BETCRETE 3.0 – Concrete with certified fly ash for drinking water plant construction

BETCRETE has been conducted as a national collaborative project addressing the challenges and necessary actions to achieve the goals set out in the roadmaps for the Swedish cement and concrete industries. The project consortium consisted of organizations impacted by and contributing to these roadmaps, representing key actors across the entire value chain. Over time, BETCRETE has established itself as an independent and recognized platform for cross-disciplinary dialogue and for driving both regulatory and technical development of innovative solutions. It serves as a value-creating knowledge and information channel for cement and concrete-related issues.

The overall objective has been to reduce CO₂ emissions from concrete by mobilizing the entire value chain around climate efforts. This includes addressing joint collaboration challenges, legislative and financial barriers, and implementing short- and long-term technical solutions using new materials and technologies. A crucial condition has been the coordination of roadmap efforts between the cement and concrete sectors, as well as the removal of obstacles to their implementation. The project also aimed to contribute to the development of cross-industry KPIs and strengthen the sector’s ability to measure, track, and communicate its sustainable transition.

As part of the BETCRETE project, the potential use of climate-improved concrete with fly ash was evaluated for drinking water infrastructure. Laboratory and field tests were conducted at two Swedish water treatment facilities to assess whether partial replacement of Portland clinker with CE-marked fly ash affects drinking water quality. Initial measurements showed slightly elevated levels of certain elements, but all remained within regulatory limits. Concentrations decreased over time and with increased water turnover, indicating a self-stabilizing effect. The results support the safe and continued use of fly ash-based concrete in contact with drinking water, enabling more sustainable construction practices.

This report is based on reviews on frost damage mechanisms, on frost requirements in different countries, on research and field studies related to frost resistance and on frost test methods all related to concrete. Focus has been on their relevance in relation to the conditions in the frost exposure classes XF1 – XF4 according to the European concrete standard EN 206.

However, from 19 years of field exposure it can be seen that road environment with de-icing salt is more aggressive than marine environment although they are both covered by exposure class XF4. It is also shown that there is also a large difference between the frost attack exhibited on concrete permanently exposed to external fresh water and one which has a high degree of humidity, but may occasionally dry, which are both covered by XF3.

The influence of carbonation on the salt-frost resistance is complex. On one hand the frost resistance is increased by a lower absorptivity and on the other hand, severe carbonation may destroy the entrained air system. Binders with low resistance to carbonation will therefore scale more than binders with higher carbonation resistance. The difference in chloride concentration between the surrounding solution and the pore solution is a driving potential for microscopic lens growth and scaling.

The report presents a proposal for material and testing requirements for concrete exposed to different frost environments, which are not identical to the exposure classes XF1-XF4. In addition, measures to increase the applicability of the frost test methods, and their reproducibility are proposed.

A demand for a more sustainable use of resources entails that recycled aggregate material need to be used in advanced applications, as in concrete. Even if regulations and standards permit the use of recycled aggregate in concrete, the amount used for this application in many countries is negligible. This caution of the potential users is partly due to the uncertainty about how recycled aggregate, from construction and demolition waste and from washed excavation masses, influence the durability of concrete, such as alkali-silica resistance (ASR), frost resistance and carbonation. Choosing a binder that mitigate damaging alkali silica reactions is an effective means to diminish the risk for damage, even with alkali-reactive recycled aggregate. However, the alkali content of crushed concrete used as aggregate must be considered. No negative effect of recycled aggregate on the carbonation of concrete was observed. The uncertainty about the influence of aggregate porosity on the frost resistance of concrete, about adequate concrete test methods, about aggregate test criteria, and about the correlation between aggregate and concrete test methods need to be settled, before porous recycled aggregate like construction and demolition waste (CDW) can be used in more demanding exposure classes with respect to frost.

BESTÅR – Durable concrete with recycled aggregate In this project the properties of different types of recycled aggregate were investigated: recycled excavated masses, recycled construction and demolition waste (CDW), and reclaimed crushed concrete from concrete production. The content of different minerals, rocks, manmade materials, and chemical substances has been analysed, as well as the freeze-thaw resistance and alkali-silica reactivity. In addition to the testing of aggregate properties, concrete with recycled CDW was tested with respect to compressive strength, freeze-thaw resistance, carbonation resistance, and the risk for deleterious alkali silica reactions. The high water absorption of recycled CDW and reclaimed crushed concrete means that these materials can not be regarded as freeze-thaw resistant. As expected, the freeze-thaw resistance testing in salt water resulted in about five times as extensive scaling for concrete where 30% of the coarse aggregate fraction consisted of recycled CDW, as anticipated with concrete with only natural aggregates of typical igneous and metamorphic rocks. The content of potentially alkali-silica reactive particles was low in all batches (<8 %) and all batches were classified as innocuous aggregate when tested with RILEM AAR-2 and NT Build 295. When concrete with 30 % of the coarse aggregate consisting of recycled CDW and with two different binder compositions was tested, neither exceeded the maximum accepted expansion value. However, the results indicated that when the effective alkali content of the concrete is calculated, the alkali content of aggregate of recycled CDW or crushed reclaimed concrete must be included. The replacement of up to 30 % of the coarse aggregate by recycled CDW did not affect the concrete strength development, and the carbonation resistance even increased. Due to the higher water absorption of recycled CDW, it should be ascertained that all accessible pores in the aggregate are filled with water during mixing of the concrete, to avoid negative effects on the water-to-cement ratio and misleading measured air content.

