Stone Mastic Cement: A Sustainable Road Surfacing Material

Table 1: Modern road/pavement surfacing materials

Demand for sustainable construction materials has skyrocketed over the last decade, thanks to the increased global construction activities. Developing infrastructure such as roads has never been a cheap venture. Notably, the raw materials needed to construct the roads continue to get depleted. Besides, concerns have been raised over the manner in which the mining activities (to get the construction materials) have caused degradation of the land and negatively affected the environment at large. Therefore, recently, there has been increased research work for economically and environmentally sustainable materials for road surfacing. Researches have focused on possible recycling of the construction materials. Notably, stone mastic cement is among the materials that potentially could offer a better alternative to the existing road surfacing materials. Traditionally, there have been a number of road surfacing materials used especially in building the street pavements. In fact Beuving & Michaut (2015) opine that in the past, people used to make pavements using wood, rubber and even iron. Later, the use of concrete, crushed stones and composites (a mix of cement and crushed stones) dominated the industry. These materials provided great road surfacing capabilities by integrating the multifunctional features with the economic advantages. Notably, they could be used by a range of users such as pedestrians, wheel chairs, vehicles, among others. However, due to the increased demand for a more economical and sustainable urban road surfacing material, there are a number of new materials that have been proposed for large scale use. It should be noted that growth of urban establishments can only be tremendous if excellent urban road networks are laid. This has been manifested almost in all countries that seriously took advantage of the construction waste and debris to re-carpet their urban roads hence facilitating urban mobility.  Now, what makes a road surfacing material to be widely accepted by users? In urban areas, people and vehicles normally move around a lot; those going to work, shopping and other road users must be integrated in the design.  According to Beuving & Michaut (2015) there are a number of critical factors which designers must consider and some of them include: safety, comfort, quietness, durability, fast construction, easy to maintain and environmental friendliness. Additionally, the designers always strive to ensure that the surfacing materials are more appealing to the users, in other words, they are aesthetically designed as well. Some of the modern pavement materials are illustrated in table 1:

Objectives

Table 1: Modern road/pavement surfacing materials

Pavement Material	Features	Limitations Save Time On Research and Writing Hire a Pro to Write You a 100% Plagiarism-Free Paper. Get My Paper
Bricks/concrete blocks	Color and shape makes it great for the construction industry	Higher noise emissions
Silent concrete	Slight noise reduction Has optimized fine structure	Requires more attention for surface evenness
Porous asphalt	Possesses noise reduction capabilities	Less durable
Porous concrete	Noise reduction Good drainage capacity	Requires additional material to ensure strength and durability
Embedded rail	Shorter building period Long life Less maintenance	Requires additional material for noise reduction
Stone mastic asphalt/cement	Durable surface type Greater capabilities for noise reduction   Aesthetically proven Recyclable

From the table 1 above, the outstanding features that would guide the choice and selection of a road surfacing material include: structural integrity, aesthetic quality, noise reduction, recyclability and durability. Therefore, for the purpose of the research work to be presented, special focus would be given to the stone mastic cement material; where its suitability to the urban area would be evaluated against other materials. In other words, does the material offer better alternative to the existing surfacing materials? How does it contribute to the improvement of the urban transport infrastructure? Does it, for example, have a mix of properties which match with the modern realities of the urban set ups?

Now, before the stone mastic cement can be explored further, it is imperative to understand its engineering and design performance.

In the construction sector, some old dilapidated structures are usually brought down so as to pave way for construction of new ones. In the process, huge amounts of demolition wastes normally pile up; contributing negatively to the environmental well being. Hence there has been a concerted effort in the recent past to recycle some of these demolition wastes. The stone mastic cement, therefore, is among the recycled demolition wastes that potentially could be reused in the industry. To explore its engineering performance further so as to match with the user expectation, there is a number of engineering design parameters that could be explored in details; they include: Loaded wheel tracking, Marshal Stability, density test, and resilient test among others (as will be discussed more in the research methodology).  

