Binder Type | S/B | W/B | Curing Conditions |
Mould/ Spray |
Physical and Mechanical Results | Ref |
---|---|---|---|---|---|---|
NHL 2 NHL 3.5 NHL 3.5 Z |
0.2 0.4 0.5 |
1.16 1.5 1.6 |
28d 20 C° 30% RH 50% RH 75% RH 98% RH |
16x16x32 cm^{3} mould | The Young’s modulus of the samples produced with NHL 3.5 binder cured in 50% RH was obtained with the maximum 9 MPa and the maximum compressive strength 0.18 MPa. As RH value increased, compressive strength decreased significantly. In samples produced with NHL 3.5Z binder cured 50% RH, compressive strength up to 0.31 MPa was provided and Young’s modulus was measured at 36 MPa. Compressive strength in samples produced with NHL 2 ranges from 0.10 MPa to 0.22 MPa and Young’s modulus ranges from 5MPa to 24 MPa. | [^{52}] |
Magnesium Phosphate Cement | 0.08 0.12 0.16 0.2 |
1 | 1d, 7d, 28d 20 ± 2 C 50–55% RH |
4x 4x16 cm^{3} mould 15x15x5 cm^{3} mould |
Compressive strength obtained 0.714 MPa and thermal conductivity obtained 0.103 Wm^{-1}K^{-1} were measured at the 20% hempcrete sample. It is reported that Young’s modulus decreases as the hemp ratio increases. It has been determined that long curing time has a positive effect on Young’s modulus. The values of maximum strain slightly increased as the hemp content increased. | [^{28}] |
72% unslaked lime 28% hydraulic lime |
0.65 | 0.36 | 2 years 23° C 50% RH |
30x30x16 cm^{3} mould | The dry density of hempcrete is 396 kgm^{-3}, the saturated moisture content is 1.805 kgm^{-}^{3}, total porosity is 81% and the specific surface area estimated from the GAB model at 23° C is 59 m^{2}g^{-1}. It has been found that the hygric capacity decreases along a scanning curve and the hysteresis has a significant effect on the storage or release of moisture in hempcrete. | [^{35}] |
70% natural lime, 30% hydraulic lime and pozzolana, natural prompt cement and citric acid |
0.4 0.5 0.67 |
0.52 0.63 | 90days 20° C 50% RH |
16x16x32 cm^{3} mould |
In samples produced with both types of binders, the thermal conductivity decreased by 8% to 30% as the hemp ratio increased. Thermal conductivity in samples produced with a lime-based binder was obtained by 20% more than samples produced with a natural prompt cement-based binder. The thermal conductivity decreases of about 9%–16% after drying. | [^{53}] |
75% hydrated lime, 15% hydraulic lime, 10% pozzolanic binder |
0.4 0.5 0.65 1 |
0.05 gg^{-1} 0.1 gg^{-1} 0.15 gg^{-1} 0.2 gg^{-1} |
23° C, 50% RH |
Spray | When the effect of water content and density values on thermal conductivity is compared, it is obtained that density has more effect on thermal conductivity than water content. In the same mixture design, the thermal conductivity of the high-density sample is 2 times higher than the thermal conductivity of the low-density sample. The thermal conductivity increases low density (250 kgm^{-}^{3}) to high density (600 kgm^{-}^{3}) by 109% at the dry state and by 117% at 0.10 gg^{-1} in water content. | [^{54}] |
Starch | 8 10 |
5.55 | 40d 50d 20°C |
15x15x1510x10x40cm^{3} mould |
Density at ambient atmosphere is 182.8 kgm^{-}^{3} for S/B=8 and 182.0 kgm^{-}^{3} for S/B=10. The tensile strength is 0.08 MPa for S/B=8 and 0.10 MPa for S/B=10. The compressive strength is 0.57 MPa for S/B=8 and 0.60 MPa for S/B=10. The Young’s modulus is 2.47 MPa for S/B=8 and 2.33 MPa for S/B=10. The thermal conductivity at the dry state varies in the range of 0.06-0.07 Wm^{-1}K^{-1}. When the S/B ratio increases, the mechanical characteristics slightly decreases due to the increase of the porosity and the decrease of the load transfer. | [^{24}] |
50% NHL 3.5 50% hydrated calcic lime |
