Ceramics-Silikáty 63, (3) 321 - 329 (2019)

The possibilities of primary paper sludge (PS) only dried at 75 °C from the paper production industry used in concrete composition are discussed. For pursuing the set object, the concrete mixes were chosen where part of the cement content was, in one case, replaced by the PS waste and, in the other case, part of the sand content was replaced by the PS waste. It was found that if 2.5 % of the sand is replaced by the PS waste, the compressive strength of the concrete increases by about 15 %, its density decreases by 4 % and the water absorption remains analogous to the reference samples. SEM analysis showed that when the content of the PS waste in the mix does not exceed 7.5 %, it adhered well to the cement stone and crystals grew on it. The X-ray images showed that analogous minerals were formed in the tested concrete samples and only their contents were different.