title: Effects of activator powders on hybrid binders based on volcanic ash and portalnd clinker based cement

authors: Hettiya Kandage, Havanjana Lanka Fernando

subjects: sustainable material

abstract: Concrete remains the most widely used construction material worldwide. However, the high energy consumption and CO₂ emissions associated with Portland cement production have driven the search for more sustainable alternatives. Volcanic ash (VA), a naturally occurring pozzolan found in abundance in regions such as Tauranga, New Zealand, presents promising potential as a partial replacement for cement. 

This thesis investigates the performance of value-added products from the Takitimu North Link (TNL) site, using chemical activation with sodium sulphate (Na₂SO₄) and calcium hydroxide (Ca(OH)₂) in hybrid binder systems. A central composite experimental design was employed to systematically vary the VA content and activator dosages. 
Mortar mixes with 25%, 50%, 75%, and 100% VA replacement were tested (Series A), with particular focus on the 25% blend. This composition underwent further testing with varying activator dosages to determine the optimal Na₂SO₄/Ca(OH)₂ (NS/CH) ratio (Series B). Compressive strength tests were conducted at 7, 28, and 90 days to assess mechanical performance. 

Additionally, microstructural characterization techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) were used to identify hydration products and evaluate binder densification. 

The results showed that a 25% replacement of Portland cement with VA, activated with 14% Na₂SO₄ at an NS/CH ratio of 1, delivered optimal compressive strength and microstructural development. While higher replacement levels generally reduced early-age strength due to weaker pozzolanic activity, appropriate activator dosages improved long-term performance significantly. 

Overall, the study demonstrates that chemically activated volcanic ash can substantially improve the sustainability profile of concrete by reducing Portland cement usage and its environmental impacts. The use of optimized hybrid binders incorporating volcanic ash offers a viable solution for developing sustainable, resilient, and cost-effective construction materials in New Zealand and other volcanic regions worldwide.

text: Effects of activator powders on hybrid binders based on volcanic ash and portalnd clinker based cement Concrete remains the most widely used construction material worldwide. However, the high energy consumption and CO₂ emissions associated with Portland cement production have driven the search for more sustainable alternatives. Volcanic ash (VA), a naturally occurring pozzolan found in abundance in regions such as Tauranga, New Zealand, presents promising potential as a partial replacement for cement. 

This thesis investigates the performance of value-added products from the Takitimu North Link (TNL) site, using chemical activation with sodium sulphate (Na₂SO₄) and calcium hydroxide (Ca(OH)₂) in hybrid binder systems. A central composite experimental design was employed to systematically vary the VA content and activator dosages. 
Mortar mixes with 25%, 50%, 75%, and 100% VA replacement were tested (Series A), with particular focus on the 25% blend. This composition underwent further testing with varying activator dosages to determine the optimal Na₂SO₄/Ca(OH)₂ (NS/CH) ratio (Series B). Compressive strength tests were conducted at 7, 28, and 90 days to assess mechanical performance. 

Additionally, microstructural characterization techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) were used to identify hydration products and evaluate binder densification. 

The results showed that a 25% replacement of Portland cement with VA, activated with 14% Na₂SO₄ at an NS/CH ratio of 1, delivered optimal compressive strength and microstructural development. While higher replacement levels generally reduced early-age strength due to weaker pozzolanic activity, appropriate activator dosages improved long-term performance significantly. 

Overall, the study demonstrates that chemically activated volcanic ash can substantially improve the sustainability profile of concrete by reducing Portland cement usage and its environmental impacts. The use of optimized hybrid binders incorporating volcanic ash offers a viable solution for developing sustainable, resilient, and cost-effective construction materials in New Zealand and other volcanic regions worldwide.

year: 2025-05-08

title: An investigation of two behavioural economic approaches to evaluating reinforcer value