Objectives

 The major aim of this research is to uncover the actual performance of stone mastic cement thereby exploring the possibility of improving the urban transport infrastructure using it as the best alternative. Hence the objectives include:

• To determine the actual engineering performance of the stone mastic cement
• To establish a correlation between the material properties and the users’ expectation
• To explore the likely economic and environmental benefits as a result of using the material

Scope of the research

The research will greatly focus on exploring the engineering characteristics of the stone mastic cement against other existing surfacing materials hence comparative analysis will dominate. Afterwards, the possibility of the material contributing positively to the urban transport infrastructure will also be explored. Importantly, therefore, great attempt shall be made to establish correlation (if any) between the material properties and the impact it will have on the environment and the urban users. Notably, however, the research work assumed all materials tested are standardized hence the analysis will not consider the material properties variation.  

Scope of the research

1. Pourtahmasb & Karim (2014) did a performance evaluation of both pure stone mastic asphalt and the recycled concrete aggregate where their mechanical properties were tested through rigorous scientific methods. The paper establishes that the properties of the virgin concrete and that of the recycled concrete are totally different due to the different levels of cement composition. For example, the RCA (recycled Concrete Asphalt) has got more cement at the surface hence contributing to greater porosity and making it to have higher water absorptive power. Besides, it was uncovered that if a 50-50 ratio of both RCA and virgin concrete were to be mixed then a higher modulus of resilience and creep resistance would result hence not only does it become more economical for use but also contributes fairly to the environmental sustainability. According to Pourtahmasb & Karim (2014), through a rigorous scientific methodology, they were able to come up with very interesting conclusion. Notably, the samples used in the experiment were obtained from the virgin hydrated limestone powder which was crushed to standard grain sizes and later mixed with crushed recycled concrete asphalt (sourced from demolished concrete structures). A number of engineering tests were done and the following conclusion was derived from the experimental result:

As the RCA content was increased, the density of the material was found to be decreasing.

Marshal stability in pure virgin aggregate was found to be higher than that of the RCA, mainly attributed to the dense gradation of the aggregates (Pourtahmasb & Karim , 2014). Remember during specimen preparation, compaction of the aggregates must have contributed to further breaking down of the particles.  

The resilience modulus also was found to be decreasing with increased RCA content, although the minimum criteria were passed. According to Pourtahmasb & Karim (2014), the minimum resilience modulus for urban pavements is about 2100MPa. One notable reason given for this is the fact that still there were some coarse grains in the RCA (as compaction process was never a sure process to obtaining uniform fine aggregates).

The wheel tracking test to ascertain the extent of permanent deformation was done and revealed, via a parameter called rut depth, that as the RCA content was increased in the stone mastic asphalt (SMA) slightly increased up to an RCA level of 40 % then dipped. This was largely due to the increased density of the material.

2. Sandberg (2009) explored the possibility of using road surfacing materials with low-noise capability. He argues that some road surfacing materials need to be avoided at all cost if noise reduction is anything to go by. Pointedly, he asserts that road surfacing materials such as TTCC (Transversely tined Concrete cement), BRCC (Brushed cement concrete), Hot rolled asphalt, and SMA (Stone Mastic asphalt ) with large chippings are some of the notoriously ‘noisy’ road surfacing materials. Instead, Sandberg (2009) advises that the following materials should be used due to their low-noise capability: Diamond grinding, Exposed aggregate cement concrete (EACC), Small aggregate surfacing dressings (SASD), thin surfacings, Asphalt rubber friction course, single and double layer surfaces. For example, in thin layer surfacing, a hot bituminous compound is machine-laid forming a coarse textured layer capable of boosting the acoustic performance of the surface. In fact, Sandberg (2009) asserts that it can reduce noise by 3 dB at minimum. However, there is no guarantee that the acoustic characteristic would remain uncompromised for years if the material is laid on roads. Through continuous acoustic performance evaluation of the surfacing material, it could be shown how the acoustic characteristic would not stand the test of times.

