The effect of calcium lignosulfonate on ettringite formation in cement paste

The effect of a softwood calcium lignosulfonate, LSs, on the ettringite formed in cement paste was investigated. Two Portland cements, mainly differing in surface area and C3A content, were used. The effect of LSs addition time was studied, by adding either the LSs immediately with the mixing water or after 10 min of hydration. After 30 min of hydration of both cement pastes, the immediate addition of LSs caused the formation of numerous small ettringite crystals. The ettringite crystals had similar shape in pastes with and without LSs addition: cubic or cuboidal shape with length between 0.1 and 0.4 μm. These small particles caused an increase in surface area, which in turn increased the LSs adsorption by the cement paste. This could potentially lead to incompatibility issues between cement and plasticizer.acceptedVersio

Microstructure and Performance of Energetically Modified Cement (EMC) with High Filler Content

Energetically Modified Cement (EMC) is produced by high intensive grinding/activation of Normal Portland Cement (NPC) together with different type and amount of filler. EMC consisting of NPC with 50 % quartz sand has been systematically investigated. Concrete with such EMC was compared to NPC based concrete in accordance with with prEN 206 using the k-factor concept in order to evaluate the contribution of the quartz. k = 0 means no contribution from quartz, k = 1 means contribution equal to cement. Alternatively, k > 0 would mean more effect of "activated" cement than NPC. The k-value for concrete with w/c = 0.60 - 0.45 was 0.7 - 0.9 for 1 day compressive strength and 1.1 - 1.3 for 28 day compressive strength. k > 1 for both capillary suction of water, water accessible porosity water vapor diffusion and chloride permeability. For carbonation resistance k was in the range 0.5-0.6. Microstructure of EMC paste with w/c = 0.40 was extensively investigated and compared with simple blends of the same constituents, in order to explain mechanisms. The quartz was extensively ground, but the overall particle size distribution was similar to NPC. However, the BET surface was increased more, which was explained by agglomerates of the smallest cement and quartz grains with high "inner" surface. DTA/TG indicated that the degree of hydration of the cement in EMC was as high as 71% after 1 day compared to 45% for the blend. However, the refiend pore size distribution of EMC versus the blend means even at equal hydration EMC will perform better. The EMC concept with 50% filler replacing NPC is of particulat interest with respect to environmental issues since it enables a 40% cut in CO2 outlet

Integrally hydrophobic cementitious composites made with waste amorphous carbon powder

© 2019 Amorphous carbon powder (ACP) is a hydrophobic by-product material from refining waste materials of paraffin production factory. ACP effects on permeability and mechanical properties of cementitious composites were investigated. A range of properties of modified cement paste and concrete including hydrophobicity, workability, porosity, compressive strength, transport properties comprising sorptivity, water absorption, water desorption rate and electrical resistivity were studied. Results showed that incorporation of 15% ACP by weight of cement reduces water absorption, sorptivity and electrical conductivity of cement paste by 23%, 86% and 65%, respectively. Sorptivity and electrical conductivity of modified concrete samples by 20% ACP by weight of cement, were reduced by 60% and 30%, respectively. Adding ACP to paste samples resulted in higher compressive strength through lowering porosity. However, in the case of concrete, no significant change was observed. It was demonstrated that ACP could reduce the wettability of cementitious composites by refining the pores and altering the hydrophobicity characteristics of cementitious composites

Integrally hydrophobic cementitious composites made with waste amorphous carbon powder

Amorphous carbon powder (ACP) is a hydrophobic by-product material from refining waste materials of paraffin production factory. ACP effects on permeability and mechanical properties of cementitious composites were investigated. A range of properties of modified cement paste and concrete including hydrophobicity, workability, porosity, compressive strength, transport properties comprising sorptivity, water absorption, water desorption rate and electrical resistivity were studied. Results showed that incorporation of 15% ACP by weight of cement reduces water absorption, sorptivity and electrical conductivity of cement paste by 23%, 86% and 65%, respectively. Sorptivity and electrical conductivity of modified concrete samples by 20% ACP by weight of cement, were reduced by 60% and 30%, respectively. Adding ACP to paste samples resulted in higher compressive strength through lowering porosity. However, in the case of concrete, no significant change was observed. It was demonstrated that ACP could reduce the wettability of cementitious composites by refining the pores and altering the hydrophobicity characteristics of cementitious composites

The effect of calcium lignosulfonate on ettringite formation in cement paste

The effect of a softwood calcium lignosulfonate, LSs, on the ettringite formed in cement paste was investigated. Two Portland cements, mainly differing in surface area and C3A content, were used. The effect of LSs addition time was studied, by adding either the LSs immediately with the mixing water or after 10 min of hydration. After 30 min of hydration of both cement pastes, the immediate addition of LSs caused the formation of numerous small ettringite crystals. The ettringite crystals had similar shape in pastes with and without LSs addition: cubic or cuboidal shape with length between 0.1 and 0.4 μm. These small particles caused an increase in surface area, which in turn increased the LSs adsorption by the cement paste. This could potentially lead to incompatibility issues between cement and plasticizer