authors: Lim, Bee Lan Linda

subjects: Behaviour economics

abstract: This study compares two approaches for comparing the value of two different reinforcers. The own-price demand method compares the changes in consumption of the reinforcers resulting from increases in the number of responses required to gain access to the reinforcers. Experiment 1 assessed own-price demand for two reinforcers. Six hens responded under increasing fixed-ratio schedules when either wheat or puffed wheat was delivered for key-pecking. The quantity consumed (measured as either numbers of reinforcers obtained or weight of food consumed) was plotted against the FR size on log-log coordinates to give the own-price demand functions. Three functions were fitted to the data and all described the data well. The parameter values from Hursh’s (1988) and Hursh and Winger’s (1995) equations were generally consistent with wheat being the preferred reinforcer data when derived from the weight of food consumed. Those derived from number of reinforcers were inconsistent. The essential value, α, from the equation proposed by Hursh and Silberberg (2008), when k was fixed at 6.5, were smaller when weight was used and were weight was used and were larger when number of reinforcers was used as the consumption measures and so suggested the essential value changed. These data show that the outcome is affected by how the consumption is measured. It seems that that the above models were similar. The cross-price demand method examines the divergence of the cross-point of two demand functions. In Experiment 2 assessed the cross-point using the same six hens responding under concurrent fixed-ratio fixed-ratio schedules over nine pairs of schedules: FR1/FR256, FR8/FR32, FR128/FR2, FR4/FR64, FR256/FR1, FR32/FR8, FR2/FR128, FR16/FR16 and FR64/FR4. In Condition 1 both schedules gave access to wheat, in Condition 2 both gave puffed wheat, and in Condition 3 one gave wheat and the other puffed wheat. The numbers of each reinforcer obtained and weight of each food consumed were plotted as functions of the left fixed-ratio values to give the cross-price demand functions. When the two reinforcers were identical the cross point tended to be around the ratio used for the equal schedules session (16) with both number of reinforcers and weight of food.. When the two reinforcers differed the cross point for most hens moved to higher ratio when weight of food consumed was used, suggesting that wheat was more valued than puffed wheat for these hens. This was not so for number of reinforcers. Both experiments show that how the consumption was assessed affected the conclusions from that method. Overall the cross-price demand analysis appeared to be the easier to interpret.

text: An investigation of two behavioural economic approaches to evaluating reinforcer value This study compares two approaches for comparing the value of two different reinforcers. The own-price demand method compares the changes in consumption of the reinforcers resulting from increases in the number of responses required to gain access to the reinforcers. Experiment 1 assessed own-price demand for two reinforcers. Six hens responded under increasing fixed-ratio schedules when either wheat or puffed wheat was delivered for key-pecking. The quantity consumed (measured as either numbers of reinforcers obtained or weight of food consumed) was plotted against the FR size on log-log coordinates to give the own-price demand functions. Three functions were fitted to the data and all described the data well. The parameter values from Hursh’s (1988) and Hursh and Winger’s (1995) equations were generally consistent with wheat being the preferred reinforcer data when derived from the weight of food consumed. Those derived from number of reinforcers were inconsistent. The essential value, α, from the equation proposed by Hursh and Silberberg (2008), when k was fixed at 6.5, were smaller when weight was used and were weight was used and were larger when number of reinforcers was used as the consumption measures and so suggested the essential value changed. These data show that the outcome is affected by how the consumption is measured. It seems that that the above models were similar. The cross-price demand method examines the divergence of the cross-point of two demand functions. In Experiment 2 assessed the cross-point using the same six hens responding under concurrent fixed-ratio fixed-ratio schedules over nine pairs of schedules: FR1/FR256, FR8/FR32, FR128/FR2, FR4/FR64, FR256/FR1, FR32/FR8, FR2/FR128, FR16/FR16 and FR64/FR4. In Condition 1 both schedules gave access to wheat, in Condition 2 both gave puffed wheat, and in Condition 3 one gave wheat and the other puffed wheat. The numbers of each reinforcer obtained and weight of each food consumed were plotted as functions of the left fixed-ratio values to give the cross-price demand functions. When the two reinforcers were identical the cross point tended to be around the ratio used for the equal schedules session (16) with both number of reinforcers and weight of food.. When the two reinforcers differed the cross point for most hens moved to higher ratio when weight of food consumed was used, suggesting that wheat was more valued than puffed wheat for these hens. This was not so for number of reinforcers. Both experiments show that how the consumption was assessed affected the conclusions from that method. Overall the cross-price demand analysis appeared to be the easier to interpret.

year: 2010

title: The waters of the Maori: Maori law and state law

authors: Durie, Edward Taihākurei

abstract: This paper is for filing in the Waitangi Tribunal in relation to a claim that existing laws do not adequately accommodate the Māori proprietary interest in natural, water resources. The claim was initiated by the New Zealand Māori Council in association with ten tribal groups. It was later accompanied by 166 other Māori groups, whom the Tribunal joined as interested parties.

text: The waters of the Maori: Maori law and state law This paper is for filing in the Waitangi Tribunal in relation to a claim that existing laws do not adequately accommodate the Māori proprietary interest in natural, water resources. The claim was initiated by the New Zealand Māori Council in association with ten tribal groups. It was later accompanied by 166 other Māori groups, whom the Tribunal joined as interested parties.

year: 2017