, especially with regards not only to their strength but also to new performance concepts which are affordability, energy efficiency and environment friendly aspects. The study comprised mainly of laboratory tests of used materials and cost estimation analysis. Study results established that the considered bamboo and mud bricks, made in ordinary soils and reinforced by sisal fibers were reusable, environment friendly materials and energy efficient, with the bamboo showing the thermal conductivity equal to 0.1496 W/mK. Regarding the compressive strength, reinforced mud bricks with sisal fibers showed an increased value from 1.75 MPA to 4.29MPA, what was in line with related previous studies. The average compressive strength of the studied Arundinaria Alpine bamboo was established at 133,7MPA, while its tensile strength was 88.16MPA and these values were reasonable with comparison to other conventional materials. It is recommended that further research in checking the performance of other types of bamboo as well as about new construction technologies be undertaken in order to enhance the service life of both bamboo and mud bricks.Keywords: Affordability, Bamboo, Conventional concrete, Materials strength, Mud reinforced bricks, Sustainability

The Rwanda Building code is in place from 2015, while the development of Rwanda standards dates from 2006 when the reviewed Law establishing Rwanda Bureau of Standards (RBS) was published. The key role of standards is technically to ensure quality, safety, reliability of constructions as stated the relevant codes. With the construction industry growing very fast, the purpose of this study was to investigate on the application of Rwanda building standards, with regards to the existing code requirements and to identify the relevant gaps. The study was conducted based on initially set specific objectives, while the research methodology was mainly comprised of visits to different public and private agencies related to construction industry, observations on the sites and interview with different experts. The study established that Rwanda building standards were still accused of a low awareness and application as well as noticeable gaps. The level of awareness among all professionals was still at 71%. In general about application, only 55% of respondents confirmed the experience in application of Rwanda building standards, even if this level was higher for some categories. A good part of respondents composing around 57% thought that Rwanda building standards documents were still incomplete. Based on the above findings, adequate strategies for improving the awareness, application process and document completion were proposed; with the introduction of Rwanda building standards into academic curriculum, increase the number of awareness meetings and recognition of adequate research before design or review of any standard, among others.Keywords: Building code, Building Standards, awareness strategy, Law and Regulations, Monitoring process

The issue of achieving sustainable environment is highlighted in different national and international strategic documents, such as Rwanda Viosion 2020, EDPRS II and MDGs. Rwanda on its track towards achieving sustainable environment, is still experiencing some challenges like Environmental degradation for the search of aggregates, energy for extraction of natural aggregates and difficulties in finding dumping sites for demolitions and construction wastes. Therefore, all those problems have created the need for developing a new source of construction materials.The idea of recycling of C&D concrete wastes aims at finding solution to the environment degradation caused by damped demolished wastes as well as producing affordable high strength concrete blocks. This research investigated the availability of C&D concrete wastes and it was discovered that up to 33.33% of C&D waste came from concrete structures while more than 23.75% of people confirmed to have been involved in demolition works more than three times a year.The research was done by collecting sample composed of C&D concrete wastes at construction site of BPR headquarter where they demolished the existed building for construction of a new multistory building in kigali city and the sample was crushed, batched and mixed with a proportion of 1:3 and 1:5 as stated by Rwanda Bureau of Standards and manufactured new concrete blocks. The research performed on series of concrete blocks: 2 series each made of different proportions of cement for recycled concrete blocks, and one serie of reference blocks made of natural aggregates. Compressive strength test gave an average of 5.13N/mm2 for recycled concrete block, which fulfills requirement of Rwanda Bureau of standards for hollow concrete blocks and which is 0.87 times the compressive strength of an ordinary block tested under same conditions. Finally, the cost effectiveness showed that the new recycled concrete block will be affordable by reducing at 15.6% of cost for that one made of natural aggregates.Keywords: Concrete wastes, Recycled concrete block, Mechanical properties, Cost effectiveness and Environmental protection