Literature Review

3. Croteau & Hanasoge (2006) reviewed the recycling process of the stone mastic asphalt (SMA). There was need to replace the binding material with a more durable and coherent one. The cold recycling process of the bituminous therefore offers a more potent method of recycling to guarantee extended durability once the surface is laid. The new binding material promises to heal and seal the material defects and loopholes in the design. Defects such as thermal cracking could substantially be reduced as a result of this cold recycling method. However, other factors would still be at play; such include: fatigue resistance, reflective cracking and other structural weaknesses. Hence usually optimal performance criteria are often employed to optimize the functional and structural requirements of the road surfacing material. However, in order to actualize these requirements, characteristics of the binder such as age and content need to be analyzed using rigorous methods. The marshal method of compaction is the most common laboratory technique that is used to determine performance related parameters hence sufficiency of the recycling system can be ascertained. Besides, other tests such as air voids and moisture resistance test could be used to reveal some hidden yet critical design parameters. For instance, in the air voids test, the assessment could used to reveal the compactability and permanent deformation of the said material. For a better performance of the SMA, the author proposes an air void of between 9% and 11 % according to the Ontario laboratory curing and harshness mixture. The bituminous aggregate is mostly preferred due to its ability to electrically bind with the recycled materials hence offering effective particle binding.  

4. Asphatic concrete pavement

This was the predominant surface material used in the 1970s in the United States. The author claims that the material had a justifiable reduction in road maintenance costs. Energy consumption and land fill space was conserved as well. He further opines that the recycled material of this caliber potentially lowered the transfer costs. The author therefore proposed a number of recycling processes that, according to him, could potentially improve the urban transport infrastructure and contribute to the sustainable environment.

5. Shodhganga (2017)

This author explored the performance of pavement vis-à-vis the user requirements. He opines that as traffic activities increase in the urban set up, so is the rate of deterioration of the surfacing materials. This is mainly attributed to the increased stresses resulting from increased road users due to increased economic activity. Therefore, designers are encouraged by the author to always consider the longevity status of the surfacing material against the backdrop of the glaring urban traffic realities. A poorly designed urban road would incur economical as well as environmental losses to the users as more surface defects would resurface after a short period of use. The common surface defects, which the author argues that arise as a result of the structural and functional integrity mishaps, include the potholes and cracks. Consequently, propagation of these surface defects would impede efficiency in movement of people and goods.

 Furthermore, the author attributes the rate of deterioration to the following factors:

• Environmental factors such as excessive rainfall, radiation, freeze-thaw temperature cycle and moisture. For instance, the thermal stresses usually result from the repeated freeze-temperature cycles of the material causing micro-cracks and then the solar radiation facilitating the cracks propagation. The excessive rainfall would then facilitate erosion of the particles from the surface hence resulting in advanced potholes which, if not timely filled, would advance into gigantic potholes rendering the road impassable.
• Structural factors which directly depend on parameters such as layer thickness, material properties and drainage capabilities (Shodhganga, 2017). The thinner the layer of the surfacing material, the faster is the rate of wear and erosion. Notably, materials with less structural integrity are more susceptible to shorter life cycle hence increasing the cost of reworks and maintenance. Thicker layers( although higher initial costs are normally incurred due to more material requirement for the same breadth and length) could last longer due to the fact that they can withstand the imposed stresses by the road users better than the thin-layered surfacing materials.
• Construction factors. Here the author pointed at key issues worth considering such as the methods, machinery, timing and quality specifications. Notably, the kinds of machinery to be invested in such projects have a direct bearing on the quality of the road constructed. Therefore, investment in modern equipments which offer faster and more efficient compaction and carpeting of these urban roads have great potential in the improvement of quality workmanship. Besides, material treatment methods consequently improve the quality of the urban roads.

Sodhganga (2017) goes ahead to propose certain models that can be used to evaluate the performance of the road pavement. He focuses on the repeated use of the roads and the thorough process involved in performance evaluation. Notably, factors worth reviewing, according to Sodhganga (2017) include sub-grade support, pavement composition & thickness, traffic loading and environmental conditions.

