Modification of the properties of the cement composites with the organic filler

Abstract The paper presents the research into the two-step modification of the properties of the cement composite with the organic filler by adding a superplasticizer and a waterproofing admixture as well as fly ash and anionic bitumen emulsion. Organic fillers utilized in composites were: common reed (fraction 2–10 and 10–20 mm) and conifer sawdust (fraction 0–2 mm). The reed, Phragmites australis, is a renewable and ecological material, which in the vegetation period absorbs carbon dioxide. The sawdust is a waste product in wood processing. To determine the influence of considered factors on the composite’s properties, the rotatable central composite design was planned. In the first experiment, we added the superplasticizer and the waterproofing admixture (0–2% and 0–4% of the cement’s mass respectively) and in the second experiment, the fly ash (0–200 kg/m 3 ) and the bitumen emulsion (0–16% of the mass of the cement and the fly ash). The physico-mechanical properties such as compressive strength, density, frost resistance, capillarity and water absorption were examined. Additionally, the ability of the cement composite with the organic filler to absorb the carbon dioxide was determined. The results indicated that all the considered variables improved the composite’s properties. Owing to the statistical analysis, the most satisfactory quantities of admixtures and additives were established. The microstructure of the composites was also investigated, and as a result, a new contact zone structure between the cement paste and the organic filler was elaborated. Favourable results of the research might help promote using the lightweight cement composites with the organic fillers in Poland and reduce the extraction of mineral aggregates.