Reducing the carbon footprint of concrete generally involves reducing the amount of calcium oxide in the cementitous materialsbyblending flyashand/or ground limestone into the cement or by replacing some of the cement with supplementary cementitious materials. This increasesthe ratio of SiO2+Al2O3+Fe2O3to CaO+MgO in the cementitious material.While reducing the CaOcontent of cementitious ma-terials is good for the environment, it may not be good for concrete exposed to de-icing salts plus repeatedcycles of freezing and thawing due to the effect of carbon-ation. Though carbonation can refine the pore structure when using only portland cement, it coarsens the pore structure when using high levels of cement replace-ment.This leads to increased scaling potential.A review of theeffects of different cementitious materials combinations on carbonationalong with an examina-tion offield performance ofconcrete exposed to deicing salt plus repeated cycles of freezing and thawingis used to developa relationship based on the ratio of SiO2+Al2O3+Fe2O3to CaO+MgOin order to determine when limitations on cement replacement, or additional protective measures may be needed when scaling is a concern

This RISE report is a short version of SVU report 2022:5 “Klimatförbättrad betong för dricksvattenanläggningar” (Low carbon concrete for drinking water infrastructure). The purpose of the project was to clarify if the carbon footprint of concrete for drinking water infrastructure can be lowered by replacing Portland cement with supplementary cementitious materials (SCM) accepted for use in concrete without influencing the quality of the drinking water negatively with regard to trace substances and PAH. In addition to reviewing the literature, leaching tests and LCA analyses were conducted on thirteen concretes mixes with varying binder compositions. The results show that it is possible to replace up to 50 % of the cement with the SCMs, ground granulated blast furnace slag (GGBS), silica fume and fly ash. All this may be GGBS and up to 35 % fly ash may be used. This is valid under condition that a drinking water facility which in its entirety is new drinking goes through a tuning period of some days up to a week during which the water quality is monitored before water is delivered to clients. Leaching of some substances is somewhat increased and others are decreased by the replacement of the cement, however the changes are so small that the content in the drinking water in a real facility is only marginally influenced. Which type of binder to use should be decided based on other these materials influence on other concrete properties, for instance on the strength development. The decrease of the carbon footprint is roughly proportional to the cement replacement ratio.

Further development of a test method for anti-graffiti products for concrete surfaces Modified test methods for the performance of anti-graffiti coatings are presented in this report. As a base a test method applied in Sweden since is used which involves outdoor exposure of concrete slabs on which the coatings are applied followed by application of the graffiti and cleaning. The modifications are based on a review of methods existing in other countries, discussions with producers of anti-graffiti coatings and a test program carried out at RISE in Borås. The tests were carried out with two sacrificial coatings and some permanent coatings. In the latter case the graffiti is applied and cleaned ten times. In the existing method, the outdoor exposure is said to be three months. However, it was found that when this exposure takes place, in winter or in summer, greatly influenced the protective capability of the coating. In this project the influence of three different exposures were investigated; three month summer exposure, three month winter exposure and twelve month exposure. The test showed that the three-month summer exposure and the twelve-month exposure gave comparable results. Hence prolonging the exposure period is not necessary. However, very deviating results were obtained after the three-month winter exposure. The evaluation of the protective capability is started with a visual inspection against certain specified assessment criteria on remaining stains and visible marks of graffiti. If the coating met the assessment criteria for the visual inspection, assessment criteria on colour changes measured with a colour measuring device shall also be met. Separate assessment criteria for measured colour changes are used for sacrificial and for permanent anti-graffiti coatings. For a sacrificial coating, the assessment criterium is given in relation to the original concrete surface, while for a permanent coating the assessment criterium is formulated in relation to the exposed surface. It was found that the performance requirement on changes in gloss was irrelevant. In the revised method the selection of colour types and water temperature and pressure used in pressure washing has been modified to be consistent with praxis. The drying between cycles including application of graffiti and cleaning was shortened. The method is divided into two methods; one for sacrificial anti-graffiti coatings and one for permanent anti-graffiti coatings that does not require the use of chemical compounds. The latter method is not applicable to permanent anti-graffiti coatings which need the help of chemical products to give satisfactory cleaning.