The performance evaluation is normally classified as either structural or functional. According to Sodhganga (2017) the performance prediction models are mathematical representation that can be used to predict the futuristic state of the pavements. Some of these models include:

• Primary response models involve the mechanistic response due to the external loadings which can be analyzed. The critical parameters for analysis include: stress, strain and deflection. The inputs to be used in this model are sourced from the secondary sources such as construction records, laboratory testing, among others.
• Functional condition models which normally measure the basic functional condition of the pavement. Safety predictions characteristics such as surface friction of pavement based on skid numbers) are also analyzed using the model. Tests such as skid-resistance are usually performed to generate the skid data for analysis.
• Damage models which .combines the functional and structural models so as to estimate the maximum and minimum levels of performance. Notably, the parameters employed in this model include: unevenness, normalized measure of distress (which incorporates potholes and surface cracks) and surface friction among others.
• Structural performance models which predict damages that result from loopholes in the material structural integrity. The essential parameters for analysis, in this case, therefore, include: fatigue cracking, corner breaks in rigid pavements.

Table 2: Structural integrity performance model

	Model description	Road surfacing models
1	Cracking initiation	=2.74 x Expon. {-2.57xCSALYR/MSN2}
2	Cracking progression	CRt/ti= 5.41 x{CSALYR/MSN}x SCRi
3	Potholes initiation	0.21x THBM0.23x Expon.[-0.18x AXLEYR]
4	Potholes progression	PHt/t= 1.49CRxAxLEYR(1+CQ)/THMBx MSN+3.47RVix AXLEYR(1+CQ)/THMBxMSN
5	Roughness progression	RGt= [58121(CSAL/SNCR5)x Expon(MPAGE)+4.13CRt+184.48PHt+ 33.46PTt+ MRGt+ 9.39Vt]

As earlier noted, a rigorous research methodology was implemented with the approach largely being scientific. Hence most of the performance results obtained was derived from the laboratory work and expert opinion. The research was divided into 3 main phases and spanned over a year. The procedures adopted were painstaking and sometimes more iteration would be performed in order to produce competent results that would thereafter guide decision making in the successive projects.

• Material Performance test methodology

A number of engineering and scientific tests were done with the aim of uncovering the practical performance level of the material; namely: air void testing, marshal stability, Water absorption test, strength test (tensile test), Aggregate gradation test, and creep test. Additionally, thermal stress analysis was performed. However, material pre-test conditioning was done at the onset. Three sets of sample material were obtained from three different cities within the country. Each sample was a mix of virgin cement, obtained from the crushing of limestone and demolished concrete structures. Only uniform aggregates were selected for testing. There was an established compositional regime for the mix, that is: the specimen preparation would involve altering the percent content of the recycled aggregate so as to monitor the contribution of the recycled aggregate. These would later be tested to determine the contribution of the said materials in the performance.

Table 3: Compositional specimen regime for Sample A

S/No.	Mix Regime	TEST PARAMETERS
		Air void	Marshal stability	H2O absorption	Strength test	Aggregate gradation	Creep test
1	10% RCA
2	20% RCA
3	30% RCA
4	40% RCA
5	50% RCA
6	60% RCA
7	70% RCA
8	80% RCA
	TOTAL

NB: The compositional specimen regime for the remaining samples B and C are generated using the same template above 

• Air void testing

According to PCA (1998) the test was used to estimate the rate of deterioration of the material by analyzing the content of air in the material hence designated as percent air content. The test result was achieved as follows: 

The displacement method was adopted such that a known volume of specimen, say 50cm³ was poured into a column containing glycerin and water. Afterwards, it was stirred to release all the air from the material. This would then flow into the water via the glycerin. Now, a submerged buoyancy recorder was used to detect the amount of air that passed through. This simple system is connected to the computer for real-time analysis. The values are therefore computer generated. Notably, during specimen preparation, the issue of aggregate size was given great credence. For accurate results, only uniform aggregates were allowed for a particular specimen. 

