Huge amounts of aggregates and sand are required for concrete production worldwide, leading to a lack of natural resources for high quality sands and aggregates. Concrete producers need to source alternatives, like manufactured, recycled or crushed sands and aggregates or sands contaminated with clay or other minerals.
Use of such alternative materials leads to changes in fresh and hardened concrete properties which cannot be controlled with conventional admixtures available. Resulting problems in concrete production can have several reasons, and thus the problems need to be analyzed before a proper solution can be found.
Sika developed a concept for finding the right solution for the issues observed by the customer related to sands and aggregates. In many cases, the reason for changing or problematic concrete properties is not obvious. Therefore, several steps are required to identify the problem to give the right support and product solutions.
With our concept, we want to help you unlock the safe using the Sika CODE method.
Solving Aggregrate Issues in Concrete Production with the Sika CODE
Four Steps in the Sika CODE
It is important to listen to the customer and understand the issues or challenges that he or she must solve. Sika experts discuss the problems with customers - namely concrete producers - while making sure to fully understand their needs.
The following issues may arise in concrete production:
The concrete requires more
water to be added for the same fresh concrete properties.
The concrete requires a higher admixture dosage.
The concrete shows higher adhesion and cohesion than before.
With the same water content, the concrete shows bleeding or even segregation.
The pumpability is reduced with the current concrete mix. This can lead to blockages during pumping or higher pumping pressure required.
Using low quality sands can lead to issues on the concrete surface, especially in precast concrete.
The workability time of the concrete is affected by the sands or aggregates used for the concrete mix design.
The next step in the Sika CODE concept is the analysis. Samples of the sands and aggregates are analyzed using several methods in the Sika technology lab.
The focus of the analysis involves the following points:
It is important to identify critical minerals within the sand which can negatively influence the concrete performance.
The correct grading curve is important for the concrete properties. This needs to be tested, and gaps need to be identified.
The aggregates and sands used in the mix can lead to absorption of water or admixtures. This depends on the mineralogy of the sands. With specially developed lab tests, this absorption behavior can be investigated.
The single particles of the sands and aggregates are analyzed regarding their shape and grain properties, which can have a high influence on the concrete behavior.
With the analytical results, the cause of the customer challenge can be diagnosed. Of course, it can be that there are several causes that lead to an issue.
However, most of them can be found in this list:
The sand or aggregates absorb water from the mix design.
The sands or aggregates absorb admixtures added to the concrete mix.
The particles have an unfavorable shape (e.g. too edgy for crushed sands).
The grading curve contains a high fine content.
The grading curve shows a lack of fine particles.
After the identification of the cause, our Sika experts can work on the most effective solution for our customer. The solution can be a product, combination of products, technical support or both products and support (as in most cases).
Amongst others, the following solutions can be offered:
A mobile phone application for calculation of concrete mix designs. With the basic information about the concrete mix ingredients, the mix design can be optimized very easily in the app to meet customer requirements.
Sika technical expertise is offered for every customer to support on site with our expert knowhow and products and in the lab with testing and analysis.
This includes the whole range of Sika water reducers - for example SikaPlast® or Sika® ViscoCrete® technology.
The Sika® Stabilizer range helps to optimize concrete properties and provides robust solutions for fluctuating sand qualities.
Sika CODE Applied in Completed Projects
Nant de Drance Plant, Switzerland
Sika Admixtures for 100% Crushed Rock in Concrete
| Customer Challenge | Operated Analysis | Diagnosis of the Cause | Effective Sika Solution |
|---|---|---|---|
High cement demand Low pumpability Low slump retention | Aspect Grading | Aggregates shape Low fines Variable grading | Sika® ViscoCrete® GTC 1 and GTC 2: Superplasticizer for concrete Sika® Fro V-5 A: Air void entrainer Sikament® 212 S: Superplasticizer for shaft concrete Sika® ViscoCrete® SC -303: Superplasticizer for shotcrete Sika® Retarder: Concrete retarder SikaPump® Start-1: Lubrication agent Sika® Sigunit® L-5601 AF: Alkali-free shotcrete accelerator Sika® Sigunit® L-93 AF: Alkali-free shotcrete accelerator |
The Nant de Drance pumped storage power plant is located in the Alps in the Valais region of Switzerland. Apart from the dam, the major construction of this project is located inside the mountains at an altitude of 1900 to 2200 meters above sea level.
The construction work included a gigantic turbine cavern, pressurized water tunnels, several smaller caverns, vertical shafts, a several-kilometer-long access tunnel system, and an elevation of the Vieux-Emosson dam. During the construction period, the concrete production was located inside the galleries as well. All kinds of concrete have been produced entirely using excavation materials.