0.5 | 1.5 | 10 months 20°C and 50% RH Outdoor |
11x22 cm^{3} mould |
The compressive strength of the samples cured in 10 months at 20 ° C and 50% RH was obtained 0.73 MPa. For 1 month curing at outdoor, the compressive strength was obtained 0.43 MPa and 10 months curing at outdoor the compressive strength was obtained 1.01 MPa. Outdoor curing improved the carbonation process, which enabled samples to reach a compressive strength of 1.01 ± 0.08 MPa after 10 months. This was attributed to favorable %RH conditions for CO_{2} diffusion and dissolution. | [^{55}] |
75% Aerial lime base 15% hydraulic lime 10% pozzolana |
0.48 0.44 |
1.37 0.77 |
22°C - 26°C 40 - 50% RH 22°C 30–60% RH |
Spray | Densities of samples, whose drying times were measured at 20 and 70 days, were measured as 430 kgm^{-}^{3} and 340 kgm^{-}^{3}. Spraying process leads to lower initial moisture content and lower density, and thus a faster drying time in comparison to the moulding or tamping process. It is observed that the manufacturing process influences the initial water content and the final density whereas the hygrothermal behaviour depends on the material formulation. | [^{37}] |
70% hydrated lime 20% cement 10% pozzolana |
0.5 0.66 1 |
1.57 1.39 1.37 |
26d 21°C 50% RH |
30.5x 30.5x7.6 cm^{3} 15.2x 15.2x 15.2 cm^{3} mould |
The thermal conductivity of the samples with a density of 233 kgm^{-}^{3} to 388 kgm^{-}^{3} varies between 0.074 Wm^{-1}K^{-1}, to 0.103 Wm^{-1}K^{-1}. The drying process of the samples took 26 days, where minimum density was stabilized. The density of the samples were 233 kgm^{-}^{3}, 316.8 kgm^{-}^{3} and 387.8 kgm^{-}^{3} respectively, while their thermal conductivity were 0.074 Wm^{-1}K^{-1}, 0.088 Wm^{-1}K^{-1}and 0.103 Wm^{-1}K^{-1}, respectively. The increase in the density of the samples caused an increase in thermal conductivity. | [^{56}] |
70% hydrated lime, 15% hydraulic lime, 15% pozzolan |
0.47 | 1.47 | Undisclosed | Spray | Densities of samples with compressive strength of 0.180 MPa to 0.8 MPa were obtained from 291 kgm^{-}^{3} to 551 kgm^{-}^{3}. Density and thermal conductivity of the samples 0.179 Wm^{-1}K^{-1} for 417 kgm^{-}^{3}, 0.421 Wm^{-1}K^{-1} for 475 kgm^{-}^{3}, 0.542 Wm^{-1}K^{-1} for 496 kgm^{-}^{3} and 0.485 Wm^{-1}K^{-1} for 551 kgm^{-}^{3} was measured. Increasing mortar density provides both thermal conductivity and mechanical properties. | [^{41}] |
75% hydrated lime, 15% hydraulic lime, 10% pozzolana |
0.33 | 0.81 | 23 – 40 °C 50% RH |
Mould Spray |
The density of the moulded sample was measured as 510 kgm^{-}^{3} and its thermal conductivity was 0.14 Wm^{-1}K^{-1}. The density of the sprayed sample was measured as 405 kgm^{-}^{3} and its thermal conductivity was 0.08 Wm^{-1}K^{-1}. Moreover, sorption desorption curves should be determined from moderate cycles of RH for proper quantification of hemp concrete hygrothermal behaviour. | [^{57}] |
Natural prompt cement | 0.5 | 1.5 | 7days in sealed mould 83days in 20°C 50% RH 10 days in 40 °C drying oven 80 days 30 °C 40%–90% –98% RH |
Mould | Density, porosity and thermal conductivity of hemp fiber used hempcrete sample are; 335 kgm^{-}^{3}, 72.5%, 0.105 Wm^{-1}K^{-1}, respectively. Density, porosity and thermal conductivity of non-fibred hempcrete samples are; 342 kgm^{-}^{3}, 75.5%, 0.102 Wm^{-1}K^{-1}, respectively. Aging affects the porosity of the hempcrete. However, the aging effect is not sufficient to lead to modifications of acoustical and thermal performances. At the same time, mold growth occurs when the relative humidity is high (98% RH) and when the pH of the binder has decreased due to its carbonation reaction. | [^{58}] |