• Marshal stability test

Firstly, according to The Constructor (2005), the specimen to be tested was prepared as follows: The specimen was weighed and then heated in an oven to the mixing temperature. A suitable binding material at this temperature was then added. Thorough mixing was then done and the mixture returned to the oven for further baking. The baked contents were then placed in a mould and a compaction machine was used to provide mechanical blows until the required shape was produced. The specimen was then allowed to cool down and later taken to the marshal testing machine where loading was applied progressively in a steady fashion.

• Water absorption test

The specimen preparation mimicked the practical construction of roads with binding materials mixed. Afterwards, a known volume of water was poured into each of the specimen simultaneously and left for 5 days. The amount absorbed was then measured and results obtained.  

• Strength test

A concrete block of known size from the aggregate material was prepared. Then it was taken to the ultimate tensile testing machine for tests. The results were then obtained.

Hence the following testing matrix results:

Table 4: Material testing matrix

Deliverables	Surface characteristics	Performance requirements
Safety	Texture Photometry Eveness	Skid resistance(friction coefficient ) Marking and reflection Contrast and pigmentation Corrugation resistance Permanent deformation
Comfort	Texture Drainability Photometry Eveness	Smooth surface (Noise reduction) Noise absorption Colors and pigmentation Long eveness
Durability	Structural integrity	Material strength Surface cracking resistance Fatigue cracking Reflective cracking resistance
Construction & maintenance efficiency	Recyclability Construction time Maintenance time	Extent of recycling Shorter construction period Easy to repair and maintain
Environmental concern	Emissions /Leaching	No leachable components

• The Expert Opinion  

It was imperative to seek the experiential expert opinion on the past performance of the various roads in the urban centers. A number of road construction companies were visited and professionals engaged in interviews. The interview questions presented were in tandem with the objectives and aims of the research. Some of the issues that required the input of the expert opinion include:

How the surfacing materials have evolved over the past 10 years. Has there been any major breakthrough in the implementation of these materials?

What are some of the major issues that the surfacing materials undergo that could potentially hinder the growth of urban traffic?

What are the stages of design in road construction?

Any information that is valuable to cement the understanding of the life cycle of these materials?

What is the frequency of repair and maintenance of these urban roads?  Is the maintenance program scheduled or it is just haphazard?

How much does it cost to construct a kilometer of these kinds of roads? Has there been any improvement in value of roads being constructed? What parameters have the engineers used in the past to design these kinds of roads?  

What opinions do the experts have when it comes to effect of the weather and environment on this urban infrastructure?

Has there been any effort from the authority in charge of constructing the roads to draft and implement policies far as environmental conservation is concerned? What policies have been implemented to justify the commitment towards this course?

Any upcoming projects in this sector that seemingly would revolutionize the industry?

Has there been any research project that has wholly been funded by the authority towards exploration of new techniques to be used in constructing sustainable infrastructure?

Notably, the issues mentioned above were designed for the various experts and professionals in the industry. Specifically, issues relating to the regulations and policies involved in construction of these roads were directed to the Australian Ministry in charge of Transport and/or Infrastructure. Besides, some very experienced professionals in this field were also consulted as there opinions were very critical for the success of this research project.

Table 5: The expert opinion template

S/No	ISSUE	OPINION	ANALYST’S REMARKS
1	Evolution of Surfacing material
2	Hindrances of urban traffic growth
3	Stages of design
4	Life cycle of the materials
5	Maintenance & Repair frequency
6	Construction cost
7	Environmental effect
8	Conservation policy commitment
9	Industry revolution
10	New sustainable techniques

• Review of the Secondary sources

These include perusal of the road construction project reports across the cities, the different regulations governing the construction of the urban roads and first hand observation of the current status of the urban roads.  Some photos of these roads were taken and closely analyzed for details on their status. Additionally, a number of past researches in this area were thoroughly perused to establish the existing facts and opinions on the subject matter. Notably, a number of key issues discussed in these papers were noted and used as stepping stones and benchmarks for the research. Some contradicting issues among the different authors and the research gaps were identified as well.  