Concrete was achieved with:
- High softness and optimal pumpability
- Perfect feasibility for self-compacting concrete
Thomas Concrete, Sweden
Sika® ViscoCrete®-3040 - The Solution to Crushed Rock Fines in Concrete
| Customer Challenge | Operated Analysis | Diagnosis of the Cause | Effective Sika Solution |
|---|---|---|---|
High water demand High cement demand Low pumpability Low slump retention | Aspect Grading | Aggregates shape Low fines | Sika® ViscoCrete®-3040 CA |
In Sweden, the government has set clear goals that the extraction of natural gravel must be reduced in order to remain in our nature for better groundwater quality. Thomas Concrete Group is one of Sweden's leading ready-mix concrete manufacturers. In one of their concrete plants in Stockholm, the use of crushed rock fines (CRF) has been gradually increased up to 30% compensation of natural sands. Due to this, cement dosage become necessary as well as the water demand of the concrete increased as observed by an increasing dosage of superplasticizer.
Concrete was achieved with:
- Concrete properties for either natural and crushed rock fines (CRF)
- CRF exchange up to 100% possible
Lujabetong, Sweden
Sika® ViscoCrete®-5030 SE for 100% Crushed Rock in Concrete
| Customer Challenge | Operated Analysis | Diagnosis of the Cause | Effective Sika Solution |
|---|---|---|---|
Concrete production with 100% crushed rock High cement demand Low pumpability Low slump retention | Aspect Grading | Aggregates shape (rough, uneven surface of particles) Low fines Variable grading | Sika® ViscoCrete®-5030 SE |
In Sweden, the government has set clear goals that the extraction of natural gravel must be reduced in order to remain in our nature for better groundwater quality. Lujabetong is a concrete producer operating in the Nordic region. For a new factory outside Stockholm, concrete production was intended to use 100% crushed rock. Aggregate quality was not homogenous, and thus, major problems arose regarding concrete rheology and slump keeping.
Concrete was achieved with:
- High softness and optimal pumpability
- Optimal slump retention
Concrebras, Brazil
Sikament® RM-380 for Concrete Production with Pit Sand
| Customer Challenge | Operated Analysis | Diagnosis of the Cause | Effective Sika Solution |
|---|---|---|---|
| High water demand | Grading | High fines | Sikament® RM-380: water reducer Technical support |
In this project with Concreband, pit sand was used for concrete production for general application. Very fine aggregates increased the water-cement ration and decreased the final strength. Stains on concrete floors and delamination was also occurring.
With the use of Sikament® RM-380 water reducer and Sika technical support, the water amount was decreased without influencing the customer's requirements and without increasing the customer's raw material costs.
Mtech Prefabrication, Brazil
Sika® ViscoCrete®-6090 HW for Concrete Production with Artificial Sand
| Customer Challenge | Operated Analysis | Diagnosis of the Cause | Effective Sika Solution |
|---|---|---|---|
High water demand Bleeding/ segregation | Absorption Grading | Water absorption | Sika® ViscoCrete®-6090 HW: water reducer Technical support |
In this project by Mtech, artificial sand from basalt was used for concrete production for prefabricated buildings. The aggregates used had a high water demand but did not absorb the water.
By adjusting the mix in the fines of the concrete with Sika® ViscoCrete®-6090 HW, reducing the mix water, and adjusting vibration and densification of the concrete, the finish was greatly improved and productivity was increased.
Concreto Cortesia, Brazil
Sikament® RM-300 for Concrete Production with Limestone Sand
| Customer Challenge | Operated Analysis | Diagnosis of the Cause | Effective Sika Solution |
|---|---|---|---|
| Slump retention | Grading | High fines | Sikament® RM-300: water reducer Sika ViscoFlow®-30 BM |
In this project with Concreto Cortesia, limestone sands were used for concrete production which required a long workability time. The fines content of the grading curve was analyzed, especially the powder to sand ratio. It was diagnosed that aggregates occurred with high fines content that, when combined with coarse aggregates, promoted a rapid loss of slump.
With the use of Sikament® RM-300 combined with Sika ViscoFlow®-30 BM, the concrete could be adjusted in a way that the slump retention fit to various applications for the customer.
RMP Concepción, Chile
Avoid Surface Cracks with the Right Plasticizer
| Customer Challenge | Operated Analysis | Diagnosis of the Cause | Effective Sika Solution |
|---|---|---|---|
Poor surface quality Bleeding | Grading | Low fines | Sika water reducer Technical support |
In this project with RMP Concepción, the concrete could not keep the water inside. Due to this challenge, surface cracks occurred after hardening. The analysis of the grading curve showed that there were very low fines content in the concrete mix. The low fines needed to be adjusted in order to achieve a much more stable mix design.
Next to the adjustment of the grading curve, the right Sika plasticizer was selected to support the stability of the concrete mix.
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