Rapporten presenterar resultat från projektet ‘Kartläggning av befintlig provnings-verksamhet för cement och betong i Sverige och bedömning av provningsbehov vid introduktion av nya cement’. Mot bakgrund av en minskad eller stoppad produktion av cement vid Cementas fabrik i Slite gav Regeringen Verket för innovationssystem (VINNOVA) den 3 november 2021 i uppdrag att kartlägga befintlig provningsverksamhet för cement och betong (N2021/02773) som finns tillgänglig för svenska aktörer och att föreslå åtgärder som kan skapa förutsättningar för en samordning vid en kraftigt ökad efterfrågan på denna verksamhet. Denna rapport behandlar hur provningsbehovet kan komma att utvecklas vid stopp i den svenska cementproduktionen i Slite vilket resulterar i ett behov av introduktion av stora volymer av ett eller flera nya cement under kort tid. Denna händelse benämns i rapporten förenklat som “cementkris”. Rapporten pekar på några förutsättningar som bör gälla för att ett cementbyte skall kunna genomföras rimligt kontrollerat. I rapporten görs det inte någon bedömning av hur byggbranschen eller samhället i stort skulle påverkas av en cementkris. Det görs inte heller någon analys av vem som tillser att produktions-bortfallet från Slite ersätts med annat cement eller varifrån detta cement kan komma. För en bedömning av provningsbehovet av betong har detta inte någon avgörande betydelse. Ett nytt cement från Kina kräver för betongtillverkaren lika mycket provning som ett nytt cement från närområdet i Europa eller för den delen Sverige. Förutsatt att cementet i sig är CE-märkt och uppfyller svenska krav.

Den huvudsakliga slutsatsen är att: Under förutsättning att inte avkall får göras på de krav som ställs på cement och betong i Sverige idag krävs det att nu använda och nya cement finns tillgängliga parallellt under en övergångsperiod på minst två och ett halvt år. Detta gäller främst betong till anläggningskonstruktioner och infrastrukturprojekt där kraven på kvalitetssäkring via provning på ackrediterade laboratorier är hög. På grund av ökat provningsbehov går det inte att genomföra ett omfattande byte av cement på ett stort antal betongfabriker under kort tid utan betydande störningar och stopp i betongleveranser till svenska byggarbetsplatser, om inte nu använda och nya cement finns tillgängliga parallellt. Inom husbyggnadsområdet är behoven av provning på ackrediterade laboratorier lägre. Hur snabbt och smidigt ett byte av cement kan göras för husbyggnadsbetong avgörs i stället av möjligheterna att utföra nödvändiga interna provningar och intrimningar på fabrikerna.

Om nu använda och nya cement till anläggningsbyggandet finns tillgängliga parallellt under minst två och ett halvt år är bedömningen att nödvändig ökning av provnings-kapacitet hinner byggas upp samtidigt som ett byte från nu använda till nya cement kan göras på ett rimligt kontrollerat sätt med avseende på behovet av extern provning. Detta förutsätter emellertid att samtliga nya cement är CE-märkta och uppfyller svenska krav samt en samordning av provningskapaciteten inom vissa kritiska provnings-områden. För att öka provningskapaciteten på nationell nivå inom kritiska provnings-områden krävs en noggrann planering av hur en sådan utökning skall genomföras (lokaler, utrustning, kompetens, vem som skall vara huvudman) och vem som skall bekosta en sådan ökning av provningskapaciteten.

 A one-day Nordic Concrete Research workshop on “Accelerated freeze-thaw testing of concrete” attracted approx. 30 participants. The workshop included presentations on various aspects, such as observed frost damage in the field and the importance of the temperature curve during testing as well as other interactions with the surroundings of the concrete. The workshop also included examples of recent research, which can improve our knowledge about the frost damage mechanism and therefore provide input to improving the standardised test methods. The present paper is a summary of the nine presentations and the discussion arising from the presentations.

It has been observed that storage of specimens with chloride gradients before determining the chloride profile can lead to changes in the shape of the chloride profile. An experimental study to quantify the influence of the duration of the storage period and the storage temperature has been carried out. It comprised three storage periods (7, 28 and 91 days) and two storage temperatures (+ 5 °C and + 20 °C). The specimens had previously been immersed in a 15% NaCl solution for 56 days and were sealed in plastics during storage. The results show that a temperature of + 5 °C diminishes the rate of redistribution considerably, compared to a storage carried out at + 20 °C, and the longer the storage period is, the more redistribution will take place. It is also shown that it is of importance to assure that the sealing of the specimens during storage is capable of maintaining the relative humidity at the surface, so that local redistribution of chlorides close to the surface will not take place. © 2021, The Author(s).