Table 5: Performance test results

S/No.	Mix Regime	TEST PARAMETERS
		Air void	Marshal stability No.	H2O absorption (ml)	Strength test(MPa) X10	Aggregate gradation	Creep test
1	10% RCA	6%	0.945	0.789	43	Null	Null
2	20% RCA	5%	0.835	0.845	67	Null	Null
3	30% RCA	4%	0.812	0.673	78	Null	Null
4	40% RCA	3%	0.809	0.976	98	Null	Null
5	50% RCA	2%	0.792	0.786	56	Null	Null
6	60% RCA	0.5%	0.723	0.765	89	Null	Null
7	70% RCA	0.7%	0.734	0.543	98	Null	Null
8	80% RCA	0.3%	0.634	0.675	100	Null	Null
	TOTAL

In the air void test, the obtained results show some general trend. As the percent content of the RCA is increased, there is a dramatic reduction in material porosity. In fact, on a closer look, a reduction of 5.7 margins in air void can be attained between the given range, that is 10-80%. This can be attributed to the fact that the RCA aggregate were finer than the virgin concrete such that as more RCA is being added, the mixture becomes less porous. Notably, porosity is a critical factor of drainage. Normally, less water, for the same amount of time, is allowed to percolate in finer aggregates than the coarse ones. Additionally, the RCA being that it was derived from an established concrete (that constituted cement as well), the cement properties would still be manifested in the RCA. However, past research work actually revealed that cement is an excellent water absorptive material (note: does not allow water percolation instead, it absorbs water in a sponge-like fashion). Nevertheless, optimization techniques can be used to come up with the best regime considering the critical factors such as drainage.

In the Marshal Stability test, from table 5, seemingly there is a uniform behavior in the Marshal Stability number. A range of 0.433 in MS number can be attained. Seemingly, this shows that the stability of the stone mastic cement would not be affected by the increased RCA content. It is likely to withstand the stresses just like the way the virgin material can withstand. However, this is not guarantee especially if you analyze the contribution of a material with marshal stability of 0.433; it is not a drop. Hence once again, decision as to which regime to select will depend on the realities on the ground. For example, roads that are frequently used would be found in the city centre and frequency of use decreases as the radius from the city centre increases. Therefore, roads in the city centre need to be of greater stability than those in the outskirts.

In water absorption, it goes hand to hand with the air void test. The regime with greater air void content, normally have higher water absorptive power due to more number of spaces in between the aggregate particles. Although the results show the water absorptive power of the material slightly is affected by the increased RCA content such that there is a slight reduction in absorptive power with increased RC content. Cities that desire excellent drainage capabilities would surely go for the regime with less RCA content. However, the environment conservation would likely be jeopardized if such a decision was to be taken as it is. Therefore, there is need to adopt a balanced approach and once again, the urban realities must greatly be considered. But experts would advise for selection of an approach that leans more on the environment conservation such that recycling of the demolished structures (only old and obsolete structures should be destroyed) would be in top gear. Besides, as noted earlier, the RCA content is almost superfluous as far as water absorption is concerned.

In strength test, there is a dramatic trend as tabulated in table 5. The strength of the material dramatically increases as the RCA content is increased. Notably, in the range of 10-80% RCA, a strength margin of 5700MPa is realized.  This is a tremendous contribution of the RCA. Now, one of the factors that can assure durability of any road is the strength of the material used. This results show a potent regime that can be implemented especially in the urban roads where there is too much stress being applied repeatedly. However, it should be noted that surface cracking would still suffice even in materials with greater strength. There a number of factors that make this happen. For example, quality of binding material used and the prevailing weather conditions. However, in a nutshell, the results obtained are encouragingly sweeter than the existing materials.  

Table 6: Expert opinion results

S/No	ISSUE	OPINION	ANALYST’S REMARKS
1	Evolution of Surfacing material	From wooden pavements , concrete asphalts dominating currently	Therefore, SMA with recycled concret offers the most potent material for road surfacing
2	Hindrances of urban traffic growth	Loose particles washing away hence potholes propagation
3	Stages of design
4	Life cycle of the materials	SMA have relatively longer life cycle
5	Maintenance & Repair frequency	Affordable and planned ensures quality and less cost
6	Construction cost	Minimum with the implementation of the current technologies
7	Environmental effect	Less effect on environment greatly desired
8	Conservation policy commitment	Much work still required
9	Industry revolution	SMA with recycled concretes promising sustainable future
10	New sustainable techniques	More researches being done

The ten issues tabulated in table 6 actually arose from the brilliant opinions of the professional and government authorities in the industry. Most experts were in agreement that the existing materials being used need a serious face-lift to guarantee not only durability and safety but also ensure a sustainable future by investing in sustainable construction technologies. For example, when asked about their opinion on practicality of the stone mastic cement with an improved RCA, most of them agreed that it is among the promising road surfacing materials if the current urban realities is anything to go by.

Table 7: Requirement matrix

Deliverables	Surface characteristics	Performance requirements	Comments
Safety	Texture Photometry Eveness	Skid resistance(friction coefficient ) Marking and reflection Contrast and pigmentation Corrugation resistance Permanent deformation	Coarse materials provide better friction coefficient and drainage
Comfort	Texture Drainability Photometry Eveness	Smooth surface (Noise reduction) Noise absorption Colors and pigmentation Long eveness	Noise reduction is still an issue worth considering
Durability	Structural integrity	Material strength Surface cracking resistance Fatigue cracking Reflective cracking resistance	Heat treatment methods can be used to reinforce the strength of the material
Construction & maintenance efficiency	Recyclability Construction time Maintenance time	Extent of recycling Shorter construction period Easy to repair and maintain	The large volumes of construction material waste could be used for this purpose
Environmental concern	Emissions /Leaching	No leachable components

After painstaking research process, the analysis resulted into a summarized requirement matrix as shown in table 7. These are major issues that have actually been discussed. Certainly, the stone mastic cement would offer the best compromise compared with the other existing road surfacing materials. For instance, from the laboratory analyses, the SMC with improved RCA is seemingly durable, safe, and comfortable and can be an environmentally sustainable material. Although its construction would require additional pre-construction treatments to boost the parameters identified.

Conclusions And Recommendation

In conclusion, therefore, it is clear that the stone mastic cement with a combined recycled aggregate will offer the best solution for the problems identified. Therefore, the properties discussed above indicate that the material provides the best alternative.  Now, the objectives of the research were: To provide real-time engineering performance of stone mastic cement, establish correlation between the road surfacing material properties and user expectation and lastly to investigate the economic and environmental benefits. Admittedly, the findings are almost in tandem with the objectives. For example, from the rigorous tests performed, real-time engineering performance of the material has been elucidated. Actually, from the analysis of results, the material engineering performance surpassed the expectation of the research. Secondly, from the expert opinion (which is actually highly invaluable) the prospect of implementing this material regime was boosted by their experiential knowledge in the field. A number of issues were identified. Perusal of the secondary sources actually revealed that the cost of road maintenance is skyrocketing. From the analysis above, combined with a more orderly maintenance and repair approach, greater cost savings can be realized should this material be implemented. Besides, the efforts of restoring the environment will receive a boost since the old and obsolete structures could be demolished and the wastes recycled to repair and maintain the urban roads. Therefore, it is highly recommended that the stone mastic cement with an improved RCA content be implemented in the urban centers especially in busy cities of the country; so as to ensure a more durable and environmentally sustainable future.

Reference

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Drüschner, L & Schäfer, V. (2005). Stone Mastic Asphalt. Available at: https://www.eapa.org/userfiles/2/DAV/sma%20englversion.pdf

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